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Blainville's Horned Lizard by Michael Marchiano 1998-10-01 The Coast or Blainville’s Horned Lizard (Phrynosoma blainvilli ) is considered to be an odd-looking creature by many people. Squat, flat bodied, and short-tailed with a wide head covered in spines, it causes one to consider the little lizard a miniature relic from the age of dinosaurs. In fact, its appearance gives rise to its nickname, “Horny Toad”. Growing to a length of five inches, this cryptic colored lizard depends far more on its appearance for survival than speed or agility. Its mottled coloration of large and small patches and bands on its body of various shades of brown, black, cream, and yellow allow it to blend into it environment almost to a point of invisibility. When threatened, it will first freeze and hope its camouflage will protect it. If attacked, it will run a short distance, stop suddenly, lay flat, and once again count on its coloration for protection. If grabbed, the horned lizard has a unique defense for repelling its attacker. It can actually squirt a quick stream of blood from the corner of its eyes with the hope of distracting or startling the predator and escaping. Another unique feature of this specialized lizard is its diet. Its primary food is native ants, such as species of harvester and carpenter ants. It does on occasion eat other arthropods such as beetles, crickets, and spiders, but 80-90 percent of its diet is indigenous ants. The introduction of Argentine ants (which have replaced native species) in areas once inhabited by Coast horned lizards has been one cause of their diminished numbers. These introduced ant species are not palatable to the lizard. Although three subspecies of this lizard inhabit California, from Baja up the Central Calley to the Sierra Buttes, the last vestige of these unique creatures in Contra Costa County is Mount Diablo. The overall population of the Coast horned lizard throughout California has been under threat because of habitat destruction, pesticides, agriculture, and the introduction of Argentine ants. Blainville’s horned lizards are generally seen in our coast range and the Central Valley from spring through fall, hibernating in burrows under ground in cold weather. Found in chaparral, mixed oak, and grey pine forest, sandy loam soil, and gravelly areas, these lizards need a mixture of open space and shrubbery with soil they can easily dig into as well as populations of native ants for food. They breed in spring, with the female laying a small clutch of eggs (average 8-12) in a burrow she excavates. Newborns hatch in late summer or early fall and are miniatures of their parents, about the size of a quarter. Once much more common in Contra Costa County, the population has decreased in recent years. On Mount Diablo keep your eyes open, especially on Eagle Peak, Twin Peaks, Black Point, White Canyon, Mount Olympia, and on the south side along Black Hawk Ridge. Because of its specialized diet and environmental conditions, this is a lizard that does not do well in captivity (horned lizards in North America can no longer be sold in the pet trade) so please enjoy them when you see them, but let them be. Enjoy this unique and marvelous creature along with the rest of the natural environment in Mount Diablo State Park. Blainville's Lizard changes color to blend with the soil. | Dan Sandri By Dan Sandri BACK TO LIST

Clayton Quarry By George Allen, Plant Manager Mount Diablo Review, Spring 2004 Article furnished courtesy of RMC Pacific Materials 2004-04-01 Clayton Quarry Two partners, Harrison and Birdwell, developed mining for construction aggregates on Mount Zion in 1947. However, this was not the first mining activity to occur in the area. The discovery of coal in approximately the 1850's brought about the first commercial mining and the subsequent settlement of coal mining towns such as Stewartville, Somersville, and Nortonville. The discovery of coal also led to additional prospecting wherein mercury and copper were discovered. It has been written that a "copper rush" occurred in the 1860's around Mount Diablo. Copper was never found in significant quantity to make commercial mining worthwhile but the Mt. Diablo mine did produce mercury until the 1950's. Gold and silver were also reported in various assays but, again, none was ever found in significant quantity to make commercial mining worthwhile. As a result of the search for the precious metals, mines and/or claims with names such as Great Republic, Superior, Pioneer, Horse Shoe, Rising Sun, San Carlos, Rough and Ready, and numerous others were developed. Today, the diggings of the Mount Zion Copper Company, Summit of Zion, San Pedro, and a few other mines can still be seen. In 1947, Harrison and Birdwell developed the Clayton quarry. The first excavation was behind the current shop building, but it was shortly moved to the east and south because of better rock on that side. In 1954, Harrison and Birdwell sold out to Pacific Coast Aggregates (later named Pacific Cement and Aggregates), who in turn sold out to Lonestar Industries in 1965. In 1988, Lonestar partnered with RMC of London, England. Today the quarry is owned by RMC Pacific Materials, a wholly owned company of RMC Ltd. of England. The quarry is located on Mount Zion and the material mined is diabase, a hard, durable rock used in the construction of roads, buildings, rail lines, dams, and levees. Over 25 different products are made to supply construction needs. The State of California has designated Mount Zion as a mineral reserve to be used to supply the construction needs of Contra Costa County. Of all the rock shipped out of the quarry, typically 72% of it goes to public sector projects. Some of the specific projects we have been involved in are B.A.R.T. (50% of all the rail ballast came from Clayton), Interstate 580 & Interstate 680 freeways, Highway 4, Highway 24, the new Giants Stadium, the Los Vaqueros Dam, Concord Naval Weapons Station, Delta levees, and many other projects. The Clayton Quarry has been in continuous production for over 50 years, and expects to be producing for many years to come. Interesting Facts: 1. Mount Zion was also known as "Pyramid Hill". 2. Elevation of Mount Zion is 1635 Feet. 3. Minerals found in the quarry are malachite, azurite, iron pyrite, magnetite and calcite. Mount Zion Reflection | Mitchell Canyon BACK TO LIST

I Hiked Them All by Stephen Smith, MDIA President Reprinted from Mount Diablo Review, Spring/Summer 2018 2023-07-01 Stephen Smith Hiking is my passion. It sustains me, brings peace, provides adventure and satiates the explorer within. Hiking has been a part of me for most of my life, and so too has Mount Diablo. It wasn’t until 2016 that I began to really devote my free time to this hobby which quite literally has its ups and downs. Exploring the trails has informed how I see myself and the world around me, and has brought me infinite joy and reward along the way. I purchased my first Trail Map of Mount Diablo State Park from the visitor center and studied it, learning how the network of trails interconnected. Then I saw it: hanging on the wall of the Mitchell Canyon Visitor Center was a t-shirt that had the map of the mountain on it and the words “Hike Them All” emblazoned across the bottom. One of the volunteer docents explained to me that there is an elite group of hikers who endeavor to hike every trail in the park and upon completion purchase the shirt and alter it to read “I Hiked Them All”. I was sold on the idea, but I would have to wait to be sold the actual shirt. How hard could it be? The first clue was in discovering that there are 162 miles of hiking trails in the park! So I developed a game plan. I would complete the challenge in one calendar year, I would hike every trail and utility road listed on the official park map, I would not trespass onto any private property without permission, and I would keep track of my progress along the way. Beginning in January 2016, I set off on the first of many outings, covering 8 miles and 1,800 feet of elevation that first day. When I got home, I got out my map and a pink highlighter and retraced my steps. It would become a much anticipated ritual following each hike, highlighting the trails I had completed and planning the route for the next adventure. A couple of months into my quest, I learned from some hiking companions that there was a Volunteers in Parks Program (VIPP) on the mountain. I completed a half-day training session and began volunteering as a backcountry docent, armed with a vest and the knowledge necessary to help out any lost or troubled hikers. I started encountering hundreds of other volunteers along the way. There were groups removing barbed wire and other debris as part of the Trash Removal Project (TRP). I ran into a large group of red-shirted volunteers who were part of the Trail Crew and learned that they maintained our trails twice a month. A small group who were handy with tools called the Maintenance Volunteer Group (MVG) was fixing some of the aging buildings and picnic areas. Still more were staffing the Mitchell Canyon Visitor Center as docents, while others were out leading nature hikes for the public. The list went on and on, and I was enamored by their conviction, passion and devotion to this state park. All the while, my journey continued. It would take over 450 miles of hiking in order to cross off the vast network of trails in the park. I once hiked 17 miles just to cross off a remote 0.1 mile long trail at Windy Point. My well-worn map was soon covered in pink highlighter. Equally well-worn were my hiking boots, yet my mind and spirit were energized and invigorated. I had met so many wonderful people along the way and reignited a love affair I have had with this mountain my entire life. My final trail was Castle Rock Trail, and in September 2016 I was joined by 40 fellow hikers who shared in a milestone I will not soon forget. I was so entranced by being a part of the mountain that I wanted to become more involved in the interpretive side of the park and joined the Mount Diablo Interpretive Association in its mission of Preservation through Education. I write to you proudly as MDIA’s Board President. You certainly don’t need to set out on a journey like mine in order to appreciate the sheer beauty of Mount Diablo. There are trails here for every hiker, casual or experienced. A great companion to our park map is the Hiker’s Guide to Mount Diablo, available in our visitor centers and online for $15. It has 50 spectacular hikes to embark on, from the 0.7 mile Mary Bowerman loop all the way up to our 26.2 mile (and 6,948 foot) Mount Diablo Marathon hike, and everything in between. It has route maps, elevation plots, descriptions of natural and cultural history as well as photographs of the scenery. I urge you to get out on the trails today, as this time of year is spectacular with wildflowers and waterfalls to behold. Check out our website at mdia.org where we feature some of our premier hikes that you can print out and take along with you. Or download our Audible Mount Diablo guides and take an audio tour of the mountain as you hike along the trail. And if you want to join the elite group who has hiked every trail, get out your highlighter and set your sights on that commemorative t-shirt! Steve on his completion of hiking all trails. Diablo and North Peak | by Stephen Smith Foxtails are a good reason to stay on the trail. Back country section of Red Road Poppies | by Stephen Smith North Peak | by Stephen Smith Summit Building | by Stephen Smith BACK TO LIST

