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The proposed Great Bear wilderness study area has very good potential for discovery of natural gas resources and somewhat lesser potential for oil production. The area contains numerous potential hydrocarbon reservoir and source rocks. Structural traps for the accumulation of gas in the subsurface cannot be determined without seismic surveys and possibly drill holes, but structural traps can be inferred from a comparison of the surface geology of the study area with that in gas producing areas to the north in Alberta, Canada. The proposed wilderness study area is in the northern disturbed belt of Montana which contains a structural and stratigraphic history similar to that in the Alberta disturbed belt which contains major reserves of gas and minor amounts of oil. Successful gas exploration has been conducted a few miles east of the study area, but no seismic or drilling operations have been conducted within the area. Five wells east of the area were drilled in the 1950's. All these wells recovered natural gas but were shut-in, or abandoned, because the region was too remote and the price of gas too low for profitable production. These wells had a total potential productive capacity of 6.3 million cubic feet ofmore » gas per day. The area contains potential hydrocarbon reservoir rocks of Devonian, Mississippian, Jurassic, and Lower Cretaceous ages of which most of them produce oil and/or gas from fields to the east on the Sweetgrass Arch. Some of the potential reservoir units thicken markedly within the study area. All potential reservoir units are overlain by shale, a common cap-rock for hydrocarbons.« less

*».« »*» INTRODUCTION »..,,.,» 1 Location and general description »......*....... .» 1 Acknowledgements t. 3 General geology ft***** 3 Sulfide mineralization ,.......* .«........».. . 6 SUQ AL KHAMIS AREA 9 Location ,.......« *....,..*».,« ».... 9 Scope and purpose 9 Sampling..., ,.......*.^... 9 Stratigraphy , *....*.»....».,..*....11 Metasedimentary rocks I.......« «..»...*. »** . ...H Metavolcanic and pyroclastic rocks 12 Siliceous dolomite? 13 Pyroclastic rocks *».... ....*..» «...13 Argillite 1^ Metasedimentary rocks II....,.» ,.».....l^ Other metamorphic rocks ....,».I1* Vein type rocks........« ,.,, *.....«15 Granite gneiss ,16 Peralkalic granite 17 Tertiary? rocks 17 Recent unconsolidated sediments........*..,.......*........I8 Mineralization 18 Wadi Sishah prospect 1^ Description...,, I8 Conclusions and recommendations 20

l INTRODUCTION i Description and objectives i Location and accessibility 3 Geography and geomorphology 5 Previous investigations 7 Acknowledgements 3 PRESENT INVESTIGATIONS ^....... 9 Introduction 9 Geologic mapping 10 Diamond drilling 13 Topographic surveys 14 Analysis of drill cores 17 GEOLOGIC SETTING 17 STEUtf IG3AFHY -20 Older metavoIconic rocks 20 Metasedimentary rocks 23 Younger matavolcanlo -cooks 25 Intrusive rocks.. 27 Tertiary and younger rocks 29