Cambrian

Canada s most productive district is in the Canadian shield at Cobalt, Ontario. Nearly 97% of the silver values in this pre-Cambrian age ore were found as great slabs of nearly pure silver. One slab was 474 kg. The huge open-pit Kidd Creek Mine has had an aimual output of over 80 t of silver. 

Kambaholz, Kambalholz, n. camwood. Kambodscha, n. Cambodia, kambrisch, a. Cambrian. 

Paleozoic Cambrian 600 Myr Climate warms, O2 levels approach current level most animal phyla present, including some that failed to survive algae and cyanobacteria diversify... 

Fig. 11-13 Volume percent of sedimentary rocks as a function of age. (Modified with permission from A. B. Ronov (1964). On the post-Cambrian geochemical history of the atmosphere and hydrosphere. Geochemistry 5,493-506, American Geological Institute.)...

Thiokol-Ventron announcement in Cambrian News, 1 -2, May 1980, K K Greelf Chemicals... 

Figure 2.8 Reconstruction of a Middle Cambrian sea floor about 600,000,000 years ago. The fauna includes siliceous sponges (the upright cones), jellyfish, and two genera of trilobites (Paradoxides, the large form, and Eliipsocephalus, the small form). Bacteria had probably already been in existence for millions of years.

Nematode neurons (Pre-cambrian) Na+/K+, Ca2+, acetylcholine glycine Butyrate, GABA Recovery by re-entering synapse... 

Chordate neurons (early Cambrian) As above plus first hydroxylations giving serotonin and dopamine iron/pterin chemistry in cytoplasm vesicle filled in centre of cell Recovery by amine oxidation (flavoenzymes)... 

Jawless fish (Cambrian) As above second hydroxylation giving norepinephrine and amidated peptides copper chemistry in vesicles Recovery additionally by hydrolysis Zinc enzymes... 

Complete vertebrates (late Cambrian) As above plus myelinated neurons use of zinc enzymes in glial cells Free zinc in nerve messages NO/haem chemistry in glial cells ... 

If the asteroid-impact theory is correct, the extinctions should be repetitive and the Ir anomaly should be observed in other geological stratigraphic levels corresponding to known extinctions. About five other massive extinctions (besides the one at the end of the Cretaceous Period) have been noted [25]. These come at the end of the Cambrian ( 500 MY ago), the Ordovician (M35 MY age), the Devonian ( 345 MY ago), the Permian ( 230 MY ago) and the Triassic ( 195 MY ago) Periods. 

According to the Illinois Environmental Protection Agency (IEPA), a series of gas blowouts has occurred at two waste injection wells in the state (Brower el al., 1989). In each case, well operators were injecting concentrated hydrochloric acid into a dolomite bed. At its plant near Tuscola, the Cabot Corporation injects acid waste from the production of fumed silica into the Cambrian Eminence and Potosi Formations below 5 000 ft (1 500 m) depth. Allied Chemical Corporation injects acid into the Potosi formation below about 3 600 ft (1 100 m). The acid, which is contaminated with arsenic, is a byproduct of the manufacture of refrigerant gas. Since some of the blowouts have caused damage such as fish kills, there is environmental interest as well as operational concern in preventing such accidents. 

In general, the calceous-dolomitic rocks from the Cambrian age are affected by their upper beds, by sulphide mineralization of lead, zinc and iron contemporaneous with sedimentation. The oxide lead and zinc minerals are disseminated through dolomitic limestone. As a consequence of the action of the descending process, these formations may assume different types of mineralization. According to the intensity of the oxidation process, which is associated with the different characteristics of the country rock, this country rock may be (a) principally calceous, (b) calceous with dolomitized zones and (c) primarily dolomitized. 

The first well-documented episode of extinction came at the time of transition from the Precambrian to Cambrian era, about 600 milhon years ago. Many species for which we have fossil evidence, the Edicarian animals, simply did not survive this... 

Finally, if we take a fruit fly and knock out one of its Hox genes and then replace it with the corresponding human Hox gene, we get a perfectly normal fruit fly. As Matt Ridley has phrased it Flies and people are just variations on a theme of how to build a body that was laid down in some worm-like creature in the Cambrian period. This is a remarkable example of the underlying unity of living organisms. 

Bendigo is a classic example of a low-sulphide gold-quartz deposit located in a folded sequence of sandstone and shale of the Cambrian-Ordovician age (Ramsay et al. 1998 Goldberg et al. 2007). Regional soil geochemistry covers an area of 4,000 km. Sampling Grid 5x5 km. 134 samples were collected as can be seen in Fig. 2, titanium anomalies form sub-... 

The mineralized district is restricted by two main strike-slip faults of Kubanan to the east and Posht e Bdam to the west (Fig. la). The host rocks are a thick sequence of Upper Precambrian-Cambrian rhyolite, tuff, alkali granite, syenite, mafic dykes, magnetitite, dolomite, gypsum, limestone, black shale, and sandstone. The Upper Percambrian-Cambrian sequence is overlain unconformably by Mesozoic and... 

Fig. 1. a) Upper Precambrian-Cambrian Bafq metallogenic province in Centrai iran (modified from NiSCO 1980. b) a simpie geology map of the Esfordi P mine (modified after Jami et al. 2007). 

Geological Setting The IRAC is hosted in folded and faulted sedimentary rocks of Cambrian to lower Ordovician age (Currie 1975). These units are the slaty-limestone of the McKay Group (Cambro-Ordovician), massive limestone of the Ottertail Formation (Cambrian), and the sheared argillaceous rocks of the Cambrian Chanceller Formation (Allan 1914, Aitken Norford 1967). 

Fyffe, L.R. PiCKERILL, R.K. 1993. Geochemistry of Upper Cambrian - Lower Ordovician black shale along a northeastern Appalachian transect. Geological Society of America Bulletin, 105, 897-910. 

McKerrow, W.S. 1998. The Cambrian-Silurian tectonic evolution of the northern Appalachians and British Caledonides history of a complex, west and southwest Pacific-type segment of lapetus. In Blundell, D.J. and Scott, A. C. (eds) Lyell The Past is the Key to the Present. Geological Society, London, Special Publications, 143, 199-242. 

Neoproterozoic to Early Paleozoic rocks of the Annidale area are interpreted to mark the southeastern margin of Ganderia in the New Brunswick segment of the northern Appalachians (Johnson et al. 2009). The area is underlain by Late Cambrian to Early Ordovician rocks of the Annidale Group and Late Neoproterozoic to Early Cambrian rocks of the Belleisle Bay Group, which are juxtaposed along a major tectonic boundary marked by the Taylor Brook Fault (Fig. 1). 

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