THE EFFECTS OF HALOKINESIS AND OROGENESIS ON CARBONATE PLATFORM DEVELOPMENT: THE UPPER CRETACEOUS SAN JOSE LENTIL, LA POPA BASIN, MEXICO

The San Jose carbonate lentil records the effects of both halokinesis and Hidalgoan (Laramide age) shortening within the La Popa basin of northeastern Mexico. The La Popa basin comprises a Cretaceous to Tertiary primarily shelfal siliciclastic depositional system that is locally punctuated by carbonate lentils that nucleated on bathymetric highs created by the extrusion of salt at or near the surface. All strata within the basin have been influenced by syndepositional salt diapirism and are organized into halokinetic sequences adjacent to salt bodies. The strata were also subjected to folding during shortening of the Sierra Madre foreland, but the timing of shortening was previously poorly constrained. The Late Cretaceous age San Jose carbonate lentil formed on salt diapir bathymetry created by diapir inflation associated with periods of slow siliciclastic sediment accumulation. The San Jose forms the basal strata of a halokinetic sequence that formed in response to changes in salt diapir rise rate relative to sediment accumulation rate.

The San Jose lentil primarily consist of off-bank facies with minor on-bank or reef deposits proximal to a 25km-long former salt wall. The salt wall has been subsequently welded out. Siliciclastic units that underlie and are interbedded with the San Jose thin towards the salt weld, whereas carbonate units are thickest nearest the weld. Halokinetic deformation of the San Jose is limited to a narrow zone (100 to 150 m wide) that parallels the salt weld. Here bedding angles change from vertical to slightly overturned nearest the salt weld to angles of 45 degrees or less (regional dip) further away (about 100 m).

A syncline whose axis is located approximately 1 km north of the salt weld and parallels it, is interpreted as resulting from Hidalgoan shortening and not salt withdrawal. Evidence supporting this is: (1) San Jose off-bank calciturbidites show thickening into the axis of the syncline and progressive thinning onto the northern limb, whereas (2) underlying siliciclastic strata do not display thickening into the syncline and are only influenced by near diapir deformation (halokinesis). The presence of syncline-related growth strata in the San Jose and not in the underlying siliciclastics constrains the initiation of Hidalgoan deformation in the La Popa basin to the Maastrichtian.