Dark Gray Shale Research Articles

Chester and Pottsville Depositional Systems, Outcrop and Subsurface, in Black Warrior Basin, Mississippi and Alabama: ABSTRACT

ABSTRACT Terrigenous clastic depositional systems of the Upper Mississippian Chester Group and the overlying Lower Pennsylvanian Pottsville Group in the Black Warrior basin of Alabama and Mississippi were deposited in distinctly different tectonic settings. The predominantly deltaic Chester sandstone units accumulated on the stable northern shelf of the basin and had a cratonic source to the north or northwest. Detailed subsurface mapping of these cratonic delta systems indicates that the northern shelf can be subdivided into a terrigenous clastic western element (Parkwood and Floyd Formations) and a largely carbonate eastern element (Bangor, Hartselle, Monteagle, and Pride Mountain Formations). Total thickness of the Chester interval on the shelf averages 1,200 ft. Pottsville sediments, in contrast, had a principal source to the southwest of the Black Warrior basin. They represent the thick clastic wedge shed from the Ouachita orogenic belt. Pottsville deposition occurred in a rapidly subsiding foreland basin and involved a maximum sediment accumulation exceeding 12,000 ft in the basinal core. With the Chester group four cycles of deltaic progradation have been identified through data gathered from 600 well logs. Individual genetic intervals between the Tuscumbia Limestone and the base of the Pennsylvanian System are bounded by thin marine transgressive carbonate units. Two deltaic depocenters, a carbonate shelf and ramp, and a shallow basin carbonaceous shale unit comprise the principal depositional systems along the northern margin of the basin. The lowest interval (Lewis) involves a high-constructive lobate delta system whose maximum sandstone axes extend southeastward from Lee and Itawamba Counties, Mississippi, as far as Tuscaloosa County, Alabama. Maximum net sandstone thickness for each of the four lobes is approximately 60 ft. The second interval includes two distinct subdelta complexes of roughly the same age: the Evans High-Destructive Wave-Dominated Delta System on the western side of the northern shelf and the more easterly Hartselle High-Destructive Wave-Dominated Delta system in northwestern Alabama. The Hartselle net sandstone isolith pattern evidences a pronounced northwest-southeast elongation parallel to the shelf edge. Based on outcrop work, some researchers have interpreted the Hartselle as being a barrier bar system. Overlying the Hartselle-Evans genetic unit are the laterally equivalent Muldon Delta complex (Mississippi) and Bangor carbonate shelf (Alabama). The Muldon system is a thick (up to 450 ft of net sandstone), multistoried, high-constructive elongate group of delta lobes that takes in the subsurface Rea, Abernathy, Sanders, and Carter Sandstones. Further to the east, Bangor Limestone thicknesses in excess of 600 ft occur over interior portions of the shelf. Despite this build up, no true shelf edge or slope systems developed. In the interval between the Millerella Limestone and the top of the Mississipian System, there is a fourth Chesterian delta cycle. The distal edge of an extensive Pennington Delta, having an Appalachian source, prograded into northeastern Alabama. Further to the west, the Gilmer high-constructive delta system marks the last Paleozoic cratonic delta system laid down on the northern shelf. With the surface and shallow subsurface Pottsville of the Black Warrior basin in Alabama, the 2,000 ft stratigraphic interval can be subdivided into a minimum of seven vertical genetic components. In contrast with the Chester units, however, laterally extensive coal seams rather than marine transgressive limestone tongues form the bounding elements. On the surface, the lowest Pottsville unit has no productive coal seams and is dominated by massive, quartz-arenite sandstone bodies interbedded with dark gray shale. These rock units record the presence of a basal Pennsylvanian microtidal barrier bar system and associated lagoon. Higher, in genetic intervals 2 through 4, the leading edge of the northward-prograding Ouachita clastic wedge reached north Alabama. It is preserved as prodelta mudstone, bar finger sands, crevasse splay units, destructional sheet sand, and delta plain facies of high-constructive deltas. Intervals 5, 6, and 7 contain a greater quantity of conglomeratic debris. Coals are less numerous, but commonly thicker in this proximal deltaic setting than with the distal delta. Petrographically, the upper Pottsville sandstone bodies are phyllarenites and polylitharenites (metamorphic, volcanic, and sedimentary rock fragments) and contain significant quantities of vein quartz and chert. Careful petrochemical study of the Pennington Delta, subsurface Lewis, Evans, and Muldon systems, and the Pottsville detaic facies should be able to document the respective Appalachian orogenic, cratonic, and Ouachita orogenic source areas for these three distinct Carboniferous terrigenous clastic elements of basinal fill in the Black Warrior basin.

