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Topic: Middle Cambrian

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	Cambrian system - LoveToKnow 1911
		The middle division covers approximately the same region as the lower one, and in addition it is found in Texas, Oklahoma, Indian Territory, Arizona, in western Montana, and possibly in western Wisconsin.
		The Cambrian system is covered by his stages "B" and "C"; the former a barren series of conglomerates and quartzites, the latter a series of grey and green fissile shales 1200 ft. thick with sandstones, greywackes and conglomerates.
		The Cambrian system is represented in the Salt Range of India by the Neobolus or Khussack beds, which may possibly belong to the middle subdivision.
	www.1911encyclopedia.org /Cambrian_system (2844 words)

	Palaeos Paleozoic: Cambrian: The Cambrian Period - 1
		Laurentia stretched across the Cambrian equator, partly submerged by the Iapetus ocean, with a mostly mostly submerged Baltica and Siberia approaching from the South-East.
		During the 53 million years that the Cambrian period lasted there was the sudden appearance and diversification of almost every major group (phylum) of animal life, as well as many types that later died out.
		The most characteristic animals of the Cambrian period were the trilobites, a primitive form of arthropod remarkable for it's highly developed eyes (unusual in such an early organism).
	www.palaeos.com /Paleozoic/Cambrian/Cambrian.htm (2818 words)

	Cambrian HSU NHM
		The Cambrian* Period begins the Phanerozoic Eon, the last 542 million years during which fossils with hard parts have existed, is the first division of the Paleozoic Era (251 - 542mya).
		Cambrian animals were organized into a unique marine fauna, one of three recognized during the Phanerozoic.
		A relatively common Cambrian fossil is the brachiopod.
	www.humboldt.edu /~natmus/lifeThroughTime/Cambrian.web/index.html (705 words)

	Cambrian (Site not responding. Last check: )
		The lower boundary of the Cambrian was traditionally set at the earliest appearance of early arthropods known as trilobites and of primitive reef forming animals known as archeocyathids.
		Exactly at the Cambrian boundary there is a marked fall in the abundance of carbon-13, a 'reverse spike' that palaeontologists call an 'excursion', It is so widespread that it is the best indicator of the position of the Precambrian-Cambrian boundary in stratigraphic sequences of roughly this age.
		The Cambrian continents are thought to have resulted from the breakup of a Neoproterozoic supercontinent called Rodinia.
	www.icyclopedia.com /encyclopedia/c/ca/cambrian.html (857 words)

	Palaeontology - Research - What are Trilobites?
		Tasmacephalus platypus Bentley and Jago, 2004, Middle Cambrian, TAS.
		Jell, P.A. Pagetia ocellata, a new Cambrian trilobite from northwestern Queensland.
		Cambrian geology and palaeontology of the Ord Basin.
	www.austmus.gov.au /palaeontology/research/trilobites03.htm (7308 words)

	Cambrian Period (Site not responding. Last check: )
		Cambrian rocks underlie the state, but like Precambrian rocks, they are nowhere exposed at the surface and have been characterized by deep drilling for hydrocarbons and by geophysical methods.
		At the beginning of the Cambrian, the core of the North American continent, including Ohio, was emergent and consisted of a gently rolling surface covered by highly weathered granite and other Precambrian crystalline rocks.
		By the end of Middle Cambrian time, a wedge of sandy deltaic sediments began to spread from north to south across the central portion of the state.
	www.ohiohistorycentral.org /entry.php?rec=2777 (323 words)

	Cambrian Summary
		Cambrian faunas include some very unusual creatures that may represent extinct phyla of organisms or organisms so primitive that they are not easily assigned to extant phyla.
		Numerous Cambrian reefs, patch reefs, and shallow-water mounds were formed by stromatolites, a layered mass of sediment formed by the daily trapping and binding action of a symbiotic growth of blue-green algae and bacteria.
		The Cambrian is a major division of the geologic timescale that begins about 542 mya (million years ago) at the end of the Proterozoic eon and ended about 488.3 Ma with the beginning of the Ordovician period (ICS, 2004).
	www.bookrags.com /Cambrian (2583 words)

