SEARCH · Search USGS

Results for “Facies”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11Linked to original sources

USGS1984

Distribution and ecology of deep-water benthic foraminifera in the Gulf of Mexico

Bathyal and abyssal foraminifera in the Gulf of Mexico are distributed among thirteen generic predominance facies. Five predominance facies nearly encircle the Gulf basin along the slope and rise; a sixth predominance facies blankets the Sigsbee Plain, and a seventh is restricted to the Mississippi Fan. The remaining eight predominance facies have more restricted distributions. The areal patterns of these predominance facies can be related chiefly to water mass and substrate characteristics; modifications are brought about by calcite dissolution, upwelling, and sill depth. Analysis of ancient generic predominance facies is useful in predicting relative paleobathymetry and other paleoenvironmental properties.

Alabama, Florida, Louisiana, Mississippi, Texas↗

USGS2017

Seismic reflection study of recessional moraines beneath Lake Superior and their relationship to regional deglaciation

Approximately 8000 km of continuous seismic reflection profiles throughout Lake Superior were examined for evidence of recessional moraines and other ice-margin deposits associated with the retreat of late Wisconsin ice. These features are correlated with the record of glacial-lake evolution in western Lake Superior. An offlapping sequence of glacial and glacial-lacustrine dediments overlying bedrock is recognized in west-central Lake Superior that is progressively younger to the northeast. The sequence underlies more recent glaical-lacustrine and postglacial sediments. Four facies are recognized on the basis of geomorphologic and acoustic properties and are interpreted to represent a southwest-to-northeast assemblage of: proglacial stratified drift (facies A), drift in major end moraines (facies B), till deposited as glacial retreat resumed, or possibly late-stage ablation till (facies C), and basal till (facies D). The prominent moraines of facies B are unusually thick and are believed to mark the ice-margin shorelines of successive major proglacial lakes that formerly occupied parts of western Lake Superior. The moraines are tentatively correlated with Glacial Lake Duluth (unit 1), Glacial Lake Washburn (unit 2), and Glacial Lake Beaver Bay (unit 3), the most prominent of lakes drained via the progressively lower outlets via the Moose Lake/ Brule-St. Croix Rivers, the Huron Mountains, and the Au Train-Whitefish regions, respectively.

Lake Superior↗

USGS1988

Paleolimnology of Lake Tubutulik, an iron-meromictic Eocene Lake, eastern Seward Peninsula, Alaska

Sideritic lacustrine mudstone was found in drill core from a uranium deposit in the Death Valley area in the eastern part of the Seward Peninsula, Alaska. The precursor sediments for this rock were deposited in an unusual “iron-meromictic” Eocene lake, herein named Lake Tubutulik, which occupied part of the Boulder Creek basin, a structural graben that is probably a southern extension of the larger Death Valley basin. The Boulder Creek basin is bounded on the west by granite of the Late Cretaceous Darby Pluton, on the east by Precambrian to Paleozoic metasedimentary rocks. The lake basin was formed by basaltic flows that dammed the river valley of the ancestral Tubutulik River in early Eocene time. Lake Tubutulik contained a nearshore facies of fine-grained organic mud and an offshore facies of laminated sideritic mud. The offshore (profundal) laminated mudstone consists of alternating layers of authigenic siderite and detrital layers containing mostly quartz and clay minerals. Both lacustrine facies contain turbidities. The lacustrine sediments graded laterally into an onshore facies of colluvial and fluvial sandstone, paludal mudstone, and coal. The ancient lake apparently occupied a small deep basin in a tectonically active area of high relief. Meromixus was probably stabilized by reduced iron and bicarbonate dissolved in the monimolimnion. The intensity of meromixus decreased as the lake became shallower from sediment filling. The source of the iron, abundant in the monimolimnion of Lake Tubutulik, was probably the Eocene basalt. Based on carbon isotope analysis of the siderite, the dissolved bicarbonate in the profundal facies was largely inorganic. Sideritic carbon in one sample from the onshore paludal facies has an isotopic signature ( δ 13 C = +16.9) consistent with residual carbon formed during methanogenic fermentation.

Alaska↗

USGS1990

Variations in fluvial deposition on an alluvial plain: An example from the Tongue River Member of the Fort Union Formation (Paleocene), southeastern Powder River Basin, Wyoming, U.S.A.

