Silurian limestone

FIGURE 9.9 Analysis of a data set fra- dry and water-saturated Silurian limestone samples (Gotland), (a) Thermal conductivity versus densit5r (b) thermal conductivity versus porosity. From Poulsen et al. (1982). 

Poulsen, K.D., Saxov, S., Balling, N., Kristiansen, J.I., 1982. Thermal conductivity measurements on Silurian limestones from the Island of Gotland, Sweden. Geol. Foren. Stockh. Forh. 103 (3), 349-356. 

In general these substances are widely distributed in the acid distillates but appear to increase in number at two stratigraphic levels (1) in the middle Silurian McKenzie Limestone and (2) in the middle Devonian shales. Furthermore, possible two- and three-ring aromatic or heteroaromatic structures show similar increases. There is also a rough correlation with the Kjeldahl nitrogen content of the samples (Table VI). 

Tonoloway Limestone, Upper Silurian, 1 mile northeast of Mt. Union, Mt. Union Quadrangle. 

Weaver (unpublished) Silurian, red shale in limestone, Mont., U.S.A. 

Banister and Whittard (1945) oolites from Silurian siltstone, Wickwar, England high Mg content is believed to be due to post-depositional Mg-rich solutions which dolomitized enclosing limestone (14 A variety). 

Further support for the weathering hypothesis for Late Ordovician glaciation comes from the strontium isotope record. A multimillion-year decline in the marine record of Sr/ Sr in limestones is reversed in the early Late Ordovician (Veizer et al., 1999), a likely consequence of collisional tectonics that initiated at this time and continued (as did the rise in Sr/ Sr) through the Silurian (Richter et al, 1992). The increase (from 0.7078 to 0.7088) rivals the Cenozoic rise, which has been attributed to the Himalayan uplift and associated with the progressive cooling leading to Quaternary glaciation (Raymo et al, 1988). 

Canada exhibits a trend toward heavy values in the Early Silurian (Goodfellow et al, 1992). Determining whether this is simply a basinal effect or reflective of a global trend must await further isotopic work a focus on extracting trace sulfate from limestones promises a much higher resolution record for this event in the near future. 

This region is located in the Canadian Shield, composed of massive Precambrian crystalline rocks, mainly granite-gneisses and granites. In the syncline of Hudson Bay, on the south shore, and on the lowlands of the River Mackenzie, there occur sedimentary deposits of Silurian and Devonian dolomites, limestones and sandstones. 

Silurian 350 Slaty and calcareous shales, limestones, flagstones, sandstones... 

Angular unconformity between highly folded Horton Flags, Silurian, below and almost horizontal Lower Carboniferous Limestone above, Helwith Bridge, North Yorkshire, England. 

A commercial product described by Toch (1916) along with Princess Mineral Brown as being derived from an ore mined in the US. Toch describes the ore as a carbonate, [which] lies between the upper Silurian and lower Devonian. It is a massive material of bluish gray color when mined, and resembles limestone, although it contains a very low percentage of lime. .. The ore is hauled to the kilns, where it is roasted, which drives of the carbon dioxid [sic] and converts it into the sesqui-oxid [sic]. The original manufacturer was Robert Prince of New York, USA, who became interested in a slate quarry in Carbon County, Petmsylvania. 

Cooper, B.J. (1975) Multi-element conodonts from the Brassfield Limestone (Silurian) of southern Ohio. Journal of Paleontology, 49 984—1008. 

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