Early Cretaceous Reef Communities in Gulf Coast: ABSTRACT

Abstract

The development of paleocommunity concepts has led to new hypotheses of Cretaceous reef structures. Important biota of Early Cretaceous Tethyan reefs were corals and algae, besides various rudists. Different communities produced distinct structures upon shelf margins, interior shelves, and carbonate ramps. Further, the communities changed through time as rudists evolved. This change in community structure influenced the types of reefs prevalent at different times. Bound framework associations consisted of coral skeletons thickly encrusted by algae and stromatoporoids and cemented by micrite soon after deposition as indicated by buried erosion surfaces. Boring organisms generated large amounts of micrite as well. Caprinids, radiolitids, and monopleurids are sparse. Bound frameworks developed upon Early Cretaceous shelf margins and carbonate ramps. Mobile associations consisted of caprinids, radiolitids, and toucasiids encrusted by algae within a loose gravel of skeletal debris. Micrite and sparry cement are both well developed. Mobile associations formed passive banks in the shallower parts of the shelf margin and in high energy parts of the interior shelves. These buildups became important in the Aptian and later replaced the bound frameworks in the Late Cretaceous. Stable associations consisted of caprinids, toucasiids, monopleurids, radiolitids, and caprotinids surrounded by calcareous mud. Many shells were thinly coated by algae and bored by sponges, among other organisms. The shells still are in a stable growth position. Micrite cement originally was more abundant than spar between grains. These biostromes, thickets, and coppices developed mainly upon interior shelves during Aptian to Maestrichtian time. End_of_Article - Last_Page 782------------