Peter Haber is a graduate student advised by Dr. Saltzman, here he describes how the Friends of Orton Hall fund contributed to his research.
Early Mississippian δ44/40Ca stratigraphy and implications for conditions of carbonate deposition
Coauthors: Matthew R. Saltzman, Elizabeth M. Griffith, Y. Datu Adiatma
A +5.5 ‰ to +7.0 ‰ magnitude δ13C excursion, known as the Kinderhokian Osagean Boundary Excursion or KOBE, is preserved in lower Mississippian strata (during the Tournasian age, ca. 353 Ma) in North America, Europe, and East Asia. This has been linked to an interval of cooling as part of a long-term shift from greenhouse to icehouse conditions. One proposed cause of the cooling is the rise of vascular land plants which increased silicate weathering, CO2 consumption, and phosphorus delivery to the oceans, which enhanced primary production and burial of organic matter to produce the δ13C excursion. However, the link between burial of organic matter and δ13C remains unclear because potential local controls on δ13C, which include diagenetic or mineralogic controls in shallow platform carbonates, can potentially decouple the shallow platform δ13C signal from the primary global DIC. This study pairs δ44Ca data with Sr/Ca and δ13C to examine the possible diagenetic and mineralogic (calcite or aragonite) controls on the magnitude of the δ13C excursion. We present a bulk carbonate δ44/40Ca record across this lower Mississippian stratigraphic interval from the Confusion Range, Utah. The beginning and end of the δ13C excursion have identical values of δ44/40Ca (relative to the SRM915a standard) around 0.80 ‰ and similar Sr/Ca while δ13C values shift from 2.64 to –0.02 ‰, suggesting there is not covariation associated with diagenetic or mineralogic controls. Future work will provide higher resolution δ44Ca data across this interval, along with Sr/Ca to pair with previously measured δ13C. The award from Friends of Orton Hall went toward costs of running samples for trace element and δ44/40Ca analyses.