Steven L Dorobek2
(1) Instituto Mexicano del Petroleo, Colonia San Bartolo Atepehuacan, Mexico
(2) Texas A&M University, College Station, TX
Abstract: Stratigraphic architecture, platform evolution, and mud-mound development in the Lower Cupido Formation (Lower Cretaceous), Northeastern Mexico
The Lower Cretaceous Cupido Formation is part of an extensive carbonate platform system that extended from northeastern Mexico to Florida. The stratigraphic architecture of the lower Cupido Formation was studied in the Huasteca-Monterrey-Bustamante corridor, where the platform-margin-to-basin transitions are located. Kilometer-scale outcrops indicate that the early Cupido platform had a ramp-like profile. Three regionally correlatable, shallowing- and coarsening-upward stratigraphic packages were identified in the lower Cupido Formation. These 25 to 170 m-thick packages are interpreted as third-order (~1-3 Myr duration) "high-frequency sequences" (HFSs) and consist of basal, lime-mudstone-dominated, transgressive strata that are overlain by more grain-rich regressive facies. These HFSs have a larger-scale, progradational stacking pattern that reflects the long-term progradation of the Cupido platform.
Four sponge-microbial mound types of were also discovered in these strata. Type 1, siliceous sponge-microbial mud mounds, are the oldest and are associated with adjacent deep ramp/basinal lime mudstone facies. Type 2, sponge-microbial mud mounds, have adjacent outer-ramp packstone/wackestone facies. Type 3, sponge-microbial-coral mud mounds, have adjacent outer-ramp packstone facies. Type 4, skeletal-rich calcisponge-microbial-coral biodetrital mud mounds, have adjacent outer-ramp packstone and ramp-crest rudist-rich packstone facies. Mound-core facies (Type 1, 2, and 3 mounds) consist of sponge-microbial boundstone. Both the length and height of individual mounds range from a few to tens of meters. Only biodetrital mounds reach several hundred meters in width and are up to 90 m thick. The systematic changes in the attributes of the mounds were largely controlled by the ramp-like depositional profile and the long-term accommodation trends that influenced the Cupido platform during Early Cretaceous time.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana