Skip to Main Content

Abstract

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.

You do not currently have access to this chapter.

Figures & Tables

Contents

GeoRef

References

Related

Citing Books via

Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal