Unnamed Unit Research Articles

A reappraisal of the stratigraphy of the upper Miocene unit X in the Maaseik core, eastern Campine area (northern Belgium)

The stratigraphy of the Tortonian-Messinian sequence from the Maaseik core, located on the shoulder of the Roer Valley Graben (RVG) in the eastern Campine area in northern Belgium, was improved. The analysis of the marine palynomorphs (dinoflagellate cysts and acritarchs) from the uppermost part of the Breda Formation, the unnamed unit X and the basal part of the Lower Waubach Member led to the recognition of the mid to upper Tortonian Hystrichosphaeropsis obscura biozone. Therefore deposition of this entire analyzed sequence took place sometime between 8.8 to 7.6 Ma. Paleoenvironmental interpretation of the palynomorphs points to shallow marine conditions and most probably a stressed environment during the deposition of unit X. A comparison with the time equivalent stratigraphy in the nearby Belgian Campine, the Dutch RVG and the German Lower Rhine Basin allowed the identification of the Inden Formation and required a shift in the base of the Kieseloolite Formation compared to the earlier lithostratigraphic interpretation of the Maaseik core. The regional stratigraphic scheme shows the progressive northwestward extension of the river facies from the Lower Rhine during the late Tortonian.

GEOLOGICAL NOTE

Abstract The term “Sukunka Formation” is proposed for a 113 to 169 metre thick mixed siliciclastic and carbonate unit lying between the Middle Devonian Stone and Dunedin Formations in the Rocky Mountain Front Ranges of northeastern British Columbia. The unit is best developed near the headwaters of the Sukunka River, where it outcrops along a series of closely spaced imbricate thrusts. In the type area, it can be divided into three (informal) members: lower, middle and upper. The lower member overlies the Stone Formation unconformably and consists of inter-bedded orthoquartzite, dolostone and sandy dolostone. It is overlain by the middle member that consists predominantly of brick red weathering siltstones interbedded with minor amounts of dolostone. These ‘red beds’ are readily recognizable in the field and can be used elsewhere in the area to identify thrust imbricates. The upper member consists of a series of thick to massive bedded, well cross-bedded and resistant weathering clean quartzose sandstones which gradationally overlie the middle member. The top of the formation is also disconformable. It is transgressed and overlain by the basal calcareous shales and limes of the Dd-1 member of the Dunedin Formation. However, lag deposits from the Sukunka Formation occur within the basal calcareous shales and limes of the Dd-1 member. This condition is thought to reflect progressive transgression of higher stratigraphic levels of the Sukunka Formation to the east by the rising waters that led to accumulation of the Dunedin Formation. Diagnostic fossils have not been recognized in the Sukunka Formation. Presently, it is dated as early Middle Devonian based solely on stratigraphic position. In the subsurface, in the same stratigraphic position between the Stone and Dunedin formations, unnamed argillaceous, sandy and silty carbonates have also been identified. These, further to the east, may be equivalent to the unnamed detrital unit of the Chinchaga Formation.

Controls on deltaic sedimentation in glacio-eustatic cycles of late Marsdenian (Namurian R 2b 4 to R 2c 1, Pennsylvanian) age in the UK Central Pennine Basin

Summary Evolution of the succession between the Bilinguites eometabilinguis (R 2b 4) and Verneulites sigma (R 2c 2) marine bands of Marsdenian (Pennsylvanian) age in the Central Pennine Basin, and its offshore extension into the North Sea Basin, is discussed. Five separate marine bands are now recognized. Two closely spaced marine bands, B. eometabilinguis and B. metabilinguis , occur at the base of the R 2b 4 cycle and a higher B. metabilinguis band occurs at the base of the R 2b 5 cycle. The overlying B. superbilinguis and V. sigma marine bands define an additional thinner and much simpler cycle (R 2c 1). These three cycles are all of glacio-eustatic origin. A new sequence-stratigraphic interpretation examines the relationship between the constituent sandstone units (currently named the Hazel Greave Grit, Beacon Hill Flags, Guiseley Grit, Ashover Grit, Roaches Grit, plus local names and unnamed units). Different types of fluvial-deltaic sequences were deposited in different phases of the cycle and some cycles lack coarse clastic lithologies. The succession in parts of Yorkshire and Lancashire contains a major non-sequence in the R 2b 5 cycle. A revised interpretation of the incised deep channels in the Roaches Grit in Staffordshire, suggesting river channel adjustment to a post-glacial climate rather than infill of a pre-eroded palaeovalley, is also presented. Many of these different features can be explained by climatic variations associated with the Carboniferous Ice Age. Variations in basin bathymetry and fault related subsidence exercised more localized controls.

