Abstract Basin-margin, Late Guadalupian carbonate strata contain units with alternating baselap patterns. Downlap occurs at the base of steeply dipping boulder-conglomerate lower slope strata; onlap occurs at the base of gently dipping wackestone-rich toe-of-slope strata. The downlap and onlap stratal patterns reflect differences in gravity-flow deposition in response to different sediment type supplied to the basin margin. The lower slope was too steep for deposition of peloidal carbonate muds transported by low-density turbidity currents, so gravity flows bypassed the slope and deposited carbonate mud-rich beds at the toe-of-slope, where they onlapped lower slope boulder conglomerates. Matrix-poor boulder conglomerates terminate by downlap in talus cones because the rock falls and low-matrix debris flows responsible for their transport reached a slope too gentle for continued transport. In contrast, steeply dipping, matrix-rich boulder-bearing debris-flow deposits interfinger downslope into finer grained debris-flow and turbidity current deposits concordant with underlying strata. The sediment type delivered to the basin margin varied systematically during the Late Guadalupian due to sea-level fluctuations. Relative sea-level stand was interpreted from correlation to the relative sea-level record of contemporaneous shelf strata and from analogy to the Bahamian Quaternary carbonate sediment history. Siliciclastic silts were deposited in the basin during lowstands as onlapping strata. Downlapping silt-matrix boulder conglomerates (units 1 and 7) were deposited during the early transgression, when fringing reefs supplied boundstone boulders and siliciclastic silt could be transported across the emergent shelf. Downlapping matrix-poor boulder conglomerates (unit 2) were deposited during the late transgression, when fringing reefs were still growing and the shelf was flooded enough to stop the basinward transport of quartz silt but was not flooded enough to pro-duce significant quantities of carbonate mud. Onlapping toe-of-slope wackestones (unit 3) were deposited during early highstand, when the flooded shelf was producing carbonate mud and the reefs either had not caught up with sea level rise or had stepped back onto the shelf. Boulder conglomerates with lime-mud matrixes (units 4, 6, and 7) formed after reefs had caught up with sea-level rise or had prograded to the shelf edge (late highstand). The stratal patterns in these Permian, basin-margin carbonates are different from those commonly interpreted in generalizations of siliciclastic sequences (e.g., Vail et al., 1984). The Late Guadalupian stratal patterns are caused by the change in carbonate sediment type and quantity with change of relative sea level, rather than by proximity to shoreline with changing relative sea level. This study demonstrates the importance of understanding the relationship between sea level, sediment supply, and depositional mechanisms before using stratal patterns to interpret relative sea levels in carbonate basin margins.

Abstract This paper summarizes a detailed investigation of the sedimentology and stratigraphic setting of the lower Seven Rivers Formation in the Guadalupe Mountains, New Mexico (Hurley, 1978). Work is confined to superb exposures in North McKittrick Canyon of a lateral facies transition from bedded shelf carbonates and siliciclastic sediments to the massive facies of the lower Capitan Limestone. The major research questions addressed are: 1. What depositional processes and environments characterize the complex facies mosaic of the lower Seven Rivers Formation and the shelfward edge of the lower Capitan Limestone? 2. Did the shelf-to-basin profile in earliest Capitan time differ from later Capitan times (Yates and Tansill) where this transition has been more thoroughly studied? 3. What is the nature of the Seven Rivers to Capitan facies transition, and what does this transition imply as to growth rate of the early Capitan?

Abstract This paper is a summary of a diagenetic study of calcite cements in the Capitan Limestone, McKittrick Canyon, West Texas (Mruk, 1985). This study deciphers the diagenetic history of the Capitan Limestone using basic field observations, detailed cathodoluminescence petrography, and carbon and oxygen isotopes.

Abstract The Guadalupian Series, with its type section in the Guadalupe Mountains, west Texas and New Mexico, has generally become the accepted worldwide standard for the Middle Permian. The Cisuralian of Russia is the accepted standard for the Early Permian; and the Lopingian of China has been accepted as the Late Permian standard. Most recently, the task of securing this threefold worldwide standard has been pursued by a host of workers in many specialties in order that no major gaps or overlaps are left for chronostratigraphic correlation. Following established international procedures for defining a chronostratigraphic boundary, the base of the Guadalupian Series is recognized at the stratigraphicaUy lowest occurrence of the conodont Jinogondolella nankingensis in a section recording continuous deposition in the middle of the El Centro Member of the Cutoff Formation, Roadian Stage, Guadalupe Mountains. This designation is in basic agreement with the ranges of important species of three other major faunal groups: the ammonoids, brachiopods, and fusulinaceans. Designation of a formal top of the Guadalupian Series has remained more elusive inasmuch as the final establishment of the base of the overlying Lopingian in China has remained in a rather unsettled state until recently. Enough is now known to insure that the Lopingian base will fall chronostratigraphicaily somewhere between the upper Lamar Limestone, Bell Canyon Formation, and the base of the Castile Formation of the Delaware Basin. This interval includes the so-called “post-Lamar beds” of the upper Bell Canyon Formation. As a means of equating the lithostratigraphy to the chronostratigraphy, we describe herein the Reef Trail Member of the upper Bell Canyon Formation by establishing its type section at McKittrick Canyon, Guadalupe Mountains, as a formal replacement name for the informal “post-Lamar beds.” We also identify the fusulinacean and conodont faunas from composited sections of Lamar Limestone and Reef Trail members, and extend their correlations biostratigraphically from the Guadalupes to the Apache and Glass mountains. The McKittrick Canyon Limestone is a new name given to the “Middle” Limestone (Brown, 1996), following his recognition that this limestone had for too long been misidentified as the McCombs Limestone. Finally, correlation of faunal zones established in the Delaware Basin from the three mountainous areas are extended globally in an attempt to reconcile chronostratigraphic problems.