Lithologic patterns in the Energy Shale Member and the origin of "rolls" in the Herrin (No. 6) Coal Member, Pennsylvanian, in the Orient No. 6 Mine, Jefferson County, Illinois

The Energy Shale Member, an argillaceous wedge associated with the Walshville Channel and Herrin (No. 6) Coal Member, consists of a lower dark-gray shale unit and an upper light-gray shale unit in the Orient No. 6 Mine of the Freeman United Coal Mining Company. The dark-gray shale has laminae about one-eighth of an tach thick, is abundantly carbonaceous, and is characterized by the presence of an expandable clay mineral. The light-gray shale has layers as much as two inches thick, contains less carbonaceous matter, lacks expandable clay minerals, and is more coarsely grained than the dark-gray shale. Thus the dark-gray shale unit is inferred to have been deposited in small, shallow water bodies within the swamp. In contrast, the light-gray shale appears to have resulted from widespread inundation of the swamp, perhaps by crevasse splays and other overbank deposits from the contemporaneous Walshville Channel. The light-gray shale is characterized by the presence of rolls--elongate shale bodies of lenticular cross-section that penetrate downward into the coal. Rolls and their associated slips, small slicken-sided normal faults, are most abundant along the margins of dark-gray shale bodies and trend more or less parallel to the boundary separating the two rock types (Krausse et al, 1979). Elsewhere in southern Illinois coal names where the roof rock is uniformly composed of light-gray shale, there are few rolls. These relationships suggest that local accumulation of dark-gray shale in depressions on the peat terminated peat deposition and caused compaction of the underlying peat. Later, when the light-gray shale deposit smothered the entire swamp, the topography of the swamp was inverted. This resulted because peat in previously uncompacted and uncovered areas condensed more than the already compacted peat beneath the dark gray shale lenses. Thereafter, rolls arose through slumping of light-gray shale, which covered the newly created mound-like masses of dark gray shale and previously compacted peat.

Cretaceous Stratigraphy of the Glacier National Park Area, Northwestern Montana

ABSTRACT A sequence of Cretaceous formations as much as 7,000 ft (2,134 m) thick crops out in the eastern and southeastern parts of Glacier National Park and in the adjoining area to the east. Recognition of the many persistent lithologic units in this Cretaceous sequence should be of value in interpreting the complex structure of the region. The oldest rocks, the Kootenai Formation of Early Cretaceous age, consist chiefly of variegated mudstone, siltstone and sandstone of nonmarine origin. In the Park area the thickness of the Kootenai is probably greater than 1,000 ft (305 m). A conspicuous black chert conglomerate, the Cut Bank Sandstone Member, forms the base of the formation and rests unconformably on Upper Jurassic rocks. The Blackleaf Formation, also of Early Cretaceous age, conformably overlies the Kootenai and is about 750 to 800 ft (229-244 m) thick. A marine unit consisting of dark-gray fissile shale and quartzose sandstone forms the basal part of the Blackleaf. Most of the formation is alternating beds of light-coloured, nonmarine clastics. The marine Marias River Shale of Late Cretaceous age unconformably overlies the Blackleaf and is about 1,200 to 1,300 ft (366-396 m) thick. Most of the Marias River is dark-gray shale that contains calcareous and ferruginous concretions and is locally sandy and calcareous. Conformably overlying the Marias River Shale is a marine transitional unit consisting of interbedded shale and sandstone, herein referred to as the Telegraph Creek Formation. The formation ranges in thickness from 120 to 170 ft (36-52 m) on the Kevin-Sunburst dome east of Glacier National Park. The Virgelle Sandstone, which averages 160 ft (49 m) thick, is a massive light-brown sandstone conformably overlying the Telegraph Creek Formation. Resting conformably on the Virgelle Sandstone is the Two Medicine Formation, a nonmarine unit that consists mostly of mudstone with minor lenticular sandstone. The formation is about 2,000 ft (610 m) thick in the Park area. A dark-gray marine formation, the Bearpaw Shale, conformably overlies the Two Medicine Formation. The Bearpaw is nearly 400 ft (122 m) thick east of the Park, but thins to only 235 ft (72 m) south of the Park. The Bearpaw grades upward into a unit of alternating sandstone, siltstone and shale that is as much as 400 ft (122 m) thick. The Horsethief Sandstone, about 90 ft (27 m) thick, is a massive cliff-forming sandstone that was deposited in a regressive marine environment above the Bearpaw. Conformably overlying the Horsethief Sandstone is the St. Mary River Formation, a nonmarine sequence. The St. Mary River Formation is about 1,000 ft (305 m) thick near the eastern margin of the Disturbed belt. Another nonmarine unit, the Willow Creek Formation, overlies the St. Mary River Formation. The Willow Creek consists of about 800 ft (244 m) of variegated clayey rocks and sandstone. The top of the Cretaceous is somewhere within this formation.

