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65-578: The Bloomsburg is defined as a grayish-red and greenish-gray claystone , argillaceous siltstone , shale , and very fine to fine-grained sandstone , arranged in fining-upward cycles. Although the Bloomsburg can sometimes be green to gray, its most dominant color is red and they are often called "The Bloomsburg Red Beds". This is significant in the Appalachian Basin since it marks the first large scale terrestrial collection of sediments in

130-431: A highly elevated zone, usually uplifted by active tectonic movement, and a lower zone, which acts as a conduit for water and sediment to the ocean. Vast quantities of mud and till are generated by glaciations and deposited on land as till and in lakes. Glaciers can erode already susceptible mudrock formations, and this process enhances glacial production of clay and silt. The Northern Hemisphere contains 90-percent of

195-419: A millimeter in size. Clay minerals are integral to mudrocks, and represent the first or second most abundant constituent by volume. They make muds cohesive and plastic, or able to flow. Clay minerals are usually very finely grained and represent the smallest particles recognized in mudrocks. However, quartz, feldspar, iron oxides, and carbonates can also weather to the sizes of typical clay mineral grains. For

260-587: A more thorough discussion. The Burgess Shale Formation comprises 10 members, the most famous being the Walcott Quarry Shale Member comprising the greater phyllopod bed. There are many other comparable Cambrian lagerstätten ; indeed such assemblages are far more common in the Cambrian than in any other period. This is mainly due to the limited extent of burrowing activity; as such bioturbation became more prevalent throughout

325-463: A quarry on the flanks of Fossil Ridge. The significance of soft-bodied preservation, and the range of organisms he recognised as new to science, led him to return to the quarry almost every year until 1924. At that point, aged 74, he had amassed over 65,000 specimens. Describing the fossils was a vast task, pursued by Walcott until his death in 1927. Walcott, led by scientific opinion at the time, attempted to categorise all fossils into living taxa, and as

390-558: A reference, and/or with a substantial contribution to the development of geological sciences through history.' The fossil-bearing deposits of the Burgess Shale correlate to the Stephen Formation , a collection of slightly calcareous dark mudstones, about 508 million years old. The beds were deposited at the base of a cliff about 160 m tall, below the depth agitated by waves during storms. This vertical cliff

455-430: A result, the fossils were regarded as little more than curiosities at the time. It was not until 1962 that a first-hand reinvestigation of the fossils was attempted, by Alberto Simonetta. This led scientists to recognise that Walcott had barely scratched the surface of information available in the Burgess Shale, and also made it clear that the organisms did not fit comfortably into modern groups. Excavations were resumed at

520-448: A simple test that can be done in the field to determine whether a rock is a siltstone or not, and that is to put the rock to one's teeth. If the rock feels "gritty" against one's teeth, then it is a siltstone. Shale is a fine grained, hard, laminated mudrock, consisting of clay minerals, and quartz and feldspar silt. Shale is lithified and cleavable. It must have at least 50-percent of its particles measure less than 0.062 mm. This term

585-450: A size comparison, a clay-sized particle is 1/1000 the size of a sand grain. This means a clay particle will travel 1000 times further at constant water velocity, thus requiring quieter conditions for settlement. The formation of clay is well understood, and can come from soil, volcanic ash, and glaciation. Ancient mudrocks are another source, because they weather and disintegrate easily. Feldspar, amphiboles, pyroxenes, and volcanic glass are

650-604: A specific area and determine salinity, water depth, water temperature, water turbidity, and sedimentation rates with the aid of type and abundance of fossils in mudrock One of the most famous mudrock formations is the Burgess Shale in Western Canada, which formed during the Cambrian . At this site, soft bodied creatures were preserved, some in whole, by the activity of mud in a sea. Solid skeletons are, generally,

715-520: Is confined to argillaceous , or clay-bearing, rock. There are many varieties of shale, including calcareous and organic-rich; however, black shale, or organic-rich shale, deserves further evaluation. In order for a shale to be a black shale, it must contain more than one percent organic carbon. A good source rock for hydrocarbons can contain up to twenty percent organic carbon. Generally, black shale receives its influx of carbon from algae , which decays and forms an ooze known as sapropel . When this ooze

