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At least 937 records · Page 52Linked to original sources
USGS1989

Constraints from fluid inclusions on sulfide precipitation mechanisms and ore fluid migration in the Viburnum Trend lead district, Missouri

Measurements on fluid inclusions in hydrothermal dolomite cements place constraints on sulfide precipitation mechanisms and on the thermal-hydrologic processes which formed the Viburnum Trend Mississippi Valley-type lead district. Homogenization temperatures and freezing point depressions were determined for fluid inclusions in Bonneterre Dolomite-hosted dolomite cements in mine samples, as well as drill core from up to 13 km outside of the district. A well-defined cathodoluminescent zonation distinguishes dolomite growth zones in the Vi-burnurn Trend as older or younger than main-stage mineralization (octahedral galena) and facilitates correlation with other dolomites outside the Viburnum Trend.Homogenization temperatures and salinities in samples from mines are not systematically different from those of samples outside of the district. Medians of homogenization temperature distributions differ by not more than 25 degrees C, so that a temperature gradient, if present, should not have exceeded approximately 25 degrees C within the study area. These observations are interpreted to indicate that the Viburnum Trend was not strongly thermally anomalous with respect to surrounding country rock and that fluid flow occurred on a broad scale through not only the Lamotte Sandstone but through the overlying Cambrian carbonates as well.The absence of a significant, recognizable decrease in temperature either vertically within the section or east-west across the district, coupled with the minor amount of silica in the district, argues against cooling as a primary cause of sulfide precipitation. Fluids whose primary aquifer was the Lamotte Sandstone, predominantly a quartz arenite, should have been in equilibrium with quartz. Quartz in the Viburnum Trend occurs as a minor, drusy, vug-lining phase, but the district lacks the intense silicification found in other Mississippi Valley-type districts such as Tri-State (Oklahoma, Kansas, Missouri). Quartz solubility is strongly temperature dependent and, under equilibrium conditions, a decrease of 10 degrees C or more should have precipitated at least as many moles of silica as galena (assuming a galena solubility of between 1 and 10 ppm). Clearly this is not the case, as galena is far more abundant than quartz in the Viburnum Trend.Ice final-melting temperatures (T m ) in fluid inclusions generally range from -14 degrees to -27 degrees C for primary dolomite-hosted inclusions. Using these T m values and cation ratios for the inclusion fluids, absolute concentrations for the individual cations and chloride were calculated using the thermochemical model of Spencer et al. (1990). The corresponding high but variable salinities, 3.9 to 5.9 chloride molality, are evidence for the presence of more than one distinct fluid during mineralization.In a reduced sulfur mineralization model with Pb carried as chloride complexes, dilution is also a possible sulfide precipitation mechanism. The difference in Pb solubility (for an equal quantity of reduced sulfur) in the extremes of the chloride concentration range, 3.9 vs. 5.9 molal, reaches 1 ppm only for pH values below approximately 4.5. Accepting 1 ppm as a minimum metal concentration for a viable ore-forming fluid, dilution only appears capable of precipitating sulfides in a fluid with pH near the lower limit of values considered geologically reasonable or attainable.Dolomite cements hosting warm (approximately 105 degrees -125 degrees C) saline fluid inclusions are ubiquitous in the porous dolomitic facies of the Bonneterre Dolomite. Based on stratigraphic reconstructions, however, it is unlikely that the Bonneterre was buried deeper than 1.5 km. The distribution of warm inclusions beyond the Viburnum Trend district implies that fluid migration was regional in scale. Fluid inclusion temperatures inconsistent with typical basement heat-flow-controlled geothermal gradients (25 degrees -35 degrees C/km) may be explained by long-distance migration of warm, basin-derived brines. Elevated temperatures observed in fluid inclusions at shallow stratigraphic depths are consistent with a gravity flow hydrologic system characterized by rapid flow rates and the capacity for advective heat transport.

