Syndepositional faults and fractures are known to affect early fluid flow in carbonate platforms. Less clear is whether they are active fluid conduits throughout the entire history of the platform strata. Syndeformational fractures in Permian (late Guadalupian) carbonates exposed in Dark Canyon, Guadalupe Mountains, New Mexico, U.S.A., address this question. Transmitted-light and cathodoluminescent petrography, stable-isotope and fluid-inclusion analyses, and clumpedisotope thermometry show that there were multiple episodes of fracturing, dissolution, cementation, and replacement in the fractures. Dolomite cement or dolomitized marine cements line the walls of some fractures and indicate the syndepositional reflux of evaporated Permian seawaters through the fractures. Fine-to medium-crystalline, luminescently zoned calcite may overlie the dolomite and marine cements, line fracture walls where those phases are absent, or cement karst breccia on fracture walls. The d 18 O values of this calcite (28.8 to 214.0% VPDB) and clumped-isotope temperatures (16u to 32uC) indicate precipitation from meteoric fluids (d 18 O SMOW of 26.2 to 210.5%) associated with episodic sea-level lowstands during the development of high-frequency depositional sequences. The early calcites can themselves be fractured, rotated, and recemented, indicating recurrent deformation and meteoric influx. Evaporite cements were once the dominant pore-filling phase in the fractures, forming both before and after the early meteoric cements. The earliest evaporites formed during deposition of Tansill limestone, probably from the same brines that formed dolomites. Evaporites that postdate the early calcite probably did not form until Permo-Triassic burial, when geomechanical analysis indicates that the syndepositional fractures were likely reactivated and brines could have been sourced from overlying bedded evaporite. All evaporite cements subsequently were calcitized, mainly by coarse-crystalline, inclusionrich calcites that formed from warm (59u to 96uC) fluids. Calculated fluid isotopic compositions (d 18 O SMOW of 20.5 to 24.7%) imply mixing of meteoric and oilfield brines. Carbon isotope values (+2 to 217%) indicate microbial degradation of hydrocarbons in some of those fluids, but not all. Geomechanical analysis indicates the potential for syndepositional fractures to have failed (reactivated) during Basin and Range extension, and the warm basinal fluids are interpreted to have migrated upward through the fractures during that event. Platform-margin fractures (unassociated with faults) witnessed cooler fluids (59u to 65uC) than outer-shelf fractures (70u to 96uC) because outer-shelf faults tapped waters from greater depths. The most recent fluid flow through the fractures generated dissolution features and laminated speleogenetic calcites, which are interpreted to result from intrastratal karsting associated with exhumation and weathering. Diagenetic features in the syndepositional fractures are equivalent to those observed in the adjacent limestone...

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We investigate the curvature-fracture re lation ship at Sheep Mountain anticline, Wyoming, by coupling fracture mapping with structural mapping using high-precision global positioning system data. Carrier-phase post-processing techniques of spatial data collected across patches of bedding surfaces result in a high-resolution data set. Differential geometry tools form the basis for curvature analysis, allowing for a quantitative understanding of the shapes of these surfaces. Comparison of principal curvature magnitudes with fracture measurements indicates that greater curvature correlates with greater spherical variance of fracture set orientations. Fracture intensities, however, correlate only loosely with curvature, because fracturing mechanisms other than curvature of bedding must be taken into account.

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