Bryophytes and Revegetation of Coal Spoils in Southern Iowa

Strip mining of coal in southern Iowa has left many scattered areas of coal spoils which provide a type of habitat unique to the region. The occurrence and distribution of 29 mosses and 2 liverworts on spoils of varying age was determined and related to processes of spoil revegetation. A higher percent cover and a greater species diversity of bryophytes was observed on the older spoils which appeared to be correlated with increased vascular plant cover. Dicranella heteromalla (Hedw.) Schimp. and Ceratodon purpureus (Hedw.) Brid. were found to be common throughout the spoils, whereas all other species were limited to more protected sites, especially on well vegetated, north-facing slopes. Mosses did not appear to colonize areas exposed to severe erosion, but were limited to areas with some protection provided, especially by vascular plants. Several disjunct or highly localized moss populations were found, including one new state record and thirteen new county records. During the past 50 years, strip mining of coal in southern Iowa has resulted in destruction of about 4450 ha (11,000 acres) of land. In the strip mining process the soil and rock strata overlying the coal, the overburden, are scooped off to expose the coal seam leaving a series of ridges and valleys, frequently with pools of water in the very low valleys. The resultant topography and soils are generally referred to as spoil banks or coal spoils. The typical undisturbed overburden in southern Iowa is composed of (from top to bottom) Wisconsin loess, Kansas glacial till, buff-colored shale and sandstone, gray shale and dark gray shale, all lying above coal-bearing rocks of Pennsylvanian age (Einspahr et al., 1955). Composition of the spoils varies, depending on how the overburden was mixed and deposited in a given place, but generally the order of the strata is essentially reversed, leaving the shales and sandstones exposed on the surface. Spoils usually are composed of a mixture of rock fragments ranging in size from massive chunks of shale and sandstone to sand, silt and clay-sized particles (Cummins et al., 1966). Many spoils are acid due to oxidation of sulfur-bearing minerals, primarily pyrite, markasite and poly-sulfides. These minerals occur in the shales overlying the coal, and acidity develops when this part of the overburden is left on the surface. The effect of this acidity on availability and solubility of chemical elements is recognized as a major problem in spoil revegetation. Especially important are iron, aluminum and manganese which are highly soluble at low pH and frequently reach toxic levels on coal 1Work sponsored by the Iowa Coal Project and conducted in the Energy and Mineral Resources Research Institute at Iowa State University. We are grateful to Dr. Paul L. Redfearn, Jr. for verification of species identifications and to Dr. Howard Crum for identification of Sphagnum. We also thank the owners of the strip-mine study areas for access to their land. 2 Dept. of Botany and Plant Pathology, Iowa State University, Ames, Iowa 50011. This content downloaded from 157.55.39.153 on Mon, 19 Sep 2016 04:57:25 UTC All use subject to http://about.jstor.org/terms 1977] CARVEY ET AL.: BRYOPHYTES AND REVEGETATION OF COAL SPOILS 631

Early Cretaceous Buried Canyon: Influence on Accumulation of Hydrocarbons in Helez Oil Field, Israel

A fossil canyon, known as Gevaram canyon and postulated to be of submarine origin, exists in the southern coastal plain of Israel. This canyon was excavated in rocks of Middle Jurassic age which unconformably underlie strata of Early Cretaceous age. The canyon runs in a northwest direction into the old Tethys through the Helez oil field and is at least 16 km long and 7 km wide. The canyon widens west of Helez. Maximum canyon depth is nearly 1,000 m; sediment fill consists mostly of dark-gray shale of the Gevaram Formation. Several sandy beds are present in the central part of the channel and limestone breccia derived from the wall rock fills the base. After the canyon was filled and buried, clastic beds of the Helez Formation accumulated in the southwestern part of the area; gray shale of the Gevaram Formation accumulated in the northwest. An embayment formed in the Helez area as a result of local subsidence caused by compaction of the shale that filled the buried canyon. Through that embayment the source beds of the Gevaram Formation reached the area in which the reservoir beds of the Helez Formation were deposited. Contact between reservoir beds and source beds thus was established, resulting in accumulation of oil in the Helez field.

Belly River Waterfloods Conception to Success

Abstract The oil-bearing Belly River pools of the Pembina area of Alberta were discovered in the search for Cardium oil and developed under skepticism by many operator. The indicated high connate water saturation, the presence of swelling clays within the formation and the lack of readily available source water provided poor waterflood potential. After producing the pools for 10 years under a primary solution gas drive mechanism, the operators initiated three water-flood projects. As a result of the outstanding performance of these projects, two reservoir simulation studies were prepared to determine the optimum waterflood scheme. These studies recommended the extension of the waterflood to the majority of the Belly River reservoirs in the area and justified an extensive infill drilling program. An analysis of the Belly River flood performance is presented and the simulation studies are reviewed. The proposed infill drilling and surface facility expansion programs are also illustrated. Introduction THE BASAL BELLY RIVER SANDSTONE is found in the central plains and south-central mountains and foothills of Alberta. Although the sand occurs commonly in these areas and is often hydrocarbon-bearing, it is generally considered as a secondary objective. The Alberta Energy Resources Conservation Board currently estimates a total of 526 million barrels of oil in place in recognized Belly River pools. Ninety per cent of this recognized Belly River oil is located in the Keystone and Buck Creek areas of the Pembina Field, which were developed in the early sixties (Fig. 1 and 2). The Belly River sand has a high connate water saturation and is infilled with kaolinitic clays. For these reasons, a cautious approach to waterflooding the Belly River reservoirs was taken and it was not until 1970 that waterflood projects were initiated in the Pembina Keystone Belly River "B", "M" and "U" pools. Within two years of the start of injection, excellent GOR and production response was observed. In some cases, the production rate had a three to four-fold increase. Consequently, the Pembina Belly River "B" North Unit ' waterflood project was restudied with a numerical simulation model to investigate infill drilling, as was the Pembina Belly River "C" Pool, which was still on primary depletion. Both studies indicated that infill drilling was extremely attractive. Accordingly, an estimated 100 infill wells will be drilled in the Keystone Belly River pools and waterflood projects will be extended to the remaining major Belly River pools in the area. Reservoir Description GEOLOGY The Upper Cretaceous Basal Belly River Sandstone is contained in a progradational sequence between the Marine Lea Park Shale and the overlying continental strata. The reservoir rock is a light grey, fairly well sorted fine to medium-grained sandstone with high clay content and interbedded calcareous sands and dark grey silty shales(1,2). The sand was deposited as offshore bars and infilled channels. Bar and channel sands of different depositional ages are discernible in the Pembina Keystone area, with communication apparent between bars and channels of common age.