The Tongue River Member of the Paleocene Fort Union Formation is an important coal-bearing sedimentary unit in the Powder River Basin of Wyoming and Montana. We studied the depositional environments of a portion of this member at three sites 20 km apart in the southeastern part of the basin. Six lithofacies are recognized that we assign to five depositional facies categorized as either channel or interchannel-wetlands environments. (1) Type A sandstone is cross stratified and occurs as lenticular bodies with concave-upward basal surfaces; these bodies are assigned to the channel facies interpreted to be the product of low-sinuosity streams. (2) Type B sandstone occurs in parallel-bedded units containing mudrock partings and fossil plant debris; these units constitute the levee facies. (3) Type C sandstone typically lacks internal structure and occurs as tabular bodies separating finer grained deposits; these bodies represent the crevasse-splay facies. (4) Gray mudrock is generally nonlaminated and contains ironstone concretions; these deposits constitute the floodplain facies. (5) Carbonaceous shale and coal are assigned to the swamp facies. We recognize two styles of stream deposition in our study area. Laterally continuous complexes of single and multistoried channel bodies occur at our middle study site and we interpret these to be the deposits of sandy braided stream systems. In the two adjacent study sites, single and multistoried channel bodies are isolated in a matrix of finer-grained interchannel sediment suggesting deposition by anastomosed streams. A depositional model for our study area contains northwest-trending braided stream systems. Avulsions of these systems created anastomosed streams that flowed into adjacent interchannel areas. We propose that during late Paleocene a broad alluvial plain existed on the southeastern flank of the Powder River Basin. The braided streams that crossed this surface were tributaries to a northward-flowing, basin-axis trunk stream that existed to the west.

Wyoming↗

USGS1963

Correlations and problems in belt series stratigraphy, Northern idaho and western Montana

A continuous strip of geologic maps has recently been completed along the Idaho - Montana state line between Clark Fork, Idaho , and Superior, Montana . New stratigraphic and petrographic information provides the basis for stratigraphic correlations and for the interpretation of facies changes in this part of the basin of deposition of the Precambrian Belt Series . Identification of facies changes is aided by the recognition of siltite (low-grade metamorphosed siltstone) as a valid rock type, in addition to quartzite and argillite, to classify most of these rocks and to establish mappable units. The older Belt rocks (Prichard through Wallace Formations) were deposited in a trough whose axis trended northwestward, perhaps approximately through Libby, Montana . Subtle facies changes suggest an ancient shore line southwest of the Coeur d'Alene district, Idaho , perhaps near the present exposed edge of the Idaho batholith. The younger Belt formations of the Missoula Group, however, thicken markedly southeastward toward Superior. Thus, the younger Belt rocks were deposited in a trough whose main axis was about at right angles to that of the older trough and perhaps was near Missoula, Montana . Deposition in the Clark Fork area was scant and often interrupted in Missoula time. The young major cross-warp in the old Belt geosyncline undoubtedly has contributed complexities to Belt correlation farther north. Detailed petrographic studies indicate that the Belt rocks from the Pend Oreille area, Idaho , are remarkably uniform in the mineralogic composition of similar rock types throughout 40,000 feet of strata. Further mineralogic studies are required to determine whether this uniformity is local or widespread.

Idaho, Montana↗

USGS2006

The Hancock County tetrapod locality: A new Mississippian (Chesterian) wetlands fauna from western Kentucky (USA)

The earliest tetrapods are known from a handful of Upper Devonian and Lower Carboniferous localities in Europe, North America, and Australia. All Upper Devonian sites and virtually all Early Carboniferous faunas are regarded as predominantly aquatic and most occur within, or are associated with, wetland habitats. A new mid- Carboniferous (Elvirian, Namurian A) fossil locality in Kentucky preserves the fi rst tetrapod fauna from the eastern portion of the Illinois Basin. Four distinct facies at the locality have yielded vertebrate material. Diverse faunas have been found in an abandoned channel/oxbow facies and a fl oodplain/lake facies. The abandoned channel/oxbow facies contains Colosteidae, Embolomeri, Rhizodontida, Dipnoi, Xenacanthiformes, Palaeonisciformes, and Gyracanthidae remains. This assemblage is similar to known Mississippian freshwater and brackishwater faunas, providing further evidence of a cosmopolitan tetrapod province during the Mississippian. A different fauna, rich in tetrapods but lacking fi sh, is associated with granular carbonate masses, rooting structures, and a paleosol in the fl oodplain/ lake facies. Isolated and associated tetrapod elements from this facies exhibit morphological adaptations that may suggest a fauna of more highly terrestrial vertebrates than previously known from the North American Mississippian. ?? 2006 Geological Society of America.

