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

Article English OPEN
Mortimer, E ; Kirstein, LA ; Stuart, FM ; Strecker, MR (2016)

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.\ud \ud 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.\ud \ud 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.
  • References (11)
    11 references, page 1 of 2

    Armstrong, P.A., Taylor, A.R., Ehlers, T.A., 2004, Is the Wasatch fault footwall (Utah, United States) segmented over million-year time scales?: Geology, 32, 385-388.

    Fitzgerald, P. G. (1992), The Transantarctic Mountains of southern Victoria Land: The application of apatite fission track analysis to a rift shoulder uplift, Tectonics, 11, 634-662, doi:10.1029/91TC02495.

    Foeken, J.P.T., Stuart, F.M., Dobson, K.J., Persano, C.P., and Vilbert, D., 2006, A diode laser system for heating minerals for (U-Th)/He chronometry: Geochemistry, Geophysics, Geosystems, v. 7, DOI: 10.1029/2005GC001190 George, R., Rogers, N., and Kelley, S., 1998, Earliest magmatism in Ethiopia: Evidence for two mantle plumes in one flood basalt province: Geology, 26, 923-926.

    Gupta, S., Cowie, P.A., Dawers, N.H, & Underhill, J.R., 1998, A mechanism to explain rift-basin subsidence and stratigraphic patterns through fault array evolution: Geology, 26, 595-598.

    Gupta, A., and Scholz, C. H., 2000, A model of normal-fault interaction based on observations and theory, Journal of Structural Geology, 22, 865-879.

    Jackson, J., and McKenzie, D., 1983, The geometrical evolution of normal fault systems: Journal of Structural Geology, 5, 471-482.

    591 Ketcham, R., 2005, Forward and inverse modeling of low temperature 592 thermochronometry data: in Reiners, P.W., and Ehlers, T.A., eds., Low-temperature 593 thermochronology: Techniques, interpretations and applications: Reviews in 594 Mineralogy and Geochemistry, 58, 275-314.

    Ketcham, R.A., Gautheron, C., and Tassan-Got, L., 2011, Accounting for long alphaparticle stopping distances in (U-Th-Sm)/He geochronology: Refinement of the baseline case: Geochimica et Cosmochimica Acta, 75, 7779-7791.

    McConnell, R.,1972, Geological development of the rift system of East Africa: GSA Bulletin, 83(9), 2549-2572, doi:10.1144/gsl.sp.1978.006.01.04.

    Nyblade, A.A., Pollack, H.N., Jones, D.L., Podmore, F., and Musjayandebvu, M., 1990, Terrestrial heat flow in East and Southern Africa: Journal of Geophysical Research, 95, 17,371-17,384.

  • Metrics
    No metrics available
Share - Bookmark