Controls on Upper Cretaceous (Maastrichtian) Heterozoan Carbonate Platforms Developed on Salt Diapirs, La Popa Basin, Ne Mexico
Published:January 01, 2008
Katherine A. Giles, Dominic C. Druke, David W. Mercer, Lela Hunnicutt-Mack, 2008. "Controls on Upper Cretaceous (Maastrichtian) Heterozoan Carbonate Platforms Developed on Salt Diapirs, La Popa Basin, Ne Mexico", Controls on Carbonate Platform and Reef Development, Jeff Lukasik, J.A. (Toni) Simo
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In the distal part of the Late Cretaceous Hidalgoan foreland basin in NE Mexico three isolated carbonate platforms nucleated on seafloor topography created by rising passive diapirs. Carbonate facies type and architecture of each platform was distinctly influenced by a combination of both short-term local conditions surrounding individual diapirs and by long-term regional conditions that affected the entire shelf. Local conditions included windward-leeward platform paleogeography, possible elevated nutrient levels at the salt- sediment interface, and halokinesis. Regional conditions included eustatic sea-level changes, foreland-basin tectonism, and siliciclastic sediment supply to the shelf.
Maastrichtian carbonate-platform facies are distributed asymmetrically across individual diapirs, reflecting windward-margin versus leeward-margin paleogeographic setting and differential minibasin subsidence related to salt withdrawal. Southern (windward) margins are dominated by steep-sided sponge, coral, and red algal reefs displaying minor fore-reef progradation (< 1.5 km) into the adjacent minibasin, thick carbonate debris-flow beds containing diapir-derived detritus, and pervasive near-diapir halokinetic fracturing. In contrast, northern (leeward) margins are dominated by foraminifera, red algal grainstone banks displaying major progradation (3-4 km) into the adjacent minibasin and lack debris-flow beds or halokinetic fracturing. Carbonate facies at all the diapirs are primarily sand-prone, heterozoan faunal assemblages that are unusual for this period of time and paleogeographic location. The presence of heterozoan faunal assemblages may be in response to high nutrient levels from local methane seeps forming at the salt- sediment interface. Carbonate facies form the bases of angular-unconformity-bounded carbonate-siliciclastic cycles called halokinetic sequences. The cycles reflect local variations in net diapiric-rise rates versus local sediment accumulation rates. Halokinetic sequences vary in number and character between the different diapirs and between the windward and leeward margins of each diapir. On leeward margins, halokinetic sequences are more numerous and carbonate facies are dominated by grainstone banks, whereas on windward margins halokinetic sequences are amalgamated and carbonate facies are dominated by fore-reef debris and debris-flow facies.
The isolated carbonate platforms are best developed within the transgressive systems tracts (TST) of third-order deltaic siliciclastic depositional sequences within the regionally marine foreland-basin depositional system. Late Cretaceous to Paleogene Hidalgoan shortening of La Popa foreland basin formed large-wavelength (> 10 km) NW-SE trending salt-cored detachment folds. Diapirs that lie in the hinges of folds were shortened or “squeezed” significantly more than diapirs that lie on the limbs of folds. Squeezed diapirs generated much higher and broader topographic relief in response to higher diapiric rise rates and are correspondingly dominated by extensive, thick, shallow-water (< 15 m deep) sponge, red algal reef and grainstone-bank facies with carbonate strata extending more than 4 km away from the diapir. Age-equivalent carbonate strata on limb diapirs contain thin, deeper-water (> 30 m deep) silty, red algal packstone facies that extend < 2 km from the diapir, reflecting lower carbonate production rates in a deeper-water setting.
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Controls on Carbonate Platform and Reef Development
Carbonate platforms and reefs emerge, grow and die in response to intrinsic and extrinsic mechanisms forced primarily by tectonics, oceanography, climate, ecology and eustasy. These mechanisms, or controls, create the physical, biological and chemical signals accountable for the myriad of carbonate depositional responses that, together, form the complex depositional systems present in the modern and ancient settings. If we are to fully comprehend these systems, it is critical to ascertain which controls ultimately govern the “life cycle” of carbonate platforms and reefs and understand how these signals are recorded and preserved. Deciphering which signals produce a dominant sedimentological response from the plethora of physical and biological information generated from superimposed regional to global-scale controls is critical to achieving this goal. With this understanding, it may be possible to extract common time- and space-independent depositional responses to specific mechanisms that may, ultimately, be used in a productive sense. Extensive research on a wide variety of carbonate platform and reefal systems in the past few decades has provided the foundation and understanding necessary to take carbonate research to a new level. With assistance from rapidly advancing computer software and an increasing use of cross-disciplinary integration, carbonate research is shifting from description and morphological analysis towards a science that is more focused on the assessment of process and genetic relationships. The aim of this special publication is to present a cross section of recent research that shows this evolution from a variety of perspectives and scales using examples distributed throughout the Phanerozoic.