076 BONN, W. L. , FARRA.ND, W. R. , and EWING , M. 1962. "Pleistocene Ice 

 Volumes and Sea-Level Lowering," Journal of Geology . Vol 70, pp 206-214. 



Based upon recent investigations of existing and of Pleistocene ice 

 sheets, revised estimates of late Pleistocene ice volumes and resulting sea- 

 level lowering are made. The thickness of Pleistocene ice sheets has been 

 determined by applying the thickness area ratio of existing ice sheets to the 

 revised areas of the past ice sheets. Revised values are given for the 

 Classical Wisconsin (less than 30,000 years B.P.), early Wisconsin (greater 

 than 30,000 years B.P.), and the Illinoian (third) glacial stages which are 

 here considered equivalent to the Weichsel, Warthe , and Saale stages, 

 respectively. The Illinoian is shown to be the stage of maximum glaciation 

 with consequent sea- level decrease about 50 percent greater than that usually 

 given for the Wisconsin (less than 30,000 years B.P.), early Wisconsin. This 

 stand of the sea is well shown by recent submarine exploration. (Authors) . 



077 DONOVAN, A. D., BAUM, G. R. , BLECHSCHMIDT, G. L. , LOUTIT, T. S., PFLUM, 

 C. E., and VAIL, P. R. 1988. "Sequence Stratigraphic Setting of the 

 Cretaceous-Tertiary Boundary in Central Alabama," Wilgus , C. K. , Hastings, B. 

 S. , Kendall, C. G. , Posamentier, H. W. , Ross, C. A. , and Van Wagoner, J. C. , 

 eds . , Sea-Level Changes: An Integrated Approach . Special Publication No. 42, 

 Society of Economic Paleontologists and Mineralogists, Tulsa, OK, pp 299-308. 



In central Alabama near the town of Braggs , a complete section across the 

 Cretaceous -Tertiary (K-T) boundary is present within the lower portion of the 

 Clayton Formation. The K-T microfauna and microfloral transition occurs 

 within a 2.5 m (8 ft.) section of interbedded sandstones and limestones that 

 directly overlies a sequence boundary, marked by regional truncation of the 

 underlying Prairie Bluff Formation. This sequence boundary is related to a 

 major eustatic fall in the late Maastrichtian (67 Ma). The interbedded 

 sandstones and limestones in the basal Clayton Formation are interpreted as 

 two backstepping marine parasequences deposited on the inner shelf during the 

 subsequent relative rise in sea- level. These two backstepping parasequences 

 are overlain, in turn, by 1.5 m (5 ft) of glauconite-rich strata representing 

 a condensed section produced during a period of slow terrigenous deposition, 

 continued parasequence backstepping, and shoreline retreat. 



Three small iridium anomalies have been identified at the Braggs 

 locality. These anomalies occur at marine- flooding surfaces, interpreted to 

 be parasequence boundaries, in the uppermost Prairie Bluff and basal Clayton 

 formations. The uppermost of these anomalies also coincides with the base of 

 the well-developed condensed section in the basal Clayton Formation. The 

 concurrence of iridium concentrations with marine-flooding surfaces at Braggs 

 suggests that iridium was present in the open ocean during the latest 

 Maastrichtian through earliest Danian but concentrated only during periods of 

 terrigenous-sediment starvation. Thus, variations in sediment supply and 

 possibly basin location are critical factors controlling iridium enrichment 

 across the K-T boundary. (Authors). ■ 



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