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

Normal fault growth models are largely based on the geometric relationship betweenfault displacement and length, and the seismically imaged record of accommodationdevelopment contained within syn-rift strata. Here, we infer variations in the style ofnormal fault growth across poorly exposed faulted margins through sedimentologicaland stratigraphic analysis of the syn-rift deposits. We analyze the along-strikevariability of normal-fault controlled deltaic systems to infer the evolution of thebasin-margin fault system. The geometry and displacement patterns are constrained.The Crati Basin (southern Italy) contains Pleistocene syn-rift deposits exposed inthe hanging wall of a c.45km-long normal fault system. We show that duringthe early extensional phase, shelf-type deltas were deposited along the entirestrike length of the fault system, suggestive of relativelyshallow-water depositsand early establishment of the fault. The later extensionalphase resulted in thedeposition of Gilbert-type deltas at the center and towards the northern end ofthe fault system, whereas shelf-type deltas persisted near the southern tip of thesystem. This stratigraphic evolution records the transition to a period when thefault system growth was characterized by displacement accumulation rather thanlengthening. We show that the detailed sedimentological and stratigraphic analysisof exposed ancient deltaic systems can be used to discriminate between modelsfor normal fault growth. Furthermore, displacement and accommodation variationsalong normal faults control the styles and depositional architecture of deltaic systemsin extensional settings. Results have important implications for interpreting basin-margin architectures and for predicting stratigraphic patterns in active extensional settings.