The Kimmeridge Clay in Dorset
Introduction
The Kimmeridge Clay Formation is the penultimate formation of the onshore British Jurrasic Succession. William Smith was the first to document this distinct formation on his map of 1815, and to name as the Oaktree Soil. In 1817, he gave the name Oaktree Clay for the layers of clay between the “Portland Rock” and “Coral Rag and Pisolite” but in 1816 Webster was the first to describe in details the formation and changed to the name now known as kimmeridge Clay Formation after the English village of Kimmeridge on Dorset’s “Jurassic Coast” a place frequently visited by fossil hunters. (Cox and Gallois, 1981).
The sediments of the Kimmeridge Clay Formation were deposited during Late Jurassic between around 160 and 145 million years ago. The outcrop and subcrop from Kimmeridge Clay in England extends from Dorset to North Yorkshire but due to the lack of exposure inland, all stratigraphic studies of the formation has occurred in the costal sections between Weymouth and Swanage in Dorset ( Figure 1) (Cox and Gallios, 1981)
Figure 1: Kimmeridge Clay Formation outcrops in the Dorset area
Is largely, but not completely exposed at the surface at Kimmeridge. Thus the thickness can not be directly measured. Seismic reflection profiles by British Petroleum Ltd have shown that the full thickness is between 535m and 585m in the area (Gallois, 2000)
Kimmeridge Clay is arguably the most economically important unit of rocks in the whole of Europe since constitutes one of the main North Sea source rock, however over onshore England and Wales, it has log responses and distinctive physical properties. Such rocks are of prime interest to oil industry while...
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...d, just above the limit of the range of Aulacostephanus ( Arkell, 1947) and at the lower limit of the range of Pectinatities( Cope, 1967).
The total thickness of the Kimmeridge area is therefore about 508 metres.
Lithology
Lithologically the Kimmeridge Clay Formation can be subdivided into four units (Figure 2), despite of beds at the base of the succession are poorly exposed. However, in contrast, the units from mid-eudoxus Zone to the top of the formation that are well seen in the Formation. At the base of the formation until the eudoxus Zone, the strata are made up almost entirely of bioturbated shelly clays and in between beds, horizons of oil and bituminous are present. The upper part of the Eudoxus Zone until the upper Pectinatus Zone the composition is kerogen-rich mudstones and coccolith limestone.
When standing on top of the butte, the rock that makes up a majority of the area is quartzite. Quartzite is a metamorphic rock that forms when existing rock is exposed to extreme amounts of heat and pressure (4). The quartzite that is found on Kamiak Butte was formed sometime around 1.47 to 1.4 billion years ago during the Paleozoic period of the Precambrian era. Many of the metamorphic rocks have been fractured and decayed due to physical and chemical weathering, but because quartzite consists of one of the strongest minerals quartz...
The coastal belt of the Franciscan Complex is composed of the youngest and least deformed units and makes up the western quarter of all Franciscan rocks. The rocks of the coastal belt are composed of arkosic sandstones, andesitic graywackes, and quartzofeldspathic graywackes interbedded with radiolarian chert (turbidite deposits) (Blake and Jones, 1981). These sedimentary rocks suggest a depositional environment of deep-sea fan systems with both oceanic and continental provenance. Parts of the belt show evidence of later metamorphism, principally due to subduction. Low-grade blueschist mineral facies are indicated by the presence of minerals such as laumonite and prehnite-pumpellyite (Blake and Jones, 1981). All rock units show evidence of thrust (imbricate) faulting due to the compressional forces of subduction. Ages of the coastal belt run from as little as 40 Ma (Eocene) to as old as 100 Ma (middle Cretaceous).
Harris, Ann G., Esther Tuttle, and Sherwood D. Tuttle. "Katmai National Park and Preserve." Geology of National Parks. 4th ed. Dubuque, IA: Kendall/Hunt Pub., 1990. 441-48. Print.
Tarbuck E., Lutgens F., Tasa D., 2014, An Introduction to Physical Geology, 5th Ed, Pearson Education, Upper Saddle River, New Jersey.