Riparian Woodlands Excerpted from MDIA's book Plants of the East Bay Parks, by Glenn Keator, Ph. D. Plant Communities of Mount Diablo State Park 1999-01-01 Madrone Canyon | Mike Woodring Riparian woodland is found only along permanent streams and rivers, where the water table remains at or just below the surface all year. Our area has no true rivers, but there are several perennial streams -- some with fairly broad floodplains -- that support riparian woodland. Because riparian woodlands have a guaranteed water supply, their component trees are very different from trees in most other environmental situations. These trees are not limited by the hot, dry days of summer; rather they can afford to grow fast and profligately right through the longest days of the year. Consequently, the derivation of riparian woodlands is entirely different from that of the rest of our flora. The closest relatives to riparian species come from summer-wet climates such as those across the Midwest and eastern parts of the United states. Wander in these forests if you are homesick for the look and feel of eastern hardwood forests. Riparian trees -- because of their ancestry from eastern United States climates -- behave as though they still were adapted to cold winters. Nearly all are deciduous in winter, for they can afford to make whole new sets of leaves the following year, come what may. Leaves are also designed in ways that suggest water wastefulness: they're broad, thin, often lobed or compound, and held horizontally -- fully exposed to the summer sun. They are also borne in thick tiers from top to bottom. Riparian trees reach maturity quickly because they're able to grow over such long periods each year. Quick growth may cause weak wood, however, and many riparian trees are liabilities because of brittle limbs. They also have relatively short life spans. BACK TO LIST

Guide to Mount Diablo Geology Mount Diablo's Rocks, Tetonic History and Mining 1998-07-01 Wind Cave | Roi Peers Part I: The Rocks of Mount Diablo - Their Type and History Rising 3,849 feet, Mount Diablo forms a prominent feature in the East Bay landscape. Our understanding of the geological history of the rocks and structure of Mount Diablo has undergone major changes during the past 30 years, and even now geologists are still trying to unravel the complicated history of the mountain. This complex history is not unique to the mountain, but to our region as a whole, since Mount Diablo has been caught up in the processes that have shaped the Coast Ranges for millions of years. Perhaps the most salient fact is that, although the rocks of which it is composed are very old, Mount Diablo only began rising recently in geological terms. The rocks are old, but the mountain itself is young. To better understand the complex geology of Mount Diablo, it is useful to divide the mountain’s rocks into three main groups. Each group has a different history and is characterized by different types of rocks. Group 1: Mount Diablo Ophiolite ( Jurassic ) Group 2: Franciscan Complex ( Jurassic and Cretaceous ) Group 3: Great Valley Group ( Jurassic and Cretaceous ) and Younger Sedimentary rocks ( Cenozoic ) Plate tectonics played a major part in the formation of the Mesozoic rocks of Mount Diablo. We now recognize at least 11 separate major plates of oceanic crust and rigid upper mantle rocks around the globe. These plates “float” on a layer of semi-molten rock, all moving against and jostling each other, creating new land forms in the process. Continents ride atop these ocean plates, being rafted along as the plates move. New oceanic crust is being continually created by the eruption of submarine volcanic material forming along ocean-spreading ridges such as the Mid-Atlantic Ridge. To compensate for the newly created oceanic crust, older existing oceanic crust is driven beneath the continental crust at subduction zones, and recycled into the earth. Group 1 - Mount Diablo Ophiolite ( Jurassic-Cretaceous ) It is generally believed that near the close of the Jurassic a subduction zone developed along what is presently represented by the modern California coast. The oceanic crust caught between this subduction zone and an earlier shoreline in the ancient Sierra foothills was preserved as the Coast Range Ophiolite and later partially exposed. Ophiolites are thought to form at oceanic spreading centers in the middle of the oceans, associated with oceanic island chains (arcs), or in narrow oceans such as the Gulf of California. Ophiolites generally form a uniform vertical rock sequence consisting, from bottom to top, of ultramafic peridotite from the top of the mantle, mafic intrusive gabbros and/or diabase that formed one or more miles below the sea floor, and mafic extrusive rocks, often in the form of pillow lava extruded beneath water. The rocks of this old ocean crust on Mount Diablo have been named the Mount Diablo Ophiolite and is considered a fragment of the Coast Range Ophiolite. The Mount Diablo Ophiolite underlies the mountain north of a line drawn from Long Ridge through Murchio Gap, encompassing the Zion Peak rock quarry, Mitchell Rock, and Eagle Peak. Radiometric and fossil-age determinations date the ophiolite as having been formed approximately 165 million years ago during the Mid-Jurassic. Mount Diablo Ophiolite Basalt: The basalt, which makes up the upper part of the Mount Diablo Ophiolite, is mostly interbedded pillow basalt lava flows. As the lava erupts under water, the outer surface of the flow “freezes” in contact with the water. More lava breaks through and again the outer surface “freezes.” This process leads to the accumulation of “pillow” structures and the resultant rock is referred to as pillow basalt or pillow lava. The basalt has a microscopic crystalline texture with a black to greenish-brown color, weathering to a yellowish-brown to dark reddish-brown soil. Well-developed pillows can be seen on Mitchell Rock. Mount Diablo Diabase: The pillow lavas are fed by a series of vertical fissures, or dikes, that allow the molten rock from below to reach the surface. The molten material in the dikes solidifies into a rock called diabase, which has the same chemical composition as basalt, but with a coarser texture. Diabase is exposed in quarries at Mt. Zion and on Eagle Peak. Mount Diablo Serpentinite: Serpentinite is a rock frequently found in association with an ophiolite. Serpentinite is derived from the basal portion of the original ocean crust and uppermost part of the mantle, but has been metamorphosed by hydration from ocean water circulating through fractures in the ocean crust. Serpentinite forms by addition of water to minerals in peridotite, changing them from olivine and/or pyroxene to the serpentine minerals antigorite, chrysotile and lizardite. Serpentinite, incidentally, is California’s state rock. On Mount Diablo, serpentinite occurs in several localities. The largest is the prominent east-west band that runs through Murchio Gap extending west along Long Ridge, separating the ophiolite on the north from the Franciscan rocks exposed in the central core of the mountain to the south. This band is characterized by a noticeable change in vegetation due to the high magnesium content of the serpentinite. Exposures of the serpentinite are typically pale green to greenish-gray, locally black, weathering to grayish-orange. In addition to the highly sheared serpentinite, ultramafic rocks of harzburgite (a variety of peridotite) and pyroxenite are present in this band as well, but are less sheared than the serpentinite. The body of pyroxenite exposed along the Burma Road Trail on Long Ridge is coarsely crystalline, sparkling in the sunlight as you walk along the trail. Exposed blocks of massive harzburgite on the westerly end of Long Ridge frequently contain veins of fibrous chrysotile. There are several pods of silica carbonate rock (altered serpentinite) found in association with the mercury mines on the northeast flank of the mountain and other scattered locations along the serpentinite band. Group 2 - Franciscan Complex ( Mesozoic ) The central Mount Diablo summit area and North Peak is underlain by an assemblage of Mesozoic rocks that have been a puzzle to California geologists for years. Our relatively new understanding of plate tectonics and subduction has finally provided an important clue to unraveling this mystery. This diverse complex of rock types is common up and down the coastal ranges of California and has been given the name Franciscan Complex. The processes of subduction can account for the mixing of such a wide variety of rock materials. The Franciscan Complex records over 140 million years of uninterrupted east-dipping subduction, during which the Franciscan formed as an accretionary complex. As the oceanic plate subducted beneath the continent, part of the upper section of the ocean crust (pillow basalt) and the material riding on the plate (chert, graywacke, shale, small islands, and sea mounts) were scraped off the upper part of the subducting plate, mixed together, partially subducted and accreted on and under the continental crust. Mount Diablo and North Peak are composed of faulted blocks of resistant basalt and chert with some graywacke and minor shale, and are expressed topographically as rugged and jagged rock masses. Wrapping around the two peaks in a rough “figure 8” shape are