Early Transgression Research Articles

Paleogeography of Eustatic Model for Deposition of Mid-Continent Upper Pennsylvanian Cyclothems: ABSTRACT

Abstract The hypothesis that eustatic sea level changes produced Upper Pennsylvanian cyclothems in Midcontinent North America has been supported by recent documentation of many episodes of Mississippian through Permian glaciation in Gondwanaland (Crowell, 1978). Changes in Midcontinent paleogeography and sedimentary facies during a single eustatic advance and retreat of the sea are described in 6 phases: 1. At maximum transgression, deep water promoted development of a thermocline, quasi-estuarine circulation cell, upwelling, and anoxic bottom conditions, all leading to widespread deposition across the Mid-continent of phosphatic black shale, which graded in shallower peripheral areas to gray marine shale and carbonates. 2. Shallowing during early regression destroyed the thermocline, which restored bottom oxygenation and changed deposition from black to gray shale, then to skeletal calcilutite as benthic algal carbonate production became established across the Midcontinent. Deltas began prograding from Oklahoma and the Appalachians, and shoreline carbonates began prograding southward from the Dakotas. 3. During late regression, shoal-water calcarenites developed over most of Kansas, carbonate shoreline facies prograded into southern Nebraska and Iowa, and deltas of Appalachian origin prograded across Illinois. 4. At maximum regression, the sea became nearly confined to the deep basins of west Texas and Oklahoma, while the exposed carbonate terrain to the north underwent formation of karst, caliche and residuum, and the extensive deltaic deposits to the east underwent channeling, alluviation, and soil and coal-swamp formation. 5. Expansion of the sea during early transgression restored shoal-water calcarenite deposition across western Kansas, caused gray shale deposition in embayments and lagoons along the inundated deltaic terrain to the east, and impounded Appalachian-derived streams flowing westward across the immense alluvial plain to form widespread coal swamps in Illinois. 6. Deepening during late transgression restored skeletal calcilutite deposition across the Midcontinent, caused marine shell accumulations over coals in Illinois, and shifted transgressive coal-swamp formation eastward into the Appalachian region. In Texas the same sea level changes resulted in much less lateral shifting of shoreline and associated facies because of greater depositional relief, narrower shelves, and closer detrital sources. Thus individual units there are less widespread, and eustatic effects are less noticeable than in the Midcontinent.

Depositional Model of Early Cretaceous Coral-Algal-Rudist Reefs, Arizona

Patch reefs composed mainly of corals and stromatolites are well developed in the Lower Cretaceous Mural Limestone of southeastern Arizona. This biota is similar to that forming buildups in the downdip Lower Cretaceous sections of the Gulf Coast at Fairway and Stuart City fields in Texas and the Golden Lane-Poza Rica field in Mexico. In contrast, updip Lower Cretaceous buildups in central Texas consist mainly of rudists, and corals are rare. The reefs of the Mural Limestone are up to 25 m thick and about 1.5 km long. They grew during the early Albian transgression from the Chihuahua trough into Arizona. The reef-core and flank facies are coral-stromatolite-rudist boundstone and coral-rudist fragment packstone. The reef-core facies is dominated by the colonial corals Actinastrea and Microsolena. The latter coral commonly is encrusted by stromatolites. Caprinids and thick-walled monopleurids are secondary in abundance. Associated perireef facies are peloid-ooid grainstone, mollusk-miliolid-orbitolinid wackestone, and ostracod-mollusk-skeletal algal wackestone and sandstone-shale. The perireef shallow shelf is characterized by Monopleura, Chondrodonta, Toucasia, and nerineids. The nearshore restricted lagoon and shoreface to tidal-flat environments were occupied by Exogyra and Crassostrea communities and the Arenicolites association. Where megafossils are absent, the shelf environment is characterized by assemblages of miliolids, Orbitolina, and agglutinated forams. The distribution of algal types is also closely related to environments. These facies and communities have predictable stratigraphic relations.