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780-507: Is cooked at desired pressure, three to six kilometers (1.8 - 3.7 miles) depth, and temperature, 90–120 °C (194–248 °F), it will form kerogen . Kerogen can be heated, and yield up to 10–150 US gallons (0.038–0.568 m ) of natural oil and gas product per ton of rock. Slate is a hard mudstone that has undergone metamorphism , and has well-developed cleavage. It has gone through metamorphism at temperatures between 200–250 °C (392–482 °F), or extreme deformation. Since slate

845-404: Is formed in the lower realm of metamorphism, based on pressure and temperature, slate retains its stratification and can be defined as a hard, fine-grained rock. Slate is often used for roofing, flooring, or old-fashioned stone walls. It has an attractive appearance, and its ideal cleavage and smooth texture are desirable. Most mudrocks form in oceans or lakes, because these environments provide

910-427: Is no reason to assume that the organisms without hard parts are exceptional in any way; many appear in other lagerstätten of different age and locations. The biota consists of a range of organisms. Free-swimming ( nectonic ) organisms are relatively rare, with the majority of organisms being bottom dwelling (benthic) — either moving about (vagrant) or permanently attached to the sea floor (sessile). About two-thirds of

975-527: Is often evidence that the sediments were deposited in arid or oxidizing conditions. The upper parts of the Bloomsburg are thought to be a marine transition zone. Early American geologists theorized that these beds correlated with Old Red Sandstone found in Scotland ., but the Old Red Sandstone is Devonian in age, or much younger than the Bloomsburg. The Bloomsburg rests conformably above

1040-693: Is the Morrison Formation . This area covers 1.5 million square miles, stretching from Montana to New Mexico in the United States. It is considered one of the world's most significant dinosaur burial grounds, and its many fossils can be found in museums around the world. This site includes dinosaur fossils from a few dinosaur species, including the Allosaurus , Diplodocus , Stegosaurus , and Brontosaurus . There are also lungfish , freshwater mollusks , ferns and conifers . This deposit

1105-433: Is the most abundant product of erosion , and these sediments contribute to the overall omnipresence of mudrocks. With increased pressure over time, the platey clay minerals may become aligned, with the appearance of parallel layering ( fissility ). This finely bedded material that splits readily into thin layers is called shale , as distinct from mudstone . The lack of fissility or layering in mudstone may be due either to

1170-515: The Cambrian explosion . It can be used to predict what Earth's climate would look like 500 million years in the future as a warming and expanding Sun, combined with declining CO 2 and oxygen levels, eventually heat the Earth toward temperatures not seen since the Archean Eon 3 billion years ago (before the first plants and animals appeared). This in turn furthers understanding of how and when

1235-762: The Clinton Group and Shawangunk Formation , and has a complex upper contact. In eastern Pennsylvania and New Jersey, the upper part of the Bloomsburg marks the Wallbridge Unconformity . To the west, the Wills Creek Formation lies conformably atop the Bloomsburg. Further west, the McKenzie Member of the Mifflintown Formation interfingers with the Bloomsburg and eventually, the Bloomsburg pinches out into

1300-655: The Walcott Quarry by the Geological Survey of Canada under the persuasion of trilobite expert Harry Blackmore Whittington , and a new quarry, the Raymond, was established about 20 metres higher up Fossil Ridge. Whittington, with the help of research students Derek Briggs and Simon Conway Morris of the University of Cambridge , began a thorough reassessment of the Burgess Shale, and revealed that

1365-571: The Yellow in China, and the Lower Mississippi in the United States are good examples of alluvial valleys. These systems have a continuous source of water, and can contribute mud through overbank sedimentation, when mud and silt is deposited overbank during flooding, and oxbow sedimentation where an abandoned stream is filled by mud. In order for an alluvial valley to exist there must be

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1430-563: The Burgess Shale fossils to the public's attention. Gould suggests that the extraordinary diversity of the fossils indicates that life forms at the time were much more disparate in body form than those that survive today, and that many of the unique lineages were evolutionary experiments that became extinct. Gould's interpretation of the diversity of Cambrian fauna relied heavily on Simon Conway Morris 's reinterpretation of Charles Walcott's original publications. However, Conway Morris strongly disagreed with Gould's conclusions, arguing that almost all