the more gentle treeless slopes of “mélange.” Such a diverse mixture of rocks, is called a "mélange" by geologists from the French for "mixture". The Franciscan mélange is essentially a chaotic mixture of an intensely sheared sandstone and shale “paste” in which are embedded blocks of basalt, chert, and graywacke along with rare exotic rocks. It is often difficult to distinguish between the mélange topography and local landslides. Franciscan rock accretion ceased with the ending of subduction in our area. Franciscan-like rocks are currently forming north of Cape Mendocino offshore or beneath the continent where the oceanic Juan de Fuca plate is still subducting beneath North America. Recent studies using modern dating techniques and temperature history studies suggest that the Franciscan Complex appears to have undergone metamorphism around 108 million years ago at a depth of approximately 12 miles. As a result, the Franciscan rocks are frequently referred to as metabasalt or metagraywacke reflecting a history of metamorphism by heat and pressure deep underground. Franciscan basalt: The blocks of basalt exposed in the Franciscan on Mount Diablo are altered oceanic pillow basalt. On the surface the rock weathers to a dark yellowish-brown to dark reddish-brown while fresh exposures are grayish-green to light olive drab. It is locally called “greenstone.” The green color comes mostly from chlorite, a green alteration mineral. The basalt blocks in the Franciscan are believed to be fragments scraped off of the upper part of subducting basaltic oceanic crust. Franciscan chert: The chert bodies in the Franciscan form prominent dark red exposures and talus slopes. Made up of silica, they are resistant to erosion and form such features as Devil’s Pulpit and Turtle Rock. Typically red in color (green and white less common), the chert layers are typically interbedded with reddish-colored shale. These banded rocks are often referred to as “ribbon chert.” The red color is derived from iron oxides. The chert in the Franciscan was formed far out at sea. Silica skeletons of minute ocean animals called radiolaria settled to the ocean floor forming a silica ooze that ultimately solidified into chert. The chert continued to slowly accumulate on top of the ocean floor as the ocean crust drifted away from the spreading center on its long journey toward subduction. The Franciscan chert ranges in age from 190 myo (million years old) to 90 myo, representing 100 million years of accumulation. Franciscan cherts are formed from the tiny (0.5 to 1.5 mm) silica shells of radiolaria. Many of these radiolaria are tropical species indicating that the sediments were deposited near the equator and were later transported northeastward by plate movements. Franciscan graywacke: Graywacke is less common on Mount Diablo than the greenstone and chert. It is typically fine-to medium-grained and massive (no stratification or bedding visible). It breaks along distinct joint planes, which helps distinguish it in outcrop from the more “shatter fracturing” of the greenstone. The graywacke consists mainly of angular quartz, plagioclase feldspar, chert fragments, and dark volcanic rock fragments. Calcite and quartz occur commonly in the criss-crossed white veins. The graywacke is younger in age than the greenstone (basalt) or chert, ranging from 90 to 108 million years in age. These rocks are thought to have formed in a subduction trench environment off the coast of North America (some researchers suggest Mexico, subsequently moving north). Franciscan shale: Approximately 10% of the Franciscan on Mount Diablo is made up of shale, most of which has been altered to argillite as a result of the earlier period of metamorphism. Most of this clay-sized material was probably deposited in less turbulent current conditions in association with the graywacke deposition. Franciscan exotic rocks: The most common so-called exotic rock present on Mount Diablo is a glaucophane schist, or “blueschist,” named for the noticeable blue color of the glaucophane. Blue schist is largely altered basalt and reflects a history of hi-pressure/low-temperature metamorphism, a condition found in subduction environments and rarely any other place. On the Summit Road as you drive toward the summit, just past the Rocky Point Picnic area, you will notice a dark blue-black boulder of blueschist about five feet across protruding from the bank on the left side of the road. Group 3 - Great Valley ( Jurassic - Cretaceous ) and Younger Sedimentary Rocks ( Cenozoic ) The name Great Valley Group refers to the thick sedimentary rocks of Upper Jurassic through Cretaceous age that were deposited between the ancestral Sierra Nevada to the east and the subduction zone to the west on top of the ophiolite basement that underlies California’s central valley. The Great Valley sequence is composed mostly of deepwater marine shale, sandstone and some conglomerates accumulating to a thickness of 60,000 feet near the western margin of the present day Great Valley, and then, in our area, thinning toward Mt. Diablo. The Upper Jurassic Knoxville Formation is 140 million years old and are the oldest beds of Great Valley in this area. Great Valley deposits on-lap the Mount Diablo area and thinner deposits intermittently covered it during this time. The general interpretation of these rocks is that they were deposited in the submerged central valley as intermittent underwater "turbidity currents" and the deposits are called turbidites. To summarize the Cenozoic in this area, it is perhaps easiest to think of the central valley of California as a low elongate basin, flooded intermittently by an encroaching shallow sea, and slowly being filled by sedimentary material eroded from the surrounding exposed land masses, primarily the “Sierra.” During the latter part of the Tertiary, newly formed highlands to the south (Diablo Range) and in the area of the present day San Francisco Bay also acted as source areas. The Mount Diablo area seemed to represent a persistent “high,” underwater, but less deep than surrounding areas and periodically exposed to erosion. Many of the formations seem to shoal out on the flanks of this area and when submerged, the strata thin over this “high.” The area, however, was not a “mountain” as we see it today, but rather a land of low relief intermittently submerged well into the Pliocene. Paleocene Rocks (55.5 - 65 million years ago) There are few Paleocene deposits present in our area indicating that the region was probably above sea-level and undergoing erosion following the close of the Cretaceous. The only nearby rocks of this age are restricted to the north side of the mountain outside of the park. Eocene Rocks (33.7 - 55.5 million years ago) During the Eocene , the climate warmed, resulting in heavy “ancestral Sierra” weathering that yielded large quantities of sands that washed into and across the Central Valley providing material to the Eocene deposits of Mount Diablo. A shallow marine basin, a sandy shoreline, a swampy backwater area—all existed in this area at different times or at the same time in different places. On the north side of the mountain, the Eocene is present in the Black Diamond Mines Regional Park. These strata contain coal beds and glass sands and have been described as a near-shore lagoonal swamp or tidal flat estuarine environment. On Mount Diablo, Eocene deposits form the ridges of tan-colored sandy rock formations that wrap around the south and west side of the mountain. These sedimentary rocks have been given the name Domengine Formation and are well exposed at Castle Rock, Rock City, Knobcone Point, and Cave Point. These sands on the south side of the mountain are characteristic of deep offshore slope deposits. They represent deep erosion of the ancestral Sierra highland spreading over the Mount Diablo area as the ocean deepened westward. Some Domengine beds represent shallower near-shore deposits that contain beds rich in Turritella fossils (marine snails). These massive sandstone beds weather easily forming features such as caves and open tunnels. Rock City, easily accessible on the South Gate Road, is a good place to view these unusual features. These massive sandstone that form the Wind Cave beds weather easily forming features such as wind caves and open tunnels. Unusual "cannonball concretions" can also be found in these sandstone beds. Rock City is a good place to view these unusual features easily accessible on South Gate Road. Oligocene Rocks (23.8 - 33.7 million years ago) The only Oligocene rocks in the area is the Kirker Tuff on the north side of the mountain outside the park boundary. Miocene Rocks (23.7 - 5.3 million years ago) On the south and west sides of the mountain, the depositional contact between the Eocene and the Miocene rocks can be recognized by the abrupt change from clean, thick-bedded, light tan sandstone in the Domengine formation (Eocene) to poorly sorted, dark gray, pebbly sandstone of the marine Miocene rocks. There is a large gap in the geologic time record between these rock units, representing erosion or non-deposition. The interval of missing time and rock equivalents includes the upper Eocene, the entire Oligocene and the lower (or earliest) Miocene. During middle Miocene time, the general drainage was directed from the east into an open ocean to the west, a pattern similar to the deposition of the earlier Eocene. By about 10 mya (million years ago), subduction had ended in central California and there was a major change in the pattern of deposition. A highland developed to the west and the Diablo Range south of Livermore began to rise. The Mount Diablo area began to accumulate marine and later non-marine deposits from these sources. Now steeply tilted upward from an original horizontal orientation, the vertical beds form the prominent “hogbacks” on Fossil Ridge and Blackhawk Ridge. Building material quarried from Fossil Ridge was used to construct the summit museum building, and numerous clam and oyster shells can be seen in the exterior walls of that building. These fossiliferous beds are called the Briones Formation. Following Briones deposition, the direction of sediment transport shifted again, bringing sands derived from the east, rich in volcanic material washed from the Sierra highlands. These volcanic sands have been named the Neroly formation. They form the grass-covered rounded hills immediately south of the underlying ridge-forming Briones strata on the south, and can be