--> Relationships Between Fluvial Architecture and Fault Growth in Continental Rift Settings: A Database Approach

AAPG ACE 2018

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Relationships Between Fluvial Architecture and Fault Growth in Continental Rift Settings: A Database Approach

Abstract

Models predicting sedimentary architectures in continental rift settings lack quantitative evidence to demonstrate the relative influence of tectonics, climate, and sediment supply on depositional environments at multiple scales. Here, analysis and comparison of data from a variety of sources provides new models of fluvio-lacustrine response to rifting. This research aims to 1) determine the key differences in fluvio-lacustrine architectures between rifted basins of different structural and climatic settings; 2) statistically analyze how these differences at a variety of scales (gross depositional environment, depositional element, architectural element, and facies) transition and interact spatio-temporally over extensional domains.

The following data types have been collected: 1) system metrics derived from satellite imagery of the East African Rift System, where 33 rift basins were analyzed to classify depositional environment types and distributions for sub-humid to semi-arid environments in different structural settings (active rift, quiescent rift, and fault-replacement rift); geometries and transitions at environment, depositional element (e.g. fluvial channel belt) and architectural element (e.g. point bar) scale have been mapped; 2) field-derived data from a rift-basin fill in the Gulf of Corinth, Greece, which has allowed for characterization of the facies architecture related to the deposition of early-rift stage fluvio-deltaic conglomerate and sandstone. These results have been compiled along with literature-derived data sets in an analog database which enables quantitative comparisons of the geometry and distributions of sedimentary units from different settings. This allows for comparisons between fluvial successions in many different rift settings, and to deposits from other basin types.

The following results are demonstrated: 1) structural variabilities are the dominant control on environment distributions and sizes via their control on sediment input locations and catchment sizes; 2) subtle variations in climate exert a broad control on distributions and sizes of smaller-scale architectural elements and facies; 3) intra-rift faulting prevents development of basin-wide lakes by diverting fluvial inputs into localized depocenters.

Understanding the evolution of fluvio-lacustrine sedimentation in continental rifts allows the de-risking of reservoirs by providing quantitative data to describe sandbody connectedness and sand-fairway extent.