20 22. Graph of current velocities required for erosion, transportation, and deposition of sediments ________________ 21 23. Nomenclature for Upper Cretaceous rocks in Sunnyside area.___________________________________________ 24. Diagrammatic sketch of restored stratigraphic section of the Blackhawk Formation and associated rocks in the Book Cliffs area of east-central Utah.________________________________________________________ 25-27. Photographs: 25. Bimodal tangential crossbedding in upper sandstone tongue of Kenilworth Member in Water Canyon. 26. Sandstone of Sunnyside Member in Slaughter Canyon_______________________________________ 27. Root marks in uppermost 1 foot of thick-bedded sandstone facies at top of Sunnyside Member. _______ 28. Fence diagram of Sunnyside coal bed and associated rocks___________________.________________________ 29. Diagrammatic sketches illustrating terminology of crossbedding _-_-_-_-_-___________________ 30-40. Photographs: 30. Tangential crossbedding in lower sandstone tongue of Kenilworth Member._____________________ 31. Ripple cross-lamination in middle thin-bedded sandstone facies of Sunnyside Member___________ 32. Bimodal crossbedding in upper thick-bedded sandstone facies of Sunnyside Member, Water Cany on __ 33. Planar upper surface of upper thick-bedded sandstone facies of Sunnyside Member,______________ 34. Oscillation ripple marks in upper thick-bedded sandstone facies of Sunnyside Member.__________ 34 35. Current ripple marks in upper thick-bedded sandstone facies of Sunnyside Member,______________ 34 36. Megaripples in middle tongue of Kenilworth Member, Slaughter Canyon._______________________ 34 37. Interference ripple marks in middle tongue of Kenilworth Member _____________________________ 38. Sandstone channel deposit in mudstone of upper unnamed shale member of Blackhawk Formation. __ 35 39. Small sandstone channel deposit in sandstone of upper tongue of Kenilworth Member_____________ 40. Sandstone channel deposit in sandstone of upper unnamed shale member of Blackhawk Formation. _ 41. Diagram of fluvial-channel environment.

Enigmatic tubular trace fossils up to eight meters long occur in the Lower Pennsylvanian Middlesboro Member of the Lee Formation. Two morphotypes occur: type 1 trace fossils are plain, smooth, vertical, nonbranching, parallel-walled, tubular structures; type 2 trace fossils branch, have walls with faint vertical striations, regularly or irregularly spaced nodes, and funnel-shaped terminations. Sandstone casts filling type 2 structures have helical spiral morphology, and, in rare individuals, faint meniscate fills have been observed. Both trace-fossil morphotypes have poorly cemented wall linings containing framboidal pyrite, amorphous carbon, quartz sand, and poorly preserved fecal material.The trace fossils occur in a massive, structureless, channel-form sandstone, originating at the contact between a channel lag and the overlying massive fill. The stratigraphic sequence is interpreted to represent a barrier island transgressing an estuarine facies. A tidal inlet within the barrier facies scoured into the underlying estuarine sediments. Subsequent rapid filling of the inlet led to the deposition of the massive sandstone.Origin of these structures is uncertain. The preponderance of evidence favors the hypothesis that the structures are escape burrows of animals that had colonized, or were concentrated in, the lag and were suddenly buried by the deposition of the massive sand. However, no likely burrower has been identified, and several characteristics of the structures and the enclosing sediments indicate that they may be completely inorganic in origin.

The Blaclchawk Formation at Sunnyside, Utah, was deposited along the western margin o:f the Western Interior Cretaceous sea during scutheastv/ard withdrawal of the sea. Sand was the dominant type of land-derived sediment deposited in the Sunnyside district during the regressive phases. Sand bodies prograded seaward in response to changing sedisient supply from a source west of Sunnyside. Yfhere conditions were favorable for the accumulation of vegetable material, peat deposits formed and were later changed to bituminous coal by diagenesis. Studies of the coal bed. show that the coals were formed from accumulation of small, low-growing plants and plant debris that was transported into the area of accumulation. Remains of large plants in the coals are rare. Trace fossils, which are tracks, trails and burrows formed by organisms and preserved in the rock, are extremely abundant in the Blackhawk rocks. These biogenic sedimentary structures are common in Cretaceous deposits throughout the western United States.

Temporary field-recording networks were installed at Gentry Mountain and Little Park Wash, Utah, during the summers of 1967 and 1968 respectively, to study seismic activity related to coal mining and geologic conditions. Tremors, many of which were small manmade earthquakes, were recorded both on chart paper and on magnetic tape; instruments were designed or modified to operate for extended periods with minimum maintenance. Hypocenter positions were estimated to be accurate within 750 feet. Results at Gentry Mountain indicated that tremors occur near mining areas and along large north-trending faults west of the mining area. At Little Park Wash they indicated that nearly all tremors originated near the south part of the Geneva mine. A well-defined belt of faults crossing Little Park Wash 5 miles south of the mine was seismically quiet.

The Sunnyside mining district is in the western Book Cliffs of Utah, at the north end of the Colorado Plateau. The region has been inhabited by humans since pre-Basket-Maker time. Bituminous coal, which forms the economic base for much of east-central Utah, has been mined extensively from the district since about 1900. Most of the coal is used to make metallurgical coke for the steel industry in the Western United States. Mining is difficult in much of the district, but the importance of the coal to the steel industry provides the stimulus for mining it. Among the difficulties that hamper mining in the district, the most important is coal-mine bumps (rockbursts in the coal), which are continuing hazards to life and property in the mines.A sedimentary sequence more than 10,000 feet (3,050 meters) thick, ranging in age from Jurassic to Eocene, crops out in the district and dips gently northeastward into the Uinta Basin. Rocks ranging in age from Precambrian to Early Jurassic in the district are known only from drill records. The exposed sedimentary rocks