1955 fieldwork. Rezak performed the majority of the ship board analyses, and Neuman and Walter took and cared for the cores. Help also was received with core handling from Donald Stewart in 1955 and from James Double in 1956.Fronr their work leading toward publication of a separate report on the Foraminifera, Ruth Todd and Doris Low have provided information on occurrence of the principal foraminiferal species; and ~iiss Low undertook the onerous responsibility of typing, checking, and processing the often con1plicated pages of this report. Kenneth Lohman studied selected samples for diatoms in the midst of heavy pressure from other work. Biological determinations have also been provided by specialists of the U.S. National 11 useum and other organizations as indicated on tables 3, 10, and 11. The fishes were identified by Leonard Schultz, of the U.S. National Museum, and plankton collections were reported on by David L. O'Berry, of the University of Miami Marine Laboratory. As usual, Frederiek M. Bayer has been a constantly available and generous source of information and advice on ecological subjects.Arrangements for work at Andros Town in 1955 were made by Kay Norton and Arne Lindroth of the Wenner-Gren Foundation. At Andros Town much courteous help was received from Gunnar Lindstrs3m, Kenneth Sundin, and Misse Peterson.Both in 1955 and in 1956, F. G. Walton Sn1ith and Hilary Moore came to the rescue at the crucial mon1ent with marine equipment from the University of Mian1i Marine Laboratory. To them and to G. E. Voss, of the Marine Laboratory, and Robert Ginsburg, of Shell Development Corp., I am warmly grateful for rnany favors and much useful advice. To Farrington Daniels I am also grateful for taking tirne out from a very busy period in Washington, D.C., for discussion of the precipitation problem and for subsequent helpful correspondence.An emergency grant of $785 fron1 the Geological Society of America permitted F. D. Sisler's employment for critically needed bacteriological work until arrangements could be completed for his assignrnent to the U.S. Geological Survey. The Department of Geology, U.S. National Museum, generously provided laboratory space and facilities for his work for the duration of this project.Most of the collaborating authors have read and criticized all sections of the report, and D. L. Graf and R. S. Boardn1an critiqued the entire report. Helpful review of individual sections was made by F.

The Frontier Formation in the Green River Basin of Wyoming, Utah, and Colorado, consists of sandstone, siltstone, and shale, and minor conglomerate, coal, and bentonite. These strata were deposited in several marine and nonmarine environments during early Late Cretaceous time. At north-trending outcrops along the eastern edge of the overthrust belt, the Frontier is of Cenomanian, Turonian, and early Coniacian age, and commonly is about 610 m (2,000 ft) thick. The formation in that area conformably overlies the Lower Cretaceous Aspen Shale and is divided into the following members, in ascending order: Chalk Creek, Coalville, Alien Hollow, Oyster Ridge Sandstone, and Dry Hollow. In west-trending outcrops on the northern flank of the Uinta Mountains in Utah, the Frontier is middle and late Turonian, and is about 60 m (200 ft) thick. These strata disconformably overlie the Lower Cretaceous Mowry Shale. In boreholes on the Moxa arch, the upper part of the Frontier is of middle Turonian to early Coniacian age and unconformably overlies the lower part of the formation, which is early Cenomanian at the south end and probably Cenomanian to early Turonian at the north end. The Frontier on the arch thickens northward from less than 100 m (328 ft) to more than 300 m (984 ft) and conformably overlies the Mowry. The marine and nonmarine Frontier near the Uinta Mountains, marine and nonmarine beds in the upper part of the formation on the Moxa arc ., and the largely nonmarine Dry Hollow Member at the top of the Frontier in the overthrust belt are similar in age. Older strata in the formation, which are represented by the disconformable basal contact of the Frontier near the Uinta Mountains, thicken northward along the Moxa arch and westward between the arch and the overthrust belt. The large changes in thickness of the Frontier in the Green River Basin were caused mainly by differential uplift and truncation of the lower part of the formation during the early to middle Turonian and by the shoreward addition of progressively younger sandstone units at the top of the formation during the late Turonian and early Coniacian. The sandstone in cores of the Frontier, from boreholes on the Moxa arch and the northern plunge of the Rock Springs uplift, consists of very fine grained and fine-grained litharenites and sublitharenites that were deposited in deltaic and shallow-water marine environments. These rocks consist mainly of quartz, chert, rock fragments, mixed-layer illite-smectite, mica-illite, and chlorite. Samples of the sandstone have porosities of 4.7 to 23.0 percent and permeabilities of 0.14 to 6.80 millidarcies, and seem to represent poor to fair reservoir beds for oil and gas. The shale in cores of the Frontier Formation and the overlying basal Billiard Shale, from the Moxa arch, Rock Springs uplift, and overthrust belt, was deposited in deltaic and offshore-marine environments. Samples of the shale are composed largely of quartz, micaillite, mixed-layer illite-smectite, kaolin, and chlorite. They also contain from 0.27 to 4...

No abstract

No abstract

No abstract