Mid-Cenozoic Fortuna Formation, East-central Tunisia; Record of Late Alpine Activity on Cratonic Margin of North Africa: ABSTRACT

The Oligocene-early Miocene paralic to nonmarine Fortuna Formation in east-central Tunisia accumulated in a cratonic basin on adjacent parts of the Tunisian Atlas province and the Pelagian block. This coarsening-upward detrital sequence was derived from west and northwest uplands and reached a maximum thickness of 1,100 to 1,200 m near the northeastern end of its northeast-trending depocenter (graben?) along the boundary between the two crustal blocks. After early Cenozoic culmination of the Alpine orogeny the Fortuna basin and source area were created during a new phase of extensional deformation that affected the western Mediterranean region. Continued differential uplift and subsidence produced an increasingly sandy Oligocene lower member composed of shallow-marine to deltaic mudstone and fine-grained sandstone, a maximum of 400 to 600 m thick along the central part of the axial trough. Detritus from the uplift was dispersed east and southeast, and the sandstone grades into a marine carbonate facies on the Pelagian shelf on the east. Accentuated vertical displacement of basin and source area produced the increasingly coarser grained fluvial upper member (lower Miocene) that was dispersed mainly east and northeastward. This member has a maximum thickness of 850 m near the northeastern end of the trough. Stringers and lenses of conglomerate in the upper part contain well-rounded pebbles of quartz, chert, and quartzite, as long as 4 cm near the northwestern border and 2 cm along the axial depocenter. Accumulation of the Fortuna Formation terminated abruptly, followed by a widespread late early Miocene marine transgression. Fortuna basin and its northwestern upland on the unstable cratonic margin of North Africa responded to remote effects of late Alpine activity. Early Oligocene to Pliocene sediments in the Fortuna basin area reflect each episode of deformation, regression, and transgression that dominated the western Mediterranean. End_of_Article - Last_Page 544------------

Dispersal and Geochemistry of Surface Sediments in Halls Bay, North-Central Newfoundland: Application to Mineral Exploration

Surficial palimpsest sediments in Halls Bay, north-central Newfoundland, are mixtures of gravel, sand, and mud deposited from a number of sources in varying quantities from late Wisconsinan to the present time. Shallow water gravel originated as till and glacio-fluvial outwash. Gravel in deep water probably is ice-rafted. Sand and mud, which occurs with shallow water gravel and in deeper water, is a combination of fluvial material and material winnowed out of till and outwash by shallow water waves and currents during early marine transgression. There also may be a contribution of fine-grained sediment from the adjacent shelf.Gravel (coarser than [Formula: see text]), very fine sand (3 to [Formula: see text]) and coarse silt (4 to [Formula: see text]) modal grain-size classes predominate in the sediments. The very fine sand mode occurs on the west side of the inlet and the coarse silt mode occurs on the east side regardless of water depth, indicating net or active easterly dispersal of fine-grained sediment. This dispersal path may result from the presence in Halls Bay of a counterclockwise gyre of the Labrador Current that has developed since early transgression, which suggests the sediment surface is adjusting to the Halls Bay modern hydraulic regime.Sandy and muddy sediments are composed of quartz, feldspar, amphibole, illite, chlorite, montmorillonite, organic matter, CaCO3, and FeS. Major, minor, and trace element concentrations vary with grain-size, owing to the different proportions of these components in different size fractions. Calculation of an average chemical composition of sediments is biased because of this grain-size effect. The grain-size effect on chemistry of a suite of sediments can be accounted for by ratioing element concentrations to clay content.Plots of the ratio trace metal concentration/clay content vs. clay content for six trace metals indicate anomalous Cu concentrations occur in surface sediments along the east side of Halls Bay in the direction of fine-grained sediment dispersal. The anomalous Cu is derived from onshore mineralization in Lushs Bight Group volcanic rocks, which Occur along the west side of the inlet.The results provide an example of the applicability of marine sedimentologic/sedimentary geochemical investigations to mineral exploration. Local geochemical anomalies in sediments can be detected by routine analysis of total metal content of bulk samples provided the grain-size effect on chemistry is accounted for. The anomalous metal can be traced to its onshore source by evaluating sediment dispersal paths from textural variations.

Sediment Sources and Dispersal Patterns of Oregon Continental Shelf Sands

ABSTRACT Heavy mineral analysis of the rivers of Oregon and northern California has been used to outline four major sources of sediments on the Oregon continental shelf. These sources include the Columbia River Basin, the Oregon Coast Range, the Klamath-Siskiyou Mountains, and terrace deposits along the central Oregon coast. Dispersal patterns of sand-size sediments show that the dominant direction of littoral transport has been to the north at least during the past 18,000 years. Sands were transported 170 miles to the north on the continental shelf during the end of the Late Wisconsin regression and the beginning of the Early Holocene transgression. The observed dispersal patterns of heavy minerals may be indicative of more efficient littoral processes during the last major sea level lowering Reduction of sand supply to the littoral zone and natural obstacles, such as erosionally resistant headlands, to the littoral transport of sand have apparently limited the northward transport of sand during the past 3,000 years.