Carboniferous Biostratigraphy, Prudhoe Bay State 1 to Northeastern Brooks Range, Arctic Alaska

The 3,000-ft-thick Carboniferous section in Atlantic Richfield/Humble Prudhoe Bay State 1 is divided into two groups. The older rocks in the section, Endicott Group, are 1,200 ft thick and unconformably overlie argillites of the pre-Mississippian Neruokpuk Formation. Within the Endicott Group, the Kekiktuk Conglomerate is 600 ft of gray to dark-gray sandstone, shale, and thin-bedded coal, deposited in a paralic environment. The overlying Kayak(?) Shale is 620 ft of quartzitic and calcareous red sandstone, siltstone, shale, and arenaceous to ooid limestone; it represents transition to marine sedimentation and contains microfossils of Zone 16s (Chesterian). Overlying the Endicott Group, the Lisburne Group is 1,770 ft thick. Within the Lisburne Group, the Alapah L mestone, 1,050 ft thick, includes arenaceous bryozoan-echinoderm wackestone and packstone to lime mudstone and microdolomite with gypsum. The age of the Alapah Limestone ranges from Zones 16s through 18 (Chesterian). The overlying Wahoo Limestone, 720 ft thick, is a series of cyclic glauconitic-bryozoan-echinoderm-ooid packstone and grainstone capped by lime mudstone and arenaceous microdolomite. These are interpreted to represent cyclic deposition of tidal-flat lime mud developed directly over ooid tidal bars. The age of the Wahoo Limestone ranges from Zone 20 to Zone 21 (Pennsylvanian). In comparison with the section penetrated by this well the outcrop data 75-112 mi southeast show that the Endicott Group is diachronous because, in the Franklin Mountains, it has a lithology similar to that found in the Prudhoe well but contains (Meramecian) Zone 11 marine microfossils. During the Meramecian the Sadlerochit Mountains were high; the Endicott Group is either absent or less than 50 ft thick here. The Alapah Limestone of Prudhoe Bay State 1 is more dolomitic and arenaceous than its equivalent in the Franklin or Sadlerochit Mountains. The Wahoo Limestone of the Prudhoe Bay subsurface is similar in lithology and in environments of deposition to the outcrop sections in the Sadlerochit Mountains.

Fluvial, Deltaic, and Slope Reservoir Sandstone in West-Central Texas: ABSTRACT

More than 300 Lower Permian sandstone oil and gas fields are present in an area of about 7,000 sq mi on the Eastern shelf and slope of the Midland basin. All these fields appear to be in stratigraphic traps in fluvial, deltaic, and slope depositional environments. Two Lower Permian Cook fluvial sandstone systems extend in a downdip direction across the Eastern shelf to the shelf edge, where progradational Cook sandstone facies form two high-constructive deltas. These are the proximal parts of a thick terrigenous clastic wedge of sediments covering the eastern slope. Outcrops of Cook channel-fill deposits grade upward from conglomerate and quartz sandstone, to gray shale. Downdip from outcrop to the shelf edge, Cook sandstone is present in one meander belt system 82 mi long. The upper 30 mi is about five mi wide and bounded by shale and two thin lenticular limestone beds. The belt narrows to about one mi where adjacent limestone beds are thicker and were more resistant to lateral channel erosion. About 58 mi downdip from outcrop, the meander belt divides into two belts. Each belt is about one mi wide and bounded by shale and thick limestone beds to the shelf edge. Point bars (with characteristic electric-log SP curves), crevasse splays, and/or natural levees are discernible in the meander belts. Many stratigraphic traps are present in point bars, in sandstone belts perpendicular to regional dip, and in belts of sandstone that overlie buried reefs, hills, structures, and other channel sandstones. Paleocreekology is applicable in locating topographic features on the paleoshelf. Both Cook sandstone deltas, nearly joining, are in an area of 295 sq mi. Delta-plain facies consist of interbedded dark gray shale, fine-grained, lenticular sandstones, and thin coal lenses underlain by thick, medium-grained sandstone facies in distributary channels. Electric-log SP curves of the channel sandstones are characteristic. Delta front distributary mouth bar and sheet-sandstone facies overlie thick prodelta shale and thin, lenticular sandstone. The Group 4000 Cisco sandstone field is the only oil field of any significance in the two deltas. It produces from delta-plain sandstone facies. West of the shelf edge, the Cook wedge of shale and sandstone lenses reaches a maximum thickness of about 1,300 ft at midslope and thins basinward. The base is a maximum gradient of about 3° at midslope. The Northeast Bloodworth Canyon sandstone field produces from Cook sandstone, probably a turbidite and slump deposit, evidently deposited in a submarine channel. The Jameson Strawn sandstone field, about 35 sq mi in area, produced from Cook lower slope sandstone lenses, probably part of a submarine fan. End_of_Article - Last_Page 420------------

Stratigraphy and Sedimentary Environments of Lower Cretaceous Rocks, Southern Western Interior

Upper Albian rocks crop out on the southern edge of the Western Interior province in Kansas, Oklahoma, northeastern New Mexico, and southeastern Colorado. Four formations are recognized in the several regions: Cheyenne Sandstone and Kiowa Formation in Kansas and western Oklahoma, Tucumcari Formation in New Mexico, and Purgatoire Formation consisting of the Lytle Sandstone Member and the overlying Glencairn Shale Member in southeastern Colorado and parts of adjacent states. Recognition of four ammonite-bivalve zones indicates that the basal Kiowa and much of the Cheyenne are time equivalents of the uppermost Fredericksburg rocks in Texas. Most of the Kiowa is equivalent to Washita units through the Denton Formation in North Texas. The Tucumcari and Glencairn correlate with upper parts of the Kiowa in southern Kansas. Part of the Lytle is equivalent to lower parts of the Kiowa and part may be older than the basal Kiowa. These rocks record the transgression and regression of the Early Cretaceous sea from the Gulf Coast region of the United States. The sequence consists of coastal-plain, sea-margin, and open-sea deposits. Cross-bedded, conglomeratic sandstones of the Cheyenne and Lytle were deposited by fluviatile processes on a coastal plain; laminated and thin-bedded sandstone and mudstone of the Kiowa, Purgatoire, and Tucumcari that commonly bear marine infaunal and epifaunal mollusks originated in the sublittoral margin of the seaway; and the dark-gray shale of these three formations, locally bearing a fauna of burrowing detritus- and filter-feeding invertebrates, originated as mud in the open seaway.

Miocene Benthonic Foraminif era from the Iwaf une Formation, Northern Niigata Prefecture

This paper reports on the benthonic smaller foraminifera from the Iwaf une formation, Miocene Daishima stage, in northern part of the Niigata oil fields. The Daishima stage smaller foraminifera is hardly studied in Japan.The benthonic smaller foraminifera occurs only the dark gray shale facies of the lowest Iwafune formation. It is consisted of three faunas as follows: arenaceous, calcareous and mixed faunas. Among them the first one is the main fauna of this formation.The foraminiferal species of these fauna is similar to that of the Nishikurosawa-lower Funakawa fauna, middle Miocene, in the oil fields of Japan; the characteristic species which indicates the definite horizon of the Daishima stage, is not to be found.The calcareous fauna is rather similar to that of the recent lower neritic-bathyal zones in the warm water. The arenaceous fauna and the lithofacies of the lowest Iwafune formation show that most of this area was under stagnant condition in the Daishima stage.

Stratigraphic Analysis of Source-Bed Occurrences and Reservoir Oil Gravities

A knowledge of hydrocarbon source-bed occurrences and lithologic types is fundamental to an understanding of the distribution of oil accumulations. A study of the relations between source-bed lithology and the crude oil in producing reservoirs in the southeastern United States and West Texas was undertaken to provide geologic data on factors affecting oil gravities and the time and direction of migration. This study shows that distinct oil-gravity characteristics can be correlated with source-bed lithologic types, and that the depth of burial which is required to convert oil to gas condensate also influences the oil-gravity characteristics. In addition, the study shows that an approximate overburden of 2,000 feet is needed for flush migration from the source bed. Statisti al analyses, theory, and major worldwide oil-field examples verify the dominant role of shale, marl, and clay as source beds for the underlying reservoirs. In contrast, shale-free carbonate sequences contain oil accumulations whose source is an underlying shaly, fine-textured, or phosphatic limestone. Crude oil in the Ellenburger of West Texas originated in shale source beds in the Simpson, Woodford, and Lower Pennsylvanian, each of which exhibits a distinctive curve showing the variations between oil gravity and depth. Other primary source-bed sequences in the Permian basin are Pennsylvanian dark gray shale, Wolfcampian and Leonardian basinal terrigenous clastic sediments (dark shale and siltstone), and Guadalupian basinal and lagoonal terrigenous clastics.

Ordovician, Silurian, and Devonian Biostratigraphy of East-Central Alaska

A predominantly shale and chert sequence has been mapped from the Canadian border at Latitude 65°00^prime N. to the Nation River about 25 miles northwest. It has Ordovician and Silurian graptolites in the lower half, and Middle Devonian corals and Upper Devonian spores in the upper half. The lower half of the sequence consists of about 400 to 900 feet of predominantly dark gray graptolitic shale with lesser amounts of grayish black laminated chert. This unit has been traced by Green and Roddick from the international border southeastward into the Dawson area of the Yukon Territory and northeastward into the Ogilvie and Richardson Mountains where it has been mapped by Jackson & Lenz, Norris, and others as the Road River Formation. In the Tatonduk-Nation Rivers area the Road River Formation rests disconformably on a sequence of Middle and Upper Cambrian limestone that locally may include Lower Ordovician (Tremadoc) beds at its top. The sequence of graptolite faunas from the Road River Formation in Alaska is essentially the same as the graptolite zones established by Elles and Wood in Great Britain. All the standard series of the Ordovician and Silurian are probably represented in the formation with the exception of the Tremadoc and possibly the Arenig and Wenlock. Overlying the Road River Formation is a formation, 200 to 800 feet thick, consisting predominantly of thinly bedded and laminated light gray to black chert and siliceous shale that is here named the McCann Hill Chert. This new formation disconformably overlies the Road River Formation, and its lower boundary is at the base of a distinctive limestone and shale member. The basal limestone and shale member of the McCann Hill Chert contains a remarkably varied fauna including corals, brachiopods, trilobites, conodonts, ostracods, and fish of Eifelian (early Middle Devonian) age. Spores from the upper part of the formation resemble those from the overlying Nation River Formation and indicate a Late Devonian age. The McCann Hill Chert is conformably overlain by the Nation River Formation--a thick succession of inter-bedded graywacke, chert conglomerate, and silty shale of Late Devonian age. In the vicinity of Jones Ridge, only 7 miles north of exposures of the Road River Formation, Upper Cambrian limestone is overlain by a pure limestone section containing Ordovician, Middle Devonian, and perhaps Silurian shelly faunas contemporaneous with the Road River Formation and the thinner basal limestone and shale member of the McCann Hill Chert. The rapid change from graptolitic shale to limestone probably reflects changes in conditions of sedimentation, but could be a result of thrust faulting. The Tatonduk-Nation Rivers area seems to lie in a transitional zone between an early Paleozoic eugeosynclinal belt south of the Yukon River and a contemporaneous miogeosynclinal belt along the Porcupine River. One puzzling feature of the lower Paleozoic sequence in the Tatonduk-Nation Rivers area is its thinness in contrast to the much thicker volcanic and detrital sequence on the south and the considerably thicker carbonate sequence on the north.