1495-443: The Burgess Shale organisms lived by feeding on the organic content in the muddy sea floor, while almost a third filtered out fine particles from the water column. Under 10% of organisms were predators or scavengers, although since these organisms were larger, the biomass was split equally among each of the filter feeding, deposit feeding, predatory and scavenging organisms. Many Burgess Shale organisms represent stem group members of

1560-405: The Cambrian fauna could be classified into modern day phyla . The Burgess Shale has attracted the interest of paleoclimatologists who want to study and predict long-term future changes in Earth's climate. According to Peter Ward and Donald Brownlee in the 2003 book The Life and Death of Planet Earth , climatologists study the fossil records in the Burgess Shale to understand the climate of

1625-459: The Cambrian, environments capable of preserving organisms' soft parts became much rarer. (The pre-Cambrian fossil record of animals is sparse and ambiguous, cf ediacaran biota .) The biota of the Burgess Shale appears to be typical of middle Cambrian deposits. Although the hard-part bearing organisms make up as little as 14% of the community, these same organisms are found in similar proportions in other Cambrian localities. This means that there

1690-465: The Earth's sedimentary geological record. They are widespread on Earth, and important for various industries. Burgess Shale The Burgess Shale is a fossil -bearing deposit exposed in the Canadian Rockies of British Columbia , Canada. It is famous for the exceptional preservation of the soft parts of its fossils. At 508 million years old ( middle Cambrian ), it is one of

1755-676: The Indian Ocean. Warm, wet climates are best for weathering rocks, and there is more mud on ocean shelves off tropical coasts than on temperate or polar shelves. The Amazon system , for example, has the third largest sediment load on Earth, with rainfall providing clay, silt, and mud from the Andes in Peru, Ecuador, and Bolivia. Rivers, waves, and longshore currents segregate mud, silt, and clay from sand and gravel due to fall velocity. Longer rivers, with low gradients and large watersheds, have

1820-545: The Mifflintown. There are numerous fossils found in the Bloomsburg, mostly in the upper parts of the formation. There are trace fossils of early land plants and brachiopod fossils in the upper marine transitional zones. Relative age dating of the Bloomsburg places it in the Upper Silurian period, being deposited between 417 and 410 (±5) million years ago. The Bloomsburg formation is a source of material for

1885-581: The Mississippi and Congo , have massive potential for sediment deposit, and can move sediments into deep ocean waters. Delta environments are found at the mouth of a river, where its waters slow as they enter the ocean, and silt and clay are deposited. Low energy deltas, which deposit a great deal of mud, are located in lakes, gulfs, seas, and small oceans, where coastal currents are also low. Sand and gravel-rich deltas are high-energy deltas, where waves dominate, and mud and silt are carried much farther from

1950-495: The beds has produced a vertical cleavage that fractures the rocks, so they split perpendicular to the fossils. The Walcott quarry produced such spectacular fossils because it was so close to the Stephen Formation – indeed the quarry has now been excavated to the very edge of the Cambrian cliff. It was originally thought that the Burgess Shale was deposited in anoxic conditions, but mounting research shows that oxygen

2015-493: The beginning of a mudrock's life as sediment at the top of a mountain, which may have been uplifted by plate tectonics or propelled into the air from a volcano . This sediment is exposed to rain, wind, and gravity which batters and breaks apart the rock by weathering. The products of weathering, including particles ranging from clay to silt, to pebbles and boulders, are transported to the basin below, where it can solidify into one if its many sedimentary mudstone types. Eventually,

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2080-460: The best carrying capacity for mud. The Mississippi River , a good example of long, low gradient river with a large amount of water, will carry mud from its northernmost sections, and deposit the material in its mud-dominated delta. Below is a listing of various environments that act as sources, modes of transportation to the oceans, and environments of deposition for mudrocks. The Ganges in India,

2145-578: The discovery of the Burgess Shale and the relatedness of mudrocks and oil. Literature on this omnipresent rock-type has been increasing in recent years, and technology continues to allow for better analysis. Mudrocks, by definition, consist of at least fifty percent mud-sized particles. Specifically, mud is composed of silt -sized particles that are between 1/16 – 1/256 ((1/16) ) of a millimeter in diameter, and clay-sized particles which are less than 1/256 millimeter. Mudrocks contain mostly clay minerals, and quartz and feldspars . They can also contain

