Abstract: The Glen Rose Formation of the Comanchean Series represents the second circum-Gulf carbonate shelf that extended fromFlorida to Mexico. The Glen Rose comprises limestone, dolomite, and thin interbeds of marl and calcareous shale that overlie the HenselSandstone and underlie the Fredericksburg Group in Texas. The Glen Rose is here formally divided into Lower and Upper, mappablemembers separated at the top of the regionally persistent “Corbula” Marker, and a boundary stratotype section is designated. The age of the Glen Rose Formation ranges from latest Aptian to near the end of the Early Albian, from approximately 113.3 Ma to 108.0Ma, and encompasses four ammonite zones. Three local assemblage zones facilitate correlation of Glen Rose outcrops in Texas. The Saleniatexana Credner Assemblage Zone spans a marl, 3 to 4 m thick, with a diverse shelf biota in the upper part of the Lower Member. The “Corbula” Range Zone is at the top of the Lower Member. The Loriola rosana Cooke Assemblage Zone is in the middle part of the UpperMember. The Glen Rose together with the underlying Hensel Sandstone comprise at least five medium-scale depositional cycles separatedby transgressive disconformities. Two types of biotic accumulations are well developed in the Lower Glen Rose Member, coral-rudist assemblages and caprinid-dominated assemblages. Coral-rudist biostromes crop out at the Narrows of the Blanco River and had no bathymetric relief and do notqualify as “reefs”. Colonial corals are common and are part of a Tethyan fauna; toucasiids and other mollusks comprise a diverseassemblage. Coral diversity is underestimated because of incomplete preservation and sampling. These biostromes are overlain bygrainstone capped by a subaerial contact that serves as a sequence boundary between cycles one and two. The younger caprinid biohermsat Pipe Creek have up to 10 m of depositional relief. The bioherm facies grade landward into shoreface grainstone and seaward into shelfwackestone. The caprinid species, Coalcomana ramosa , dominates this low-diversity assemblage and is endemic to the Caribbean Province.The bioherm facies are overlain by dolomitic, stromatolitic facies with dinosaur tracks. The contact with the overlying Salenia Zone is asequence boundary between cycles two and three. Two more long-term cycles may be identified in the Upper Glen Rose Member. The coral-rudist biostromes and the caprinid bioherms formed paleocommunities on the landward ramp of the interior marine shelf.The coral-rudist biostromes developed below normal wave base but above storm wave base and shoaled above wave base and weresubaerially exposed. The caprinid bioherms formed on a ramp and grew into the zone of normal wave action in mainly normal marinesalinities.

Abstract Community structure of Gulf Coast reefs changed significantly during the Albian. Paleoecologic analyses of cores and outcrops of these reefs document the taxonomic composition, the relative abundances, and the diversity of reefal paleocommunities. Reefal-community structure differed between open-sea shelf margins and ramps around intrashelf basins. Three well-documented shelf margin reefs are the Rodessa, Stuart City, and E1 Abra formations. In these units, corals are abundant in the deeper parts of the reef and grade downward into slope and basin deposits. Rudists are abundant in shallow-water and generally higher energy facies. However, in the El Abra, corals are nearly absent and rudist communities were founded upon rudist sand banks. Three excellent examples of ramp reefs around the intrashelf basins are the Sunniland, Edwards, and Devils River formations. Caprinid and radiolitid rudists comprise reef communities that overlie current- and/or wave-swept carbonate sands. Caprotinids are scarce and are associated with the caprinids. In lower energy lagoonal facies, requieniids form densely packed biostromes. The mainly Albian age of these reefs is documented by the ranges of foraminifera, rudists, calcareous algae, and corals. The stratigraphic position relative to ammonite-bearing beds and tintinnids constrain the ages also. Major sequence boundaries that can be traced regionally are developed at the top of the Sligo Formation, the top of the Stuart City-Edwards Formation, the top of the Devils River Formation, and at the top of the El Abra Formation. Additional sequence boundaries may also be present. The Rodessa Formation is mainly lower Albian; the Stuart City Formation is middle to basal upper Albian; the Devils River Formation is upper Albian; and the El Abra Formation is Albian–Cenomanian.

