14 Soils: Processes at the Bio-Geo Interface

Sunday, 17 March 2019
1:30 PM - 5:30 PM
Connecticut Room

RECONSTRUCTION OF MIDDLE PLEISTOCENE INTERGLACIAL PALEOCLIMATE FROM TWO BURIED PALEOSOLS IN THE PO PLAIN, NORTHERN ITALY AND COMPARISON TO PALEOSOLS IN THE EASTERN US

Paper number: 14-10
Program: Theme Sessions
Time: 4:30 PM – 4:50 PM

Authors

Abstract

Pleistocene soils and paleosols integrate a paleoclimate record of past environmental conditions that are a window into future environmental trends driven by global change. Exposed in the Enza River valley, a tributary to the Po River of northern Italy are continuous, cyclic, Pleistocene deposits with several well-preserved, buried paleosols of diverse color, thickness, and parent material. Here we present data that interprets paleosol formation in the context of glacial-interglacial climate and cyclic deposition of variable parent material in a subsiding basin. Two soils, one at the top (~600ka, Qt1) and a second at the base (~160ka, Qt3) of the Enza exposures were sampled for this study at 20-40 cm vertical intervals. These soils have been analyzed for texture (particle size distribution anaylsis, PSDA), the iron oxalate-extractable to dithionite-extractable ratio (FeO/FeD), and the goethite to hematite ratio (G/H) which stand as proxies for total degree of chemical alteration, degree of iron crystallinity and climate seasonality, and mean annual precipitation, respectively. Textural analyses show expected concentrations of pedogenic clay consistent with field descriptions of soil horizons. Differences in FeO/FeD and G/H are expected to match the field observations in soil color and presence of iron oxide and magnesium oxide nodules. For example, the Qt1 paleosol has deep red (2.5R) colors and ironstone at horizon boundaries. In contrast, the Qt3 paleosol has red-orange colors and distinctive 2 cm ironstone nodules. Variations in iron oxide chemistry for these paleosols are compared to a growing database of similar aged paleosols on the east coast of the United States with the goal of determining a global versus local paleoclimate signal. The paleosol data also helps to evaluate an emerging model for the climatic drivers of depositional unsteadiness in the Po Plain.

Geological Society of America Abstracts with Programs. Vol. 51, No. 1

doi: 10.1130/abs/2019NE-326625

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