NEW ICHNOLOGICAL, PALEOBOTANICAL, AND DETRITAL ZIRCON DATA FROM AN UNNAMED ROCK UNIT IN YUKON-CHARLEY RIVERS NATIONAL PRESERVE (CRETACEOUS: ALASKA): STRATIGRAPHIC IMPLICATIONS FOR THE REGION

A paleontological reconnaissance survey on Cretaceous and Paleogene terrestrial units along the Yukon River drainage through much of east-central Alaska has provided new chronostratigraphic constraints, paleoclimatological data, and the first information on local biodiversity within an ancient, high-latitude ecosystem. The studied unnamed rock unit is most notable for its historic economic gold placer deposits, but our survey documents its relevance as a source rock for Mesozoic terrestrial vertebrates, invertebrates, and associated flora. Specifically, new U-Pb ages from detrital zircons combined with ichnological data are indicative of a Late Cretaceous age for at least the lower section of the studied rock unit, previously considered to be representative of nearly exclusively Paleogene deposition. Further, the results of our survey show that this sedimentary rock unit preserves the first record of dinosaurs in the vast east-central Alaska region. Lastly, paleobotanical data, when compared to correlative rock units, support previous interpretations that the Late Cretaceous continental ecosystem of Alaska was heterogeneous in nature and seasonal.

Testing Alternative Tectono-Stratigraphic Interpretations of the Late Palaeozoic−Early Mesozoic Karakaya Complex in NW Turkey: Support for an Accretionary Origin Related to Northward Subduction of Palaeotethys

Lower Carboniferous-Upper Triassic rocks of the Karakaya Complex exposed E-W across Turkey are critical to reconstructions of Palaeotethys in the Eastern Mediterranean region. Despite decades of research, the origin and emplacement of the Karakaya Complex remains controversial because it is mapped either as an overall stratigraphic succession of sedimentary olistostromes or as a stack of thrust sheets and mélange. Tectonic models include a continental rift, a back-arc rift, a marginal oceanic basin, and an accretionary prism formed by subduction of a wide ocean. Subduction is seen as either northwards or southwards. To test the alternatives, the various litho-tectonic units and their contact relations were studied in nine outcrops across northwestern Turkey. Our field evidence indicates that the Karakaya Complex was assembled by regional-scale thrust faulting without evidence of stratigraphical contacts or even of deformed sedimentary contacts between the main units. The structurally lower levels of the Karakaya Complex of Triassic age (~lower Karakaya assemblage) are dominated by an imbricated, mainly volcaniclastic sequence (~Nilüfer Unit) that was metamorphosed under high pressure-low temperature conditions and rapidly exhumed. Structurally higher, lower-grade rocks (~upper Karakaya assemblage) are characterised by several coherent lithotectonic units, including the Upper Permian-Lower Triassic Çal Unit, dominated by alkaline volcanics and shelf to redeposited carbonates, a contrasting mainly Upper Permian unit including terrigenous sediments, and the Triassic Ortaoba Unit, dominated by mid-ocean ridge-type basalts, radiolarian sediments and sandstone turbidites. Two associated composite units (Hodul and Orhanlar units) are interpreted as accretionary mélanges (rather than olistostromes) that were tectonically assembled and emplaced during Late Triassic time. Pre-Karakaya-age meta-siliciclastic sedimentary rocks (~Kalabak unit) are intruded by Devonian and Lower Carboniferous granites in several areas. Arkosic cover sediments (Halılar Formation) above the Kalabak unit accumulated during Late Triassic (Norian) time prior to final emplacement of the Karakya Complex. The 'basement units' are interpreted as thrust slices that were emplaced to a high structural level during final emplacement of the Karakaya Complex in latest Triassic time. Transgression by shelf sediments followed from the Early Jurassic onwards following regional uplift and erosion. In our proposed tectonic model, Palaeotethyan oceanic crust (~Triassic Ortaoba Unit) subducted northwards beneath the Sakarya Continent. Seamounts capped with carbonate build-ups formed near the southern margin of Palaeotethys (~Çal Unit). The Upper Permian neritic carbonates associated with terrigenous clastics (unnamed unit) probably rifted from the Tauride continent to the south. Large oceanic seamounts erupted within the Triassic ocean (~Nilüfer Unit). The seamounts