2210-697: The earliest fossil beds containing soft-part imprints. The rock unit is a black shale and crops out at a number of localities near the town of Field in Yoho National Park and the Kicking Horse Pass . Another outcrop is in Kootenay National Park 42 km to the south. The Burgess Shale was discovered by palaeontologist Charles Walcott on 30 August 1909, towards the end of the season's fieldwork. He returned in 1910 with his sons, daughter, and wife, establishing

2275-453: The fauna represented were much more diverse and unusual than Walcott had recognized. Many of the animals present had bizarre anatomical features and only the slightest resemblance to other known animals. Examples include Opabinia , with five eyes and a snout like a vacuum cleaner hose and Hallucigenia , which was originally reconstructed upside down, walking on bilaterally symmetrical spines. With Parks Canada and UNESCO recognising

2340-435: The field. At first sight, the rock types appear quite similar; however, there are important differences in composition and nomenclature. There has been a great deal of disagreement involving the classification of mudrocks. A few important hurdles to their classification include the following: Mudrocks make up 50% of the sedimentary rocks in the geologic record and are easily the most widespread deposits on Earth. Fine sediment

2405-406: The following particles at less than 63 micrometres: calcite , dolomite , siderite , pyrite , marcasite , heavy minerals, and even organic carbon. There are various synonyms for fine-grained siliciclastic rocks containing fifty percent or more of its constituents less than 1/256 of a millimeter. Mudstones , shales , lutites , and argillites are common qualifiers, or umbrella terms; however,

2470-426: The inevitable home of mudrock sediments is the oceans. Reference the mudrock cycle below in order to understand the burial and resurgence of the various particles. There are various environments in the oceans, including deep-sea trenches , abyssal plains , volcanic seamounts , convergent , divergent , and transform plate margins. Not only is land a major source of the ocean sediments, but organisms living within

2535-534: The last living things on Earth could potentially die out. See also Future of the Earth . After the Burgess Shale site was registered as a World Heritage Site in 1980, it was included in the Canadian Rocky Mountain Parks WHS designation in 1984. In 2012, the discovery was announced of another Burgess Shale outcrop in Kootenay National Park to the south. In just 15 days of field collecting in 2013, 50 animal species were unearthed at

2600-434: The manufacture of brick and other clay products, as well as a local building stone. Claystone Mudrocks are a class of fine-grained siliciclastic sedimentary rocks . The varying types of mudrocks include siltstone , claystone , mudstone and shale . Most of the particles of which the stone is composed are less than 1 ⁄ 16  mm (0.0625 mm; 0.00246 in) and are too small to study readily in

2665-448: The modern animal phyla, though crown group representatives of certain phyla are also present. The fossils of the Burgess Shale are preserved as black carbon films on black shales, and so are difficult to photograph; however, various photographic techniques can improve the quality of the images that can be acquired. Other techniques include backscatter SEM, elemental mapping and camera lucida drawing. Once images have been acquired,

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2730-405: The most likely resource for petroleum. Mudrocks have low porosity, they are impermeable, and often, if the mudrock is not black shale , it remains useful as a seal to petroleum and natural gas reservoirs. In the case of petroleum found in a reservoir, the rock surrounding the petroleum is not the source rock, whereas black shale is a source rock. As noted before, mudrocks make up fifty percent of

2795-399: The most useful qualifying term, because it allows for rocks to be divided by its greatest portion of contributing grains and their respective grain size, whether silt, clay, or mud. A claystone is a lithified and non-cleavable mudrock. In order for a rock to be considered a claystone, it must consist of at least fifty percent clay ( phyllosilicates ), whose particle measures less than 1/256 of

2860-434: The mouth of the river. Coastal currents, mud supply, and waves are a key factor in coastline mud deposition. The Amazon River supplies 500 million tons of sediment, which is mostly clay, to the coastal region of northeastern South America. 250 tons of this sediment moves along the coast and is deposited. Much of the mud accumulated here is more than 20 meters (65 feet) thick, and extends 30 kilometers (19 mi) into