Special Paper of the Geological Society of America↗

USGS2002

Flank collapse at Mount Wrangell, Alaska, recorded by volcanic mass-flow deposits in the Copper River lowland

An areally extensive volcanic mass-flow deposit of Pleistocene age, known as the Chetaslina volcanic mass-flow deposit, is a prominent and visually striking deposit in the southeastern Copper River lowland of south-central Alaska. The mass-flow deposit consists of a diverse mixture of colorful, variably altered volcanic rocks, lahar deposits, glaciolacustrine diamicton, and till that record a major flank collapse on the southwest flank of Mount Wrangell. The deposit is well exposed near its presumed source, and thick, continuous, stratigraphic exposures have permitted us to study its sedimentary characteristics as a means of better understanding the origin, significance, and evolution of the deposit. Deposits of the Chetaslina volcanic mass flow in the Chetaslina River drainage are primary debris-avalanche deposits and consist of two principal facies types, a near-source block facies and a distal mixed facies. The block facies is composed entirely of block-supported, shattered and fractured blocks with individual blocks up to 40 m in diameter. The mixed facies consists of block-sized particles in a matrix of poorly sorted rock rubble, sand, and silt generated by the comminution of larger blocks. Deposits of the Chetaslina volcanic mass flow exposed along the Copper, Tonsina, and Chitina rivers are debris-flow deposits that evolved from the debris-avalanche component of the flow and from erosion and entrainment of local glacial and glaciolacustrine diamicton in the Copper River lowland. The debris-flow deposits were probably generated through mixing of the distal debris avalanche with the ancestral Copper River, or through breaching of a debris-avalanche dam across the ancestral river. The distribution of facies types and major-element chemistry of clasts in the deposit indicate that its source was an ancestral volcanic edifice, informally known as the Chetaslina vent, on the southwest side of Mount Wrangell. A major sector collapse of the Chetaslina vent initiated the Chetaslina volcanic mass flow forming a debris avalanche of about 4 km3 that subsequently transformed to a debris flow of unknown volume.

Canadian Journal of Earth Sciences↗

USGS1973

Iron-formation in South America

Except for recent studies by certain South American governmental and quasi-governmental companies and agencies, little effort has been devoted to study of the iron-formations from which the great iron ore deposits of South America formed. Great gaps in basic information exist. Iron-formation is found in the Guayana and Brazilian Precambrian Shields as a common rock type and also occurs in Chile and astride the Bolivian-Brazilian border. Only the carbonate and oxide facies are known, the former being quite rare. The dominant oxide facies occurs in major units averaging more than 100 m in thickness and extending over hundreds of square kilometers, generally in a miogeosynclinal or intra-cratonic basin environment. The relation of such deposits with volcanism is tenuous and obscure, if indeed there is any direct relation. Smaller units of oxide facies iron-formation occur in many minor beds from widely varying geologic environments. The carbonate facies is found in a eugeosynclinal suite in Minas Gerais, Brazil, and is of the Algoma type. The deposits range in age from about 3,200 m.y. to late Precambrian or early Paleozoic; although the major epoch of deposition is debatable, it probably was about 2,000 m.y. ago. The South American oxide facies iron-formations are richer than many in the Northern Hemisphere, those of early and middle Precambrian age averaging about 40 percent in Fe and the same in SiO 2 . Younger iron-formations are still richer, averaging perhaps 50 percent Fe. Scanty trace element data do not indicate volcanic affiliations. The iron is present as magnetite, hematite, and martite; most rocks have been metamorphosed, and accordingly it is not known how much of the magnetite is metamorphic and how much is diagenetic or depositional in origin. Hematite and martite are dominant in most iron-formations. South American iron-formations are quite similar in lithology and occurrence to the major deposits in Africa and India and possibly formed when these continents were contiguous. These formations differ from those in the Northern Hemisphere in having a narrower range in lithologic facies and a generally higher iron content. In few areas can any direct relation with volcanism be demonstrated. © 1973 Society of Economic Geologists, Inc.

