Neogene current-modified submarine fans and associated bed forms in Mexican deep-water areas
Access full-text files
Date
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
The Mexico’s Gulf of Mexico Neogene record reflects the dynamic interaction
between high rates of sedimentation and tectonic processes. Distinctive Pliocene to
Miocene-age shingled seismic clinoforms reflections were identified in a previous study
using older data and interpreted as contourite drift deposits located east of the Mexican
Ridges in paleowater depths exceeding 400 meters. The database for this thesis includes
new and recently reprocessed seismic data, well logs and core information. Large scale
bedforms with seaward-dipping accretion sets (SDAS) are documented in several
geobodies mapped in the study area.
The objectives of this research are to evaluate the paleogeographic evolution of the
southwestern Gulf of Mexico and deepwater systems during Neogene, evaluating several
hypotheses for development of these unique SDAS deepwater bedforms, placing
observations in a regional context, and interpreting likely sediment sources and transport
pathways.
The SDAS were present in four geobodies, two of Upper Miocene (UM) age, one
in the Mio-Pliocene (PL1) and another in the Pliocene (PGa) genetic sequence. Time
structure maps show progressive infill of the deep-water Veracruz Trough from the
southwest. Isochron maps show individual SDAS geobodies thinning basinwards,
paralleling trends of adjacent submarine fans. The geobodies were likely formed during an
episode of high precipitation and river discharge, modulated by tectonics, and a steep slope
that may have allowed frequent bypass of sediments to the basin. SDAS show a series of
internal structures climbing upward and landward that are interpreted as cyclic steps
bedforms deposited by high-velocity, supercritical turbidity flows. Geobody 2 is associated
with an adjacent channel complex and may be a product of unconfined, levee overbanking
flows. Other geobodies are associated with submarine fan mounds.
The Mexican Ridges foldbelt may have steered southerly longshore and along slope
flow into the nearby Cañonero Canyon, then diverting turbidity flows to the east. The early
forming Mexican Ridges may also have created a steep slope gradient and bottom
roughness that facilitated local development of hydraulic jumps, a prerequisite for
generation of cyclic steps bedforms. Identification of these unusual bedforms in Pliocene
and Miocene strata of deepwater Mexico represents one of first documented occurrence in
subsurface settings.