2925-700: The mudrock will move its way kilometers below the subsurface, where pressure and temperature cook the mudstone into a metamorphosed gneiss. The metamorphosed gneiss will make its way to the surface once again as country rock or as magma in a volcano, and the whole process will begin again. Mudrocks form in various colors, including: red, purple, brown, yellow, green and grey, and even black. Shades of grey are most common in mudrocks, and darker colors of black come from organic carbons. Green mudrocks form in reducing conditions, where organic matter decomposes along with ferric iron. They can also be found in marine environments, where pelagic, or free-floating species, settle out of

2990-711: The new site. In respect of the site being 'characterized by exceptional soft-tissue preservation, [and containing] the most complete fossil record of Cambrian ( Wuliuan ) marine ecosystems', the International Union of Geological Sciences (IUGS) included the 'Burgess Shale Cambrian Paleontological Record' in its assemblage of 100 'geological heritage sites' around the world in a listing published in October 2022. The organisation defines an 'IUGS Geological Heritage Site' as 'a key place with geological elements and/or processes of international scientific relevance, used as

3055-407: The ocean contribute, as well. The world's rivers transport the largest volume of suspended and dissolved loads of clay and silt to the sea, where they are deposited on ocean shelves. At the poles, glaciers and floating ice drop deposits directly to the sea floor. Winds can provide fine grained material from arid regions, and explosive volcanic eruptions contribute as well. All of these sources vary in

3120-605: The ocean. Much of the sediment carried by the Amazon can come from the Andes mountains, and the final distance traveled by the sediment is 6,000 km (3,700 mi). 70-percent of the Earth's surface is covered by ocean , and marine environments are where we find the world's highest proportion of mudrocks. There is a great deal of lateral continuity found in the ocean, as opposed to continents which are confined. In comparison, continents are temporary stewards of mud and silt, and

3185-433: The only remnants of ancient life preserved; however, the Burgess Shale includes hard body parts such as bones, skeletons, teeth, and also soft body parts such as muscles, gills, and digestive systems. The Burgess Shale is one of the most significant fossil locations on Earth, preserving innumerable specimens of 500 million year old species, and its preservation is due to the protection of mudrock. Another noteworthy formation

3250-432: The original texture or to the disruption of layering by burrowing organisms in the sediment prior to lithification . From the beginning of civilization, when pottery and mudbricks were made by hand, to now, mudrocks have been important. The first book on mudrocks, Geologie des Argils by Millot, was not published until 1964; however, scientists, engineers, and oil producers have understood the significance of mudrocks since

3315-562: The principle donors of clay minerals. A mudstone is a siliciclastic sedimentary rock that contains a mixture of silt- and clay-sized particles (at least 1/3 of each). The terminology of "mudstone" is not to be confused with the Dunham classification scheme for limestones. In Dunham's classification, a mudstone is any limestone containing less than ten percent carbonate grains. Note, a siliciclastic mudstone does not deal with carbonate grains. Friedman, Sanders, and Kopaska-Merkel (1992) suggest

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3380-472: The quiet waters necessary for deposition. Although mudrocks can be found in every depositional environment on Earth, the majority are found in lakes and oceans. Heavy rainfall provides the kinetic motion necessary for mud, clay, and silt transport. Southeast Asia, including Bangladesh and India, receives high amounts of rain from monsoons, which then washes sediment from the Himalayas and surrounding areas to

3445-546: The rate of their contribution. Sediment moves to the deeper parts of the oceans by gravity, and the processes in the ocean are comparable to those on land. Location has a large impact on the types of mudrocks found in ocean environments. For example, the Apalachicola River , which drains in the subtropics of the United States, carries up to sixty to eighty percent kaolinite mud, whereas the Mississippi carries only ten to twenty percent kaolinite. We can imagine

3510-528: The reef edge. Later reactivation of faults at the base of the formation led to its disintegration from about 509  million years ago . This would have left a steep cliff, the bottom of which would be protected from tectonic decompression because the limestone of the Cathedral Formation is difficult to compress. This protection explains why fossils preserved further from the Cathedral Formation are impossible to work with – tectonic squeezing of

3575-546: The rock record. Most of the sediments that were deposited before this time were marine, or a small scale terrestrial zone. In New Jersey, the Bloomsburg Red Beds were previously called the "High Falls Shale" or "High Falls Formation". The depositional environment of the Bloomsburg was mostly terrestrial or shallow marine deposits resulting in a molasse sequence produced by the Taconic orogeny . The red color