AN EDRIOASTEROID-DOMINATED ECHINODERM ASSEMBLAGE FROM A LOWER PENNSYLVANIAN MARINE CONGLOMERATE IN OKLAHOMA

Abstract Four species of isorophinid edrioasteroids, Ulrichidiscus forbesi n. sp., Neoisorophusella whitesidei n. sp., Postibulla westergaardi n. sp., and Parapostibulla graysoni n. sp., are described from unnamed unit 1 of the Golf Course Formation, Dornick Hills Group, Lower Pennsylvanian (Morrowan), at Forbes Ranch, north of Marietta, southern Oklahoma. This locality is the first report of edrioasteroids attached to extraformational clasts, and they exhibit extremely high specimen density and the highest taxonomic diversity known from the post-Ordovician. The associated fauna consists of the stemless crinoid Paragassizocrinus tarri, serpulid worm tubes, and the acrothoracic barnacle boring, Rogerella, along with a few brachiopods, rugose corals, and other open marine organisms. Edrioasteroids show no preference for clast type, size, or shape. Intraspecific spatial competition is shown by polygonal specimen outlines in highly crowded conditions, whereas interspecific competition results in specimen over...

Ordovician chitinozoan biozonation of the Brabant Massif, Belgium

Chitinozoans from seven Ordovician units (Abbaye de Villers, Tribotte, Rigenée, Ittre, Bornival, and Brutia formations and a new unnamed unit, here provisionally called the Asquempont unit) belonging to the mainly concealed Brabant Massif, Belgium are described herein. Fifty-six samples were taken from rocks cropping out at the south-eastern rim of the massif in the Orneau, Dyle–Thyle and Senne–Sennette valleys. Microfossil preservation is moderate to poor, and the chitinozoans occur in low numbers. Taxonomically, the recovered chitinozoans are distributed into 29 taxa, some placed under open nomenclature. Together with earlier published graptolite and acritarch data, the analysis of the chitinozoan assemblages resulted in an improved chronostratigraphy of the investigated formations. We propose a local chitinozoan biozonation with 11 zones for the Brabant Massif. The oldest investigated units yielded chitinozoans typical for North Gondwana, and younger units (starting in the middle Caradoc), yielded some taxa also common in Baltica. As the Brabant Massif formed part of the microcontinent Avalonia, the chitinozoan assemblages recovered from the massif support the inferred drifting of Avalonia from high latitudes towards middle latitudes in the Ordovician as was suggested earlier.

Quaternary stratigraphy and paleoenvironments of the Texas Rolling Plains

The Lingos Formation (new) comprises a thick sequence of Quaternary alluvial-fan, lacustrine, fluvial, and eolian deposits. These strata cover 9,250 km 2 of the western Rolling Plains of Texas. The Lingos Formation is part of the newly designated Paducah Group, which includes three previously recognized middle to upper Pleistocene formations in addition to the Lingos Formation and several unnamed or uncorrelated stratigraphic units. The origin of these formations is closely associated with westward retreat of the Caprock Escarpment and with subsidence resulting from regional intrastratal dissolution of Permian evaporites. Dissolution produced subsidence basins, which gradually filled with sediment derived from the retreating escarpment. Lakes occupied at least some of the subsidence basins and were sustained by emergent ground water rather than by surficial inflow. Stratigraphic relations and paleofaunas document significant Quaternary environmental change linked to subsidence, stream incision, and climatic variation. Chronologic control is afforded by diagnostic vertebrate faunas (Rancholabrean and Holocene), Paleoindian through historic archeological remains, and more than 50 radiocarbon ages. On the basis of these data, deposition of the Lingos Formation spanned the period from less than 300 ka ago to the present. The depositional history of the Lingos Formation provides a model for the origin of the Paducah Group as a whole, and for Quaternary landscape evolution throughout the Rolling Plains.

