Abstract The Mayaguana and Caicos platforms are both located in the SE Bahamas. Caicos is one large edifice supporting small islands, whereas Mayaguana is smaller and comprises one island covering most of the bank surface. Providenciales (Caicos) and Mayaguana islands predominantly consist, in different proportion, of reefal framestones and oolitic grainstones dating from the last interglacial period. Oolitic ridges are widely exposed on Providenciales, whereas reefal deposits are confined to the west coast. On this island, the older substrate consists of oolitic and bioclastic eolianites of middle Pleistocene age. On Mayaguana, oolitic ridges are subordinate to the reefs, and the oldest rock units include altered eolianites containing fragments of benthic foraminifers that became extinct in the Pliocene and fine-grained dolostone of possible middle Miocene age. This difference in the distribution of upper Pleistocene facies could be related to the extent of emerged land on platform tops or to the thickness of the water layer covering the latter during the last interglacial highstand. The oolitic and bioclastic substrates exposed on Providenciales are similar to those observed in the northern Bahamas. If confirmed, the pre-Quaternary age of the dolomitic and eolian units on Mayaguana would question some fundamentals of Bahamian geology.

Abstract A variety of buildup types occur in the upper Paleozoic Auernig and Rattendorf Groups, Carnic Alps, at the present-day Austrian-Italian border, including coral, diverse algal (Anthracoporella, Archaeolithophyllum,Rectangulina, and phylloid green), bryozoan, brachiopod, and sponge buildups. Thin mounds and banks have a diverse fossil association (e.g., Archaeolithophyllum-bryozoan- brachiopod mounds) and occurin siliciclastic-dominated intervals, as do coral buildups. Some of the biodiverse thin mounds occur in stratathat were deposited in cooler water. However, the thickest mounds are nearly monospecific (e.g., Anthracoporella mounds) and grew in carbonate-dominated, warm-water environments. Most of the mounds considered in this paper, particularly algal mounds, grew in quiet-water environments below wave base but within the photic zone. Mound growth was variously stopped by siliciclastic input, e.g., auloporid coral mounds, sea-level rise, e.g., the drowning of Anthracoporella mounds of the RattendorfGroup, influence of cool water, e.g., algal mounds of the Auernig Group overlain by limestone of cool-water biotic association, or sea-level fall, e.g., phylloid algal mounds that were subsequently exposed subaerially. Thereis no indication of ecological succession during mound growth. Growth, dimensions, biotic association, and termination of mounds seem to have been controlled by extrinsic factors, mainly sea level and water temperature. Phylloid algal mounds are similar to those described from other late Paleozoic settings. Auloporid coral buildups, and Rectangulina and Anthracoporella algal buildups, however, have not previously been reported from other regions, although these fossils are described from several localities outsidethe Carnic Alps.

Abstract Algal buildups from five stratigraphic intervals in the Pennsylvanian of eastern Kansas, Midcontinent, U.S.A., display three basic fabrics based on their: a) dimension, b) morphology, c) fossil content, d) algal growth forms, and e) nature of framework cavities. Type 1. Constructional mounds composed of cup-shaped in situ algal growth forms are typically small bioherms, either isolated (e.g., Frisbie Limestone Member) or thickened intervals within carbonate banks(e.g., Sniabar Limestone Member), and are basically formed by phylloid green algae. Fossil diversity is very low. Mud and cement fill the abundant small intercup voids within individual mounds. Calcareous sponges, crinoids, and bryozoans, probably cavity dwellers, fill the larger intermound cavities between the smaller mounds. Type 2. Constructional mounds of algae with undulatory growth forms are basically red algae with recognizablethalli characteristics of Archaeolithophyllum, and, only rarely, of phylloid green algae. Buildups of this kind are laterally persistent. Thickening of the banks is generally recognizable at a large scale (ten of meters to kilometers). Smaller, meter-scale bioherms constructed of algae with undulatory growth forms donot occur in the sites studied. Fossil diversity is higher than in type (1) mounds, with calcareous sponges, brachiopods, and bryozoans common throughout the mound, rather than exclusively in cavities between small mounds ofthe type 1 cup-shaped algae. When built by green algae (e.g., parts of the Captain Creek Limestone Member), mounds have a lower diversity than those constructed by red algae (e.g., Spring Hill Limestone Member). Solitary corals, calcareous sponges, and bryozoans occur attached to the walls of the cavities. The abundance of open pores is striking. Type 3. Mounds of accumulated algae with undulatory growth forms are formed by the red algae Archaeolithophyllum missouriense, Archaeolithophyllum lamellosum, and the green alga Eugonophyllum. Depositional relief is not visible on the outcrop, but large-scale variations in bank thickness are notable (e.g., lower part of the Captain Creek Limestone Member). Bryozoans and Thartharella (a probable worm tube) are common. Multiple types of cavities occur, and most are cement-filled. Although the mound types differ in their form, fossil content, and type and distribution of voids, they sharean overall common peloidal clotted matrix that accumulated in specific areas, along with an abundance of gravity-defying peloidal micritic structures in the matrix, and of thin crusts within marine cement that may be relatedto microbial activity. Microbes probably played a crucial role in carbonate precipitation and in lithificationofalgal-dominated buildups.