Abstract Names: Cupido and Aurora around Coahuila block, Golden Lane (Tuxpan), and Valles–San Luis Potosí platforms Authors: J. L. Wilson and W. C. Ward Location: From 96° to 102° west longitude and 20° to 28° north latitude, northeastern and east-central Mexico Geologic time interval: Two periods of platform development: Neocomian–Aptian and Albian-Cenomanian, separated by a transgressive shale Tectonic-sedimentary setting: Rifted and dissected passive margin Basin type: Marginal cratonic Paleoclimate: Semitropical, generally humid but with two semi-arid periods in early Aptian and middle Albian Platform type: Rimmed shelves around major positive basement blocks and isolated platforms developed over positive blocks Platform geometry: Thickness of a few hundred meters to 2000 m. Rimmed shelves as much as 80 km wide and hundreds of km long. Isolated platforms are 65 by 145 km and 200 by 300 km Facies and fossils: Multitextured carbonates, minor amounts of terrigenous clastics. Both extensive pelagic biotas and shallow water benthos of foraminifers, algae, corals, and various molluscs, particularly rudists. Systems tracts: Sabkha evaporites, intertidal carbonate cycles, grainstone shoals, coarse rudist–coral–sponge–hydrozoan–red algae at shelf margin, lithoclastic debris, pelagic rhythmites in basin. Mostly highstand systems tracts leading into starved basins. Only minor lowstand systems tracts. Stacking patterns: Progradations of simple sigmoid sequences, some rising in the sequence as they prograde (Barremian–Aptian). Some of the Albian-Cenomanian platforms are predominantly aggradational, although progradational sequences are documented on the southeastern margin of the Valles platform and the southern flank of the Coahuila block.

Abstract: Five new Barremian to Upper Albian rudist zones are defined in depositional cycles of the Trinity, Fredericksburg, and Washitagroups of the U.S. Gulf Coast. The stratigraphically lowermost Barremian-Lower Aptian Huetamia buitronae Assemblage Zone isrecognized in Texas, Mexico, and Trinidad. This assemblage in the Sligo Formation consists of Huetamia buitronae Alencaster and Pantoja-Alor, 1998 , Pantojaloria sphaerica Alencaster and Pantoja-Alor, 1995 , Caprina douvillei Paquier ( Skelton, 1982 ), and Douvillelia skeltoni Alencaster and Pantoja-Alor, 1998 . In coeval formations in southern Mexico this assemblage zone also includes Amphitriscoelus waringi Harris and Hodson, 1922 , Amphitriscoelus pluriloculata Alencaster and Pantoja-Alor, 1996 , and Caprina massei Alencaster and Pantoja-Alor(1995 , 1998 ), three species endemic to the Western Hemisphere. The Sligo is correlated with the Barremian to Lower Aptian stage /substageby benthic foraminifers and nannofossils and by its stratigraphic position below Lower Aptian deposits of the OAE1a chemostratigraphicevent. Rudists are quite abundant in the interior-shelf and shelf-margin facies of the Sligo. The Upper Aptian James Limestone in theFairway field of East Texas ( Achauer, 1985 ) also has rudists, as in south Texas, where requienids overlie coral-stromatolite boundstone( Loucks and Bebout, 1984 ). But, these species have not yet been identified. The uppermost Aptian to Lower Albian Coalcomana ramosa Interval Zone spans the total range of this species. This zone contains fourrudist species in the Glen Rose Formation of Texas and the Mural Limestone of Arizona: Coalcomana ramosa Boehm, 1898 , Planocaprinatrapezoides Palmer, 1928 , Caprinuloidea perfecta Palmer, 1928 , and Caprinuloidea multitubifera Palmer, 1928 ( Scott, 2002 ). The first two of thesefour species appear to be restricted to the Glen Rose and equivalent strata, but the latter two species range up into the Middle to lowermostUpper Albian Fredericksburg Group. The uppermost Lower to lowermost Upper Albian Caprinuloidea Interval Zone is the interval from the last appearance of Coalcomanaramosa to the last appearance of Caprinuloidea. Four rudist species occur in this assemblage: Caprinuloidea perfecta, Caprinuloidea multitubifera , Texicaprina orbiculata ( Palmer, 1928 ), and Texicaprina vivari ( Palmer, 1928 ). This interval generally spans much of the Middle to basal UpperAlbian Fredericksburg Group ( Scott, 2002 ). The Upper Albian Kimbleia Interval Zone is defined as the interval from the first appearance of Kimbleia to the first appearance of Mexicaprina , and it includes the rudist species Kimbleia albrittoni Perkins, 1961 , and Kimbleia capacis Coogan, 1973 . This zone spans the lowerpart of the Upper Devils River Limestone, which correlates with the Adkinsites bravoensis Zone, the Eopachydiscus marcianus Zone ( Scott, 2002 ), and the Drakeoceras wintoni Zone ( Scott, 2002 ). The Upper Albian Mexicaprina Interval Zone is the total range of Mexicaprina including M. cornuta Coogan, 1973 (1977) , M. quadrata Alencaster and Oviedo-Garcia, 1998 , and M. alata Filkorn (2002) . This interval correlates withthe uppermost Albian Plesioturrilites brazoensis Zone and directly underlies the Lower Cenomanian Del Rio Shale.