Evidence of Paleogene sedimentation on Graham Island, Queen Charlotte Islands, west coast, Canada

The palynomorph taxa Ctenosporites eskerensis, Pesavis tagluensis, and Tilia spp. demonstrate that an unnamed sedimentary unit in the Union Port Louis well and float from Mud Bay Creek, Skidegate Inlet, British Columbia, most likely fall in the age range Early Eocene to Early Oligocene. These two localities, 66 km apart, have yielded the oldest Tertiary sediments yet confirmed on the Queen Charlotte Islands or in the Queen Charlotte Basin. The sediments are apparently continental. They exhibit high thermal maturity, which may be due to local volcanism, plutonism, or regional subsidence. The relationship of the Paleogene sediments to the late Tertiary Skonun Formation has not been determined.

Burlington Conodonts and Tournaisian-Visean Boundary, Hannibal, Missouri, and Burlington, Iowa: ABSTRACT

At its type-locality in Iowa, the Burlington Limestone consists of thick-bedded white limestones of the Dolbee Creek and Cedar Fork Members separated by the brown, iron-rich, and dolomitic carbonates of the Haight Creek Member. At Hannibal, Missouri, however, the Burlington has five divisions. An unnamed unit underlies the Dolbee Creek Member and another overlies the Cedar Fork; both unnamed units resemble the Haight Creek Member. Dolbee Creek sections at both locations are nearly the same age. The Cedar Fork, however, is younger at Hannibal than at Burlington. Bactrognathus distortus occurs in the uppermost Dolbee Creek and lower Haight Creek at Hannibal and is restricted to the lower Haight Creek near Burlington. Eotaphrus occurs through most of the Cedar Fork and within the uppermost Haight Creek near Burlington, but ranges from the middle Haight Creek into basal Cedar Fork at Hannibal. In Iowa, Taphrognathus is not present in the Burlington Limestone, but first appears at the base of the overlying Keokuk Limestone. At Hannibal, Taphrognathus occurs through most of the uppermost unnamed unit of the Burlington. At Hannibal, the Tournaisian-Visean boundary occurs in the upper part of the Burlington Limestone. Near Burlington, it coincides with the Burlington-Keokuk contact.

Sedimentology and stratigraphy of the Miocene Zia sand of New Mexico

The Zia Sand was named and described by Galusha (1966), who presented a summary of field work in the Zia Sand by Frick Laboratory parties under his direction. Rocks included in the formation are partly, but not entirely, the same as those included in the Lower Gray Member of the Santa Fe Formation by Bryce and McCann (1937). Galusha and Blick (1971) summarized previous publications on rocks assigned to the Zia Sand. On biostratigraphic evidence, they excluded from the formation several exposures Bryan and McCann (1936) and Spiegel (1961) included in or correlated with the Lower Gray Member. Manley (1978) redefined the Zia Sand to. include the overlying rocks Galusha regarded as an unnamed unit or units equivalent in age to, but lithologically distinct from, the Tesuque Formation of the Santa Fe Group, in the Espanola basin. Kelley (1977) likewise combined the Zia Sand with the overlying units, retaining the name Zia for eolian sands. These revisions are rejected here; the limits of the Zia Sand used are very nearly those set by Galusha, in publications (1966; Galusha and Blick, 1971) and in the records of the Frick Laboratory. The rocks equivalent in age to the Tesuque Formation should receive further study and separate names. The Zia Sand as used here is a distinct depositional sequence. Galusha excluded the Zia Sand from the Santa Fe Group; other authors have included it. This paper does not attempt to resolve the question.