found on the west and north sides of the mountain as well. Andesitic Neroly sandstone alters easily, and in most places the sand grains are coated with a thin layer of bluish clay that is clearly exposed in an often visited site in Shell Ridge Open Space in Walnut Creek. Beds rich in fossil marine shells are well exposed at this site and also in Sycamore Canyon on the southern flank of Mt. Diablo. Around nine million years ago, during the late Miocene, the sea again receded from the Mount Diablo area, marking a permanent change from marine deposition to non-marine stream and lake deposition. One of the nine million-year-old stream deposits on the south side of the mountain has captured and preserved an abundant and diverse collection of animal fossils. The Blackhawk Ranch Quarry has yielded numerous vertebrate fossils of horses, rhinos, camels, and smaller animals. A large mastodon skull, a Gomphotherium , has been removed from this site. All give evidence that late Miocene mammals abounded in the newly created forests and flood plains stretching away to low hills to the west and south. There are several volcanic tuff deposits in the late Miocene and Pliocene derived from the volcanic fields of Sonoma County. There was still no Mount Diablo at the time. Plio-Pleistocene to recent rocks (5.3 million years ago to present) Non-marine deposits continued to collect in the area during Pliocene time (5.3-1.8). It was during Plio-Pleistocene time, by 4 mya and continuing to the present, that Mount Diablo was formed as a topographic feature. From that time on, Mount Diablo has been feeding erosion materials into surrounding valleys. Pliocene sources were predominantly from Great Valley rocks. Pleistocene sources were predominantly from Franciscan, indicating unroofing and erosion of deeper terranes. The 4.83 million-year-old Lawlor Tuff is a widespread marker bed around the mountain. The fact that it was laid down on a relatively flat landscape and is now steeply folded indicates that Mount Diablo must have begun its growth after the tuff was deposited. Part II: Forming the Foundation - Mount Diablo's Tectonic History Although Mount Diablo is old in terms of its rock history, it is very young as a topographic feature. The rising of Mount Diablo to its present height is the result of a complex interplay of tectonic forces. The Franciscan Complex presumably underlies all of Contra Costa County. It was emplaced below the Coast Range Ophiolite by accretionary faulting during Cretaceous time, so the contact between the Franciscan and Coast Range Ophiolite (locally called the Mount Diablo Ophiolite) as well as the overlying Great Valley Sequence is everywhere a fault plane. This fault is known as the Coast Range fault. Recent field studies suggest that following the emplacement of the Franciscan Complex at depth in this area, the rocks underwent a period of metamorphism. This appears to have occurred at depths of approximately 12 miles. During late Cretaceous through early Eocene time, the overlying cover rocks were significantly thinned by extensional faulting along the Coast Range Fault plane and ductile thinning in the serpentinite component of the ophiolite. As a result of this slow structural thinning of the overburden, the Franciscan rocks of the future mountain rose vertically to a depth of around two miles. There appears to be no evidence that these rocks were above sea level during this period. The final two miles of uplift and exhumation of the Franciscan Rocks occurred during Pliocene to present time. It was during this last phase that the Franciscan rocks, and overlying Great Valley strata, were folded by compressional forces associated with what is believed to be a blind thrust fault beneath the mountain. These geological processes have created a complex uplifted compressional asymmetric fold that has been moving southwest on the blind thrust. The recognition of the possible existence of a blind thrust fault under Mount Diablo has resulted in the issuance of an advisory by the USGS in September, 1999, predicting a four-percent probability of a 6.7 or larger earthquake occurring on the blind thrust fault underlying the mountain. Geologists believe the mountain is still rising at about 2 millimeters per year. Extensive erosion has exposed the Franciscan in the center of the fold to produce the majestic Mount Diablo we see today. Part III: Mount Diablo Mining History - Boom to bust The most important minerals and rocks that have been mined or excavated on and around Mount Diablo include mercury, diabase, graywacke, white sands, coal, blue schists, travertine, copper, and farther north and east, gas and oil. Mercury Mercury has been mined on the northeast flank of Mount Diablo off and on since its discovery in 1863. Prior to that, Indians used the colored mineral for ceremonial purposes. The mercury (also referred to as quicksilver) occurs in the form of cinnabar (red mercury sulfide) and metacinnabar (a black mercury sulfide). The host rock for ore is silica-carbonate rock, itself formed from the hydrothermal alteration of serpentine, lying in the boundary fault zone that separates Franciscan from Great Valley rocks. The silica-carbonate rock is made up of varying quantities of silica (chalcedony and opal) together with magnesian carbonates and stained rusty red by alteration of iron sulfide minerals. The rock is commonly spongy in appearance. Topographically, silica-carbonate rock forms resistant outcrops. It is believed that the mercury minerals were deposited from hydrothermal solutions which formed mostly in fractures in the silica-carbonate rock. Ryne Mine produced most of the cinnabar while metacinnabar was produced at the Mount Diablo Mine. A man named Welch discovered cinnabar at what is known as the Ryne Mine in 1863. It operated for about 10 years before becoming uneconomic. In 1933 it was discovered that black metacinnabar in the area known as the Mount Diablo Mine also contained mercury and was more abundant than cinnabar. The demand for mercury during the second world war resulted in an expansion of operation that was to continue until 1958 when mining operations again ceased. It is estimated that about $1,500,000 worth of mercury was extracted from the mines. Unfortunately a continuing legacy of the mining is the acid mine water emptying into and contaminating Marsh Creek. Building Stones and Rip-rap The diabase quarries on the northside of the mountain (Zion Peak) are currently being excavated for crushed rock and rip rap material. There were several excavations in graywacke on the northside of the mountain for the same purposes, but they are now abandoned. Blue schist from the Franciscan rocks on Mount Diablo yielded good dimension stone and was popular for building construction due to its color. Copper and Precious Metals About 40,000 pounds of copper was produced from the mines in the diabase in the 1860's, but there is no activity now. Minor amounts of gold and silver associated with the copper were also produced. It was rumored that the best area to discover gold or silver was in the Back Canyon area (unfortunately inside the park boundary). Travertine Travertine, a finely crystalline massive calcium carbonate deposit frequently associated with hot springs, was quarried along the northside of Mount Diablo (Lime Ridge) for many years by the Cowell Cement Company. Coal and White Sand North of Mount Diablo and outside the park in the Black Diamond Mines area, lignite coal beds in the Domengine Formation were the largest known and most extensively mined Coal deposits in California. From the 1860's to the beginning of this century, the Mount Diablo coal field supplied coal to the rapidly expanding urban and industrial centers of the San Francisco Bay area. Finally closed as newer and cheaper energy sources were discovered, during its lifetime the mines produced approximately 4,000,000 tons of coal valued between $15 and $20 million. At the base of the Domengine Formation exposed in the Black Diamond Mines Regional Park, there is a thin section of white sands called the "Ione" sands, a description carried across the Central Valley from major white sand deposits in the Ione Formation on the east side of the Valley. The sands appear to be continuous across the valley subsurface and of equivalent age. The white sands, that were used for making glass, were mined from two deposits in the area from 1920 until 1949 when they ceased operation. The caverns are a fascinating place to visit on guided tours. Gas and Oil The Domengine Formation also acts as a reservoir for natural gas and the Martinez Formation produces oil in the subsurface northeast of Mount Diablo. Resource: Geologic Guide to Mount Diablo State Park Full color folding geology map of Mount Diablo State Park. Map side contains an overlay of our trail map showing the geologic formations that make up the mountain. The reverse contains detailed descriptions of formations, geologic timelines and more. A must have for all those interested in geology. Highly sheared serpentine | Roi Peers Franciscan graywacke sandstone | Roi Peers Franciscan beds of folded red chert | Roi Peers Turritella Fossils | Mike Woodring Wind Caves | Roi Peers BACK TO LIST

