SIMS, DARRELL, DAVID A. FERRILL, and
JOHN A. STAMATAKOS
CNWRA, Southwest Research Institute, San
Antonio, TX
Abstract: Pull-apart Basin Development Controlled by Rheology and Thickness of Detachment Zone
Classically, pull-apart basins are rhomb-shaped normal-faulted grabens or half grabens that form at releasing bends in strike-slip fault systems. Natural examples include Death Valley, eastern California. The structural styles of many basins in transtensional settings along strike-slip systems do not fit the classic Death Valley model. Pull-apart basins with normal-oblique-slip master faults along asymmetric basins are developed in the Gulf of Elat (Aqaba) and the Gulf of Paria (Venezuela and Trinidad). Experimental results from physical models of pull-apart basins indicate that detachment zone rheology and thickness controls structural style in pull-apart basin development. Models with a 5 cm thick sandpack riding upon a thin, strong detachment layer (plastic sheet) result in rhomb-shaped single basins with normal-slip master faults. Models with a thick (1.0 cm) viscous layer (silicone putty) separating sandpack from plastic sheet result in elongate, isolated asymmetric sub-basins with normal-oblique-slip master faults. Models with a thin (0.5 cm) viscous layer result in coalescing elongate asymmetric sub-basins with normal-oblique-slip master faults separated by intra-basin highs. Death Valley, a halfgraben pull-apart terminated by strike-slip faults, is replicated in strong detachment models. The Gulf of Elat, an elongate, narrow system of asymmetric sub-basins with normal - obliqueslip master faults and detachments in shale and salt is replicated in models with a thick viscous layer. The Gulf of Paria, a coalescing system of sub-parallel, elongate, asymmetric basins with normal-oblique-slip master faults separated by intra-basin highs is replicated in models with thin viscous layers.
* Work supported by the U.S.NRC (Contract NRC-02-97-009). This work is an independent product of the CNWRA and does not necessarily reflect the views or regulatory position of the NRC.
AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas