Relationship Between Upper Miocene-Pliocene Depocenters in Offshore Southern Laguna Madre-Tuxpan and Modern River Axes in Eastern Mexico: Clues to Neogene Sediment Dispersal in the Southwestern Gulf of Mexico

Edgar H. Guevara¹, William A. Ambrose¹, Mario Aranda-García², Dallas B. Dunlap¹, Timothy F. Wawrzyniec³, Khaled Fouad¹, and Ulises Hernández-Romano^2
1 Bureau of Economic Geology, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas
² Pemex Exploración y Producción, Poza Rica, México
³ University of New Mexico, Albuquerque, New Mexico

A comparison was made between the locations of upper Miocene-Pliocene depocenters in the offshore Laguna Madre-Tuxpan continental shelf and axes of principal modern fluvial networks in the eastern Mexico coastal plain. The study was conducted to help understand Neogene dispersal patterns by ascertaining relationships between the seismically interpreted offshore depocenters and sites of significant sedimentation in the southwestern Gulf of Mexico.

From north to south, the principal rivers in the study area are Soto La Marina, Pánuco, Tuxpan, Cazones, Tecolutla, and Nautla. The Pánuco and Tuxpan rivers have built Holocene wave-dominated deltas that reflect local, relatively large fluvial input and subsequent marine transport and modification by longshore currents and waves. Also, local sand-rich facies along the coast and older beach ridges at Cabo Rojo (a prominent coastal feature south of the Pánuco river that is largely controlled by the Cretaceous shelf margin) are examples of marine reworking of modern and relict sediments, respectively.

The offshore upper Miocene-Pliocene-age depocenters are inferred from regional trends on isochron maps. They are as much as 70 km long and 1-20 km wide and largely reflect growth-fault control of lowstand progradational wedges. They contain discrete thickness maxima as much as 25 km long and 1-20 km wide that locally extend basinward as thinner intervals interpreted as lowstand deposits downdip from these depocenters.

Neogene depocenters shifted through time and exist today largely as clusters downdip of modern fluvial axes. This suggests that they contain lowstand deposits of ancestral, shifting fluvial networks, reworked by marine processes.

AAPG Search and Discovery Article #90032©2004 GCAGS 54th Annual Convention, San Antonio, Texas, October 10-12, 2004