Close Call: The Near-Extinction of Peregrine Falcons by Anastasia Hobbet 2024-01-01 Dave Furseth Lea este artículo en español The fastest animal on earth is a neighbor of yours. It’s the peregrine falcon, clocked at well over 200 miles per hour during its precipitous dives while hunting. Address? Mount Diablo State Park and surroundings, where at least two pairs are now readying themselves to nest in the dramatic pinnacles of Pine Canyon and the remote Black Hills above Black Hawk, where they will spend the spring and summer brooding the eggs and nurturing the youngsters until the kids become independent. Sounds rosy, but there’s a big “if" needed at this point: if the birds can get enough privacy and seclusion. They need a lot of quiet space, and with well more than 100,000 visitors per year now visiting Pine Canyon, is privacy possible for any creature? The responsibility for ensuring some seclusion for the Pine Canyon birds falls to two parks: Castle Rock, which is an East Bay Regional Park; and Mount Diablo State Park. The main access to lower Pine Canyon is via the former, but Pine Canyon's sandstone cliffs lie just over the boundary inside the State Park, forming a section of its westernmost edge. Two annual nesting closure zones stretching from Februrary 1 through July 31 help these blistering-fast aerial hunters feel some confidence in their security. The staffs of the two adjacent parks cooperate in enforcing the closure, but it's tough for a park supervisor working with a tiny staff to dispatch anyone fast, which is key. Widespread use of DDT beginning in the late 1950's almost wiped out peregrines in the U.S. and across the western world. It interfered with calcium deposition, thinning the mother's eggshells so much that they cracked when she tried to sit on them. The embryos died, pitching the population into collapse. DDT was finally banned in the U.S. in 1972, and some years later, Save Mount Diablo inspired a massive, successful effort to return the birds to Castle Rock. Keeping the birds safe during their six-month breeding has proved dicey. The Covid era drove cabin-fevered people into the parks -- all parks everywhere -- and even the most secluded places on and around Mount Diablo, on legal trails and hacked trails, became patterned with boot prints, bike tires, and horse hooves. MDIA volunteers formed the Peregrine Team in 2015 to support the closure zone enforcements of the rangers and staff in the two parks. This (2024) is the team's 10th season. In addition to informing hikers about the closure, they spot hikers in the closure area, and, if possible, gently interact with them when they return to the legal trail -- or even better: before they leave it -- about the ethics and benefits of respecting closure zones. You can help too. Plan to hike Stage Road in Pine Canyon and the trails from Curry Point. You'll see closure signage. Visit with other hikers as you go. If you spot people who may be headed into the closure zones, draw their attention gently to the signs. If they choose to trespass, don't intervene. They'll remember your words. Crowd-sourcing works -- eventually. Back to the Peregrine Team Page Peregrine in Flight | Scott Hein Peregine Team in action. Peregrine Team members lead group hikes during the nesting season into Pine Canyon BACK TO LIST

Bob's Pond Hike by Frank Valle-Riestra Reprinted from Mountain News, Spring/Summer 2013 Frank's Favorite Hikes 2013-05-01 In 1998, the Save Mount Diablo organization completed purchase of the Silva cattle ranch land, some 430 acres of beautiful, hilly landscape in the upper reaches of Riggs Canyon. Five years later, the acquisition was incorporated into the Mount Diablo State Park. It remains today a sparsely visited corner of the park in its eastern extremities, a hidden treasure well worth exploring. The centerpiece of this extraordinary landscape is Bob’s Pond, a man-made stock pond cradled in a hollow on the flanks of Windy Point. It is named after Bob Adams, an erstwhile director of Save Mount Diablo and a guiding presence during the procedures to acquire the land. (For more detail, see Rich McDrew’s book, Mountain Lore, available in our Visitor Centers.) The lovely green pond, with its ring of magnificent sycamore trees, stands like an emerald jewel among the undulating meadowy hills, a welcome focus to the area’s wildlife. Tassajara Creek Trail forms a grand loop encompassing the pond. It was built at the time of the land acquisition by the East Bay Trail Dogs, a group of volunteer trail enthusiasts. This well-laid-out and engineered trail lies in pretty remote country, and it takes some effort to get to it. It is most readily reached from two park trailheads. One is located at the end of the paved Finley Road, which runs north from Camino Tassajara east of the Blackhawk development in Danville. The other trailhead is at Red Corral, my own preference. Red Corral is reached from the town of Clayton by following Marsh Creek Road to its junction with Morgan Territory Road. Turn right onto Morgan Territory Road and continue on it for 4.2 miles to reach twin one-lane bridges. Red Corral is 0.5 miles beyond, and you will spot it on your left, still red after all those years. There is very limited parking at the trailhead on the right edge of the road; be sure not to block off the entrance gate to inholdings. Before you start your hike, take a quick look at a stone memorial to Jeremiah Morgan, first settler in this area (1857), placed there by the Save Mount Diablo organization. It is located behind a locked gate in the Red Corral (to discourage vandals); the inscription on the memorial is reproduced in the Mountain Lore book. After passing through the well-marked park gate, continue straight ahead and upward on Morgan Creek Road. The steadily rising road parallels Jeremiah Creek, in a dense deciduous forest, which brings welcome coolness during the hot summer and fall months. It is part of a pattern you will experience during your hike: tree-less high meadows in full sun, interspersed with picturesque, gentle oak groves and deep, dark forested canyons. At a sharp bend of the steeply rising road, look for a post to your right announcing the start of Jeremiah Creek Trail. The trail is just a delight: a narrow, single-track path meandering through an unspoiled by Frank Valle-Riestra Reprinted from Mountain News, Spring/Summer 2013 Frank’s Favorite Hikes bob’s pond hike wilderness, rising gently up to the crest of Highland Ridge. It is here, in the midst of an oak savannah and along the banks of Jeremiah Creek with its pools and ponds, that you may experience that peace of mind engendered by a truly remote corner of nature. When you reach the crest at Old Finley Road, stop for a moment to take in the magnificent view of Riggs Canyon far below you, a panorama that expands to include many distant Bay Area highlands as you ascend Highland Ridge Road to your right. The road climbs toward the park boundary and is quite steep at times, but you will find some welcome rest stops on mossy rocks under venerable old oaks. Be on the lookout on your left for a post marking the beginning of the Tassajara Creek Trail. At first the trail follows an old farm road but soon veers off as another intimate single-track path. After all of the climbing you have done, it is a pleasure to march along this gentle path as it follows contours in its descent toward the headwaters of Tassajara Creek. Here you are mostly in the midst of meadows. The tall grasses do not favor great wildflower displays, but California Poppies manage to push through during a good part of the year, golden explosions to gladden the eye. Eventually, Bob’s Pond comes into view, in a hollow below the trail; the path then slowly circles around to an overlook marked by, of all things, a nice picnic table. It is not something one might expect in this remote location—clearly a labor of love to drag it all this way. It is a good place for a little picnic, to sit and rest and admire the panorama. A short way beyond, the trail plunges into the depths of the canyon carved out by Tassajara Creek, a silent, mysterious world of a dense riparian forest. The trail builders did a fine job of negotiating the complex stream topology. You will delight in the ever-changing scenery and the cool air—and the forest flowers, particularly in spring: Giant Trillium and Checker Lilies bloom in profusion. At its end, the trail breaks out again into open country and rises steeply to meet Old Finley Road. A left on the road brings you back to the junction with Jeremiah Creek Trail after another short climb. Retrace your steps along Jeremiah Creek Trail and Morgan Creek Road to Red Corral—mostly down-hill!—to complete one of the park’s great hikes. A word of caution: On the Jeremiah Creek Trail in particular, there are luxuriant stands of poison oak at trail side, but these are easily avoided with some care. Long stretches of Tassajara Creek Trail in the upper meadows have been badly churned up in wet weather by horses, stray cows, and wild boars. The total distance covered is about 5.5 miles; expect to climb some 1,870 feet and to spend four to five hours, with a few rest stops. BACK TO LIST

Wrentit by Dan Sandri 2024-01-01 Dan Sandri Perhaps a Wrentit (Chamaea fasciata) has been curious enough to have briefly shown itself to you? Wrentits are often heard and less-commonly seen, although if you wait one out, it may pop up for you. The male’s call is a distinctive sound of the chaparral landscape: an accelerating sequence of toots, sounding like a bouncing ball. Another description is it sounds like 3 – 5 pits, followed by an accelerating trill. The female’s call is a series of pits. A Wrentit is about the size of a Song Sparrow, with a yellow eye, round head and short wings, such that it appears plump in appearance. It has long legs and a quite a long tail, which is often held up and away from its body. Its bill is short and slightly curved. Males and females are visually indistinguishable from each other. Wrentits are found primarily in chaparral and brush along the coasts of Oregon, California and Baja California, although it is also in the Sierra foothills. On Mount Diablo, look for wrentits in the chaparral areas and in poison oak, such as along Red Road and Twin and Eagle Peaks. Wrentits don’t usually migrate - a bird may spend its entire adult life in an area of just a couple of acres. They are primarily insect eaters, but will also eat berries, including those of poison oak! Wrentits mate for life, and males and females take turns incubating eggs during the daytime, but females incubate the eggs at night. Wrentits belong to Family Paradoxornithidae - the Parrotbills, and all other birds in the family are found in SE Asia. It is the only member of Genus Chamaea. A rare bird indeed! Bird Guide: https://www.mdia.org/birds-1-1/wrentit Wrentit (Chamaea fasciata ) 2 DSandri.jpeg Wrentit (Chamaea fasciata ) 3 DSandri.jpeg BACK TO LIST

