Tectonic driven changes in Tertiary Burgos basin sediment provenance, Gulf of Mexico

Abstract

Reconstruction of reservoir composition and location contributes to risk reduction in hydrocarbon exploration providing insight in the presence and quality of reservoir rock in the basin. To address these issues, the source-to-sink relationship needed to be established between hinterland as the source and the basin as the sink over the geological period of interest. This link is provided by the rivers that erode the sediments from their source and that transport these sediments to the basin. The river networks dynamically evolve over time, though they are often regarded as fixed. Over short geological periods that may be true. In Mexico however, continued deformation, magmatism, uplift and erosion resulted in a differential topographic evolution of the hinterland. Recent studies have attempted to establish a source-to-sink relationship using petrographic information from cores taken from wells and field data for the basins in the Mexican Gulf of Mexico. In this paper we focus on changes in drainage that have taken place during the Pliocene to Present (part of full study of the Tertiary) and what the consequences have been on the provenance of clastic Pliocene reservoirs in the Burgos Basin in the Gulf of Mexico. Our integrated morpho-tectonic, drainage and denudation analysis combined with gravity and magnetic data interpretation of the hinterland enables to reconstruct paleo-drainage, paleo-geographic and paleo-geologic maps, an approach that is successfully applied in Petroleum Exploration along passive, transform and active margins. The Rio Bravo drainage system in northern Mexico and southwestern USA for instance developed in response to the Oligocene/Miocene Rio Grande rifting events and thereby shaping the main conduit for the upstream proto Bravo drainage. Although originally the drainage basin was restricted to the graben proper, the tributaries and preserved geomorphology show evidence of later incision of the rift flanks, capturing the rift shoulder hinterland on both sides of the rift. The Bravo trunk river located downstream started to migrate upward from the paleo coastline, capturing drainage basins in the north and northwest including the evolving Rio Grande Rift and El Barreal and various other river networks. The El Barreal is one of those isolated drainage basins at present, located in the NW of the larger Bravo drainage basin. From the integrated analyses it is concluded that it recently became disconnected from the larger paleo Bravo drainage basin. After the basin-and-range deformation ceased in the Oligocene, the evolving divides that formed the barriers to rivers were produced by NW-SE strike-slip faults and N-S normal faults and associated folds. Elsewhere in the drainage basin, salt supporting anticlines and salt extrusions forced the rivers to detour. In addition, volcanic activity in the region contributed to stream deflections as in the case of El Barreal-Bravo divide. The analyses on potential fields data proved very useful in the detection of subsurface structures that played a role in the changing river networks. We demonstrate that not only the denuded rock volume changed during the various Tertiary intervals, and with particular focus on the Pliocene here, with changing drainage area and denudation magnitudes but also the bedrock mineral composition changed as exhumation exposed older rocks to the surface and igneous activity and salt tectonics added new rocks – bedrock available for erosion and sand supply to the Burgos basin.

AAPG Datapages/Search and Discovery Article #90325 © 2018 AAPG Europe Regional Conference, Global Analogues of the Atlantic Margin, Lisbon, Portugal, May 2-3, 2018