Abstract The origin of the Massive Member of the Capitan Formation in the Guadalupe Mountains of West Texas and New Mexico is controversial. It has been inteipreted in many different ways, including as a barrier reef, a deep water skeletal wackestone mound, a cement boundstone mound, and a linear complex of buildups. The reality is that it is not simply one or the other, but a complex with characteristics of all of the above — a reefal complex that changes both in time and space. The Massive Member of the Capitan Formation contains the components of a framework reef: frame-building organisms — bryozoans, platy sponges, and Tubiphytes', binding organisms — Archaeolithoporella and microbialite; infilling internal sediment; and marine cement. Much of the Capitan was probably deposited below wave base as a diverse framework reef. The profile of the Capitan reef varied throughout its deposition. At the mid-point of Capitan development, the slope of the reef was very steep (80° or more) and the living reef extended to a depth of approximately 140 m. The organisms that lived on the reef varied with depth. The shallowest portions of the reef were inhabited by Collenella and a diverse assemblage of other organisms. In slightly deeper water, large platy sponges formed meter-scale over-hangs and cavities, which were inhabited by a cryptic community dominated by sponges. In the deepest parts of the reef, frondose bryozoa created decimeter-scale framework and internal cavities inhabited by cryptic pendant sponges. These internal cavities were filled by a succession of encrustations and cements, beginning with thick layers (1-3 cm) of microbialite followed by profuse botryoidal aragonite (up to tens of centimeters thick), thin (1—4 mm) layers of radiaxial fibrous cal- cite, and much later, large crystals of meteoric spar. The Capitan reef influenced deposition in surrounding environments. Throughout its growth the Capitan was a “sediment factory” that generated prolific amounts of sediment that accumulated in the fore-reef. Study of the upper Capitan at Walnut Canyon suggests that the living Capitan reef probably created a depositional high that modified sedimentation in the lee of the reef on the outer shelf. Study of the middle Capitan and equivalents at McKittrick Canyon suggest that at other times circulation on the outer shelf was unrestricted by the reef escarpment and its living surfaces. Many questions about the Capitan remain unresolved, for example, what was the response of the reef to sea-level change? How did the reef profile change through time? Is there consistent evidence of exposure in the reef? Does diagenesis vary throughout the reef? How diverse is the biota in the lower and middle Capitan, and does biotic diversity change through time?

Abstract The Guadalupe and Hueco Mountains are exquisite natural laboratories for studying the stratigraphy, depositional facies, and diagenetic overprint of Permian platform and reef carbonates. Well-studied outcrops from these two classic localities serve as important analogs for other areas where the data is more limited. In addition, studies from the two areas have had immediate application to subsurface hydrocarbon exploration and exploitation efforts in the immediately adjacent Permian Basin. Our field trip of three days will emphasize the stratigraphic framework, facies, and diagenesis of a Lower Permian (Wolfcampian) low-relief carbonate platform outcropping in the Hueco Mountains and an Upper Permian (Guadalupian) steep-rimmed platform of the Guadalupe Mountains. We invite questions and discussion at all field stops, as our group has diverse backgrounds and interests and any discussion will be beneficial to all. The focus of the trip in the Hueco Mountains is on the evolution of the shelf-margin architecture and fauna! change. The exposures allow us to view the architectural elements of a prograding and retrograding shelf margin in ice-house conditions as well as the biotic response to environmental change. A relevant part of the exposure to visit is the facies variability both temporally and laterally. Our emphasis in the Guadalupe Mountains is on the Capitan margin, as well as the related shelf and basin deposits. Large-scale outcrops like that of McKittrick Canyon offer an unparalleled view into the inside of a progradational platform, and we hope you will agree that the hike up the Permian Reef Geology Trail presents an