ABSTRACT Coral-nidist buildups are known from three outcrop areas of Cretaceous age (Berriasian to Maestrichtian) in France. These are: 1. Paris Basin, 2. Sud-Est Basin, and 3. Aquitaine-Pyrénées Basin. During Berriasian time coral-rudist buildups were limited to the Sud-Est Basin, and here they only occur locally in relation to “Purbecktype” sediments. The Vaianginian Stage corresponds to an extensive phase of marine shallow water carbonate sedimentation containing coral-rudist buildups. These deposits are recorded from both the Jura Subalpine and Provence-Pyrénées Platforms, while isolated coral beds have been reported from the Paris Basin. During the Hauterivian, regional tilting of former carbonate platforms caused a reduction of coral-rudist buildups, nevertheless isolated coral beds have been reported from the Paris Basin. Barremian and lower Aptian times were marked by a considerable extension of platform-type carbonates in the Sud-Est Basin and in the Pyrénées. In these areas “Urgonian” limestones are better represented than coral beds. During the upper Aptian deepening of the Sud-Est Basin led to the disappearance of coral-rudist buildups in most areas, except in the Aquitaine-Pyrénées region. Albian tectonism caused the disappearance of most shallow water carbonates. The Cenomanian transgression followed, leading to reestablishment of coral-rudist buildups, especially in the Aquitaine-Pyrénées and Provence regions. In lower Turonian time another deepening phase occurred and caused the disappearance of shallow water carbonates. During upper Turonian time a new surge of rudist buildups occurred coincident with an increasingly more important influx of terrigenous sediments. Only relatively small carbonate platforms containing lenses of rudists have been recorded from the lower Senonian of the Pyrénées-Provence region. The upper Senonian is mainly a regressive sequence characterized by an extension of deltaic deposits and restriction of coral-rudist lenses primarily to the Aquitaine-Pyrénées Basin. Two groups of coral-rudist formations have been distinguished: 1. those associated with off-shore “highs,” and 2. those associated with carbonate platforms. Three types of off-shore “highs” have been recognized. These are: 1. coral “highs,” known only from the Lower Cretaceous, 2. oobioclastic/coral “highs” from the lower Barremian of the subalpine area, and 3. rudist banks present only in the Upper Cretaceous. We regard “highs” as topographic units of limited lateral extent that can be divided into a small number of ecological and sedimentological zones, and are surrounded by deeper water sediments. Platforms are regarded as morphological units of regional extent composed of several adjacent biofacies and lithofacies related to the hydrodynamic properties of their aquaeous environment, and which may laterally grade into a continental facies. A platform may be subdivided into two zones: 1. an outer zone with high energy deposits and organic buildups (mainly corals in the Lower Cretaceous and corals and rudists in the Upper Cretaceous), and 2. an inner zone of quiet to moderate energy deposits characterized by abundant rudists. Development of coral-rudist formations appears to be governed by six important factors. These are: 1. shallow water conditions, mainly infralittoraJ, 2. relative basement stability (although in some instances tectonism may create “highs” on which organisms may thrive), 3. eustatic stability or transgression, 4. low terrigenous influx, 5. absence of organism restricting océanographie conditions, and 6. a warm climate of tropical to subtropical nature.

The Lower Cretaceous marine strata in east-central Sonora are as much as 2,500 m thick and consist of six mappable lithostratigraphic units. This sequence is important not only for delineating the paleogeography of western Mexico, but also for correlating the sections in eastern Mexico with those in western Mexico and Baja California. The Lampazos sequence is near the boundary between the North American and Yaqui blocks, and the stratigraphy is clearly similar to that of the North American block. Calcareous algae, benthic foraminifers, corals, and rudists described here complement the molluscan assemblage previously reported. Three species of algae are widespread in Caribbean Lower Cretaceous strata. Two additional species of orbitolinids, besides O. texana , are documented in the Caribbean province for the first time. These and six other species of foraminifers enable the recognition of Barremian-lower Aptian, lower Albian, and middle-upper Albian. Three corals and two caprinids support the stadial interpretations, which are enhanced by an assemblage of late Aptian ammonites and younger bivalves and gastropods reported previously.

