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 them to the basins. The river networks dynamically evolve over time, though they are often regarded as fixed. Over short geological periods that may be occasionally true. In Mexico, however, continued deformation, magmatism, uplift and erosion resulted in very dynamic topographic evolution of the hinterland. Recent studies have attempted to establish a source-to-sink relationship using petrographic information from cores obtained from boreholes as well as field data for the basins in the Mexican Gulf of Mexico. In this paper we focus on the evolution of the drainage networks in Mexico for the Pliocene to Present time interval in terms of changes in the provenance and possible composition of clastics delivered to the Burgos (Perdido Fold Belt) Basin in the Gulf of Mexico (Figure 1). Our integrated morpho-tectonic, drainage and denudation analysis combined with gravity and magnetic data interpretation of the hinterland facilitated the reconstruction of paleo-drainage, paleo-geographic and paleo-geologic maps, an approach that is successfully applied in Petroleum Exploration along various continental margins from passive, transform and to active margins. The present 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 the drainage basin was restricted only to the graben proper in the beginning, the tributaries and preserved geomorphology provide evidence of later incision of the rift flanks, capturing the drainage network on the rift shoulder hinterland on both sides of the rift. The downstream part of the Bravo trunk river migrated upwards from the paleo coastline, capturing drainage basins in the north and northwest including the evolving Rio Grande Rift and El Barreal and various other smaller and isolated river networks. The El Barreal is one of those isolated drainage basins at present, located in the NW of the larger Bravo drainage basin. Our analyses show that it recently became disconnected from the larger paleo Bravo drainage basin (Figure 2). 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 cored anticlines and salt extrusions forced the rivers to detour occasionally. In addition, volcanic activity and deep seated structures detected on potential fields data contributed to the stream deflections as happened in front of the El Barreal-Bravo divide. We demonstrate that not only the denuded rock volume changed during the various Tertiary intervals, but also the drainage area and denudation magnitudes changed. 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. The drawdown also profoundly affected the petroleum geology of the Gulf of Mexico, most obviously by deposition of the basal Wilcox “Whopper Sand” in U.S. and Mexican waters. Further petroleum ramifications include porosity enhancement by leaching and fresh water infiltration of a) reefal carbonates of the Golden Lane Atoll, b) deep-water carbonate detritus reservoirs in the Poza Rica Trend and c) the Campeche Sound K/T breccias.

AAPG Datapages/Search and Discovery Article #90330©2018 AAPG Hedberg: Geology of Middle America – the Gulf of Mexico, Yucatan, Caribbean, Grenada and Tobago Basins and Their Margins “Integration of the geology of the area from the southern onshore of North America to the northern onshore of South America”, Siguenza, Guadalajara, Spain, July 2-5, 2018