Pedogenic carbonate carbon isotopic constraints on paleoprecipitation: Evolution of desert in the Pacific Northwest, USA, in response to topographic development of the Cascade Range

The Cascade Range in the northwestern U.S. acts as an orographic barrier to the easterly movement of humid air masses from the Pacific Ocean, producing a massive rain shadow with arid to semi-arid climate conditions on the leeward side of the range. Pedogenic carbonates formed in the C 3-dominated l...

Full description

Saved in:
Bibliographic Details
Published in:Chemical geology 2010-10, Vol.277 (3), p.323-335
Main Authors: Takeuchi, Akinori, Hren, Michael T., Smith, Shane V., Chamberlain, C. Page, Larson, Peter B.
Format: Article
Language:English
Subjects:
Carbonates
Cascade Range
Cascades
Desertification
Deserts
Mountains
Northwest
Paleoprecipitation
Pedogenic carbonate
Rain
Regional
Shadows
Stable isotopes
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The Cascade Range in the northwestern U.S. acts as an orographic barrier to the easterly movement of humid air masses from the Pacific Ocean, producing a massive rain shadow with arid to semi-arid climate conditions on the leeward side of the range. Pedogenic carbonates formed in the C 3-dominated landscapes east of the range have δ 13C carbonate that is enriched by approximately 4‰ relative to carbonates formed in sub-tropical C 3-dominated ecosystems. We measured stable isotopic compositions of pedogenic carbonates preserved in the Quaternary and Neogene sedimentary rock units in the inland Pacific Northwest, and examined the impact of long-term aridification and paleohydrology on their isotopic compositions. The determined δ 13C carbonate record shows a gradual increase of 5‰ from approximately − 10‰ in older pedogenic carbonates to − 5‰ in younger ones whereas δ 18O carbonate record indicates a decrease of approximately 4‰ in the late Neogene. In addition, the Quaternary δ 13C carbonate and δ 18O carbonate records indicate the highest δ 13C and δ 18O among the samples during the Pleistocene and significant fluctuation over the time period. The gradual increase in the δ 13C carbonate and the decrease in the δ 18O carbonate in the late Neogene are interpreted by the development of the rain shadow as a result of topographic development of the Cascade Range. Changes in the Quaternary isotope records suggest a decrease in regional precipitation and isotopically depleted winter precipitation, resulting from changes in large-scale atmospheric circulation patterns due to advance and retreat of northern hemisphere continental ice sheet. The isotope record from pedogenic carbonates provides a direct record of climatic change, suggesting that long-term carbon isotope data can provide useful constraints on timing and intensity of regional desertification, and its associated climate and topographic interaction. ► Deserts exist on the leeward side of mountain ranges. ► δ 13C of pedogenic carbonates increase with decreasing in MAP. ► Cenozoic ™13C soil carbonate in the Pacific Northwest increases with decreasing age. ► Evolution of the Cascade Range resulted in the regional desertification.
ISSN:0009-2541
1872-6836
DOI:10.1016/j.chemgeo.2010.08.015