Petrography and Origin of the Silurian Rochester and McKenzie Shales, Morgan County, West Virginia

ABSTRACT The Rochester Formation consists mainly of black, fissile clay shale; highly abraded biosparite limestone occurs at the base, with thin beds of finer-grained ostracod, pellet, or micrite limestone in the upper portions. All original micrite has recrystallized to microspar, with partial obliteration of fecal pellets. The lower limestones accumulated in a high-energy shell bank adjoining the Keefer barrier bar, whereas the upper dark gray shales and fine limestones formed in a brackish, stagnant lagoon protected by the Keefer bar. Occasional storms formed edgewise conglomerate beds within the shale. The McKenzie Formation is chiefly olive to gray clay shale with siltier laminae and burrow fillings. Ostracod biosparites are common, and fibrous sparry calcite overgrowths on the shells have greatly expanded the fabric in some specimens. All of the originally micritic rocks have recrystallized to microspar; some contain brachiopod shells with geopetal fecal pellets and syngenetic primary dolomite crystals filling the former body cavities. The dolomite is optically perpendicular to, and molded on top of, fibrous sparry calcite overgrowths. The McKenzie was deposited in an open marine area with variable salinity, affected by influx of muddy river water.

Revision of Colorado Group on Sweetgrass Arch, Montana

The writers propose that the rocks formerly assigned to the Colorado shale on the Sweetgrass arch of northwestern Montana be divided into a lower unit, the Blackleaf formation with four named members, and an upper unit, the Marias River shale with four named members. The Blackleaf formation, of Early Cretaceous age, consists of marine and non-marine rocks that include much sandstone and sandy shale. It is divided into the Flood, Taft Hill, Vaughn, and Floweree members. The oldest member, the Flood, consists of brown-weathering ledge-forming sandstone beds and dark gray fissile shale probably marine in origin. It is 138 feet thick at its type section. The Taft Hill member, a marine sequence that is 240 feet thick as its type locality, consists of greenish gray glauconitic sandstone and gray soft bentonitic siltstone and shale. The Vaughn bentonitic member is characterized by light-colored bentonitic and tuffaceous siltstone that contains small crystals of orange-red heulandite. This non-marine unit is 97 feet thick at its type locality. The Bootleg er member, 330 feet thick at its type locality, is a marine sequence of interbedded sandstone, siltstone, and shale, but includes some layers of bentonite and chert-pebble conglomerate. The Marias River shale, of Late Cretaceous age, consists of 900-1,200 feet of dark gray marine shale. It is divided into the Floweree, Cone, Ferdig, and Kevin members. The Floweree (basal member) is mostly non-calcareous shale and siltstone; it is 63 feet thick at its type locality. The Cone calcareous member, 54 feet thick, consists of calcareous shale, thin beds and concretions of limestone, and some layers of bentonite. Sandy non-calcareous shale characterizes the Ferdig shale member which is 225 feet thick at its type locality. The Kevin shale member, 620 feet thick, contains numerous gray, yellow, and brown limestone concretions and dusky red dolostone concretions as well as many thin layers of bentonite. The middle of the member is marked by the MacGowan concretionary bed, a thi unit of dolostone and limestone that contains pebbles of chert and phosphatic siltstone.

Pierre Shale Along Western and Northern Flanks of Black Hills, Wyoming and Montana

The marine Pierre shale, of Late Cretaceous age, on the northern and western flanks of the Black Hills, consists of dark gray shale with some sandy shale and sandstone, and many beds of bentonite. It ranges in thickness from 2,000 to 2,700 feet. In this area the Pierre shale may be divided into several members on the basis of lithologic differences in the shale and the presence of sandy and bentonitic units. In ascending order, these are the Gammon ferruginous member (including the Groat sandstone bed), the Mitten black shale member, and an unnamed upper part that consists of half or more of the formation. This upper part is chiefly dark gray shale but contains at the base a gray silty shale unit and near the top the Monument Hill and Kara bentonitic members. Studies in progress by Cobban reveal at least 16 ammonite zones in the Pierre shale on the western flank of the Black Hills.