Economic Geology↗

USGS2007

Type region of the Ione Formation (Eocene), central California: Stratigraphy, paleogeography, and relation to auriferous gravels

The middle Eocene Ione Formation extends over 200 miles (320 km) along the western edge of the Sierra Nevada. Our study was concentrated in the type region, 30 miles (48 km) along strike. There a bedrock ridge forms the seaward western side of the Ione depositional tract, defining a subbasin margin. The eastern limit of the type Ione is locally defined by high-angle faults. Ione sediments were spread over Upper Mesozoic metamorphic and plutonic bedrock, fed by gold-bearing streams dissecting the western slope of the ancestral Sierra Nevada. By middle Eocene time, a tropical or subtropical climate prevailed, leading to deep chemical weathering (including laterization) and a distinctively mature mineral assemblage was fed to and generated within Ione deposits. The Ione is noted for its abundant kaolinitic clay, some of it coarsely crystalline; the clay is present as both detrital grains and authigenic cement. Quartz is abundant, mostly as angular grains. Heavy mineral fractions are dominated by altered ilmenite and zircon. Distribution of feldspar is irregular, both stratigraphically and areally. Non-marine facies are most voluminous, and include conglomerates, especially at the base and along the eastern margins of the formation where they pass into Sierran auriferous gravels. Clays, grading into lignites, and gritty sands are also common facies. Both braided and meandering fluvial facies have been recognized. Shallow marine waters flooded the basin probably twice. Tongues of sediment exhibiting a variety of estuarine to marine indicators are underlain and overlain by fluvial deposits. Marine body fossils are found at only a few localities, but burrows identified as Ophiomorpha and cf. Thalassinoides are abundant in many places. Other clues to marginal marine deposition are the occurrence of glauconite in one bed, typical relations of lagoonal to beach (locally heavy-mineral-rich) lithofacies, closed-basin three-dimensional morphology of basinal facies, and high sulfur content of some marginal coals. The Ione has been said to be deltaic; however the two transgressional-regressional cycles we propose imply that only the regressional parts were deltaic. At other times, much of the type Ione would better be termed an intertidal estuary. Because the lower marine sequence was deposited against a paleobasin margin on the west, deltaic morphology was constrained, but apparently progradation was from north to south despite drainage into the basin from the east. Relations to the south are unclear due to the Stockton arch. The eastern margin of the type-Ione basin, and to some extent even its marine facies, are poorly constrained. A surface on Sierran bedrock to the east may have been stripped of some Ione basinal facies, leaving only coeval entrenched fluvial channel deposits.

California↗

USGS1953

Progress report on the Killigwa anticlinorium, 1953

This report was prepared to assist in the planning of seismic profiles to be run across the anticlinorium in the vicinity of the Kiligwa River. The stratigraphy and structure of the mapped area south of the anticlinorium are reviewed. Two facies of the Lisburne formation, a calcarenite-hydroclastic limestone facies and a black shale, black chert and dark limestone facies, have been distinguished. In the southern foothills, the black shale facies appears to have been thrust from the south over the limestone facies. The available evidence indicates that the Lisburne formation, as limestone or a more proximal facies was doposited over the area of the anticlinorium. Following a redefinition of the Torok formation in the type area, strata formerly mapped as Torok have here been designated Castle Mountain formation. The depositional history of the Castle Mountain formation reflects active orogeny. Lenses of coarse clastics appear to have been dumped in local basins; equivalent beds to the north are much finer. A basal zone of sandstone may be more extensive and may correlate with the sandstones noted along and north of the anticlinorium.

