Stromatolitic bioherms.
No bioherms in shallow water. 
Abstract of ref. 2041:
Most of what is known about the biotic recovery from the end-Permian mass extinction has been recovered from strata deposited in shallow-water environments. Yet, properties of the deep-ocean have been invoked as causes for the mass extinction as well as the unusually prolonged biotic recovery from this crisis. A nearshore to shelf transect of the Lower Triassic Virgin/Schnabkaib Limestones of the Moenkopi Formation (southern Nevada) was studied for changes in facies types and biofabrics as well as comparison with the coeval outer slope to deep basin Union Wash Formation (eastern California).

A number of biofabric trends were documented across this transect. Vertical burrows are common in nearshore strata, while horizontal burrows are prevalent in shelf strata. Intervals with relatively high ichnofabric indices (ii 4-5) are more common in shelf than nearshore strata. The most intriguing biofabric trend is the lack of microbial structures, such as stromatolites, in the most nearshore section, with their greatest occurrence found in shelf strata. This anachronistic onshore-offshore trend of stromatolitic development points to offshore and oceanic environments as a likely influence on their formation. Presence of seafloor carbonate cements in coeval slope and deep basin Union Wash strata, implying an offshore presence of water masses supersaturated in calcium carbonate, suggests that unusual ocean chemistry may have played a significant role in the development of Early Triassic shelfal stromatolites. 