Lower Cretaceous of Southern Alberta and Adjoining Areas

The total stratigraphic interval studied in southern Alberta and northern Montana includes all of the Lower Cretaceous strata between the sub-Cretaceous unconformity and the base of the Fish Scale sandstone, which occurs near the Lower Cretaceous-Upper Cretaceous boundary. Abrupt facies changes in the Lower Cretaceous sediments in western Alberta necessitate a different nomenclature in the Foothills area than in the Plains area. In the southern Alberta Foothills the continental sediments of the Blairmore group can be divided into two distinct lithologic parts. The lower Blairmore consists dominantly of gray shale and gray to buff protoquartzite-type sandstones and contains two members. The Cadomin member at the base of the lower Blairmore is a persistent chert and quartzite pebble conglomerate which can be traced throughout the Alberta Foothills. The Calcareous member, consisting of gray to buff argillaceous limestones, calcareous shale, and buff calcareous quartzose sandstone, occurs at the top of the lower Blairmore. The upper Blairmore sediments show a marked change in color and lithologic character from those below. The sediments are dominantly green, and the sandstones are usually highly feldspathic an chloritic arkosic graywackes and lithic graywackes. The Crowsnest formation overlies the Blairmore group in the southwestern corner of Alberta and is composed of a series of tuffs, agglomerates, breccias, and flows. In the Plains area the Lower Cretaceous is divided into four major lithologic units, in ascending order: Mannville group, Joli Fou formation, Viking formation, and an unnamed unit above the Viking formation and below the base of the Fish Scale sandstone. The Mannville group is dominantly non-marine but contains some marine strata in central Alberta. The lower Mannville usually contains a basal quartzose sandstone member called the Cut Bank and Sunburst sandstones in southern Alberta, and the Ellerslie sandstone in central Alberta. The top of the lower Mannville is placed at the top of the Calcareous member which is correlated lithologically with the Calcareous member in the Blairmore group. The upper Mannville consists of kaolinitic subgraywacke-type sandstones, siltstones, shales, and thin coal beds, and is equivalent to the lower part of the upper Blairmore at the west. In central Alberta a marine Glauconitic sandstone occurs near the base. The Joli Fou formation is a marine dark gray shale body at the base of the Colorado group which loses its lithologic identity in western and southern Alberta. The Viking formation consists of a marine succession of salt-and-pepper protoquartzites interbedded with gray siltstones and shales. In southern Alberta the Viking and Joli Fou formations are not recognizable as two distinct units, and the entire succession is called the Bow Island formation, which is correlated with parts of the upper Blairmore and Crowsnest formations in the Foothills area. An isopach map of the Lower Cretaceous indicates the Alberta Foothills was the site of a marginal basin in Lower Cretaceous time. Petrographic and lithofacies studies suggest the Lower Cretaceous End_Page 590------------------------------ sediments were mainly derived from an orogenic positive area in south-central British Columbia, with minor contributions from a mildly positive area in northern Saskatchewan and Manitoba. The lithologic character of the lower Blairmore suggests a meta-sedimentary source area, whereas the arkosic sediments of the upper Blairmore are indicative of an igneous source. The abrupt decrease in the feldspar content of the sandstones eastward, accompanied by an increase in kaolinitic clay matrix, is attributed to physical and chemical processes, and to dilution of the western derived sediments by clastics from an eastern source.

Geology of the Clay Deposits in the Olive Hill District, Kentucky

AbstractTHE Olive Hill fire clay bed of Crider (1913) is the principal source of the raw material used in the refractory industry of eastern Kentucky. The bed is a discontinuous underclay from 1 to 20 ft above a prominent unconformity which separates Mississippian and Pennsylvanian rocks. Upper Mississippian rocks consist of ten marine limestone and shale units all truncated by the unconformity. Pennsylvanian rocks are chiefly: (a) massive deltaic sandstone; (b) cut-and-fill deposits of shale, siltstone and sandstone which contain several beds of coal and underclay including the Olive Hill fire clay of Crider (1913); and (c) dark-gray shale beds.The Olive Hill fire clay of Crider consists of approximately one-third flint clay, two-thirds semiflint clay, and minor amounts of plastic clay. The clay mineral content ranges from nearly pure kaolinite to kaolinitic clay containing about 40 percent illite and mixed-layer clay. The kaolinite ranges from highly crystalline to very poorly crystalline “fireclay” kaolinite. The degree of crystallinity of the kaolinite and hardness of the clay vary inversely with the amount of illite and mixed-layer clay present. The nearly pure kaolinite is believed to have formed by removal of silica and alkalies from mixtures of kaolinite, illite and mixed-layer clay by leaching shortly after deposition.An isopach map shows that Crider’s Olive Hill fire clay occurs in irregular, lens-shaped deposits. Fossil plant rootstocks with rootlets attached in the clay clearly indicate it supported plant growth. The overlying coal and presence of some organic material in the clay suggest that the Olive Hill fire clay was deposited under a reducing environment in swamps.