Cowell Cement Industry Author: Craig Lyon (Compiled from several references - 1997) Cowell and Its Cement Industry 1997-01-01 Large Smokestack As one drives easterly on Ygnacio Valley Road across Lime Ridge northwest of Mount Diablo, scars from open pit quarry operations can be seen to the right of the road. To the left is a tall smokestack in an area that in past years was called Cowell but which is now part of Concord. This was the site of the Cowell Lime and Cement Company that produced Portland cement from 1905 to 1946. The cement plant was one of the largest employers in the area in the early 1900's. The rock was quarried in the Lime Ridge area and carried on a narrow gauge railroad, or by truck, to the Cowell plant where it was crushed, mixed with clay, and then converted to cement in roasting kilns. Sacked cement, which was marketed as "Mount Diablo Cement", left Cowell daily on the company's standard gauge Bay Point and Clayton Railroad, At Bay Point, the cars went on their way to other areas via Southern Pacific, Western Pacific, or Santa Fe railroads. Through the years farmers threatened to sue the Cowell plant over the air pollution which coated their vines and orchards with fine cement dust. The cement company built a 235-foot-high smokestack in 1934 in an effort to dissipate the dust into the atmosphere. Labor problems forced the plant to close in 1946. The plant was later torn down and the smokestack and quarries are all that remain of this once-thriving industry. The rock quarried at Lime Ridge and used to make cement is called travertine, It is the same composition as limestone - almost pure calcium carbonate. The rock is hard, sometimes shows banding, and is colored a light tan by the inclusion of a small amount of iron oxide. Cave formations are formed from the same kind of material. The travertine at Lime Ridge formed, probably in fairly recent geologic time, from circulating waters carrying calcium carbonate in solution which came to the surface through a very porous sandstone called, by geologists, the Domengine formation of Eocene age (about 50 million years old). The water evaporated, leaving behind the travertine which formed a layer on top of the sandstone that originally covered an area 2.5 miles long and 0.5 miles wide and varied in thickness up to a maximum of 20 feet. The Domengine sandstone is exposed in the light-colored quarry faces and can also be seen in the large roadcut just east of the entrance to Cal. State Hayward. BACK TO LIST

Halcones peregrinos de Pine Canyon y el equipo MDIA Peregrine por Anastasia Hobbet 2024-06-01 por Dave Furseth Read this article in English El animal más rápido del mundo es vecino tuyo. Es el halcón peregrino, que alcanza más de 200 millas por hora durante sus precipitadas inmersiones mientras caza. ¿DIRECCIÓN? Mount Diablo State Park y sus alrededores, donde al menos dos parejas ahora se están preparando para anidar en los espectaculares pináculos de Pine Canyon y las remotas Black Hills sobre Black Hawk, donde pasarán la primavera y el verano empollando los huevos y criando a los jóvenes hasta los niños se vuelven independientes. Suena optimista, pero en este punto se necesita un gran "si": si las aves pueden tener suficiente privacidad y aislamiento. Necesitan mucho espacio tranquilo, y con más de 100.000 visitantes por año visitando Pine Canyon, ¿es posible la privacidad? ¿Para cualquier criatura? La responsabilidad de garantizar cierto aislamiento para las aves de Pine Canyon recae en dos parques: Castle Rock, que es un parque regional de East Bay; y el Parque Estatal Mount Diablo. El acceso principal a la parte baja de Pine Canyon es a través del primero, pero los acantilados de arenisca de Pine Canyon se encuentran justo sobre el límite dentro del Parque Estatal, formando una sección de su borde más occidental. Dos zonas anuales de cierre de anidación que se extienden desde el 1 de febrero hasta el 31 de julio ayudan a estos veloces cazadores aéreos a sentir cierta confianza en su seguridad. El personal de los dos parques adyacentes coopera para hacer cumplir el cierre, pero es difícil para un supervisor del parque que trabaja con un personal reducido despachar a alguien rápidamente, lo cual es clave. El uso generalizado del DDT a partir de finales de la década de 1950 casi acabó con los peregrinos en Estados Unidos y en todo el mundo occidental. Interfirió con la deposición de calcio, adelgazando tanto las cáscaras de los huevos de la madre que se agrietaron cuando intentó sentarse sobre ellas. Los embriones murieron, provocando el colapso de la población. El DDT finalmente se prohibió en los EE. UU. en 1972, y algunos años más tarde, Save Mount Diablo inspiró un esfuerzo masivo y exitoso para devolver las aves a Castle Rock. Mantener a las aves a salvo durante los seis meses de reproducción ha resultado complicado. La era Covid llevó a la gente con fiebre de cabaña a los parques (a todos los parques en todas partes) e incluso los lugares más apartados en Mount Diablo y sus alrededores, en senderos legales y senderos pirateados, quedaron llenos de huellas de botas, neumáticos de bicicletas y cascos de caballos. Los voluntarios de MDIA formaron el Equipo Peregrine en 2015 para apoyar la aplicación de la ley en las zonas de cierre por parte de los guardabosques y el personal de los dos parques. Esta (2024) es la décima temporada del equipo. Además de informar a los excursionistas sobre el cierre, los detectan en el área de cierre y, si es posible, interactúan gentilmente con ellos cuando regresan al sendero legal, o mejor aún: antes de que lo abandonen, sobre la ética y los beneficios. de respetar las zonas de veda. Tú también puedes ayudar. Planee caminar por Stage Road en Pine Canyon y los senderos desde Curry Point. Verás señales de cierre. Visite a otros excursionistas a medida que avanza. Si ve personas que podrían dirigirse a las zonas de cierre, dígales cuidadosamente las señales. Si deciden invadir la propiedad, no intervenga. Recordarán tus palabras. El crowdsourcing funciona... eventualmente. Volver a la página del Equipo Peregrine por Scott Hein Peregrino en vuelo Lleva al equipo a la acción Los miembros del equipo Peregrine lideran caminatas grupales durante la temporada de anidación en Pine Canyon BACK TO LIST

The Rocks of Mount Diablo - Their Type and History Geology Guide Part 1 1998-07-01 Wind Cave | Roi Peers Rising 3,849 feet, Mount Diablo forms a prominent feature in the East Bay landscape. Our understanding of the geological history of the rocks and structure of Mount Diablo has undergone major changes during the past 30 years, and even now geologists are still trying to unravel the complicated history of the mountain. This complex history is not unique to the mountain, but to our region as a whole, since Mount Diablo has been caught up in the processes that have shaped the Coast Ranges for millions of years. Perhaps the most salient fact is that, although the rocks of which it is composed are very old, Mount Diablo only began rising recently in geological terms. The rocks are old, but the mountain itself is young. To better understand the complex geology of Mount Diablo, it is useful to divide the mountain’s rocks into three main groups. Each group has a different history and is characterized by different types of rocks. Group 1: Mount Diablo Ophiolite ( Jurassic ) Group 2: Franciscan Complex ( Jurassic and Cretaceous ) Group 3: Great Valley Group ( Jurassic and Cretaceous ) and Younger Sedimentary rocks ( Cenozoic ) Plate tectonics played a major part in the formation of the Mesozoic rocks of Mount Diablo. We now recognize at least 11 separate major plates of oceanic crust and rigid upper mantle rocks around the globe. These plates “float” on a layer of semi-molten rock, all moving against and jostling each other, creating new land forms in the process. Continents ride atop these ocean plates, being rafted along as the plates move. New oceanic crust is being continually created by the eruption of submarine volcanic material forming along ocean-spreading ridges such as the Mid-Atlantic Ridge. To compensate for the newly created oceanic crust, older existing oceanic crust is driven beneath the continental crust at subduction zones, and recycled into the earth. Group 1 - Mount Diablo Ophiolite ( Jurassic-Cretaceous ) It is generally believed that near the close of the Jurassic a subduction zone developed along what is presently represented by the modern California coast. The oceanic crust caught between this subduction zone and an earlier shoreline in the ancient Sierra foothills was preserved as the Coast Range Ophiolite and later partially exposed. Ophiolites are thought to form at oceanic spreading centers in the middle of the oceans, associated with oceanic island chains (arcs), or in narrow oceans such as the Gulf of California. Ophiolites generally form a uniform vertical rock sequence consisting, from bottom to top, of ultramafic peridotite from the top of the mantle, mafic intrusive gabbros and/or diabase that formed one or more miles below the sea floor, and mafic extrusive rocks, often in the form of pillow lava extruded beneath water. The rocks of this old ocean crust on Mount Diablo have been named the Mount Diablo Ophiolite and is considered a fragment of the Coast Range Ophiolite. The Mount Diablo Ophiolite underlies the mountain north of a line drawn from Long Ridge through Murchio Gap, encompassing the Zion Peak rock quarry, Mitchell Rock, and Eagle Peak. Radiometric and fossil-age determinations date the ophiolite as having been formed approximately 165 million years ago during the Mid-Jurassic. Mount Diablo Ophiolite Basalt: The basalt, which makes up the upper part of the Mount Diablo Ophiolite, is mostly interbedded pillow basalt lava flows. As the lava erupts under water, the outer surface of the flow “freezes” in contact with the water. More lava breaks through and again the outer surface “freezes.” This process leads to the accumulation of “pillow” structures and the resultant rock is referred to as pillow basalt or pillow lava. The basalt has a microscopic crystalline texture with a black to greenish-brown color, weathering to a yellowish-brown to dark reddish-brown soil. Well-developed pillows can be seen on Mitchell Rock. Mount Diablo Diabase: The pillow lavas are fed by a series of vertical fissures, or dikes, that allow the molten rock from below to reach the surface. The molten material in the dikes solidifies into a rock called diabase, which has the same chemical composition as basalt, but with a coarser texture. Diabase is exposed in quarries at Mt. Zion and on Eagle Peak. Mount Diablo Serpentinite: Serpentinite is a rock frequently found in association with an ophiolite. Serpentinite is derived from the basal portion of the original ocean crust and uppermost part of the mantle, but has been metamorphosed by hydration from ocean water circulating through fractures in the ocean crust. Serpentinite forms by addition of water to minerals in peridotite, changing them from olivine and/or pyroxene to the serpentine minerals antigorite, chrysotile and lizardite. Serpentinite, incidentally, is California’s state rock. On Mount Diablo, serpentinite occurs in several localities. The largest is the prominent east-west band that runs through Murchio Gap