Economic Geology↗
USGS2004

Characterization of ichthyoplankton within the U.S. Geological Survey's Northeastern Gulf of Mexico study area - based on analysis of Southeast Area Monitoring and Assessment Program (SEAMAP) Sampling Surveys, 1982-1999. NEGOM ichthyoplankton synopsis final report

This synthesis was undertaken to characterize the occurrence and abundance of fish eggs and larvae in the northeastern Gulf of Mexico (NEGOM) and to assess the region's relative importance in the early life history of fishes as compared to the entire U.S. Gulf of Mexico. Data for 66 selected taxa from 1,166 bongo and neuston net samples at 72 localities [comprising the UGSG NEGOM Ichthyoplankton Synopsis (UNIS) Study Area] were analyzed. These data were taken during annual Southeast Area Monitoring and Assessment Program (SEAMAP) gulfwide surveys from 1982-1999, and were summarized by the NMFS to accomplish this objective. Comparison of the UNIS Study Area with the overall SEAMAP survey area revealed that the larvae of 16 taxa occurred more frequently and were relatively more abundant in the UNIS Study Area than the entire SEAMAP survey area while for other taxa occurrence and relative abundance were comparable. These taxa represented fishes from mesopelagic, continental shelf, and reef assemblages reflecting the wide diversity of habitats available in the NEGOM and included the young of two important resource taxa, Rhomboplites aurorubens (vermilion snapper) and Seriola spp. (amberjacks). Distinct distribution patterns were observed among larvae in the UNIS Study Area that appear to be associated with the presence of the DeSoto Canyon. One notable pattern was the predominance of certain taxa to either the west or east of longitude 86.5-87.0o W. Larvae of several characteristic reef-fish families were most common to the east of this apparent zoogeographic faunal discontinuity. An alternative pattern was seen among taxa whose larvae occurred primarily at locations over depth contours outlining the canyon. Additionally, the UNIS Study Area contributed more fish eggs, total larvae, and zooplankton to survey totals than would be expected from the number of samples taken in the study area. This pattern was more evident during spring than fall surveys. It may relate to the close proximity of UNIS Study Area stations to the Mississippi River and the penetration of DeSoto Canyon, with its nutrient-rich deep slope water, into the inner shelf. The consistent presence of fish eggs throughout the NEGOM at mean abundances exceeding 100 eggs per 10 m? sea surface indicates that this region of the Gulf of Mexico is an important spawning area. The present synopsis has revealed that the NEGOM, as represented by the UNIS Study Area, should be considered an important, if not critical, habitat for the young stages of a diverse assemblage of fish taxa. The greatest biological deficiency in this synopsis is our current inability to identify the larvae of all species to a consistent taxonomic level.

Scientific Investigations Report↗
USGS1968

Seismic seiches from the March 1964 Alaska earthquake

Seismic seiches caused by the Alaska earthquake of March 27, 1964, were recorded at more than 850 surface-water gaging stations in North America and at 4 in Australia. In the United States, including Alaska and Hawaii, 763 of 6,435 gages registered seiches. Nearly all the seismic seiches were recorded at teleseismic distance. This is the first time such far-distant effects have been reported from surface-water bodies in North America. The densest occurrence of seiches was in States bordering the Gulf of Mexico. The seiches were recorded on bodies of water having a wide range in depth, width, and rate of flow. In a region containing many bodies of water, seiche distribution is more dependent on geologic and seismic factors than on hydro-dynamic ones. The concept that seiches are caused by the horizontal acceleration of water by seismic surface waves has been extended in this paper to show that the distribution of seiches is related to the amplitude distribution of short-period seismic surface waves. These waves have their greatest horizontal acceleration when their periods range from 5 to 15 seconds. Similarly, the water bodies on which seiches were recorded have low-order modes whose periods of oscillation also range from 5 to 15 seconds. Several factors seem to control the distribution of seiches. The most important is variations of thickness of low-rigidity sediments. This factor caused the abundance of seiches in the Gulf Coast area and along the edge of sedimentary overlaps. Major tectonic features such as thrust faults, basins, arches, and domes seem to control seismic waves and thus affect the distribution of seiches. Lateral refraction of seismic surface waves due to variations in local phase-velocity values was responsible for increase in seiche density in certain areas. For example, the Rocky Mountains provided a wave guide along which seiches were more numerous than in areas to either side. In North America, neither direction nor distance from the epicenter had any apparent effect on the distribution of seiches. Where seismic surface waves propagated into an area with thicker sediment, the horizontal acceleration increased about in proportion to the increasing thickness of the sediment. In the Mississippi Embayment however, where the waves emerged from high rigidity crust into the sediment, the horizontal acceleration increased near the edge of the embayment but decreased in the central part and formed a shadow zone. Because both seiches and seismic intensity depend on the horizontal acceleration from surface waves, the distribution of seiches may be used to map the seismic intensity that can be expected from future local earthquakes.

