Tagasi otsingusse
Bromley & Asgaard, 1975

Sediment structures produced by a spatangoid echinoid: a problem of preservation

Bromley, R. G., Asgaard, U.
URL
Aasta1975
AjakiriBulletin of the Geological Society of Denmark
Köide24
Number3-4
Leheküljed261–281
Tüüpartikkel ajakirjas
Keelinglise
Id17020

Abstrakt

A strange paradox is presented by the great abundance of body fossils of spatangoid echinoids in Cretaceous to Recent rocks and the extreme rarity of burrows attributable to them. The macrofaunas of the Miocene sediments of Malta are dominated by spatangoid body fossils, but a search for corresponding trace fossils proved fruitless. Similarly, species of Micraster occur commonly at some horizons in the Upper Cretaceous chalk of NW Europe, but burrows attributable to these spatangoids have not been detected. In contrast, the Pleistocene Rhodos Formation of Rhodes, Greece, has been bioturbated almost exclusively by the spatangoid Echinocardium cordatum, five specimens of which have been retrieved at the end of their burrows in life position. The burrows are well preserved owing to selective calcite cementation, which has emphasized their meniscate backfill structure. The single drain and uncommon vertical funnels have also been cemented. Distribution of the cement corresponds to that of mucus as observed in burrows of E. cordatum today. Survival of the burrows of E. cordatum in the Rhodos Formation is considered to be due to the fact that this spatangoid burrowed to a depth of some 15 cm below the seafloor. In contrast, most spatangoids burrow relatively shallowly, and the general failure of pre-servation of their traces is probably due to their subsequent destruction by the activity of more deeply burrowing organisms.

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