	GeoFacts No. 20, The Geology of Ohio--The Cambrian (Site not responding. Last check: )
		Were it not for this dramatic occurrence, the 65-million-year-long Cambrian Period would not be regarded as the beginning of a new, and perhaps the most significant, era in the history of the Earth.
		As the Cambrian sea continued to flood the craton during the opening of the Iapetus Ocean, the waters deepened across Ohio, and carbonate deposition began in eastern Ohio as the Rome Formation accumulated.
		Cambrian rocks in Ohio have been the last of the Paleozoic systems to be explored for economic benefits because of their great depth below the surface.
	www.ohiodnr.com /geosurvey/geo_fact/geo_f20.htm (1568 words)

	Cambrian bibliography
		---, 1977, A redescription of the Middle Cambrian worm Amiskwia sagittiformis Walcott from the Burgess Shale of British Columbia: Palontologische Zeitschrift, v.
		Lokhmatov, G. I., 1966, Change of contents of lower Cambrian carbonate deposits under the influence of consediment formation of geological structures (south of Siberian Platform): Academy of Sciences of the USSR Reports, v.
		Zharkov, M. A., Chechel', E. I., and Knyasev, I. M., 1963, Cambrian deposits of middle and upper stream of the river Kirenga: Academy of Sciences of the USSR Reports, v.
	www.talkorigins.org /origins/biblio/cambrian.html (2135 words)

	Cambrian Period
		The Cambrian was brought to a close by a ‘mass extinction’ event which notably decimated the trilobites.
		In 1994, Zhang and Pratt reported Middle Cambrian spherical fossils, 0.3 mm in diameter, that under a smooth membrane preserved a polygonal pattern which they interpreted as remains of blastomeres belonging to 64- and 128-cell stages of arthropod embryos.
		Extinction rates were generally high throughout the Cambrian, typically between 20 and 30%, but two major peaks in the mid Cambrian (Upper Solvan) and at the close of the Cambrian (Dolgellian) qualify as mass extinctions.
	www.peripatus.gen.nz /paleontology/Cambrian.html (4724 words)

	Geological Society of America - GSA Today - v. 10, no. 5, May 2000 (Site not responding. Last check: )
		The subsequent rapid rise during the latter half of the Middle Cambrian to peak values in the early Late Cambrian is interpreted to record the large magnitude of coeval orogenic events in Antarctica and Australia (Goodge et al., 1993; Curtis and Storey, 1996; Encarnacion and Grunow, 1996).
		Sr values during the terminal Early Cambrian cannot be clearly resolved, given that the C isotope trend was defined, in part, by marine components that were not suitable for Sr isotope analysis.
		Curtis, M.L., Leat, P.T., Riley, T.R., Storey, B.C., Millar, I.L., and Randall, D.E., 1999, Middle Cambrian rift-related volcanism in the Ellsworth Mountains, Antarctica: Tectonic implications for the palaeo-Pacific margin of Gondwana: Tectonophysics, v.
	www.geosociety.org /pubs/gsatoday/gsat0005.htm (4065 words)

	The Cambrian Period
		The Cambrian Period marks an important point in the history of life on earth; it is the time when most of the major groups of animals first appear in the fossil record.
		It was once thought that the Cambrian rocks contained the first and oldest fossil animals, but these are now to be found in the earlier Vendian strata.
		The Cambrian Period is part of the Paleozoic Era.
	www.ucmp.berkeley.edu /cambrian/camb.html (272 words)

