Geothermal and Geopressure Relations as Tool for Petroleum Exploration: ABSTRACT; Textural Parameters of Rocks From Borehold Measurements and Their Applications in Determining Depositional Environments: ABSTRACT; Discrimination Among Grain-Size Dist... 916 Association Round Table age of the rocks overlying both unconformities seems to indicate slow transgressive marine overlap in the two basins. MILLER, BETTY M., U.S. Geol. Survey, Denver, Colo. GEOTHERMAL AND GEOPRESSURE RELATIONS AS TOOL FOR PETROLEUM EXPLORATION The Uinta basin represents a timely model for the study of many interesting geologic and geochemical problems that are pertinent t o current exploration re- search investigations and to technical problems con- cerning petroleum production wliich face the petro- leum industry, particularly in light of the present energy crisis. The primary areas of investigation in this reported study on the Uinta basin concern the com- plexities in the exploration of ultraparaffinic crudes from fresh- and brackish-water lacustrine sedimentary deposits. An investigative study of the subsurface tempera- ture and pressure distribution patterns within the po- tentially productive section of the Wasatch Formation (Eocene) has produced highly favorable results as an exploration tool in predicting the recent successful ex- ploratory trends within the Uinta basin. A direct rela- tion has been documented between the occurrence of productive hydrocarbons within the Wasatch Forma- tion and the simultaneous occurrences of high geotem- peratures, abnormally high pressures, and the presence of an organic-rich shale fades. These relations currently are being investigated as a potential tool for the ex- ploration of stratigraphic traps in Tertiary basins. In addition, this study illustrates an application of computer techniques to geologic evaluations on a re- gional basis: rapid data-processing methods, data banks, computer-contoured maps, and statistical analysis of geologic data. PICKETT, G. R., and J. L. BEDWELL, Colorado School Mines, Golden, Colo., and J. C. CARLOSS, Consultant, Bismarck, N.D. TEXTURAL PARAMETERS OF ROCKS FROM BOREHOLD MEASUREMENTS AND THEIR AP- PLICATIONS IN DETERMINING DEPOSITIONAL ENVIRONMENTS No abstract available. POOLE, DAVID M., Marathon Research, Denver, Colo. DISCRIMINATION AMONG GRAIN-SIZE DISTRI- BUTIONS BY CANONICAL ANALYSIS AS AID TO ENVIRONMENTAL INTERPRETATION Grain-size analyses of sediments and sedimentary rocks have been made for many purposes. During the last 10 to IS years, grain-size analyses have been made of sands and sandstones as a means of determining their depositional environments. Most of the pub- lished work on discrimination of depositional environ- ments has been based on modern sands which contain little fine materiaL The resxilts of this work generally cannot be applied t o sandstones because of the pre- sence of considerable amounts of diagenetic silt- and clay-sized material that often is present in sandstones. In the present study, sandstones were used rather than sands. A problem that always occurs when using grain- size analyses, regardless of whether they are of sands or sandstones, is that of comparing the size distribu- tions. Canonical analysis is a statistical method of com- paring grain-size distributions. The primary aim of canonical analysis is to determine numerical character- istics that best separate size distributions or determine the characteristics they have in common. In using canonical analysis, a typical or model size distribution is selected against which all the size distributions are compared. If physical theory can be applied to the choice of a reference distribution or weight function, then the results may be interpreted more easily in a physical sense. Two sets of numerical values are cal- culated for each size distribution. The discriminate functions show which variable or variables, size classes in this case, are important for discrimination; and the discriminate moments show how the size distributions are related so they may be sorted and classifled. A set of characteristic roots or eigenvalues also are calcu- lated. These eigenvalues, arranged in decreasing numer- ical order, show the proportion of variation among the distributions. Generally, two to three characteristic roots, each having a set of discriminate functions and moments, account for most of the variation among the size distributions. Canonical analysis techniques were applied to grain-size distributions of samples from known depo- sitional environments to see if discrimination could be achieved. Outcrop samples from the Gallup Sandstone of the San Juan basin, and Brushy Canyon Formation of the Delaware basin, and core samples from the " J " formation of the Denver basin were used. Even though the samples contained considerable amounts (greater than 20%) of silt- and clay-sized material, consistent grouping of similar types of size distributions were ob- tained. It was not possible to assign, from the grain- size data alone, groups of sandstone samples to specific depositional environments. The numbers generated by canonical analysis are not unique to a particular en- vironment. However, by using the canonical analysis techniques with grain-size data combined with a knowledge of sed- imentary structures of the same samples, a geologist can obtain more information about transportation mechanisms and depositional environments than could be obtained by the use of either approach separately. REYNOLDS, MITCHELL W., U.S. Geol. Survey, Denver, Colo. EARLY CAMPANIAN (CRETACEOUS) DELTA- FRONT SEDIMENTATION, SOUTH FLANK OF WIND RIVER BASIN, WYOMING Upper Cretaceous rocks of the Mesaverde Forma- tion, exposed between Hudson and Muskrat Creek on the south flank of the Wind River basin, accumulated in an ascending accession of delta-front, tidal-flat, and delta-plain environments. Rocks of the lower two en- vironments grade east and northeast into strata de- posited in an offshore marine environment, whereas rocks of the youngest environment grade east into de- posits of a delta-front platform. During early Campan- ian time, the delta-front facies accumulated across a 14-km-wide belt near Alkali Butte, Repeated fluctua- tions of strand position produced interbedded units of siltstone and sandstone in the facies, and intermittent development of low-relief bars permitted accumulation of estuarine or swamp sediments across subjacent deposits of the delta front. Sandstone units of the delta-front facies show an upward gradation from siltstone and sandy siltstone