53 Devonian Climate and Paleoecology—Insight from Stratigraphic Studies II

Tuesday, 22 March 2011
8:00 AM - 12:00 PM
Conference A

MIDDLE DEVONIAN LANDSCAPES, CLIMATES AND THE CORRELATION OF CONTINENTAL STRATA IN THE NORTHERN APPALACHIAN BASIN

Paper number: 53-2
Program: Symposia Sessions
Time: 8:20 AM – 8:40 AM

Authors

Abstract

Middle Devonian terrestrial strata deposited in the Appalachian Basin, known as the Catskill Delta, record dynamic landscapes influenced by rainfall seasonality, tectonically driven changes in sedimentation and the onset of forested ecosystems. The Catskill Delta is a clastic wedge created by the Acadian orogen which formed during the Devonian as a series of tectophases as the island arc Avalon accreted obliquely onto the Laurentian continent. These tectophases are a series of orogenic events that generated accommodation and increased sediment yield into the Appalachian Basin. From this study we measured over 450 meters of nearly continuous outcrop exposure along Plattekill Creek in West Saugerties, New York, to develop a sequence stratigraphic framework using alluvial stacking pattern analysis. The analysis reveals several orders of cyclicity that correspond with Acadian tectophases and previously documented marine depositional sequences. As such, we present a terrestrial to marine stratigraphic correlation in the Appalachian basin.

Paleosols in this succession are dominantly hydromorphic in nature and are classified as paleo-Vertisols and paleo-vertic Inceptisols. Hydromorphic features include slickensides, gleying of paleosol matrix and concentrations of Fe/Mn nodules. These paleosols preserve the earliest examples of forested ecosystems on earth which occurred in a variety of landscapes. This onset of forestation increased landscape stability and pedogenesis, which had major impacts on many surficial processes. One such impact we explore is the potential effects of forestation on marine organic productivity through increased weathering of bio limiting nutrients.

The depth to Bk horizon within paleosols suggest that the Devonian paleoclimates of the Appalachian Basin ranged from semi-arid to arid. Using the paleo-precipitation proxy CALMAG, a geochemical ratio from bulk soil material in vertic paleosols, we analyze a suite of 37 paleosols in the Middle Devonian that suggests humid climates rather than semi-arid in the Middle Devonian. We compare paleosol morphologies and relative base-level through the section to these different paleosol paleoclimate proxies to suggest potential causes for discrepancies in data.