Alaska↗

USGS1987

Late Mississippian gastropods of the Chainman Shale, west-central Utah

The Chainman Shale of Mississippian (Osagean to late Chesterian) age, well exposed in the Confusion Range of western Utah, has yielded a profusion of fossils during investigations conducted by the U.S. Geological Survey in the past 30 years. Conspicuous among these fossils are gastropods, which range in age from latest Meramecian to late Chesterian. In west-central Utah, not far from the State boundary, the Chainman outcrop belt stretches from Granite Mountain south to the northern part of the Needle Range, a distance of69 miles (110 km). The Chainman thickens from north to south; the section at Granite Mountain is 1,315 feet (401 m) thick and that at Jensen Wash in the Burbank Hills, 2,203 feet (671 m). The rocks of the Chainman Shale record a general though irregular shallowing of the area from moderate depths of 330 feet (100 m) or so to quite shallow depths of perhaps locally little more than 3-6 feet (1-2 m). Most of the gastropods occur with ammonoids in a facies of shale or shale containing phosphatic limestone concretions, In this lutaceous facies, Glabrocingulum is predominant and Lunulazona and Retispira are common; these genera are represented by a succession of species. A thick limestone unit is present in some areas in the upper part of the formation, particularly in the vicinity of Skunk Spring, where it is 318 feet (97 m) thick. This limestone unit represents a calcareous shoal facies having an entirely different gastropod fauna, characterized by Catazona and species of Naticopsis. The Chainman Shale could be easily zoned by gastropods, but we are not proposing such azonation. A framework of ammonoid and foraminiferal zones already is available, and we prefer to regard the gastropod assemblages as part of this framework. The assemblages are confined to the major ammonoid and foraminiferal zones, and only three of the gastropod species seem to range across major zonal boundaries. These species are Bellerophon (Bellerophon vespertinus Gordon and Yochelson and Straparollus (Euomphalus intermedius Gordon and Yochelson, both of which are present in Mamet Foraminifer Zones 17 and 18, and Bellazona polita n. sp., which locally seems to range from Mamet Foraminifer Zone 16s into the basal part of Zone 17. Eight assemblages, seven of them in ascending stratigraphic order, are recognized within the gastropod fauna of the Chainman Shale; the eighth assemblage is a facies equivalent of the sixth highest. The seven mud-dwelling assemblages are characterized mainly by species of Glabrocingulum and Lunulazona, which together account for 80 percent of the gastropod specimens in our Chainman collections. The eighth assemblage, that in the shallow-water carbonate facies, is the one characterized by Catazona and species of Naticopsis. The lowermost gastropod assemblage, that of Lunulazona nodomarginata (McChesney), includes 10 species and is restricted to the northern end of the study area, where it occurs in the upper part of the Goniatites americanus Ammonoid Zone, in beds equivalent to the lower part of Mamet's Foraminifer Zone 16i. We regard the entire G. americanus Zone as late Meramecian in age. All the zones higher in the Chainman are Chesterian in age. The second assemblage is that of Lunulazona costata Sadlick and Neilsen, which includes six gastropod species; it occurs in the Goniatites granos us Ammonoid Zone, equivalent to Mamet's Foraminifer Zone 16s. Three gastropod assemblages are recognized within the Paracravenoceras barnettense Ammonoid Zone, equivalent to Mamet's Foraminifer Zone 17. The earliest, that of Lunulazona sadlicki, includes five species; the intermediate, that of Glabrocingulum hosei n. sp., four species; and the highest, that of Glabrocingulum confusionense n, sp., two species (the second being G. hosei). Two laterally equivalent facies-controlled assemblages are present within the Cravenoceras hesperium Ammonoid Zone, most of which is equivalent to Mamet's Foraminifer Zone 18

Professional Paper↗

USGS2022

A geomorphic-process-based cellular automata model of colluvial wedge morphology and stratigraphy

The development of colluvial wedges at the base of fault scarps following normal-faulting earthquakes serves as a sedimentary record of paleoearthquakes and is thus crucial in assessing seismic hazard. Although there is a large body of observations of colluvial wedge development, connecting this knowledge to the physics of sediment transport can open new frontiers in our understanding. To explore theoretical colluvial wedge evolution, we develop a cellular automata model driven by the production and disturbance (e.g., bioturbative reworking) of mobile regolith and fault-scarp collapse. We consider both 90 and 60 ∘ dipping faults and allow the colluvial wedges to develop over 2000 model years. By tracking sediment transport time, velocity, and provenance, we classify cells into analogs for the debris and wash sedimentary facies commonly described in paleoseismic studies. High values of mobile regolith production and disturbance rates produce relatively larger and more wash-facies-dominated wedges, whereas lower values produced relatively smaller, debris-facies-dominated wedges. Higher lateral collapse rates lead to more debris facies relative to wash facies. Many of the modeled colluvial wedges fully developed within 2000 model years after the earthquake, with many being much faster when process rates are high. Finally, for scenarios with the same amount of vertical displacement, differently sized colluvial wedges developed depending on the rates of geomorphic processes and fault dip. A change in these variables, say by environmental change such as precipitation rates, could theoretically result in different colluvial wedge facies assemblages for the same characteristic earthquake rupture scenario. Finally, the stochastic nature of collapse events, when coupled with high disturbance, illustrates that multiple phases of colluvial deposition are theoretically possible for a single earthquake event.

