Tectono-Stratigraphic Development of the Progreso Pull-Apart Basin in Southwestern Ecuador

Palencia, Ally; Aleman, Antenor; Aguilar, Rafael; Barba, Diego P.; Lezama, Eduardo; Rivadeneira, Marco; and Ortega, Richard A.^1
1[email protected]

The Oligocene to late Miocene Progreso pull-apart Basin is bounded by the La Cruz and Carrizal main faults to the southwest and northeast respectively. The pull-apart developed as a result of anticlockwise rotation of the Chongon-Colonche High, which also explains the odd orientation of this structural feature. Alternatively, this pull-apart basin can also be explained if the La Cruz Fault was originally a left lateral and The Carrizal Fault a synthetic Riedel.

Nevertheless, 3D seismic interpretation is consistent and supports the anticlockwise rotation as documented by episodic deposition of sedimentary sequences that record the temporal and spatial activity of the main faults. Rotation and pronounced footwall uplift of the Carrizal Fault was concomitant with development and deposition of thick alluvial fans and fan-deltas as recorded on wells while deposition along the La Cruz Fault was dominated by relative thin fluvio-deltaic facies reworked by waves and currents. Persistence of episodic anticlockwise rotation is documented by development of progressive unconformities and thicker depositional sequences along the Carrizal Fault from Oligocene until early late Miocene when rotation terminated. Cessation of rotation is recorded by significant depositional shifting coeval with conspicuous footwall uplift along La Cruz Fault and development of a distinctive unconformity near the base of Late Miocene sequence. This thick Late Miocene deposition along this fault documented rotation termination and initiation of pervasive strike slip faulting incision in the basin. Indeed, two possible transfer faults developed during pull-apart opening were perhaps reactivated during the Late Miocene as synthetic Riedels of the Guayaquil Fault. The variable pathway of these Riedels gave rise to complex transpressive and transtensive deformation and Late Miocene sharp thickness and facies changes. The northernmost, the Rodeo Riedel has been interpreted as possible conduits for hydrocarbon migration for the oil fields in the Santa Elena Peneinsula.

AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013