Loess-paleosol carbonate clumped isotope record of late Pleistocene-Holocene climate change in the Palouse region, Washington State, USA

Document Type

Article

Publication Date

9-1-2018

Publication Title

Quaternary Research United States

Keywords

Clumped isotope, LGM, Loess, Paleoclimate, Paleosol, Palouse, Pedogenic carbonate

Abstract

The Channeled Scabland-Palouse region of the Pacific Northwest (PNW) of the United States preserves geomorphic and pedosedimentary records that inform understanding of late Pleistocene-Holocene paleoclimate change in a region proximal to the last glacial period Cordilleran Ice Sheet. We present a clumped (Δ47) and conventional (δ18O, δ13C) isotopic study of Palouse loess-paleosol carbonates in combination with carbonate radiocarbon (14C) dating to provide new measures of regional late-last glacial (31-20 cal ka BP) and Holocene soil conditions. Average clumped isotope temperatures (T(Δ47)) for last glacial Palouse loess-paleosol carbonates (9±4°C) are significantly lower than those for Holocene-aged carbonates (T(Δ47)=18±2°C) in study sections. Calculated soil water δ18OVSMOW values (-16±2‰) for last glacial carbonates are also offset relative to those for Holocene-aged samples (-11±1‰), whereas calculated soil CO2 δ13CVPDB values are similar for the Holocene (-16.9±0.2‰) and late-last glacial (-16.7±1.1‰) periods. Together, these paleoclimate metrics indicate late-last glacial conditions of pedogenic carbonate formation in the C3 grassland soils of the Palouse were measurably colder (9±5°C) than during the Holocene and potentially reflect a more arid last glacial paleoclimate across the Palouse, findings in agreement with previous proxy studies and climate model simulations for the region.

Volume

90

Issue

2

First Page

331

Last Page

347

ISSN

00335894

E-ISSN

10960287

DOI

10.1017/qua.2018.47

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