. Bulletin. Natural history; Natuurlijke historie. STRATIGRAPHIC DESCRIPTIONS 29 FEET r 100 i 0 10 20 t^ 13 ks MILES )mountains yERMOPOUS/ \ BIG HORN ^ ^ BASIN j-^ / OWLCRK ( N MOUNTAINS 1 ^^<r "" PRE-" ^CRETACEOUS | â "~-J ^S. ROCKS 1 ⢠SHOSHONI WIND RIVe"r '^ 1/ BASIN ARM INTO 1 INDEX MAP. |~~_~| SHALE [-----1 SILICEOUS l-"-""'"-l SHALE |;:^*:| bentonite |-_"_| siltstone i i sandstone Figure 5. Tentative correlation of a distinctive Shell Creek shale bentonite bed between the Big Horn and Wind River Basins. Half-foot shale samples were ta
. Bulletin. Natural history; Natuurlijke historie. STRATIGRAPHIC DESCRIPTIONS 29 FEET r 100 i 0 10 20 t^ 13 ks MILES )mountains yERMOPOUS/ \ BIG HORN ^ ^ BASIN j-^ / OWLCRK ( N MOUNTAINS 1 ^^<r "" PRE-" ^CRETACEOUS | â "~-J ^S. ROCKS 1 ⢠SHOSHONI WIND RIVe"r '^ 1/ BASIN ARM INTO 1 INDEX MAP. |~~_~| SHALE [-----1 SILICEOUS l-"-""'"-l SHALE |;:^*:| bentonite |-_"_| siltstone i i sandstone Figure 5. Tentative correlation of a distinctive Shell Creek shale bentonite bed between the Big Horn and Wind River Basins. Half-foot shale samples were taken immediately below and above five ben- tonite beds in the Shell Creek and Thermopolis shales in different localities, in order to survey the effect of ash falls on the benthonic foraminiferal faunas. Foraminifera were absent above only one of the bentonites and here some sponge spicules occurred. Immediately above three of the bentonites, a few specimens of some of the species which occurred below them were found. This shows that after ash falls had buried the bottom foraminiferal populations, the new bottom sur- faces were repopulated rapidly by some of the same species. The results of the samples taken above and below the fifth bentonite, a bed in the upper part of the Thermopolis shale, were entirely unexpected. No foraminifera occurred immedi- ately below this bentonite, but immediately above it they were profuse. Here the change in bottom conditions must have been distinctly favorable for the ben- thonic fauna. Table 1 summarizes the results of the five sets of Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Peabody Museum of Natural History. New Haven : The Museum
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Keywords: ., bookcentury1900, bookcollectionbiodiv, booksubjectnaturalhistory