	"Early Cambria -- Information of Lower Cambrian and Older Faunas - v0.01"
		It stretches to include soft bodied forms from the Middle Cambrian since the record of soft bodied forms from that period is better studied than the Early Cambrian.
		The relationship of the Abrigo to the Upper Cambrian Muav Limestone of the Grand Canyon is unclear.
		An animal of unknown affinity from the Middle Cambrian Burgess Shale of British Columbia.
	bio.cc /Scientists/Dan_Bolser/EARLYCAM.HTM (13366 words)

	Amazon.com: "Middle Cambrian": Key Phrase page (Site not responding. Last check: )
		The Ecology of the Cambrian Radiation by Andrey Zhuravlev
		MIDDLE CAMBRIAN In the Middle Cambrian, Laurentia continued to drift toward the equator, while Iapetus became wider (figure 3.3).
		Proterozoic or Early Cambrian deposits in the Mongolian People's Republic (1980), Early Cambrian deposits in China (1982) and Kazakhstan (1984), Middle Cambrian deposits in Australia (1978), Late Cambrian potentially phosphatic sediments in the Great Basin of the western USA (1979), and phosphorites...
	www.amazon.com /phrase/Middle-Cambrian (466 words)

	HALKIERIIDS IN MIDDLE CAMBRIAN PHOSPHATIC LIMESTONES FROM AUSTRALIA Journal of Paleontology - Find Articles
		A decline during the Cambrian in conditions necessary for the early diagenetic phosphatization of shallow-shelf and platform limestones may have effectively closed this taphonomic window, potentially biasing apparent patterns of diversity change through the period.
		THE EARLY Cambrian fossil record is characterized by unique skeletal assemblages that include the spongelike archaeocyathans and a number of mostly problematic small skeletal elements, known collectively as small shelly fossils (SSFs; Matthews and Missarzhevsky, 1975).
		These assemblages are distinctive enough from Middle and Upper Cambrian assemblages that Sepkoski (1992) recognized the "Tommotian" fauna as a discrete evolutionary fauna separate from his Cambrian fauna sensu stricto.
	findarticles.com /p/articles/mi_qa3790/is_200405/ai_n9377598 (742 words)

	Characteristics of Early Cambrian Faunas from Eastern San Bernardino County, California
		The lower Cambrian rocks consist of a conformable sequence of shallow marine, clastic and carbonate sediments which overlies cratonic Precambrian plutonic or metamorphic rocks to the south and Precambrian marine sediments to the north.
		The youngest subzone of the Early Cambrian is the Olenellus multinodus Subzone.
		Middle Cambrian stratigraphy and faunas of the Canadian Rocky Mountains.
	members.cox.net /jdmount/cambmojave1.html (2299 words)

	Walcott Mystery
		When we began our comprehensive study of the Middle Cambrian trilobite faunas of the Pioche Shale in 1993, we realized that the type species of two very important groups of trilobites; the kochaspids and oryctocephalids, had been described from the Pioche Shale by Walcott (1886).
		The first Cambrian trilobites to be found from the Pioche Mining district were in 1871 by geologists of the Wheeler Survey (Gilbert, 1875).
		Sundberg, F.A., and McCollum, L.B., 1997, Oryctocephalids (Corynexochida: Trilobita) of the Lower-Middle Cambrian boundary interval from
	www.geology.ewu.edu /mccollum/Walcottmystery.htm (2354 words)

	Middle Cambrian articulate brachiopods from the Southern New England Ford Belt, Northeastern N.S.W., Australia Journal ...
		Middle Cambrian articulate brachiopods from the Southern New England Ford Belt, Northeastern N.S.W., Australia
		ABSTRACT-Calcareous articulate brachiopods are rare components of the high diversity, phosphatic, silicified, and epidote coated shelly fauna derived from Middle Cambrian (Floran-Undillan) allochthonous limestone clasts from the Murrawong Creek Formation, southern New England Fold Belt, northeastern New South Wales, Australia.
		MIDDLE CAMBRIAN fossils were first reported from basal sequences of the southern New England Fold Belt by Cawood (1976) (Fig.
	www.findarticles.com /p/articles/mi_qa3790/is_199807/ai_n8799782 (714 words)

