|
Description:
|
Major and trace element concentrations and microfaunal distributions were determined for a detailed section of the Haskell -Cass cycle (upper Vinland Shale , Haskell Limestone , and lower Robbins Shale ) near Peru , Kansas . Total organic carbon (TOC ) , loss on ignition (LOI ) , detrital elements , carbonate elements , trace and minor metals , and rare earth elements were analyzed and compared to the abundances of conodont elements and holothurian sclerites .
The lower Robbins Shale is a low organic carbon ( < 2 .0 wt . percent ) gray shale . This offshore shale is atypically thick due to moderate influx of fine terrigenous elastics . A geochemically anomalous interval occurs in the lower Robbins Shale . This interval has the highest TOC , limited siliceous detritus , and when normalized to aluminum , moderate peaks of vanadium , nickel , chromium , and copper . This geochemical pattern suggests that a brief period of high marine productivity ultimately caused reduced conditions . Vanadium is more concentrated higher in the section , unlike Ni , Cr , and Cu , and is a geochemical indicator of open marine conditions . Conodont abundance is unusually low and sclerites are absent in the anomalous interval , but conodonts return to the expected "core shale" levels higher in the section . Gondolella appears higher in the section where vanadium levels are greater . |