A detailed study of the Pennsylvanian Indian Basin Field of New Mexico, USA is used to develop a conceptual model that predicts reservoir porosity in clean down-depositional-dip marine carbonate, where repeated fracturing allows for hydrothermal fluid flow. Strata updip probably experienced repeated events of subaerial exposure, resulting in mineralogical stabilization and extensive calcite cementation that prevented extensive hydrothermal alteration. Clean, carbonate sediment deposited downdip was more prone to alteration by hydrothermal fluids. In the reservoir, cement stratigraphy shows regionally persistent zones closely associated with fracturing. Fluid inclusion data show high temperatures and repeated rises and falls, indicating tectonic valving in a hydrothermal system. Salinity data support this and indicate a late event of meteoric influx. Srand O-isotope data indicate higher temperature and less rock-water interaction in fault damage zones, evidence for intensified fluid flow in such areas. Formation of vugs and molds was associated with the hydrothermal fluid flow, which was driven by convection, probably initiated during 40-30 Ma intrusive activity and continuing after the onset of Basin and Range uplift and unroofing.

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We characterized the skeletal crystallography of representatives of nine rhombiferan, three diploporan, and three paracrinoid species. Crystallographic data from these groups are similar to data from previous studies of crinoids, echinoids, and blastoids in that 1) orientations ofcaxes are consistent within species and within higher taxonomic groups; 2)caxes typically are oriented subparallel to the medial plane of their respective plates; and 3) the inclination of axes within the medial plane varies between taxa. Rhombiferancaxes are oriented normal to plate surfaces whereas diploporancaxes are tangential to plate surfaces. Paracrinoids more closely resemble diploporans in having irregular patterns of thecal plating but theircaxes are approximately perpendicular to plate surfaces as in rhombiferans.In contrast tocaxes,aaxes in all specimens show little regularity and cannot be distinguished from random orientations.The rhombiferanCaryocrinites ornatusdisplays minor differences in the inclinations ofcaxes depending on the location of skeletal elements on the theca. Plates at the base of the theca have slightly aborally inclined axes, whereas distal plates have axes inclined slightly adorally. This pattern matches orientations in some early crinoids, suggesting similarities between rhombiferans and crinoids in development or skeletal construction.Skeletal crystallography in various echinoderms can be compared in light of hypotheses of homology proposed in the Extraxial-Axial Theory (EAT). Skeletal elements homologized under the EAT do not correspond to any particular crystallographic axis orientation, suggesting that the homologies proposed in the EAT encompass significant underlying skeletal variation.