Abstract 1. Albian to lower Cenomanian shelf margin reefs in the Gulf Coast are developed within the Rodessa, Stuart City, and El Abra formations, among others. Reefs in the lower Glen Rose and Mooringsport members remain to be documented. 2. Early and medial to early-late Albian shelf margin reefs consist of a lower, deeper water paleocommunity of corals and algae, and a higher, shallower paleocommunity dominated by rudists. High-energy carbonate sands overlie these assemblages, and lagoonal rudist assemblages lie behind the shelf margin. Early Cenomanian reefs were dominated by rudists that occupied sandy substrates. 3. Albian reefs also developed upon ramps that encircled the interior platform basins such as the East Texas Embayment and the Maverick Basin. These reefs were dominated by rudists growing upon wave- and/or current-swept carbonate sands. 4. The biostratigraphy of these cores and outcrops is based upon a diverse set of microfossils and megafossils. These demonstrate that the Rodessa and Sunniland formations are mainly lower Albian; the Stuart City and Edwards formations are medial and early-late Albian; the Devils River Formation is late Albian; and the El Abra Formation is mainly late Albian to early Cenomanian. 5. These different depositional models of Cretaceous reefs require different exploration strategies for predicting the geometry, size and porosity of these reefal reservoirs.

Abstract There are thousands of problematic organisms — organisms unassigned to a specific phyletic group, or ones that were assigned to different groups by different workers. We have simply picked a few that are particularly distinctive and/or that are important in rocks of hydrocarbon exploration interest. We list prior phyletic assignments and age ranges below and provide descriptions and keys to recognition in the figure captions. Receptaculitids - grouped with sponges, corals, dasycladacean green algae, or problematica — common from Early Ordovician to Late Devonian, with smaller, more globular forms extending into the Permian Nuia - grouped with problematic codiacean algae or as an unassigned organism — Late Cambrian-Ordovician Palaeoaplysina - grouped with sponges, phylloid algae, or hydrozoans — Mid. Pennsylvanian-Early Permian Tubiphytes - variously grouped with cyanobacteria/blue-green algae, red algae, calcareous sponges, foraminifers, hydrozoans — at least Late Carboniferous to Late Jurassic Lithocodium - grouped as codiacean algae or loftusiid foraminifers — Late Triassic to Early Cretaceous (Albian) Hensonella - grouped as mollusks (scaphopods), coralline red algae, or dasycladacean green algae — Cretaceous (Hauterivian-Albian) A cross section of the wall structure of Calathium sp., with its central cavity and moderately well-preserved radiating wall structure. Calathids are the earliest receptaculitids — they had ovoid or tubular skeletons that strongly resemble sponges (one of the groups in which receptaculitids commonly are classed). The sparry calcite-filled areas (and micrite-filled circles) are recrystallized, originally aragonitic, elongate pillars that constituted the skeletal wall (see Nitecki et al., 1999); the rest of the micritic sediment has filled areas of former void spaces or sites of later-decomposed organic tissues.

Abstract Middle Albian shelf margin reef and bank facies are widespread around the Gulf of Mexico, Central America, and in the Caribbean (Scott, 1984a; Winker and Buffler, 1988). In Texas, these facies comprise the Stuart City Formation. Behind the shelf margin in Texas, the Comanche Platform was divided into intrashelf basins and platforms that controlled sedimentation (Fig. 23). Reef facies and communities are quite well developed and diagenetic changes are understood (Bebout and Loucks, 1974). Significant hydrocarbon reserves are known from these facies (Cook, 1979). The updip equivalent of these facies, the Edwards Formation, has strongly influenced our knowledge of Early Cretaceous reefs. The documentation of the relative abundance of corals and nidists in the subsurface will refine and clarify our understanding of the biotic organization of these reefs. The Stuart City Formation is cored in numerous wells along the Comanchean Shelf margin. Cores from the Shell No. 1 Chapman well in Waller County (Fig. 24) and from the Shell No. 1 Tomasek in Bee County (Fig. 25) provide a basis for defining the community structure of the middle Albian reefs in the Gulf Coast. The "Stuart City reef trend" was applied to a thick rudist reefal limestone in the subsurface of south Texas and the Stuart City Formation included strata between the Pearsall and Georgetown formations (Winter, 1961; Wilson, 1986). The type area is the Stuart City Field, LaSalle County, Texas; no type section was designated. A thick section of reefal limestone was penetrated in well number 3 in the