Earth Surface Dynamics↗

USGS1976

Sedimentary depositional environments of uranium and petroleum host rocks of the Jackson Group, south Texas

Determination of depositional environments in rocks of the Jackson Group of late Eocene age aids in the exploration for uranium and petroleum in south Texas. During deposition of the Jackson Group, conditions were similar to those existing along the modern Gulf Coast of Texas except for a less arid climate and a greater supply of volcanic sediment. Sedimentary depositional environments recognized in both the modern coast and the Jackson rocks, in order from sea toward land, are: shoreface, beach, lagoon and bay, and paludal. Sediment deposited in these environments in places is interbedded with or transected by fluvial sediment. Both uranium and petroleum are found in the shoreface, beach, and fluvial facies. These facies are characterized by permeable well-sorted sandstone, which is commonly overlain and underlain by less permeable mudstone. A typical vertical sequence in ascending order through a unit containing a beach sandstone facies is (1) lagoonal or paludal clay stone and siltstone, (2) crossbedded fine-grained beach sandstone which contains Ophiomorpha burrows and, which, in places, is locally interbedded with lacustrine or lagoonal mudstone, (3) weakly laminated beach sandstone which contains root impressions at the top and Ophiomorpha , and (4) lagoonal or paludal claystone and siltstone. Gulfward, the beach sandstone apparently grades into highly burrowed, generally finer grained, more poorly sorted, less porous shoreface rocks. The beach facies may include barrier island beaches and mainland beaches, some of which were probably cheniers. Beach facies sandstone units extend many miles along the depositional strike, which nearly parallels the present outcrop strike, but extend only a mile or two (2-3 km) normal to the depositional strike into the subsurface. Recognition of the various facies in outcrops and drill holes is necessary for determination of true stratigraphic relations and for aid in exploration for beach and fluvial sandstone favorable for uranium and petroleum accumulations.

Texas↗

USGS1991

Hydrologic reconnaissance of the Sevier Lake area, west-central Utah

The hydrologic system of the Sevier Lake area, at the terminus of the Sevier Lake drainage basin in west-central Utah, was studied during 1987-88 to determine baseline hydrologic conditions prior to anticipated development. Sevier Lake was reestablished during 1983-87 on the normally dry playa as a result of record volumes of surface-water runoff, but the lake was receding during the study. In June 1985, the lake reached a maximum depth of about 13 feet, with a water-surface altitude of 4,527 feet above sea level. The basin-fill aquifer includes a coarse-grained facies at higher altitudes of the alluvial slopes, and a fine-grained facies at lower altitudes around Sevier Lake. Water levels indicate a potential for lateral groundwater movement away from the lake and toward the northwest, west, and south. Transmissivity of the coarse-grained facies, determined from one well, was 4,120 feet squared per day. Transmissivity values for the fine-grained facies ranged from 1 X 10 -3 to 5 X 10 -2 foot squared per day, determined from slug tests of shallow wells near the shoreline of the lake, and 5.2 feet squared per day determined from a well in the lakebed. The predominant constituents of water sampled in the Sevier Lake area are sodium, sulfate, and chloride. The concentration of dissolved solids ranges from 480 to 120,000 milligrams per liter. Smaller concentrations of dissolved solids were determined for water from wells completed in the coarse-grained facies, and larger concentrations were determined for water from wells completed in the fine-grained facies.

