The growth fabric of gregarious rudist elevators (hippuritids) in a Santonian carbonate platform in the southern Central Pyrenees

摘要: Abstract The growth fabrics of living congregations erect sessile epifauna range between two extremes. With superstratal growth, the growing skeletons project well (∼ metres) above ambient sedimentary surface, creating an upstanding framework, which may be secondarily filled by sediment, as in modern tropical coral reefs. constratal contrast, tips little centimetres) from seafloor, such that bulk skeletal fabric is embedded in, and supported by, accumulating interstitial Pinna, oyster beds. Here we investigate original palaeorelief hippuritid Santonian rudist formations around Sant Corneli anticline, near Tremp southern Central Pyrenees. study particularly concentrates on a lithosome, exposed over some 0.25 km2, northern flank anticline. Four aspects are analysed. (1), lithosome shown to have tabular (biostromal) geometry, and, like others area, covered laterally accreted bioclastic blanket. (2) Specimens upright life position show pioneers paucispecific grew bouquets, but later recruits settled flanks established, fallen shells. Adults were only loosely clustered sediment. (3) Most shells, however, now horizontal with respect bedding densely stacked (“dense fabric”, or “d.h.f.”). This result current-induced removal sediment toppling (4) In contrast open marine aspect overlying sediments, fine matrix lithosomes faunally restricted, appears largely derived situ biodegradation We conclude constratally (i.e. without any supporting biogenic framework), they formed biostromal accumulations lacking relief. So there no justification for calling them reefs authors done. Rather, these rudists gregarious sediment-dwellers restricted waters platform top, where sporadically disturbed storms, eventually blanketed material swept margin.