Professional Paper↗
USGS2022

Tennessee and Landsat

From the flat, rich soil of western Tennessee to the Appalachian Mountains in the east, and rolling hills in between, “the Volunteer State” enjoys a wealth of natural resources. The Tennessee, Cumberland, and Mississippi Rivers supply economically crucial navigation routes, along with recreation for residents and visitors. Additionally, 14 million acres of hardwood and softwood forests cover roughly one-half of the State, contributing an estimated $24 billion and nearly 100,000 jobs to Tennessee’s economy. Within a span of more than 400 miles, the State’s diverse agricultural products include cotton, corn, soybeans, poultry, horses, cattle, goats, hay, vegetables, nursery crops, and tobacco. Energy production is important to Tennessee and the region, and power sources range from coal and nuclear to hydroelectric sources. Tourism also is a key industry, and music attractions and historical sites are balanced by natural features such as the Great Smoky Mountains National Park, which recorded 14.1 million visits and ranked second for most visited National Park Service site in the United States in 2021. Landsat imagery’s broad geographic scale and rich historical archive have proven useful to land managers and State agencies for monitoring natural resources. Here are several ways Landsat has benefited Tennessee.

Tennessee↗
USGS2014

Sedimentary facies of the upper Cambrian (Furongian; Jiangshanian and Sunwaptan) Tunnel City Group, Upper Mississippi Valley: new insight on the old stormy debate

New data from detailed measured sections permit a comprehensive revision of the sedimentary facies of the Furongian (upper Cambrian; Jiangshanian and Sunwaptan stages) Tunnel City Group (Lone Rock Formation and Mazomanie Formation) of Wisconsin and Minnesota. Heterogeneous sandstones, comprising seven lithofacies along a depositional transect from shoreface to transitional-offshore environments, record sedimentation in a storm-dominated, shallow-marine epicontinental sea. The origin of glauconite in the Birkmose Member and Reno Member of the Lone Rock Formation was unclear, but its formation and preserved distribution are linked to inferred depositional energy rather than just net sedimentation rate. Flat-pebble conglomerate, abundant in lower Paleozoic strata, was associated with the formation of a condensed section during cratonic flooding. Hummocky cross-stratification was a valuable tool used to infer depositional settings and relative paleobathymetry, and the model describing formation of this bedform is expanded to address flow types dominant during its genesis, in particular the importance of an early unidirectional component of combined flow. The depositional model developed here for the Lone Rock Formation and Mazomanie Formation is broadly applicable to other strata common to the early Paleozoic that document sedimentation along flooded cratonic interiors or shallow shelves.