Sedimentary Structures and Depositional Environments, Potsdam Formation, Upper Cambrian: GEOLOGICAL NOTES

The Upper Cambrian Potsdam Formation (orthoquartzitic sandstone and conglomerate) in eastern Ontario, southwestern Quebec, and northern New York State, was deposited during an early Paleozoic transgression over the Precambrian surface of the Canadian shield. Rock types and sedimentary structures indicate three distinct environments: (1) Terrestrial, talus sheet wash fan (quartzite breccia), Frontenac arch, Thousand Islands region; (2) marine and (or) fluvial channel (cross laminated sandstone), Ontario and northern New York; and (3) low-energy, littoral to nearshore (laminated sandstone and some siltstone) Quebec and New York State. Reference outcrops are cited; bibliography is comprehensive.

Les niveaux quaternaires marins des Alpes-Maritimes. Correlations avec les industries prehistoriques

Abstract Deposits along the Maritime Alpine coast of France and Monaco reveal six shorelines between the greatest extent of the Plaisancian transgression and present sea level. During the transgression at the end of the Pliocene, the sea was 165 meters above its present position. The post-Pliocene regression marks the Tertiary-Quaternary boundary. During the eustatic Calabrian transgression, the sea reached a maximum altitude of 108 meters. During the transgression in early Pleistocene time the sea reached an altitude of 83 meters. The extensive early Pleistocene regression resulted in the formation of the caves in the Nice-Grimaldi area. The sea reached a height of only 30 meters during the second early Pleistocene transgression. The Mindel-Riss transgression is represented by littoral deposits as high as 23 meters in Monaco. A warm water molluscan fauna from littoral deposits marks the Tyrrhenian Riss-Wuerm transgression which reached a height of 12 meters. Excavations produced remains of mammals, human industries, and cryoclastic deposits.

ALEGRIA-VAQUEROS (OLIGOCENE-MIOCENE) SEQUENCE NEAR GAVIOTA, CALIFORNIA

Calcareous sandstone lenses in the Oligocene Alegria formation resemble the overlying lower Miocene Vaqueros sandstone. These lenses are remnants of the late Oligocene shore line, and the Vaqueros consists of sand and gravel that accumulated along this shore line during the late Oligocene and were deposited during an early Miocene transgression.

Oil Accumulation Related to Geologic History of Muenster Arch and Associated Basins in North Texas: ABSTRACT

The chief geologic asset of the region is the thick sedimentary section of Ordovician and Pennsylvanian deposited on the flanks and adjacent to the Muenster arch in the Marietta and Fort Worth basins. These beds contain ample reservoir rocks and abundant source materials for petroleum and natural gas. The dominance of progressive onlap over the arch during the majority of Pennsylvanian time is the second most important feature. A third important factor is the orogenic history. The extensive and complex faulting may be ascribed to four dominant periods of movement. 1. There was widespread block faulting of probable late Morrowan age, associated with the transformation of the Arbuckle sedimentary basin into partly separated troughs. 2. After erosion had truncated the Ordovician deeply on the Muenster arch and even on fault blocks now low in the adjacent basins, subsidence allowed the Dornick Hills (Bend) beds to overlap the fault blocks with subsequent and sometimes contemporary rejuvenation of some of the faults. (On the northeast flank and in the Gordonville trough area, normal sands were deposited on buried hills like the Sherman and Big Mineral highs and as updip pinch-outs like Sadler field. On the southwest side of the uplift in the Fort Worth basin, beds of this early transgression contained numerous lenses of conglomerate which are prospective for oil and gas in most any structural situation.) 3. Uplift of the Ouachitas, regional westward tilting, tremendous subsidence of the Marietta basin, Gordonville trough, and to less extent, the Fort Worth basin, produced foundering of grand proportions along the trough margins. The long period of progressive inundation of the Muenster arch and its final burial by detritus, chiefly derived from the Ouachita uplift on the east, was probably responsible for much of the oil accumulation in the abundant Pennsylvanian sands. Many stratigraphic traps were formed due to the lenticularity of the sands and updip porosity terminations, where structure may play only a minor role in accumulation. Some of these onlapping beds likewise seal the truncated edge of the Oil Creek (Simpson) sand on the north flank of the arch, where aided some by faulti g, three commerical accumulations have been found. 4. A final period of folding and faulting took place during the late Pennsylvanian-Arbuckle compressional movement which resulted in overturning and thrusting in some places. Oil accumulation at Big Mineral and Sherman was aided considerably by this crustal movement. End_of_Article - Last_Page 1775------------