"Sedimentary Rocks." Backyard Nature with Jim Conrad. N.p., 18 May 2015. Web. 25 Oct. 2015.
Since Walcott’s discovery in 1901, due to extraordinary preservation, these restricted yet still widespread assemblages still remain slightly confusing; biologists, geologists, and me included research and wonder how these amazing specimens have been kept so well for millions of years (Gaines 2012). Academic Journal ‘Mechanism for Burgess Shale-type Preservation’ Robert Gaines along with many other infamous authors explain exactly that – they demonstrate in great detail just what the title says, the mechanisms of Burgess Shale-type preservation using many possibilities such as geochemical and sediment data from six different principal Burgess shale-type deposits and compare the different areas and the things and sediment found there (Gaines 2012).
Bibliography Wikipedia. The World of the. Gould, Stephen. Jay. Charles Lyell, Principles of Geology.
Krinitzsky, E. L., and Willard Jay Turnbull. Loess Deposits of Mississippi. New York: Geological Society of America, 1967. Print.
During the Jurassic period, Pangea began to break up and by the time of the Late Cretaceous, ~94 Mya, the Atlantic Ocean began to open and Pangea continued to break apart. Due to this breakage of continents, there were extreme volcanic activity and much evidence can be seen of this all around the world today. In Anglesey, there are many igneous dykes and sills that have intruded older rocks that have been dated back to this time. This movement of continents continued into the Cenozoic era which is the current and most recent geological era consisting of the past 65 million years. It was during this time that Anglesey reached its current, present day
...nd Stromatoporoids (a kind of sponge with a layered skeleton) were common rock builders of the Northern Hemisphere. Moss was common in shallow seas. Among the arthropods, the giant eurypterids (sea scorpions) have been found in the Old Red Sandston facies (see image above). The first insect was part of a group of wingless insects that feed off of debris and soil. Conodonts were vertebrate animals abundant in marine life. Many of the fish were heavily armored and the earlier fish (agnathans) had no jaws and were mud eaters and scavengers. Chondrichthians are sharklike fishes that were first found in the Middle Devonian. In terms of plants, many vascular plants emerged and a varied flora was established. There is evidence of algae, bryophytes, and charophytes. Algae and fungi also existed. As previously stated, the first known forests are from the Devonian Period.
P.Wellman, Ian McDougal,(1974),Cainozoic igneous activity in Eastern Australia, Research School of Earth Sciences, ANU Canberra, Elsevier Scientific Publishing Company,pg 52
"NPS: Nature & Science» Geology Resources Division." Nature.nps.gov » Explore Nature. Web. 05 Dec. 2011. .
To begin diamonds are can be found all over the world including countries like, Botswana, Canada, Namibia, Russia, South Africa, Australia, and Tanzania. Yet, diamonds are still quite rare and are only found from two dominant deposits. The primary deposits often consist of diamond-bearing “pipes” of volcanic rock called kimberlite. Deep within th...
The fine-grained variety of limestone is known as Kota stone,It is usually available in the Kota district of Rajasthan state of India. Kota stones have the unique properties of limestones. They are very tough, non–water absorbent, non-slip, non-porous and have excellent stain removability. Moreover, their resistance to wear and delamination is higher than other stones. It is an excellent building stone for humid regions and freezing regions, The varieties include Kota Blue Natural, Kota Blue Honed, Kota Blue Polished, Kota Blue Cobbles, Kota Brown Natural and Kota Brown Polished.
mineral equilibria of metamorphic carbonate ejecta (2). Fluid inclusions ([CO.sub.2] and [H.sub.2]O-[CO.sub.2]) in clinopyroxenes from cumulate and nodules indicate a trapping pressure of 1.0 to 2.5 kbar at about 1200 [degrees]C, suggesting that these minerals crystallized at depths of 4 to 10 km (3). The differentiated magma fraction was about 30% of the total magma in the reservoir, and a volume of about 2 to 3 [km.sup.3] was