NP 7 nannoplankton zone
Primarily corraline algae, sponges and corals in a muddy matrix.
Corals and demo(?)sponges associated. Coralline algae more in fore reef position.
Abstract of ref.  551:
The Late Paleocene Salt Mountain Limestone from southwestern Alabama (USA) is a coral-algal-sponge buildup which further characterizes the faunal makeup of early post-Cretaceous reefs. Thin sectioning has disclosed a variety of lithologies, including large foram-algal packstone, algal bindstone, and sponge bafflestone. A low-diversity fauna of massive scleractinian corals caps the sequence, but may be developed intermittently throughout the section as well. The constructional importance of coralline algae and the low diversity of scleractinian corals are characteristic of Paleocene reefs in general. Sponges, however, are virtually unknown in earliest Tertiary sediments. Their abundance in the Salt Mountain demonstrates not only their local contribution to Early Tertiary reefs, but may also reflect an opportunistic response of sponges as reef constructors following the extinction of oligotrophic, rudist-coral reef communities of the Late Cretaceous. 

Abstract ref. 2185:
The slow recovery of reef coral communities after the K-T extinctions has long been recognized, but the scarcity of Paleocene corals and reefs has inhibited study of early Tertiary reef diversification. A key question regarding this recovery concerns the extent to which changes in coral diversity affect the establishment of coral reef communities. Specifically, is the scarcity of Paleocene reefs the result of low coral diversity? We examined this question through investigations of the oldest Paleocene reef from the Gulf of Mexico region (the Salt Mountain Limestone) and newly revised generic level occurrence data for the Caribbean. The Salt Mountain Limestone is a Thanetian (Late Paleocene) shallow water patch reef in southern Alabama. It contains 12 species of reef corals including massive and platy zooxanthellate forms co-occurring with abundant branching-nodular apozooxanthellate species. The species richness and ecology of this Paleocene fauna approximates that of later Tertiary and modern reef communities from the northern Gulf of Mexico. Unlike younger reefs, however, the Salt Mountain reef community is dominated not by corals, but by coralline algae and a diverse group of hexactinellid sponges. Thus, Paleocene corals were comparable to later faunas, but the reef community was not. Looking at generic records, 23 reef coral genera are known from or range through the Caribbean Paleocene. This is lower than the number known from the later Tertiary and modern Caribbean, but only slightly so. There are numerous examples of later Tertiary coral reefs composed of fewer genera suggesting that lower taxonomic richness was not the primary reason for the lack of Paleocene coral build-ups. The absence of coral reefs was more likely the result of a break-down in coral-algal symbiosis or the lack of a few key taxa that structure Tertiary through Recent reef communities.