Organic Materials of Early Middle Devonian, Mt. Union Area, Pennsylvania

The name Newton Hamilton formation is here applied to the widespread shaly facies of the Onondaga group in central Pennsylvania. The formation is divisible into two members: the Hares Valley dark gray shale and limestone member, above, a new name; and the Beaverdam Run dark gray shale, below, a name modified from the usage of Willard. The bituminous materials of the Devonian shales in the Mt. Union area range from .002 to .24 per cent of the rock, with the Marcellus black shale containing the largest quantities. The bitumens, on separation by means of column chromatography, were found to contain fractions referable to saturated hydrocarbons, aromatic hydrocarbons, asphaltenes, and polar compounds. Experiments with gas chromatography of the bituminous materials suggest that most of the column chromatographic fractions consist of compounds having carbon numbers above 20. Upward from the Ridgeley sandstone to the Newton Hamilton, Marcellus, Mahantango, and Burket shales, the saturated hydrocarbons form an increasing percentage of the bitumens and of total hydrocarbons whereas the aromatic hydrocarbons decrease upward. This relation is believed to have a paleogeographic significance, resulting from the greater stagnation and poorer circulation of the Oriskany through Marcellus seas as compared with the Mahantango and Burket. A resume is given of some of the relations of the bitumens to the petrologic-environmental types (petrai); the nearshore petra and depressional sapropelic petra are relatively more favorable for hydrocarbon preservation than some of the other types. Free sulphur is found in many of the Newton Hamilton and Marcellus samples but is less common in the overlying Mahantango. The sulphur-bearing layers, also characterized by increased content of aromatic and tarry fractions, imply restricted poorly circulated seas under stillstand or regressive conditions during deposition of the Onondaga and Marcellus. Separation of a humic acid constituent having absorptive peaks at 264-272 mµ was made by sulphuric acid hydrolysis and paper chromatography. This material, believed to be a pyridine compound, ranges from .04 to 2 per cent of the Devonian rocks, with the greatest concentrations occurring in the Marcellus and Burket black shales.

Producing Viscous Fluids

Abstract The discovery in March, 1946, of the Boscan low gravity-high viscosity crude oil accumulation presented the Richmond Exploration Co. with a multitude of problems almost unique in the industry. Solution of these problems through experience and cut-and-try methods has resulted in the successful development of a large source of rod-building materials. Introduction Among the oil companies operating in Venezuela, to which heavy crude means some 14° to 15° API gravity oil, the name Boscan has practically become a synonym of "viscous fluid." Indeed, Boscan crude has an average 10° API gravity fluctuating from 9° to 12° and an average viscosity of 26,000 SSU at 122°F fluctuating from 17,000 to 50,000 SSU. This asphalt-looking oil has to be pumped out of the ground, shipped 25 miles away and loaded on tankers. When the Boscan field was discovered, the technical obstacles brought up by the physical characteristics of its crude made questionable the commercial exploitation of a petroleum so difficult to produce. However, three years later, Richmond was shipping 14,000 B/D of Boscan crude. Even if the figure does not seem impressive, it means the practical answers to a large sequence of major production problems which had to be solved within the rates of the available equipment through constantly improving methods and designs. The drilling of a Boscan well is not a difficult task; it is when the rig is removed that obstacles start arising. Geology The Boscan field is located 26 miles southwest of Maracaibo in the State of Zulia in the western part of the Maracaibo basin. The stratigraphic sequence encountered in and above the production section in the Boscan area includes Eocene, Oligocene, Miocene and Pliocene sediments. The Upper Eocene consists of the Las Flores formation with interbedded sands and dark gray carbonaceous shales. In the upper part, two zones of beach and bar sands (designated as Upper Boscan and Lower Boscan) produce heavy oil. The Lower Oligocene overlies the Eocene and contains poor to well developed beach sands interbedded with light gray sandy claystone. Effectively permeable sands in this formation (designated Basal Icotea) locally are oil productive. The middle of Oligocene, principally claystone, contains thin sands which are oil productive in the eastern part of the field. This is Middle Icotea.

Jurassic Subsurface in Southern Alberta: ABSTRACT

Jurassic rocks underlie all of southern Alberta from its eastern and southern boundaries to the Rocky Mountain front on the west. The northern boundary is roughly crescent shape, approximately coinciding with the South Saskatchewan River and its tributary, the Oldman River, to within a few miles of Lethbridge. From that point the boundary trends northwest, passing a few miles east of Calgary. On Alberta plains, Jurassic strata are readily divisible into three formations, which were originally described and named in Montana, and which are, in ascending order, Sawtooth, Rierdon, and Swift. In Alberta Foothills, Jurassic strata are called the Fernie formation, which is roughly the equivalent of the three formations of the Plains. Jurassic strata in southern Alberta rest unconformably on the Rundle formation of Mississippian age. On the Plains they are overlain unconformably by the basal sandstones of the Blairmore formation which have been correlated with the Cutbank and Sunburst sands of Montana. The unconformity at the top of the Jurassic truncates the formations so that they wedge out northward; consequently, the Swift, being the uppermost, has a very limited distribution in Alberta having been eroded completely from the crest of the Sweetgrass arch and remaining only in the extreme southeastern corner of Alberta and in a narrow belt paralleling the Foothills. The Rierdon and Sawtooth formations extend northward approximately to the limits of the Jurassic as defined. In the Foothills the Fernie is overlain y Kootenay sandstone and shale. The Sawtooth formation consists of two sandstone members, separated by green, pyritic, non-calcareous shale. The upper sand is a reservoir for oil and gas in several small fields in Alberta. The formation has a maximum thickness of about 235 feet. The Rierdon formation is made up of an alternation of gray calcareous shale and greenish gray limestone with some pyrite, glauconite, and iron-stone, and has a maximum thickness of 200 feet. The Swift formation lies unconformably on the Rierdon and has a maximum thickness of 150 feet. It consists of glauconitic sandstone, siltstones, concretions, dark gray shale, and usually has chert pebbles at the base. Facies changes take place from west to east in the Sawtooth, Rierdon, and Swift formations so that at the eastern boundary of Alberta they may be readily correlated with the Gravelbourg, End_Page 414------------------------------ Shaunavon, and Vanguard formations of Saskatchewan. However, they are not the exact equivalents of these formations since some overlapping occurs. End_of_Article - Last_Page 415------------