Utah↗

USGS2009

Basin development along the Late Mesozoic and Cainozoic California Margin: A plate tectonic margin of subduction, oblique subduction and transform tectonics

Along the Californian margin of the North American plate, the configuration and structural stability of late Mesozoic and Cainozoic basins are related to plate kinematics. Three tectonic regimes are recorded; orthogonal high-angle subduction, oblique low-angle subduction, and transform slip. During the first, regionally extensive forearc basins developed; during the second and third, borderland settings formed as a consequence of wrench faulting. In the forearc basins, sedimentological facies constitute regional belts that persist for hundreds of kilometres, with stratigraphic sequences that are 1–15 km thick. Shorelines are relatively straight, shelf facies are broad and well developed, and basin fill is composed of shallow marine, shelf and coalescing submarine-fan facies. Sediment transport in the deeper water facies commonly is parallel to the basin axis. Borderland basins reflect tectonic instability. A principal effect of wrench tectonics is the vertical reciprocation of crustal blocks. Shorelines are generally irregular, and narrow shelves pass abruptly into deep basins. Lithofacies change dramatically along strike, and stratigraphic thicknesses are variable from basin to basin, from tens of metres up to 6 km. Basin-margin facies are marked by unconformities, slump aprons, lithological pinch-outs and submarine canyon channels. Penecontemporaneous slip along the basin-margin faults complicates these lithofacies patterns. Borderland type palaeogeography is most extensively developed in the transform tectonic regime, and therefore the more seaward offshore basins are relatively depleted of terrigenous debris owing to transport barriers.

California↗

USGS2006

Protolith and metamorphic ages of the Haiyangsuo Complex, eastern China: A non-UHP exotic tectonic slab in the Sulu ultrahigh-pressure terrane

The Haiyangsuo Complex in the NE Sulu ultrahigh-pressure (UHP) terrane has discontinuous, coastal exposures of Late Archean gneiss with amphibolitized granulite, amphibolite, Paleoproterozoic metagabbroic intrusives, and Cretaceous granitic dikes over an area of about 15 km2. The U-Pb SHRIMP dating of zircons indicates that theprotolith age of a garnet-biotite gneiss is >2500 Ma, whereas the granulite-facie metamorphism occurred at around 1800 Ma. A gabbroic intrusion was dated at ???1730 Ma, and the formation of amphibolite-facies assemblages in both metagabbro and granulite occurred at ???340-460 Ma. Petrologic and geochronological data indicate that these various rocks show no evidence of Triassic eclogite-facies metamorphism and Neoproterozoic protolith ages that are characteristics of Sulu-Dabie HP-UHP rocks, except Neoproterozoic inherited ages from post-collisional Jurassic granitic dikes. Haiyangsuo retrograde granulites with amphibolite-facies assemblages within the gneiss preserve relict garnet formed during granulite-facies metamorphism at ???1.85 Ga. The Paleoproterozoic metamorphic events are almost coeval with gabbroic intrusions. The granulite-bearing gneiss unit and gabbro-dominated unit of the Haiyangsuo Complex were intruded by thin granitic dikes at about 160 Ma, which is coeval with post-collisional granitic intrusions in the Sulu terrane. We suggest that the Haiyangsuo Complex may represent a fragment of the Jiao-Liao-Ji Paleoproterozoic terrane developed at the eastern margin of the Sino-Korean basement, which was juxtaposed with the Sulu terrane prior to Jurassic granitic activity and regional deformation. ?? Springer-Verlag 2006.

Conference Paper↗

USGS2002

Sea level controls on the textural characteristics and depositional architecture of the Hueneme and associated submarine fan systems, Santa Monica Basin, California

