Combining bulk sediment OSL and meteoric 10 Be fingerprinting techniques to identify gully initiation sites and erosion depths

Portenga, E.W., Bishop, P., Rood, D.H. and Bierman, P.R. (2017) Combining bulk sediment OSL and meteoric 10 Be fingerprinting techniques to identify gully initiation sites and erosion depths. Journal of Geophysical Research: Earth Surface, 122(2), pp. 513-527. (doi: 10.1002/2016JF004052)

Abstract

Deep erosional gullies dissect landscapes around the world. Existing erosion models focus on predicting where gullies might begin to erode, but identifying where existing gullies were initiated and under what conditions is difficult, especially when historical records are unavailable. Here we outline a new approach for fingerprinting alluvium and tracing it back to its source by combining bulk sediment optically stimulated luminescence (bulk OSL) and meteoric 10Be (10Bem) measurements made on gully-derived alluvium samples. In doing so, we identify where gully erosion was initiated and infer the conditions under which such erosion occurred. As both 10Bem and bulk OSL data have distinctive depth profiles in different uneroded and depositional settings, we are able to identify the likely incision depths in potential alluvium source areas. We demonstrate our technique at Birchams Creek in the southeastern Australian Tablelands—a well-studied and recent example of gully incision that exemplifies a regional landscape transition from unchanneled swampy meadow wetlands to gully incision and subsequent wetland burial by post-European settlement alluvium. We find that such historic alluvium was derived from a shallow erosion of valley fill upstream of former swampy meadows and was deposited down the center of the valley. Incision likely followed catchment deforestation and the introduction of livestock, which overgrazed and congregated in valley bottoms in the early 20th century during a period of drought. As a result, severe gully erosion was likely initiated in localized, compacted, and oversteepened reaches of the valley bottom.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Portenga, Mr Eric and Rood, Dr Dylan and Bishop, Professor Paul
• Authors: Portenga, E.W., Bishop, P., Rood, D.H., and Bierman, P.R.
• College/School: College of Science and Engineering > School of Geographical and Earth Sciences; College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Journal of Geophysical Research: Earth Surface
• Publisher: Wiley
• ISSN: 2169-9003
• ISSN (Online): 2169-9011
• Published Online: 11 January 2017
• Copyright Holders: Copyright © 2017 American Geophysical Union
• First Published: First published in Journal of Geophysical Research: Earth Surface 122(2):513-527
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher