Universität zu Köln

Binnie, A., Binnie, S. A., Parteli, E. J. R. and Dunai, T. J. (2020). The implications of sampling approach and geomorphological processes for cosmogenic Be-10 exposure dating of marine terraces. Nucl. Instrum. Methods Phys. Res. Sect. B-Beam Interact. Mater. Atoms, 467. S. 130 - 140. AMSTERDAM: ELSEVIER. ISSN 1872-9584

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Abstract

Concentrations of cosmogenic nuclides in rocks at the Earth's surface are routinely measured by AMS (accelerator mass spectrometry) to obtain exposure ages. One particular application of this technique has been to derive ages for the formation of marine terraces, thus allowing constraints to be placed on rates of tectonic uplift. However, multiple rock samples from the same terrace surface have typically shown an amount of scatter in cosmogenic nuclide concentrations in excess of analytical uncertainties, potentially undermining the confidence in the resulting uplift rates. In addition, earlier works have considered the application of bedrock samples for exposure age dating marine terraces, but little attention has been directed towards the validity of sampling clasts exposed on terrace surfaces. Here, we use Be-10 and Al-26 measurements from a flight of marine terraces in northern Chile to compare the results from pebbles with those from bedrock samples and to investigate assumptions that sample pre-exposure and burial are negligible. We examine the influence that processes of surface deflation and pebble erosion will have on cosmogenic nuclide concentrations using a Monte Carlo model, the results of which are compared to our Be-10 measurements. We find good agreement of Be-10 concentrations between bedrock and pebble samples. At the sampled location, sample burial is rare and Be-10 inheritance in pebble samples is low relative to the age of the terraces. Our modelling suggests that in arid environments, such as northern Chile, pebble erosion will be a secondary effect compared to surface deflation and that multiple periods of deflation will result in multimodal distributions of Be-10 concentrations. More broadly, our findings show that measuring multiple surface clasts from a single marine terrace reveals the geomorphological processes influencing exposure ages, and may also be used to help identify the operation of past surface processes such as episodic deflation.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Binnie, A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Binnie, S. A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Parteli, E. J. R. UNSPECIFIED UNSPECIFIED UNSPECIFIED Dunai, T. J. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-340925
DOI:	10.1016/j.nimb.2019.12.017
Journal or Publication Title:	Nucl. Instrum. Methods Phys. Res. Sect. B-Beam Interact. Mater. Atoms
Volume:	467
Page Range:	S. 130 - 140
Date:	2020
Publisher:	ELSEVIER
Place of Publication:	AMSTERDAM
ISSN:	1872-9584
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language NUCLIDE PRODUCTION-RATES; FLUVIAL TERRACES; UPLIFT RATE; AL-26; QUATERNARY; CALIFORNIA; FJORDLAND; SURFACES; ROCKS; RIVER Multiple languages Instruments & Instrumentation; Nuclear Science & Technology; Physics, Atomic, Molecular & Chemical; Physics, Nuclear Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/34092