Hueneme and Dume submarine fans in Santa Monica Basin consist of sandy channel and muddy levee facies on the upper fan, lenticular sand sheets on the middle fan, and thinly bedded turbidite and hemipelagic facies elsewhere. Fifteen widely correlatable key seismic reflections in high-resolution airgun and deep-towed boomer profiles subdivide the fan and basin deposits into time-slices that show different thickness and seismic-facies distributions, inferred to result from changes in Quaternary sea level and sediment supply. At times of low sea level, highly efficient turbidity currents generated by hyperpycnal flows or sediment failures at river deltas carry sand well out onto the middle-fan area. Thick, muddy flows formed rapidly prograding high levees mainly on the western (right-hand) side of three valleys that fed Hueneme fan at different times; the most recently active of the lowstand fan valleys, Hueneme fan valley, now heads in Hueneme Canyon. At times of high sea level, fans receive sand from submarine canyons that intercept littoral-drift cells and mixed sediment from earthquake-triggered slumps. Turbidity currents are confined to ‘underfit’ talweg channels in fan valleys and to steep, small, basin-margin fans like Dume fan. Mud is effectively separated from sand at high sea level and moves basinward across the shelf in plumes and in storm-generated lutite flows, contributing to a basin-floor blanket that is locally thicker than contemporary fan deposits and that onlaps older fans at the basin margin. The infilling of Santa Monica Basin has involved both fan and basin-floor aggradation accompanied by landward and basinward facies shifts. Progradation was restricted to the downslope growth of high muddy levees and the periodic basinward advance of the toe of the steeper and sandier Dume fan. Although the region is tectonically active, major sedimentation changes can be related to eustatic sea-level changes. The primary controls on facies shifts and fan growth appear to be an interplay of texture of source sediment, the efficiency with which turbidity currents transport sand, and the effects of delta distributary switching, all of which reflect sea-level changes.

California↗

USGS1990

Metamorphism in the Adirondacks: II. The role of fluids

Quantitative estimates of metamorphic fluid speciation, stable isotopic analyses, and studies of fluid inclusions all document the local complexity of fluids in the deep crustal rocks exposed in the Adirondack Mountains, NY. Estimates of the activity of H 2 O in the granulite facies are substantially lower than in the amphibolite facies gneisses. The onset of low water activities in semi-pelitic gneisses generally correlates with migmatitic textures in the uppermost amphibolite facies, suggesting that partial melts absorbed H 2 O at the peak of metamorphism. In granulite facies marbles and calc-silicates, conditions varied from extremely undersaturated in H 2 O-CO 2 fluid to fluid saturated, and α H2O and α CO2 show sharp gradients within single outcrops. Low values of f O2 and f H2O , or of f CO2 , and f H2O indicate fluid-absent conditions for some orthogneisses and marbles, which are inferred to have been ‘dry’ rocks before and during granulite facies recrystallization. Wollastonite is preserved from early contact metamorphism and serves as an index mineral for fluid-absent conditions in granulites where α H2O is low. Values of f O2 range from near the hematite + magnetite buffer in metamorphosed iron formation to substantially below the quartz + magnetite + fayalite buffer in some orthogneisses. The anorthosite suite is more oxidized than some associated granitic gneisses. Halogens (F and Cl) substitute extensively for OH in micas and amphiboles, extending their stability, although F 2 , Cl 2 , HCl, and HF are minor components in any fluid. Oxybiotite-type exchanges involving O for OH are also important, extending the stability of biotite. Stable isotopic ratios of O and C demonstrate that premetamorphic whole-rock compositions are commonly preserved whereas mineral compositions generally reflect equilibration at the peak of metamorphism. The Marcy Anorthosite Massif was intruded as a high δ 18 O magma. The combination of mineral equilibria, stable isotope data, and fluid inclusions is used to identify and to distinguish among pre-orogenic contact metamorphic/hydrothermal events, peak metamorphic events, and retrograde/postmetamorphic events. Polymetamorphism is documented at skarn zones adjacent to anorthosite, where large volumes of hydrothermal fluid were channeled during early, shallow contact metamorphism and where conditions were fluid poor during subsequent regional metamorphism. Peak metamorphic events are inferred to have been caused primarily by magmatic processes of intrusion and anatexis. Partial melting has caused low values of α H2O in many rocks, but in other cases low values of α H2O are recorded in orthogneisses derived from H 2 O-poor magmas. Isotopic studies show that maximum fluid/rock ratios were <0·l and possibly 0·0 for infiltrating fluids at the peak of metamorphism in many localities. No evidence of pervasive, regional infiltration by a fluid at the peak of metamorphism has been substantiated in the Adirondacks. Fluid inclusions containing high-density CO 2 or CO 2 + H 2 O represent conditions from after the peak of metamorphism and document isobaric cooling, in agreement with estimates from garnet zoning. Fine-scale retrograde veins are common and are associated with high-density CO 2 -rich fluid inclusions.

New York↗