	WCSB Atlas Chapter 8 Middle Cambrian to Lower Ordovician Strata (Site not responding. Last check: )
		Figure 8.1 Index map showing the present distribution of Middle Cambrian to Lower Ordovician sediments, tectonic and topographic controls on sedimentation, post-sequence tectonic and topographic features, and the positions of regional cross sections and reference logs.
		Figure 8.5 Diagrammatic stratigraphic cross section of the Cathedral carbonate lithosome, a body of Middle Cambrian platformal carbonate rock that is regional in extent and surrounded by siliciclastic mudrocks.
		Figure 8.20d Distribution of Middle Cambrian carbonates (limestones and dolomites combined), as a percentage of total thickness.
	www.ags.gov.ab.ca /publications/ATLAS_WWW/A_CH08/CH_08.shtml (691 words)

	Palaeos Paleozoic: Cambrian: The Middle Cambrian Epoch
		We know this because, in the Early Cambrian, calcium carbonate precipitated out of seawater as aragonite, a the preferred crystal form of calcium carbonate when relatively high concentrations of magnesium are present.
		This was to last throughout the remainder of the Early and Middle Paleozoic.
		The habitat destruction of the Middle Cambrian may only have selected for even bigger and more mobile forms able to take advantage of the open sea bottom.
	www.palaeos.com /Paleozoic/Cambrian/MidCam.html (405 words)

	NYS Museum - Staff: Landing, Ed
		Geyer, G., and Landing, E. Middle Cambrian of Avalonian Massachusetts: Stratigraphy and correlation of the Braintree trilobites.
		Arthropod Traces in the Middle Cambrian of Morocco.
		Landing, E. Lower Cambrian of southeastern Newfoundland: Epeirogeny and Lazarus Faunas, Lithofacies-Biofacies Linkages, and the Myth of a Global Chronostratigraphy.
	www.nysm.nysed.gov /staff/details.cfm?staffID=52 (2265 words)

	Trilobita Trilobites
		The Lichida are variously shown as having arisen from either the Redlichiida or Corynexochida in the Middle Cambrian.
		Asaphida, Proetida, and Harpetida arose from Ptychopariida in the Cambrian.
		Perhaps unraveling the complex ancestry of the trilobite from among the diverse arthropod cousins of the Cambrian Explosion and into the Precambrian will never be satisfactorily accomplished – different consensus opinions are likely to hold sway until giving way to a new one.
	www.fossilmuseum.net /Tree_of_Life/PhylumArthropoda/ClassTrilobita.htm (1413 words)

	Cambrian
		In the Cambrian, the deeper water fissile shale facies is characterized by a lack of a large and diverse benthic infauna and the presence of a high diversity benthic fauna including sponges, hyolithids, brachiopods and a trilobite assemblage composed of both endemic and cosmopolitan species, with a higher percentage of complete specimens.
		McCollum, L.B., 1999, Biostratigraphic correlation of the Lower-Middle Cambrian boundary interval of the Cordilleran region of Laurentia.
		McCollum, L.B., 2000, Ptychopariid trilobites from the Lower-Middle Cambrian boundary interval, Pioche Shale, southeastern
	www.geology.ewu.edu /mccollum/research1.htm (15576 words)

	Geosciences Journal
		Defining the base of a series that replaces the traditional Middle Cambrian is among the difficult tasks of Cambrian stratigraphy.
		Non-traditional concepts (such as carbon isotope signatures), microplankton (such as acritarchs), and most invertebrate fossils (e.g., brachiopods) may act as auxiliary tools for intercontinental correlation of regional calibration but are unable to provide the base for fine-scaled global correlation at present.
		Five possible levels of correlation within the traditional Lower-Middle Cambrian boundary interval have been discussed: (1) the FAD of Oryctocephalus indicus; (2) the FAD of Ovatoryctocara granulata and/or Kiskinella cristata; (3) the FAD of Arthricocephalus chauveaui; (4) the base of the Acidiscus-Cephalopyge assemblage ¡°zone¡±; and (5) the base of the STH ¡°band¡±.
	www.geosciences-journal.org /home/journal/library/abstract_view.asp?articleUID={A4E25BC8-BC84-42FE-B93D-6331B86CB402} (255 words)

	Trilobites In The Nopah Range, Inyo County, California (Site not responding. Last check: )
		In the Grapevine Mountains of eastern California, the Jangle yields a diverse and abundant middle Cambrian trilobite fauna consisting of Mexicella grandoculus, Mexicaspis radianis, Nyella climlimbata, Ptarmiganoides hexantha and Volocephalina connexa.
		The algal nodules are usually referred to by sedimentologists as oncolites, and were theoretically formed by direct precipitation of calcium carbonate from Cambrian sea-waters, unlike modern algal bodies from the Bahamas that develop directly through accretionary capturing of the surrounding oceanic muds.
		The oldest unit in the Carrara Formation, lying directly atop the lower Cambrian Zabriskie Quartzite (which yields vertical trace fossil worm borings paleontologists usually called Scolithus, which is usually considered a member of the Phylum Phoronida, or the Horseshoe Worms) in stunning fashion, is the terrigeneous Eagle Mountain Shale Member.
	members.aol.com /Waucoba5/cf/carfieldtrip.html (2885 words)

	HALKIERIIDS IN MIDDLE CAMBRIAN PHOSPHATIC LIMESTONES FROM AUSTRALIA Journal of Paleontology - Find Articles
		The Monastery Creek Formation provides a valuable window on Middle Cambrian life, both because it provides information that is distinct from but complementary to other, similarly aged windows (e.g., the Burgess Shale) and because it represents a taphonomic window similar to those that preserve Early Cambrian small shelly problematica.
		A decline during the Cambrian in conditions necessary for the early diagenetic phosphatization of shallow-shelf and platform limestones may have effectively closed this taphonomic window, potentially biasing apparent patterns of diversity change through the period.
		THE EARLY Cambrian fossil record is characterized by unique skeletal assemblages that include the spongelike archaeocyathans and a number of mostly problematic small skeletal elements, known collectively as small shelly fossils (SSFs; Matthews and Missarzhevsky, 1975).
	www.findarticles.com /p/articles/mi_qa3790/is_200405/ai_n9377598 (742 words)

	Lower and Middle Cambrian trace fossils from the Láncara and Oville formations in the area of Presa del Porma
		The overlying Middle Cambrian Oville Formation consists of greenish mudstones and scarce fine-grained sandstones.
		The basal part of the upper member is Middle Cambrian in age (Sdzuy, 1995), and consists of 11 m of glauconitic, light grey limestones.
		The middle part of the upper member of the Láncara Formation is made up by 8 metres of mainly pink and reddish glauconitic limestones.
	www.unt.edu.ar /fcsnat/INSUGEO/Libro_Cambrian/091_lower_and_middle.htm (1203 words)

	Fossils In Death Valley National Park
		Algae Nodules from the Lower Cambrian Mule Spring Limestone, Esmeralda County, Nevada; the dark, circular to oval structures are the remains of an extinct blue-green algae called Girvanella sp.
		Sponge Spicule from the Middle Cambrian Emigrant Formation, Esmeralda County, Nevada; an indeterminate spicule from a siliceous sponge.
		Horse Tooth from the Middle Pliocene Coso Formation, Inyo County, California; a cheek tooth from Equus simplicidens, the so-called Hagerman Horse (named for its spectacular, abundant occurrence at Hagerman Fossil Beds National Monument in Idaho), which is the oldest known member of the genus Equus, which includes all modern equids.
	members.aol.com /Waucoba5/dv/dvfossils.htm (4989 words)

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