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Quantification of Normal Fault Dimensions and Growth Evolution: Insights from mid-Ocean Spreading Ridges

Fox, Jeff L.1; Trudgill, Bruce 1
1 Geology, Colorado School of Mines, Golden, CO.

During the development of a rift system it is commonly observed that the early rift episode is characterized by a large population of short, low displacement faults. Through time the fault population tends to reduce while the active faults increase in length as well as displacement. Understanding which mechanism is applicable in fault growth and linkage is important in basin development as areas between overlapping faults prior to linkage are important sediment pathways into hanging-wall depocenters via relay-ramps. For the hydrocarbon exploration industry, these pathways can provide areas of high net to gross deposition. Despite the widespread occurrence of extensional fault systems within oceanic crust, and mid-ocean spreading ridges in particular, very little attention has been focused on how normal fault segments grow and interact in these tectonic regimes. Interpretation of Mid-Ocean Ridge morphology was performed using side-scan data to map structures and measure fault length, heave and separation. Initial results from data show evidence of faults connected at depth prior to linkage at the surface. Breached relay ramps are prevalent within the data set supporting this statement. The presence of abandoned fault “tails” is another strong indicator of linkage through the breaching of relay ramps. Linkage of faults at the surface occurs rapidly during the development of the rift, as the longest faults in the data set occur closest to the rift axis. The implication for such rapid fault linkage through relay ramp breaching would indicate that these ramps are short lived features and potential variability in fault growth evolution depending on the crustal material involved (oceanic vs transitional vs continental) needs to be considered in any general model for fault growth.


AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009