Spatio-temporal trends in normal-fault segmentation recorded by low-temperature thermochronology: Livingstone fault scarp, Malawi Rift, East African Rift System

Mortimer, E., Kirstein, L. A., Stuart, F. M. and Strecker, M. R. (2016) Spatio-temporal trends in normal-fault segmentation recorded by low-temperature thermochronology: Livingstone fault scarp, Malawi Rift, East African Rift System. Earth and Planetary Science Letters, 455, pp. 62-72. (doi:10.1016/j.epsl.2016.08.040)

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Abstract

The evolution of through-going normal-fault arrays from initial nucleation to growth and subsequent interaction and mechanical linkage is well documented in many extensional provinces. Over time, these processes lead to predictable spatial and temporal variations in the amount and rate of displacement accumulated along strike of individual fault segments, which should be manifested in the patterns of footwall exhumation. Here, we investigate the along-strike and vertical distribution of low-temperature apatite (U–Th)/He (AHe) cooling ages along the bounding fault system, the Livingstone fault, of the Karonga Basin of the northern Malawi Rift. The fault evolution and linkage from rift initiation to the present day has been previously constrained through investigations of the hanging wall basin fill. The new cooling ages from the footwall of the Livingstone fault can be related to the adjacent depocentre evolution and across a relay zone between two palaeo-fault segments. Our data are complimented by published apatite fission-track (AFT) data and reveal significant variation in rock cooling history along-strike: the centre of the footwall yields younger cooling ages than the former tips of earlier fault segments that are now linked. This suggests that low-temperature thermochronology can detect fault interactions along strike. That these former segment boundaries are preserved within exhumed footwall rocks is a function of the relatively recent linkage of the system. Our study highlights that changes in AHe (and potentially AFT) ages associated with the along-strike displacement profile can occur over relatively short horizontal distances (of a few kilometres). This is fundamentally important in the assessment of the vertical cooling history of footwalls in extensional systems: temporal differences in the rate of tectonically driven exhumation at a given location along fault strike may be of greater importance in controlling changes in rates of vertical exhumation than commonly invoked climatic fluctuations.

Item Type:Articles
Additional Information:Funding for fieldwork, and analyses were provided to M.R. Strecker by DFG (Deutsche Forschungsgemeinschaft) grants STR 373/15-1 and 19-1.
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Stuart, Professor Finlay
Authors: Mortimer, E., Kirstein, L. A., Stuart, F. M., and Strecker, M. R.
College/School:College of Science and Engineering > Scottish Universities Environmental Research Centre
Journal Name:Earth and Planetary Science Letters
Publisher:Elsevier
ISSN:0012-821X
Published Online:04 October 2016
Copyright Holders:Copyright © 2016 Elsevier B.V.
First Published:First published in Earth and Planetary Science Letters 455: 62-72
Publisher Policy:Reproduced in accordance with the publisher copyright policy

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