Minnesota;Wisconsin↗
USGS2008

Citronelle Dome: A giant opportunity for multizone carbon storage and enhanced oil recovery in the Mississippi Interior Salt Basin of Alabama

The Citronelle Dome is a giant, salt-cored anticline in the eastern Mississippi Interior Salt Basin of southern Alabama that is located near several large-scale, stationary, carbon-emitting sources in the greater Mobile area. The dome forms an elliptical, four-way structural closure containing opportunities for CO2-enhanced oil recovery (CO2-EOR) and large-capacity saline reservoir CO2 sequestration. The Citronelle oil field, located on the crest of the dome, has produced more than 169 million bbl of 42-46?? API gravity oil from sandstone bodies in the Lower Cretaceous Rodessa Formation. The top seal for the oil accumulation is a thick succession of shale and anhydrite, and the reservoir is underfilled such that oil-water contacts are typically elevated 30-60 m (100-200 ft) above the structural spill point. Approximately 31-34% of the original oil in place has been recovered by primary and secondary methods, and CO2-EOR has the potential to increase reserves by up to 20%. Structural contour maps of the dome demonstrate that the area of structural closure increases upward in section. Sandstone units providing prospective carbon sinks include the Massive and Pilot sands of the lower Tuscaloosa Group, as well as several sandstone units in the upper Tuscaloosa Group and the Eutaw Formation. Many of these sandstone units are characterized by high porosity and permeability with low heterogeneity. The Tuscaloosa-Eutaw interval is capped by up to 610 m (2000 ft) of chalk and marine shale that are proven reservoir seals in nearby oil fields. Therefore, the Citronelle Dome can be considered a major geologic sink where CO2 can be safely stored while realizing the economic benefits associated with CO2-EOR. Copyright ?? 2008. The American Association of Petroleum Geologists/Division of Environmental Geosciences. All rights reserved.

Environmental Geosciences↗
USGS2000

Cruise report RV Ocean Surveyor cruise O-1-00-GM the bathymetry and acoustic backscatter of the Pinnacles area, northern Gulf of Mexico May 23, through June 10, 2000 Venice, LA to Venice, LA