Oil and Gas Potential of San Luis Basin, South-Central Colorado: ABSTRACT

Are there major oil and gas traps in the San Luis basin? Gas and oil seeps have been reported and used at ranches in this basin since the late 1800s. Despite the presence of porous and permeable sandstones, thick widespread clays for seals, and hydrocarbons, only 15 oil and gas tests have been drilled in 2,500 sq mi (4,023 sq km), most before 1955. Recent seismic work has helped delineate the structure and stratigraphy of the eastern half of the basin where gas occurs in all water wells. A high on the Precambrian basement surface dominates the center of the basin with sediments faulted and dipping down to the east to a depth of about 20,000 ft (6,096 m) adjacent to the Sangre de Cristo Mountains. The basin fill is Tertiary clastic and volcanic rocks that can be divided into four units using seismic work, well samples, and palynology. The uppermost unit, the Alamosa Formation (Pliocene-Pleistocene), is green lacustrine clay and sandstone. The underlying Santa Fe Formation (Miocene-Pliocene) is red fluvial-lacustrine clay and sandstone with a few thin volcanic flows. An unnamed unit (middle Paleocene to Eocene) is angularly unconf rmable with the overlying Santa Fe and similar in lithology. The oldest unnamed unit consists of thick volcanic flows interbedded with volcaniclastics and claystones and is also unconformable with the overlying unit. Potential trapping mechanisms are major sedimentary-rock pinch-outs and truncations in the unnamed unconformable units as well as in channels in the overlying fluvial sandstones. Porous volcanic rocks and sandstones on the fault blocks, fault traps, and structural closures are also possible traps in the oldest unit. The paucity of drilling and the presence of traps and hydrocarbons make the outlook optimistic for this basin. End_of_Article - Last_Page 714------------

Age of the Ogilvie Formation (Devonian), Northern Yukon: Based Primarily on the Occurrence of Brachiopods and Conodonts

The Ogilvie Formation, formerly dated as Eifelian and Givetian, is locally confined to the Early Devonian, Emsian. Regionally the top of the Ogilvie is markedly diachronous ranging in age from Emsian to Givetian. The Ogilvie Formation conformably overlies the Late Silurian to Early Devonian Gossage and/or early Emsian Michelle and Cranswick Formations. The stratigraphic thickness of the Ogilvie varies from 200–3500 ft (61–1068 m) over relatively short geographic distances. The ages of the lower and upper beds of the Ogilvie are based on brachiopods, conodonts, corals, and trilobites. Locally, the lower part of the overlying unnamed shale unit is regarded as a lateral equivalent to parts of the younger Ogilvie carbonate sections. The Eifelian age of the basal beds of the unnamed shale unit is derived from a few strategically located dacryoconarid tentaculite collections. The Ogilvie Formation is a shallow water carbonate shelf deposit, locally reefal, which had its most extensive development in the later part of the Emsian. From the later part of the Emsian through Givetian, the carbonate shelf was gradually inundated by shales until in the late Givetian only a very small area of carbonate deposition remained in the western Yukon (Mount Burgess).The brachiopod affinities lie with the Cordilleran Subprovince of the Old World Province and with forms of similar age described from central Nevada. The conodonts and trilobites are correlative with forms from Arctic Islands, eastern Alaska, and Nevada. The Emsian tetracoral fauna is similar to that of the Emsian of eastern Australia whereas the Eifelian fauna is similar to that of other parts of northwestern Canada.Five informal conodont faunal units, ranging in age from Emsian through Eifelian, are proposed for the Michelle–Ogilvie sequence. In addition, the P. varcus Zone (Givetian) is recognized at the top of the Ogilvie at one section.

Late Triassic palynofloras of North America and their European correlatives

Upper Triassic continental strata in the United States contain rare horizons which yield pollen assemblages. The Dockum Group and Chinle Formation of the American Southwest, as well as certain rock units within the Deep River, Richmond, and Taylorsville Basins of the Newark Group, contain palynomorphs which exhibit stratigraphically restricted ranges in Europe. The presence of Vallasporites ignacii, Camerosporites secatus and Ovalipollis ovalis in the Dockum Group, Chinle Formation, Cumnock Formation of the Deep River Basin, Vinita Formation of the Richmond Basin, and unnamed units in the Taylorsville Basin suggest that all these units are approximately contemporaneous. The occurrence of these and other stratigraphically diagnostic pollen taxa, particularly Patinasporites densus, further indicates a Middle to Late Karnian age for these units. The palynostratigraphy also implies that the Pekin Formation of the Deep River Basin is slightly older than the above mentioned units.

