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: The recently formed Canyon Lake Spillway Gorge in Comal County, Texas, U.S.A., exposes a continuous 63-m-thick section ofthe middle part of the Glen Rose Formation (Lower Albian). This part of the Lower and Upper Members of the Glen Rose consists of shallow-shelf carbonate rocks with depositional cycles on several scales. These strata can be grouped into sixty-two high-frequency cycles whosevertical succession defines two relative orders of asymmetric, intermediate-scale cycles. The lower-order cycles correspond to thelithostratigraphic units of Stricklin et al. (1971) . We propose that these widespread lithostratigraphic units of Stricklin et al. (1971) areregionally correlative because they are intermediate-scale sequences or significant portions of sequences (e.g., sequence sets). Intervals that historically have been used as stratigraphic markers are mainly transgressive units of the high-frequency sequences and are predicted to be extensive. The exception is the “Corbula” interval, which we interpret to occur in the lower highstand of a high-frequencysequence. The correlation of the “Corbula” interval has been based in part on the succession of the underlying Salenia Interval to theoverlying solution-collapse interval. We suggest that this is correlating on the scale of high-frequency sequences and not individual beds. Six postulated high-frequency sequences occur in the Gorge (Gorge-1 to Gorge-6). The lower three are characterized by highstandrestricted facies and relatively thin beds and cycles. The upper three are characterized by toucasid and Orbitolina texana limestones. It ispossible that these cycles are grouped into two larger-scale, lower-order sequences, one consisting of Gorge 1, 2, and 3, and the otherconsisting of at least Gorge 4, 5, and 6. The facies, the asymmetry of the intermediate-scale cycles, and the well-developed high-frequencycycles in the Upper Glen Rose are consistent with being in the highstand of both a supersequence and the composite sequence.