MSEC data sets record glacially driven cyclicity: Examples from the arrow canyon Mississippian-Pennsylvanian GSSP and associated sections

Here we report magnetic susceptibility (MS) analyses from three, mainly marine sections, the Mississippian-Pennsylvanian (Mid-Carboniferous) Global Boundary Stratotype Section and Point (GSSP) in Arrow Canyon, SE Nevada, and two secondary sections nearby-one in Arrow Canyon (similar to 200 in distant) and the second in Battleship Wash, (similar to 2 km south of the GSSP). All three sections are easily correlated using the magnetosusceptibility event and cyclostratigraphy method (MSEC). Cyclicity is clearly apparent in all three sections, and Time-Series analysis independently verifies the MS zonation developed from the smoothed data set. The periods determined in the three sections support the argument that deposition of these Mid-Carboniferous rocks resulted from climate-controlled glacio-eustatic fluctuations that were driven by Gondwana glaciation. Given the published average thicknesses of T-R cycles (> 50 m) and the estimates for timing of glacial-interglacial cyclicity during the Mid Carboniferous, we assign the strong FT peak observed for the three MS data sets a value of similar to 400,000 years, corresponding to the Milankovitch El eccentricity band. We then calculate a Floating Point Time Scale (FPTS) for the sampled sequence. The FPTS results indicate that (1) sediment accumulation rates bracketing the Mid-Carboniferous boundary averaged similar to 0.7 cm/1000 years, and (2) were relatively constant for these reference sections. (c) 2007 Elsevier B.V. All rights reserved.