CARBONIFEROUS AND PERMIAN GLACIGENIC AND NON-GLACIAL STRATA OF THE TEPUEL-GENOA BASIN, PATAGONIA, ARGENTINA: A NEAR-CONTINUOUS, DEEP-WATER RECORD OF SOUTH POLAR GONDWANA DURING THE LATE PALEOZOIC ICE AGE
In our study, we identify 11 facies, which include: 1) wave-rippled and hummocky cross-bedded sandstone; 2) thick fossiliferous mudrock; 3) lonestone-bearing mudrock; 4) sandstone blocks overlying shear planes; 5) deformed sandstone overlying shear planes; 6) thin-bedded sandstone; 7) massive sheet and channel-form sandstone; 8) microbially-mediated sandstone; 9) massive, stratified, and thin-bedded diamictite; 10) graded, reverse-graded, and massive clast-supported sheet and channel-form conglomerate; and 11) deformed conglomerate resting on shear planes. We interpret these units as wave-influenced shelf, neritic, hemipelagic, iceberg-rafted, glaciomarine meltwater plume, mass movement (slides/slumps), turbidite, sandy debris flow, muddy debris flow, and submarine channel deposits. Analysis of grooved and striated surfaces suggests formation of these features as glide planes beneath slide/slump blocks and as iceberg keel marks.
The occurrence of clinoforms suggests deposition near the shelf-slope break and farther basinward. Wave-rippled and hummocky cross-stratified sandstone and mudrock within topset beds and near the top of dipping clinoforms indicate deposition on the outer shelf and upper slope. Thick successions of hemipelagic mudrock, slump/slide blocks, dropstones, diamictites and channelized and sheet turbidites within clinoforms suggest deep-water sedimentation on the slope and on the basin floor. The arrangement of the deposits suggests that during relative sea-level low stands, clastic systems, including glaciers, transited the shelf and shed clastics into the deep basin. Fossil-bearing horizons occur above low-stand deposits and may represent condensed zones that developed during transgression/high-stand and/or the retreat of glaciers and clastics across the shelf.