Geomorphic significance of postglacial bedrock scarps on normal-fault footwalls
Tucker, G.E. and McCoy, S.W. and Whittaker, A.C. and Roberts, Gerald P. and Lancaster, S.T. and Phillips, R.J. (2011) Geomorphic significance of postglacial bedrock scarps on normal-fault footwalls. Journal of Geophysical Research: Earth Surface 116 , ISSN 0148-0227.
The existence of well-preserved Holocene bedrock fault scarps along active normal faults in the Mediterranean region and elsewhere suggests a dramatic reduction in rates of rock weathering and erosion that correlates with the transition from glacial to interglacial climate. We test and quantify this interpretation using a case study in the Italian Central Apennines. Holocene rates are derived from measurements of weathering-pit depth along the Magnola scarp, where previous cosmogenic Cl-36 analyses constrain exposure history. To estimate the average hillslope erosion rate over similar to 10(5) years, we introduce a simple geometric model of normal-fault footwall slope evolution. The model predicts that the gradient of a weathering-limited footwall hillslope is set by fault dip angle and the ratio of slip rate to erosion rate; if either slip or erosion rate is known, the other can be derived. Applying this model to the Magnola fault yields an estimated average weathering rate on the order of 0.2-0.4 mm/yr, more than 10 times higher than either the Holocene scarp weathering rate or modern regional limestone weathering rates. A numerical model of footwall growth and erosion, in which erosion rate tracks the oxygen-isotope curve, reproduces the main features of hillslope and scarp morphology and suggests that the hillslope erosion rate has varied by about a factor of 30 over the past one to two glacial cycles. We conclude that preservation of carbonate fault scarps reflects strong climatic control on rock breakdown by frost cracking.
|School:||Birkbeck Schools and Departments > School of Science > Earth and Planetary Sciences|
|Date Deposited:||17 Jun 2011 10:56|
|Last Modified:||17 Apr 2013 12:20|
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