An extensive deep (~100 m) reef tract occurs on the Mississippi-Alabama outer continental shelf (OCS). The tract, known as "The Pinnacles", is apparently part of a sequence of drowned reef complexes along the "40-fathom" shelf edge of the northern Gulf of Mexico (Ludwick and Walton, 1957). It is critical to determine the accurate geomorphology of deep-reefs because of their importance as benthic habitats for fisheries. The Pinnacles were mapped by Ludwick and Walton (1957) using a single-beam echo sounder but the spatial extent and morphology were interpreted from a series of widely separated, poorly navigated bathymetric profiles. Other recent studies, supported by Minerals Management Service (MMS), used towed sidescan sonars and single-channel seismic-reflection profiling. None of the existing studies provide the quality of geomorphic data necessary for reasonable habitat studies. The fish faunas of shallow hermatypic reefs have been well studied, but those of deep ahermatypic reefs have relatively ignored. The ecology of deep ahermatypic reefs is fundamentally different from hermatipic reefs because autochthonous intracellular symbiotic zooxanthellae (the carbon source for hermatypic corals) do not form the base of the trophic web. Instead, exogenous plankton, transported to the reef by currents, serves as the primary carbon source. Deep OCS reefs also lie below the practical working depths for SCUBA; consequently, remote investigations from a ship or in situ investigations using submersibles or ROVs are required. Community structure and trophodynamics of demersal fishes of the Pinnacles are presently the focus of USGS reseach. A goal of the research is to answer questions concerning the relataive roles played by geomorphology and surficial geology in the interaction with and control of biological differentiation. OCS reefs are important because we now know that such areas are important coral reef fish havens, key spawning 2 sites, and a critical early larval and juvenile habitats for economically important sport/food fishes. Also, deep-reef ecosystems as well as the fish populations they sustain are impacted by intensive oil-field development. It is now known that deep OCS reefs function as a key source of re-population (via seasonal and ontogenetic migration) of already heavily impacted inshore reefs. A reflection of this realization is the recent closure by the Gulf States Fisheries Management Council of a 600 mi 2 area of the Florida Middle Grounds (another unmapped major "40-fathom" OCS reef complex) to commercial fishing to preserve grouper spawning aggregations. It is known that the Pinnacles reefs support a lush fauna of ahermatypic hard corals, soft corals, black corals, sessile crinoids and sponges—together forming a living habitat for a well-developed fish fauna. The fish fauna comprises typical Caribbean reef fishes and Carolinian shelf fishes, plus epipelagic fishes, and a few deep-sea fishes. The base of the megafaunal invertebrate food web is plankton, borne by essentially continuous semi-laminar currents flowing predominantly out of the SW, up, along and across the shelf edge. These currents are intercepted by pinnacles reefs, which lie roughly in two linear tracts, parallel to the coastline (see fig. 1 in report). USGS research initiated in 1997 (Sulak et al., in progress) has demonstrated that the Pinnacles reef fish fauna is dominated by planktivorous fishes. Ongoing food habits, trophic web and stable isotope analyses by the USGS are reinforcing a basic picture of deep OCS reefs as ecosystems based on exogenous current-borne plankton. Long-term current meter deployments have demonstrated that the >3 m, <16m relief of the Pinnacles reefs disrupts the prevailing currents, inducing local complexity (F. Kelly, Texas A&M Univ., pers. comm.) favorable to plankton and planktivores. Geodetically accurate bathymetry maps, coregistered with calibrated acoustic backscatter maps, are critical to delineate benthic biotopes, and are essential to correlate biological community differentiation with the physical environment. Previous mapping of the Pinnacles area using the TAMU towed single-beam sidescan system (Anonymous., 1999) employed technology with inherent deficiencies in backscatter calibration, bathymetric precision, and geo-referencing. The resulting bathymetric interpretations of TAMU data are further degraded by ship-track-parallel artifacts that obliterate geomorphology rendering them inadequate to provide high-resolution mapping of individual target reefs (typical maximum relief 15 m, diameter 200-500 m). The sidescan-sonar surveys of the area (Laswell et al., 1990) suffer many of the same deficiencies as the TAMU data so they add no quantitative and little qualitative information about the geomorphology and surficial geology.

Gulf of Mexico, the Pinnacles area↗
USGS2002

Latest Quaternary stratigraphic framework of the Mississippi River delta region

Previous researchers separated the uppermost Quaternary stratigraphy of the Mississippi River delta region into two major lithofacies. The stratigraphically lower of these, "substratum," primarily consists of coarse-grained sediment deposited within lowstand-incised stream valleys. Relatively finer-grained "topstratum" overlies substratum; above interfluves, topstratum directly overlies weathered late Pleistocene sediments. However, the onshore to offshore distribution and architecture of these lithofacies was not well constrained. This study integrates published and unpublished lithostratigraphic data with high-resolution seismic profiles from the continental shelf to aid in mapping the regional distribution of major substratum deposits and thickness of topstratum sediments. A transgressive sand sheet commonly marks the base of the topstratum deposits, providing a stratigraphic marker to aid in regional lithostratigraphic correlations. Radiocarbondated deposits and boreholes tied to oxygen isotope chronologies provide chronostratigraphic control. Excellent correlation between these multiple datasets has been found to exist, enabling construction of regional isopachous and structural elevation maps and cross sections detailing elements of the Late Quaternary stratigraphy.

Louisiana↗
USGS1994

Carbonate-Sulfate Volcanism on Venus?