extending west along Long Ridge, separating the ophiolite on the north from the Franciscan rocks exposed in the central core of the mountain to the south. This band is characterized by a noticeable change in vegetation due to the high magnesium content of the serpentinite. Exposures of the serpentinite are typically pale green to greenish-gray, locally black, weathering to grayish-orange. In addition to the highly sheared serpentinite, ultramafic rocks of harzburgite (a variety of peridotite) and pyroxenite are present in this band as well, but are less sheared than the serpentinite. The body of pyroxenite exposed along the Burma Road Trail on Long Ridge is coarsely crystalline, sparkling in the sunlight as you walk along the trail. Exposed blocks of massive harzburgite on the westerly end of Long Ridge frequently contain veins of fibrous chrysotile. There are several pods of silica carbonate rock (altered serpentinite) found in association with the mercury mines on the northeast flank of the mountain and other scattered locations along the serpentinite band. Group 2 - Franciscan Complex ( Mesozoic ) The central Mount Diablo summit area and North Peak is underlain by an assemblage of Mesozoic rocks that have been a puzzle to California geologists for years. Our relatively new understanding of plate tectonics and subduction has finally provided an important clue to unraveling this mystery. This diverse complex of rock types is common up and down the coastal ranges of California and has been given the name Franciscan Complex. The processes of subduction can account for the mixing of such a wide variety of rock materials. The Franciscan Complex records over 140 million years of uninterrupted east-dipping subduction, during which the Franciscan formed as an accretionary complex. As the oceanic plate subducted beneath the continent, part of the upper section of the ocean crust (pillow basalt) and the material riding on the plate (chert, graywacke, shale, small islands, and sea mounts) were scraped off the upper part of the subducting plate, mixed together, partially subducted and accreted on and under the continental crust. Mount Diablo and North Peak are composed of faulted blocks of resistant basalt and chert with some graywacke and minor shale, and are expressed topographically as rugged and jagged rock masses. Wrapping around the two peaks in a rough “figure 8” shape are the more gentle treeless slopes of “mélange.” Such a diverse mixture of rocks, is called a "mélange" by geologists from the French for "mixture". The Franciscan mélange is essentially a chaotic mixture of an intensely sheared sandstone and shale “paste” in which are embedded blocks of basalt, chert, and graywacke along with rare exotic rocks. It is often difficult to distinguish between the mélange topography and local landslides. Franciscan rock accretion ceased with the ending of subduction in our area. Franciscan-like rocks are currently forming north of Cape Mendocino offshore or beneath the continent where the oceanic Juan de Fuca plate is still subducting beneath North America. Recent studies using modern dating techniques and temperature history studies suggest that the Franciscan Complex appears to have undergone metamorphism around 108 million years ago at a depth of approximately 12 miles. As a result, the Franciscan rocks are frequently referred to as metabasalt or metagraywacke reflecting a history of metamorphism by heat and pressure deep underground. Franciscan basalt: The blocks of basalt exposed in the Franciscan on Mount Diablo are altered oceanic pillow basalt. On the surface the rock weathers to a dark yellowish-brown to dark reddish-brown while fresh exposures are grayish-green to light olive drab. It is locally called “greenstone.” The green color comes mostly from chlorite, a green alteration mineral. The basalt blocks in the Franciscan are believed to be fragments scraped off of the upper part of subducting basaltic oceanic crust. Franciscan chert: The chert bodies in the Franciscan form prominent dark red exposures and talus slopes. Made up of silica, they are resistant to erosion and form such features as Devil’s Pulpit and Turtle Rock. Typically red in color (green and white less common), the chert layers are typically interbedded with reddish-colored shale. These banded rocks are often referred to as “ribbon chert.” The red color is derived from iron oxides. The chert in the Franciscan was formed far out at sea. Silica skeletons of minute ocean animals called radiolaria settled to the ocean floor forming a silica ooze that ultimately solidified into chert. The chert continued to slowly accumulate on top of the ocean floor as the ocean crust drifted away from the spreading center on its long journey toward subduction. The Franciscan chert ranges in age from 190 myo (million years old) to 90 myo, representing 100 million years of accumulation. Franciscan cherts are formed from the tiny (0.5 to 1.5 mm) silica shells of radiolaria. Many of these radiolaria are tropical species indicating that the sediments were deposited near the equator and were later transported northeastward by plate movements. Franciscan graywacke: Graywacke is less common on Mount Diablo than the greenstone and chert. It is typically fine-to medium-grained and massive (no stratification or bedding visible). It breaks along distinct joint planes, which helps distinguish it in outcrop from the more “shatter fracturing” of the greenstone. The graywacke consists mainly of angular quartz, plagioclase feldspar, chert fragments, and dark volcanic rock fragments. Calcite and quartz occur commonly in the criss-crossed white veins. The graywacke is younger in age than the greenstone (basalt) or chert, ranging from 90 to 108 million years in age. These rocks are thought to have formed in a subduction trench environment off the coast of North America (some researchers suggest Mexico, subsequently moving north). Franciscan shale: Approximately 10% of the Franciscan on Mount Diablo is made up of shale, most of which has been altered to argillite as a result of the earlier period of metamorphism. Most of this clay-sized material was probably deposited in less turbulent current conditions in association with the graywacke deposition. Franciscan exotic rocks: The most common so-called exotic rock present on Mount Diablo is a glaucophane schist, or “blueschist,” named for the noticeable blue color of the glaucophane. Blue schist is largely altered basalt and reflects a history of hi-pressure/low-temperature metamorphism, a condition found in subduction environments and rarely any other place. On the Summit Road as you drive toward the summit, just past the Rocky Point Picnic area, you will notice a dark blue-black boulder of blueschist about five feet across protruding from the bank on the left side of the road. Group 3 - Great Valley ( Jurassic - Cretaceous ) and Younger Sedimentary Rocks ( Cenozoic ) The name Great Valley Group refers to the thick sedimentary rocks of Upper Jurassic through Cretaceous age that were deposited between the ancestral Sierra Nevada to the east and the subduction zone to the west on top of the ophiolite basement that underlies California’s central valley. The Great Valley sequence is composed mostly of deepwater marine shale, sandstone and some conglomerates accumulating to a thickness of 60,000 feet near the western margin of the present day Great Valley, and then, in our area, thinning toward Mt. Diablo. The Upper Jurassic Knoxville Formation is 140 million years old and are the oldest beds of Great Valley in this area. Great Valley deposits on-lap the Mount Diablo area and thinner deposits intermittently covered it during this time. The general interpretation of these rocks is that they were deposited in the submerged central valley as intermittent underwater "turbidity currents" and the deposits are called turbidites. To summarize the Cenozoic in this area, it is perhaps easiest to think of the central valley of California as a low elongate basin, flooded intermittently by an encroaching shallow sea, and slowly being filled by sedimentary material eroded from the surrounding exposed land masses, primarily the “Sierra.” During the latter part of the Tertiary, newly formed highlands to the south (Diablo Range) and in the area of the present day San Francisco Bay also acted as source areas. The Mount Diablo area seemed to represent a persistent “high,” underwater, but less deep than surrounding areas and periodically exposed to erosion. Many of the formations seem to shoal out on the flanks of this area and when submerged, the strata thin over this “high.” The area, however, was not a “mountain” as we see it today, but rather a land of low relief intermittently submerged well into the Pliocene. Paleocene Rocks (55.5 - 65 million years ago) There are few Paleocene deposits present in our area indicating that the region was probably above sea-level and undergoing erosion following the close of the Cretaceous. The only nearby rocks of this age are restricted to the north side of the mountain outside of the park. Eocene Rocks (33.7 - 55.5 million years ago) During the Eocene , the climate warmed, resulting in heavy “ancestral Sierra” weathering that yielded large quantities of sands that washed into and across the Central Valley providing material to the Eocene deposits of Mount Diablo. A shallow marine basin, a sandy shoreline, a swampy backwater area—all existed in this area at different times or at the same time in different places. On the north side of the mountain, the Eocene is present in the Black Diamond Mines Regional Park. These strata contain coal beds and glass sands and have been described as a near-shore lagoonal swamp or tidal flat estuarine environment. On Mount Diablo, Eocene deposits form the ridges of tan-colored sandy rock formations that wrap around the south and west side of the mountain. These sedimentary rocks have been given the name Domengine Formation and are well exposed at Castle Rock, Rock City, Knobcone Point, and Cave Point. These sands on the south side of the mountain are characteristic of deep offshore slope deposits. They represent deep erosion of the ancestral Sierra highland spreading over the Mount Diablo area as the ocean deepened westward. Some Domengine beds represent shallower near-shore deposits that contain beds rich in Turritella fossils (marine snails). These massive sandstone beds weather easily forming features such as caves and open tunnels. Rock