Revision to Nomenclature of the Zarah Subgroup of the Kansas City Group (Pennsylvanian) in Kansas

This paper provides a summary review of proposed nomenclatural revisions to the Zarah Subgroup of the Kansas City Group (Pennsylvanian) in Kansas and outlines changes adopted by the Kansas Geological Survey. The Iola Limestone, which comprises in ascending order the Paola Limestone, Muncie Creek Shale, and Raytown Limestone Members, is now considered the basal formation of the Zarah Subgroup. We reinstate the overlying Liberty Memorial Shale as originally defined by Clair (1943) in the area of Kansas City, Missouri. We also restrict the Wyandotte Limestone to include only, in ascending order, the Frisbie Limestone, Quindaro Shale, and Argentine Limestone Members. Furthermore, the Lane Shale is restricted in use and encompasses all strata within the shale-dominated interval between the top of the Argentine Limestone Member of the Wyandotte Limestone and the base of the overlying Plattsburg Limestone. Within the revised Lane Shale, the KGS now formally recognizes, in ascending order, the Lower Farley Limestone, Middle Farley Shale, and Upper Farley Limestone Members. The Bonner Springs Shale is now demoted in rank and included as the uppermost member within the Lane Shale.

Asynchronous δ13Ccarb and δ13Corg records during the onset of the Mulde (Silurian) positive carbon isotope excursion from the Altajme core, Gotland, Sweden

High-resolution paired analyses of δ13Ccarb and δ13Corg from a new drill core from Gotland, Sweden, demonstrate asynchronous positive change in the carbon isotope records during the onset of one of the major Silurian biogeochemical events known as the Mulde Event or “Big Crisis”. The detailed carbon isotope record presented here provides Δ13C (the difference between δ13Ccarb and δ13Corg) and allows the calculation of changes in organic carbon burial (forg) throughout the late Wenlock. The paired data suggest a ~ 38% increase in forg during the peak of the positive δ13Ccarb excursion and the high-resolution record reveals several short-lived inflections in Δ13C that have not been previously identified. When combined with sedimentological and sequence stratigraphic data from multiple paleocontinents, the new data presented here provide strong evidence for a transient global decrease in CO2, in support of previous interpretations of regression and global cooling coinciding with the Mulde Extinction Event

Decoupling δ13Ccarb and δ13Corg at the onset of the Ireviken Carbon Isotope Excursion : Δ13C and organic carbon burial (forg) during a Silurian oceanic anoxic event

Paired records of δ13Ccarb and δ13Corg across the Llandovery-Wenlock boundary demonstrate asynchronous behavior during the onset of the Ireviken Biogeochemical Event (IBE). The extremely high-resolution data produced from the Altajme Core, drilled from Gotland, Sweden, capture a negative excursion in δ13Corg during the initiation of the Ireviken Extinction Event (IEE) and prior to the onset of the Ireviken positive δ13Ccarb Excursion (ICIE). The record of carbon isotopic changes through this interval illustrate that both Δ13C (the difference between δ13Ccarb and δ13Corg) as well as the relative flux of organic carbon burial (forg) vary in unique ways and at different times during the progression of the IBE. Both process-oriented variables within the global carbon cycle (Δ13C and forg) track a series of events that help to demonstrate potential causative mechanisms of both the extinction and carbon cycle perturbation. The sequence of events demonstrated here largely mirror the cascade of events that took place during the Cretaceous Oceanic Anoxic Event 2 (OAE2) and a detailed comparison between the two events is provided here for the first time. The unique insight into the IBE presented in this work results primarily from the novel, nearly Neogene-scale resolution of the paired isotope data, which demonstrates the critical importance of high-resolution chemostratigraphic research to evaluating ancient perturbations to the Earth-life system. Additional data sets of equal or greater resolution through this interval will be critical to evaluate the global synchroneity of these short-lived events during the IBE, and similar high-resolution studies of other Paleozoic biogeochemical events may shed light on potentially similar causative mechanisms

Cyclo and chemostratigraphic characteristics of the Middle Silurian in Gotland, Sweden

peer reviewe

Expansion of Reducing Marine Environments During the Ireviken Biogeochemical Event : Evidence From the Altajme Core, Gotland, Sweden

New δ34Spy (pyrite) and δ34SCAS (carbonate-associated sulfate) across the Llandovery-Wenlock boundary (∼432 Ma) provide evidence for the expansion of reduced marine environments during the Ireviken Biogeochemical Event. This event consists of a major positive carbon isotope excursion, increased biotic turnover, and other major perturbations and changes within biogeochemical cycles. This interval of time has been hypothesized to coincide with an expansion of reducing marine environments that caused increased organic carbon burial and led to the Ireviken positive carbon isotope excursion (ICIE). Previous high-resolution carbon isotope work in the Altajme core from Gotland, Sweden provides the highest resolution record of the ICIE yet documented and provides an ideal expanded stratigraphic section to study this event. Local expansion of reduced marine environments within the deeper shelf setting of the Altajme core is indicated by a positive shift in δ34Spy values and increase in pyrite sulfur concentrations at the onset of the ICIE. These data are indicative of increased microbial sulfate reduction within this portion of the Baltic Basin. Combined with new δ34SCAS data from this core, as well as additional data from distant basins, the new data presented here suggest a global expansion of reduced environments led to an increase in organic carbon burial and the ICIE