3640-401: The rock, and it may be best summarised as the physical breaking apart of a rock. One of the highest proportions of silt found on Earth is in the Himalayas, where phyllites are exposed to rainfall of up to five to ten meters (16 to 33 feet) a year. Quartz and feldspar are the biggest contributors to the silt realm, and silt tends to be non-cohesive, non-plastic, but can liquefy easily. There is

3705-412: The second most abundant source of mudrocks, behind marine mudrocks. Ancient lakes owe their abundance of mudrocks to their long lives and thick deposits. These deposits were susceptible to changes in oxygen and rainfall, and offer a robust account of paleoclimate consistency. A delta is a subaerial or subaqueous deposit formed where rivers or streams deposit sediment into a water body. Deltas, such as

3770-588: The significance of the Burgess Shale, collecting fossils became politically more difficult from the mid-1970s. Collections continued to be made by the Royal Ontario Museum . The curator of invertebrate palaeontology, Desmond Collins , identified a number of additional outcrops, stratigraphically both higher and lower than the original Walcott quarry. These localities continue to yield new organisms faster than they can be studied. Stephen Jay Gould 's book Wonderful Life , published in 1989, brought

3835-556: The term mudrock has increasingly become the terminology of choice by sedimentary geologists and authors. The term "mudrock" allows for further subdivisions of siltstone , claystone , mudstone , and shale . For example, a siltstone would be made of more than 50-percent grains that equate to 1/16 - 1/256 of a millimeter. "Shale" denotes fissility, which implies an ability to part easily or break parallel to stratification. Siltstone, mudstone, and claystone implies lithified, or hardened, detritus without fissility. Overall, "mudrocks" may be

3900-534: The use of "lime mudstone" to avoid confusion with siliciclastic rocks. A siltstone is a lithified, non-cleavable mudrock. In order for a rock to be named a siltstone, it must contain over fifty percent silt-sized material. Silt is any particle smaller than sand, 1/16 of a millimeter, and larger than clay, 1/256 of millimeter. Silt is believed to be the product of physical weathering, which can involve freezing and thawing, thermal expansion, and release of pressure. Physical weathering does not involve any chemical changes in

3965-458: The water and decompose in the mudrock. Red mudrocks form when iron within the mudrock becomes oxidized, and depending on the intensity of red, one can determine if the rock has fully oxidized. Fossils are well preserved in mudrock formations, because the fine-grained rock protects the fossils from erosion, dissolution, and other processes of erosion. Fossils are particularly important for recording past environments. Paleontologists can look at

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4030-526: The world's lakes larger than 500 km (310 mi), and glaciers created many of those lakes. Lake deposits formed by glaciation, including deep glacial scouring, are abundant. Although glaciers formed 90-percent of lakes in the Northern Hemisphere, they are not responsible for the formation of ancient lakes . Ancient lakes are the largest and deepest in the world, and hold up to twenty percent of today's petroleum reservoirs . They are also

4095-485: Was composed of the calcareous reefs of the Cathedral Formation , which probably formed shortly before the deposition of the Burgess Shale. The precise formation mechanism is not known for certain, but the most widely accepted hypothesis suggests that the edge of the Cathedral Formation reef became detached from the rest of the reef, slumping and being transported some distance – perhaps kilometers – away from

4160-517: Was continually present in the sediment. The anoxic setting had been thought to not only protect the newly dead organisms from decay, but it also created chemical conditions allowing the preservation of the soft parts of the organisms. Further, it reduced the abundance of burrowing organisms – burrows and trackways are found in beds containing soft-bodied organisms, but they are rare and generally of limited vertical extent. Brine seeps are an alternative hypothesis; see Burgess Shale type preservation for

4225-421: Was formed by a humid, tropical climate with lakes, swamps, and rivers, which deposited mudrock. Inevitably, mudrock preserved countless specimens from the late Jurassic , roughly 150 million years ago. Mudrocks, especially black shale, are the source and containers of precious petroleum sources throughout the world. Since mudrocks and organic material require quiet water conditions for deposition, mudrocks are

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