Biostratigraphy of Upper Mississippian and Associated Carboniferous Rocks in South-Central Idaho

Carboniferous rocks above the Milligen Formation in the central Lost River Range of south-central Idaho range in age from Late Mississippian (middle Meramecian or middle Visean) through Pennsylvanian (Atokan or Westphalian), as determined by small calcareous foraminifers, corals, and brachiopods. The lower part of the post-Milligen sequence, composed largely of limestone, is Mississippian and is divided into four formations first described by Huh in the Lemhi and Lost River Ranges. These rocks are overlain by an unnamed Pennsylvanian sandstone unit which, in turn, is overlain by a thick sequence of unnamed Pennsylvanian limestone. The composite section in the Lost River Range has a minimum exposed thickness of 7,000 ft. Two partial sections in the Hawley Mountains are des gnated reference sections for the four formations of Mississippian age in the Lost River Range--the Middle Canyon Formation at the base, the Scott Peak Formation, the South Creek Formation, and the Surrett Canyon Formation at the top. Foraminiferal Zones 13(?) through 21 are recognized in the Carboniferous rocks. Zone 19, the Homoceras ammonoid time equivalent, is described herein for the first time from North America. Representatives of megafaunal Zones Pre-E through Post-K are also recognized in the Mississippian and the directly overlying rocks of the Carboniferous sequence. Microfaunas and megafaunas indicate that the Meramec-Chester boundary is near the middle of the Scott Peak Formation, that the Visean-Namurian boundary is near the base of the Surrett Canyon Formation, and that the Mississippian-Pennsylvanian boundary is about at the base of the unnamed sandstone unit. Carbonate lithologies and associated faunas and microfaunas indicate deposition in a marine environment in which there was a general change from quiet water having locally restricted circulation during Middle Canyon Formation deposition to turbulent water that was freely circulating during deposition of the upper strata. Sand in the basal Pennsylvanian rocks may indicate a distant orogenic pulse very near the Mississippian-Pennsylvanian time boundary.

Sub-La Jolla Unconformity in Vicinity of San Diego, California

Rock units of the San Diego area include two basic divisions separated by a high-relief unconformity: (1) an intensely deformed late Mesozoic basement complex and (2) an essentially flat-lying succession of latest Cretaceous and Cenozoic sedimentary rocks. The lower part of the latter division in the northern part of the San Diego area consists of several Upper Cretaceous rock units and the Eocene La Jolla Formation. Upper Cretaceous (Campanian-Maestrichtian) marine sandstone and shale of the Rosario formation crop out along the coastal area at Point Loma, La Jolla, and near Carlsbad. The Rosario is overlain unconformably by the La Jolla Formation. Another Upper Cretaceous unit crops out in the vicinity of Rancho Santa Fe east of the Rosario outcrop belt; in marked contrast to the Rosario, it is nonmarine and is dominantly a massive reddish boulder conglomerate. This unnamed unit unconformably overlies the basement complex and is separated from the La Jolla Formation by a high-relief (up to 450 ft) disconformity. The unnamed boulder conglomerate at Rancho Santa Fe apparently correlates with a sub-Rosario conglomeratic redbed unit reported from several wells in the San Diego area, and a conglomerate-sandstone unit beneath the Rosario near Carlsbad. If this correlation is correct, and if the contact between the Rosario and the unnamed unit is essentially planar, these relations indicate a post-Rosario uplift and slight westward tilting, an episode of erosion exposing both the Rosario and the sub-Rosario conglomerate, and subsequent La Jolla deposition on either of the Cretaceous formations, or on the basement complex, but without total destruction of the pre-La Jolla topography.

NEW GEOLOGICAL CONCEPTS, CASTERTON AREA, OTWAY BASIN, VICTORIA

The Casterton area of the north-west margin of the Otway Basin contains thick Mesozoic and Tertiary sediments along a shoreline composed of Cambro-Ordovician metamorphics and associated intrusives. Subsurface and structural information has been gained from two deep wells and a structure drilling programme, and from reflection and refraction seismic work. A large structure has been outlined which is at present being drilled by a third deep well, Casterton No. 1.The Mesozoic sediments are represented by an Upper Cretaceous unnamed sand unit overlying the Paaratte Formation and by the Lower Cretaceous Merino Group. The Merino sediments have been divided into seven lithological units in the Heathfield No. 1 well, the upper four of which can be correlated with intervals in the Tullich No. 1 well. Below Unit 4 is an unconformity apparent from dipmeter surveys.The Merino Group consists of mudstones, siltstones, sandstones and shales. The coarser sediments vary from lithic sandstone, through lithic greywacke to calcareous sandstone, and also include some replacement limestone. They contain considerable volcanic detritus, as well as lithic grains derived from adjacent basement areas. Plant fragments and carbonaceous materials are common. The sediments were deposited in a near-shore, shallow-water, marginal marine environment.Structurally the area has been influenced mainly by vertical tectonics. Structure drilling and refraction seismic show that this faulting is not responsible for the Kanawinka escarpment in the Casterton area. Large basement faults with a throw of up to 6,000 feet exist to the north-east of the Kanawinka escarpment.

