Along-strike variability of fault-controlled deltaic systems (Crati Basin, southern Italy)

Normal fault growth models are largely based on the geometric relationship between fault displacement and length, and the seismically imaged record of accommodation development contained within syn-rift strata. However, it is possible to infer variations in the style of normal fault growth across poorly exposed faulted margins through the analysis of the sedimentology and stratigraphic architecture of the associated syn-rift deposits. Here, we analyze the stratigraphic and along-strike variability of normal-fault controlled deltaic systems to infer the evolution of their related basin-margin fault system, for which the geometry and displacement patterns are poorly constrained. The Crati Basin (southern Italy) contains Pleistocene syn-rift deposits exposed in the hangingwall of a c. 45 km-long normal fault system. We show that during an early extensional phase, shelf-type deltas were deposited along the entire strike length of the fault system, suggestive of relatively shallow water depths and early establishment of fault length. In contrast, a later extensional phase resulted in the deposition of Gilbert-type deltas at the center and towards the northern end of the fault system, whereas shelf-type deltas persisted near the system southern tip; this stratigraphic evolution records the transition to a period when the fault system growth was characterized by displacement accumulation rather than lengthening. We show that the detailed sedimentological and stratigraphic analysis of exposed ancient deltaic systems can be used to discriminate between models for normal fault growth and that, conversely, displacement and accommodation variations along normal faults control the styles and depositional architecture of deltaic systems in extensional settings.