728 Association Round Table be acquired by open-cut, adit, or test drilling. Core log- ging is particularly important for determination of the engineering characteristics of rocks. Structure-contour, isopach, overburden, and interburden maps are re- quired in mine design, and ultimately in mine devel- opment. Reclamation requires determinations of over- burden and interburden chemistry. Cost and time advantages result if hydrologic and soils/rock quaUty data are collected early, thereby sav- ing time in the permitting process, and reducing the ulti- mate cost of reclamation. JACOBSEN, S. R., Chevron U.S.A., Denver, CO, and D. J. NICHOLS, U.S. Geol. Survey, Denver, CO AppUcation of Cingulum Index to Dinogymnium in Mil- liard Shale, Southwestern Wyoming The cingulum index (CI) was defined for fossil dino- flagellates of the genus Dinogymnium as a two-digit number expressing the distance from the middle of the cingulum to the apex divided by the total length of the test and multiplied by 100. This morphologic statistic, which is independent of specimen size, was interpreted as a character of interspecific taxonomic importance. Analysis of CI values of specimens of Dinogymnium sp. from the Milliard Shale (Upper Cretaceous) of south- western Wyoming suggests that the CI has biostrati- graphic significance. CI values were calculated for Dinogymnium from the Milliard Shale at Cumberland Flats, Lincoln County, Wyoming. When plotted against stratigraphic position of samples, mean and maximum CI values for succes- sive populations show an increasing trend upward through the formation. Population size and sample spacing are variable, and it is uncertain whether evolu- tion or paleoecology is the controlling factor, but the progressive change through more than 1,000 m is useful for biostratigraphic zonation of the formation. The cu- mulative frequency distribution for all specimens mea- sured in this study is quadramodal, suggesting that four morphologic variants, indistinguishable by transmitted light microscopy, are present. JADO, ABDUL RAOF, Univ. Petroleum and Miner- als, Dhahran, Saudi Arabia Stratigraphic Relations of Permian Formations in Parts of Colorado and Utah This study suggests that the Permian rocks in north- western Colorado and northeastern Utah were depos- ited in shallow-marine shelf, transitional, and terrestrial environments. The Wolfcampanian and early Leonardi- an upper layers of the Weber formation are predomi- nantly eolian quartz sandstones deposited in a broad coastal area of low relief. This coastal area was at the northwestern end of the ancestral Uncompahgre uphft, and was intermittently covered by seawater as indicated by the few thin marine carbonate rocks. The upper We- ber intertongues with the Grandeur Member of the Park City Formation in the study area. The carbonates and cherts of the Grandeur were deposited in shallow-ma- rine waters during a transgressive cycle which was prob- ably caused by a crustal downwarping of the shelf. The Meade Peak Member of the Phosphoria Forma- tion was deposited on top of the Grandeur by cold, phosphorous-rich, upwelUng water as a result of contin- ued Early Permian transgression. Landward from the phosphorites, carbonates were contemporaneously de- jwsited, and further landward, siltstones. Regression near the end of Leonardian shifted the depositional enviroimient belts westward and resulted in deposition of the Franson Member carbonates and cherts on top of the phosphorites. Maximum regression during the Guadalupian produced very shallow and highly saline waters in the area and subaerial exposure for long periods, combined with a significant increase of terrestrial, fine-grained sediment supply. These condi- tions led to the deposition of interstratified gypsum, silt, and shale of the Mackentire Tongue redbeds. The eastern half of the study area is characterized by greenish-gray and tawny beds which are partly time- equivalent of the Meade Peak, Franson, and Macken- tire. The environments of deposition are interpreted to be those of a reducing, restricted marine embayment. These beds are more closely related to the Goose Egg Formation in central Wyoming than to any other for- mation in the area and are so designated. Extensive regression beginning in late Guadalupian continued into the Triassic and caused the deposition of the Moenkopi red beds. JOHNSON, HOWARD D., and BRUCE K. LEVELL, Koninklijke/Shell Exploratie en Produktie Laborato- rium, Rijswijk, Netherlands Sedimentology of Lower Cretaceous Subtidal Sand Complex, Woburn Sands, Southern England The Lower Cretaceous Wobum sands have long been considered a transgressive and p>artly open marine tidal sand deposit. They form a 60-m thick, northward-wedg- ing sandstone body between Jurassic shales, which they unconformably overlie, and a transgressive marine clay which oversteps them northward. Our studies identify three southward-imbricated, ero- sionally bounded sand units as follows. Orange Sands (oldest) comprise alternations of cross- bedded, channel-fill sands and thinner bedded, biotur- bated, heterolithic sands. Bidirectional paleocurrents show a dominant northeasterly flood direction. Silver Sands are characterized by tabular cross-bed sets (up to 3 m thick) which overlie subhorizontal, low- angle (4 to 8°) or concave-upward erosion surfaces. Bi- directional paleocurrents reflect a slight dominance of the southwesterly ebb direction. Red Sands (the youngest) are structurally similar to the Silver Sands but are distinctive on the basis of abun- dant detrital ferric oxide and strong horizontal burrow- ing. Northeasterly dipping cross-bedding is relatively uncommon, producing an overwhelmingly dominant southwesterly, ebb-directed paleocwrent mode. The interfingering of high-energy tidal channel-fill deposits and heterolithic beds is typical of subtidal es- tuarine deposits. Furthermore, the upward decrease in the proportion of heterolithic facies and burrowing in- tensity, the upward increase in the proportion of large- scale cross-bedding and channel width/depth ratios.