City, easily accessible on the South Gate Road, is a good place to view these unusual features. These massive sandstone that form the Wind Cave beds weather easily forming features such as wind caves and open tunnels. Unusual "cannonball concretions" can also be found in these sandstone beds. Rock City is a good place to view these unusual features easily accessible on South Gate Road. Oligocene Rocks (23.8 - 33.7 million years ago) The only Oligocene rocks in the area is the Kirker Tuff on the north side of the mountain outside the park boundary. Miocene Rocks (23.7 - 5.3 million years ago) On the south and west sides of the mountain, the depositional contact between the Eoceneand the Miocene rocks can be recognized by the abrupt change from clean, thick-bedded, light tan sandstone in the Domengine formation (Eocene) to poorly sorted, dark gray, pebbly sandstone of the marine Miocene rocks. There is a large gap in the geologic time record between these rock units, representing erosion or non-deposition. The interval of missing time and rock equivalents includes the upper Eocene, the entire Oligocene and the lower (or earliest) Miocene. During middle Miocene time, the general drainage was directed from the east into an open ocean to the west, a pattern similar to the deposition of the earlier Eocene. By about 10 mya (million years ago), subduction had ended in central California and there was a major change in the pattern of deposition. A highland developed to the west and the Diablo Range south of Livermore began to rise. The Mount Diablo area began to accumulate marine and later non-marine deposits from these sources. Now steeply tilted upward from an original horizontal orientation, the vertical beds form the prominent “hogbacks” on Fossil Ridge and Blackhawk Ridge. Building material quarried from Fossil Ridge was used to construct the summit museum building, and numerous clam and oyster shells can be seen in the exterior walls of that building. These fossiliferous beds are called the Briones Formation. Following Briones deposition, the direction of sediment transport shifted again, bringing sands derived from the east, rich in volcanic material washed from the Sierra highlands. These volcanic sands have been named the Neroly formation. They form the grass-covered rounded hills immediately south of the underlying ridge-forming Briones strata on the south, and can be found on the west and north sides of the mountain as well. Andesitic Neroly sandstone alters easily, and in most places the sand grains are coated with a thin layer of bluish clay that is clearly exposed in an often visited site in Shell Ridge Open Space in Walnut Creek. Beds rich in fossil marine shells are well exposed at this site and also in Sycamore Canyon on the southern flank of Mt. Diablo. Around nine million years ago, during the late Miocene, the sea again receded from the Mount Diablo area, marking a permanent change from marine deposition to non-marine stream and lake deposition. One of the nine million-year-old stream deposits on the south side of the mountain has captured and preserved an abundant and diverse collection of animal fossils. The Blackhawk Ranch Quarry has yielded numerous vertebrate fossils of horses, rhinos, camels, and smaller animals. A large mastodon skull, a Gomphotherium , has been removed from this site. All give evidence that late Miocene mammals abounded in the newly created forests and flood plains stretching away to low hills to the west and south. There are several volcanic tuff deposits in the late Miocene and Pliocene derived from the volcanic fields of Sonoma County. There was still no Mount Diablo at the time. Plio-Pleistocene to recent rocks (5.3 million years ago to present) Non-marine deposits continued to collect in the area during Pliocene time (5.3-1.8). It was during Plio-Pleistocene time, by 4 mya and continuing to the present, that Mount Diablo was formed as a topographic feature. From that time on, Mount Diablo has been feeding erosion materials into surrounding valleys. Pliocene sources were predominantly from Great Valley rocks. Pleistocene sources were predominantly from Franciscan, indicating unroofing and erosion of deeper terranes. The 4.83 million-year-old Lawlor Tuff is a widespread marker bed around the mountain. The fact that it was laid down on a relatively flat landscape and is now steeply folded indicates that Mt. Diablo must have begun its growth after the tuff was deposited. Highly sheared serpentine | Roi Peers Franciscan graywacke sandstone | Roi Peers Franciscan beds of folded red chert | Roi Peers Turritella Fossils | Mike Woodring Wind Caves | Roi Peers BACK TO LIST

Redwood Forest Excerpted from MDIA's book Plants of the East Bay Parks by Glenn Keator, Ph. D. Plant Communities of Mount Diablo State Park 1999-01-01 Redwood National Forest, Humboldt County Redwood forests are represented in our area by isolated fragments found in the deepest, most protected canyon bottoms with reach of summer fogs. Although historically we know that other stands of redwoods once clothed coast-facing slopes in Oakland and Berkeley hills, redwood forest was never a major plant community in this part of California. Redwoods are remarkable trees that extend back in time to the beginnings of the cone-bearing trees called conifers. Once, great forests of various kinds of redwoods covered large tracts in North America, Europe, and Asia. Now they exist only in protected pockets as relics from a time when the climate was more uniformly wet and had moderate year-round temperatures. The present distribution of coast redwood -- canyon bottoms and slopes in the fog belt of coastal central and northern California -- reminds us of how these trees are prevented from growing elsewhere. To the north, winters become too cold; to the south, summers are too hot and winters have too little rain; to the west, heavy salt-laden winds thwart growth next to the ocean; and to the east, summers lack fog and are too hot. Redwoods are also restricted from climbing higher than two- to three- thousand feet, owing to cold winter temperatures. Redwoods -- if allowed to grow unhindered for hundreds of years -- exclude other trees by their tall, needle-covered branches that effectively shade out everything else. Where virgin redwood forest grows unimpeded, few smaller trees or shrubs live happily under the deep shade that their branches create. Yet redwood forest habitat is full of berry-producing shrubs. These favor forest edges and streamsides, especially in second-growth forests, where immature trees have not completed their overshadowing canopies. In the deep shade of mature redwood forests live several smaller, herbaceous plants, such as various ferns, and sword fern (Polystichum munitum ) in particular. Also in this shade are redwood sorrel (a ground-cover-forming oxalis); various violets; inside-out flower; various members of the lily family (such as trillium; false Solomon's seal, fetid adder's tongue and bead lily); wild ginger; and several saxifrages (sugar scoops, fringe-cups, piggyback plant). All must do with short, periodic bursts of sunlight, and all take advantage of their locales by vegetative means of increasing their territory. Many of these forest denizens are limited in abundance in areas with minimal winter rainfall or only periodic summer fogs; to see the redwood forest understory at its best, journey to Humboldt and Del Norte counties in the northwestern extreme of our state. Two fascinating aspects of redwood forest plants include the abundance of fleshy-fruited, berry-producing shrubs along streams, where birds depend on them for food and so help in their dispersal; and the many ant-dispersed seeds in the shade of mature redwoods. Ant-dispersed seeds have easily-seen white elaisomes (oil bodies) appended to the main seed body. Ants are attracted by them, carry the seeds away, eat the elaiosomes, and discard the main seed with its embryo. Unrelated plants -- trillium, fetid adder's tongue, western bleeding heart, smooth yellow violet and inside-out-flower -- have hit upon this strategy as the best bet for moving their seeds. Because deep shade creates cool, moist conditions most of the year, redwood-forest-floor plants have broad, water-wasteful leaves with maximum surface area t trap as much of the sun's light energy as possible. Trail plant (Adenocaulon bicolor ), western coltsfoot (Petasites palmatus ), and redwood sorrel all show thin, broad leaves that wilt easily in strong summer sun, yet that manage to remain turgid and healthy in the refreshing shade of forest aisles. Many plants here even have highly divided, fernlike leaves for efficient trapping of light energy; western bleeding heart, inside-out-flower, and baneberry are examples. Despite the fact that redwoods create a very special niche for low-growing herbaceous plants -- cool, moist, acid soils -- these plants are seldom exclusive to redwood forests. Many other coastal forests provide the same cool, moist conditions. So although closed-cone ping and Douglas fir forests, for example, are missing from our area, they are home to the same array of plants. Fire and flooding have helped to maintain redwood forests where otherwise redwoods might be outcompeted by other kinds of trees. Redwood bark resists burning, since it lacks pitch and sap; mature trees also recover their fire wounds efficiently. Flooding may uproot old redwoods, but seeds are adapted to germinate in litter-free, sun drenched soils such as those left behind after floods. And trees not uprooted by floods may send roots upward toward the surface or build a whole new set of roots near the surface even when the trunk and roots have been deeply buried under silt. Redwoods are also efficient at replacing themselves when they're burned to the ground or, in the case of human intervention, at growing after being felled by logging. Dormant buds at the base of each tree are the secret; the grow into stump sprouts every year but are inhibited from growing more than a few feet tall by hormones produced by the top crown of the parent trunk. Once that source of hormones has been eliminated, the stump sprouts are free to grow, and grow they do. Circles of these sprouts become rings of mature trees in relatively short time. This ability to regrow is what has saved many now-protected redwood forests that have been logged one or more times. Download Common Ferns of Mitchell Canyon (pdf) Prairie Creek Redwoods Ferns of Mitchell Canyon BACK TO LIST