Paleozoic Sequence in Eastern Brooks Range, Alaska

The sequence described lies in the eastern Brooks Range in northeastern Alaska. Rocks of late Paleozoic age predominate but rocks as young as Jurassic are present. Rocks of Devonian and possibly older age occur in two east-trending belts. In the southern belt the Skajit Limestone, 500-2,600(?) feet thick, formerly believed to be of Silurian age, is now determined to be of Middle(?) and Late Devonian age. An unnamed unit of limestone and siltstone (Upper Devonian), 0-2,500(?) feet thick, rests on the Skajit. The limestone-siltstone unit intertongues with and is overlain by an unnamed unit of slate and sandstone (Upper Devonian) 2,000-4,500 feet thick, which locally rests disconformably on the Skajit. The Kanayut Conglomerate (Upper Devonian), 0-5,000 feet thick, conformably overlies the slate-sandstone unit and probably grades into it laterally. Rocks in the northern belt comprise the four members of the Neruokpuk Formation of Late(?) Devonian or older age; a quartzite-schist member more than 4,000 feet thick, a limestone member 1,000± feet thick, a limestone-phyllite member 1,000± feet thick, and a phyllite-chert member, as much as 3,300 feet thick, which overlies the other members, locally with strong angular unconformity. The Kekiktuk Conglomerate, a new formation of Devonian or Mississippian age, 0-400 feet thick, unconformably overlies the Neruokpuk Formation. The formations of Mississippian age occur in both belts. The Kayak Shale (Lower Mississippian) and Kayak(?) Shale (Lower(?) and Upper Mississippian), 400-1,200 feet thick, rest on the Kanayut and Kekiktuk Conglomerates and, locally, on the Neruokpuk Formation. The Lisburne Group comprises three formations. The Wachsmuth Limestone (Lower Mississippian), 0-950 feet thick, disconformably overlies the Kayak Shale in the western part of the area. The Alapah Limestone (Upper Mississippian), 600-1,950 feet thick, rests disconformably on the Wachsmuth Limestone. Where the Wachsmuth is absent, the Alapah rests conformably on the Kayak(?) Shale. The Wahoo Limestone (a new formation of Pennsylvanian(?) and Permian age), 0-1,400 feet thick, overlies the Alapah with probable disconformity. The Siksikpuk Formation (Lower(?) Permian), is more than 600 feet thick and consists mostly of shale. It rests unconformably on the Wahoo Limestone at Galbraith Lake and on the Alapah Limestone west of Galbraith Lake. East of Galbraith Lake the Sadlerochit Formation (Permian and Triassic) overlies the Wahoo limestone. The Sadlerochit is more than 1,000 feet thick, and consists of sandstone, siltstone, and shale. Unconformities suggest uplift during early Late Devonian time and folding during Late Devonian to Early Mississippian time. The regional unconformity between Mississippian and Permian rocks diminishes eastward and deposition may have been continuous through Pennsylvanian time in part of the eastern Brooks Range.

New Devonian and Mississippian Formations in De Long Mountains, Northern Alaska

The Kugururok formation, of Late Devonian age, consists largely of dolomite and limestone with minor shale, sandstone, and conglomerate, and is probably more than 2,000 feet thick. The Mississippian Lisburne group is divided into three marine formations: the Utukok, Kogruk, and Tupik. The Utukok formation is at least 2,500 feet thick at its type locality and consists mostly of ferruginous sandy limestone, calcareous and quartzitic sandstone, and calcareous shale. The Kogruk formation, as much as 1,500 feet thick, is composed of thick-bedded, fine- to coarse-grained, gray limestone with minor beds and lenses of chert. The Tupik formation, as much as 700 feet thick, is predominantly dark gray to black, finely crystalline limestone and black chert. Geographic distribution of these units is shown, and they are compared with the Devonian and Mississippian sequence in the Shainin Lake area, central Brooks Range. Other unnamed Devonian and Mississippian units in and near the De Long Mountains area are briefly described.

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.