Abstract: Comparison of Characteristic Genetic Sediment Body Types from a Campanian Carbonate Platform With the Coniacian--Santonian, South-Central Pyrenees, Spain
S. D. Davey
Within a Campanian platform, south-central Pyrenees, eight genetic sediment body types have been characterised aiming at increased knowledge of diagnostic criteria and quantified size--shape--orientation data for predictive reservoir modelling.
The detailed make-up of carbonate depositional sequences is possibly limited by short spatial and temporal variations in main grain types. It is desirable to establish whether repetitive elements are present in more than one outcrop analogue to enable application of outcrop information. This is attempted with Coniacian--Santonian outcrops in the area to draw comparison with an established Campanian analogue.
Detailed differences exist, but some similar facies are developed within each platform. Rarely, localised rudist--bioclastic constructions are present, although size and faunal assemblage differs. Similarly, alternations of highly progradational quartz-sand rich (15-35 %) grainstones with packstones or grainstones essentially lacking detrital quartz are present. Whereas the quartz-rich units are comparable in dimensions, fabrics and sedimentary structures, the Coniacian--Santonian shows a rhythmic alternation of these units with packages of dominantly packstone texture, gently onlapping in the opposite direction, but there is no such simple pattern in the Campanian interpackaged quartz-poor units. Here a more complex array of sub-lithotypes of parallel-bedded grainstones or p ckstones (fine-rained peloidal, coarse mixed peloidal--bioclastic, poorly sorted bioclastic) is developed. Higher in the stratigraphy than these current dominated units, rudist-dominated fabrics (locally toppled floatstones, dense floatstone--rudstones) are present in both platforms. Again, detailed information on the rudist palaeoecology, faunal assemblages and depositional environment for individual buildups differ, but gross geometries, typical thicknesses and to a lesser extent the lateral persistence of these bodies are similar.
AAPG Search and Discovery Article #90956©1995 AAPG International Convention and Exposition Meeting, Nice, France