Climate in Earth History Studies in Geophysics (1982) / Chapter Skim
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10 Climate Significance of Lake and Evaportie Deposits
10 Climate Significance of Lake and Evaportie Deposits
Pages 105-111
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From page 105... ...
Because deposi105 tional and postdepositional processes form a continuum, mineral textures and sedimentary structures must be interpreted with great care. LAKE DEPOSITS The study of ancient lake deposits has been helped immeasurably by limnologists, sedimentologists, and geochemists, who make observations on active lakes, and by geologists, who have concerned themselves with Pleistocene lakes and their Holocene residues.
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From page 106... ...
. SALINE LAKES Saline lakes form in hydrologically closed basins under conditions where evaporation exceeds inflow.
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From page 107... ...
There is no doubt that the most valuable climatic information contained in lake deposits relates to short-term temporal changes and to local differences between adjacent basins. This is most clearly documented in the Eocene Green River deposits of Utah, Colorado, and Wyoming.
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From page 108... ...
, in a comparison of the drainage basins and sedimentation histories of the two basins, take the opposite posidon: "Basin filling and enlargement of the drainage system were probably a consequence of tectonic activity and stability of the basins and adjacent uplifts although climatic condibons that increased sediment yield and runoff in the hydrographic basins also could have hastened their filling. However, it is difficult to explain patterns of evaporite minerals, oil shale, Redstone, and sandstone formed in Lakes Gosinte and flints if climate was the dominant factor." While Lakes Gosiute and IJinta v ent through their evolutionary changes, the much smaller Fossil Lake to the west (Figure 10.2)
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From page 109... ...
, who at tempted to correlate mean annual humidity with stage and in tensity of evaporation. The activity of Ho, a LOO, of a brine is a direct measure of the humidity of the air in equilibrium with such a brine, as PH20 brine THEO PH-O water and RH = 100aH2O, 109 where PH20 is the water-vapor pressure and RH is the relative humidity in percent.
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From page 110... ...
CONCLUSIONS Lake deposits are sensitive indicators of palcoclimatic changes. Particularly useful are glacial and saline lakes.
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From page 111... ...
. A comparison of evaporites facies in the late Paleozoic Amazon and the Middle Cretaceous South Adantic salt basins, Econ.
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