Venusian canali, outflow channels, and associated volcanic deposits resemble fluvial landforms more than they resemble volcanic features on Earth and Mars. Some canali have meandering habits and features indicative of channel migration that are very similar to meandering river channels and flood plains on Earth, venusian outflow channels closely resemble water-carved outflow channels on Mars and the Channeled Scabland in Washington, collapsed terrains at the sources of some venusian channels resemble chaotic terrains at the sources of martian outflow channels, venusian lava deltas are similar to bird's-foot deltas such as the Mississippi delta, and venusian valley networks indicate sapping. The depositional fluvial-type features (deltas, braided bars, and channeled plains) are generally among the smoothest terrains at the Magellan radar wavelength (12.6 cm) on Venus. These features suggest the involvement of an unusual lava, unexpected processes, and/or extraordinary eruption conditions. Possibly the lava was an ordinary silicate lava such as basalt or a less common type of silicate lava, and conditions unique to Venus or to those particular eruptions may have caused an unusual volcanological behavior. We have developed the alternative possibility that the lava had a water-like rheology and a melting point slightly greater than Venus' surface temperature, thus accounting for the unusual behavior of the lava. Unlike silicate lavas, some carbonatites (including carbonate-sulfate-rich liquids) have these properties; thus they can flow great distances while retaining a high fluidity, significant mechanical erosiveness, and substantial capacity to transport and deposit sediment. Venusian geochemistry and petrology are consistent with extensive eruptions of carbonatite lavas, which could have crustal and/or mantle origins. Venus' atmosphere (especially CO2, HCl, and HF abundances) and rocks may be in local chemical equilibrium, which suggests that the upper crust contains large amounts of calcite, anhydrite, and other salts. Chemical analyses indicate, according to some models, that Venusian rocks may contain 4-19% calcite and anhydrite. Mixtures of crustal salts could melt at temperatures a few tens to a few hundred Kelvins higher than Venus' surface temperature; hence, melting may be induced by modest endogenetic or impact heating. Salts may have many of the same geologic roles on Venus as water and ice have on Mars. A molten salt (carbonatite) "aquifer" may exist beneath a few hundred meters to several kilometers of solidified salt-rich "permafrost." Many geologic features can be explained by carbonatite magmatism: (1) impact melting of crustal salts can explain crater outflows, (2) small, sustained eruptions from molten salt aquifers can explain sapping valleys, (3) large, sustained eruptions may explain canali and their flood plans, and (4) catastrophic outbursts may have formed outflow channels and chaotic terrain. Landforms created by carbonate-rich lavas would be thermally stable on Venus' surface, though some minerals may weather to other solid substances.

Icarus↗
USGS2014

Sequence stratigraphy of the Upper Cambrian (Furongian; Jiangshanian and Sunwaptan) Tunnel City Group, Upper Mississippi Valley: Transgressing assumptions of cratonic flooding

New data from detailed measured sections permit comprehensive analysis of the sequence framework of the Furongian (Upper Cambrian; Jiangshanian and Sunwaptan stages) Tunnel City Group (Lone Rock Formation and Mazomanie Formation) of Wisconsin and Minnesota. The sequence-stratigraphic architecture of the lower part of the Sunwaptan Stage at the base of the Tunnel City Group, at the contact between the Wonewoc Formation and Lone Rock Formation, records the first part of complex polyphase flooding (Sauk III) of the Laurentian craton, at a scale smaller than most events recorded by global sea-level curves. Flat-pebble conglomerate and glauconite document transgressive ravinement and development of a condensed section when creation of accommodation exceeded its consumption by sedimentation. Thinly-bedded, fossiliferous sandstone represents the most distal setting during earliest highstand. Subsequent deposition of sandstone characterized by hummocky or trough cross-stratification records progradational pulses of shallower, storm- and wave-dominated environments across the craton before final flooding of Sauk III commenced with carbonate deposition during the middle part of the Sunwaptan Stage. Comparison of early Sunwaptan flooding of the inner Laurentian craton to published interpretations from other parts of North America suggests that Sauk III was not a single, long-term accommodation event as previously proposed.

Minnesota;Wisconsin↗
USGS2012

CO 2 –rock–brine interactions in Lower Tuscaloosa Formation at Cranfield CO 2 sequestration site, Mississippi, U.S.A.

A highly integrated geochemical program was conducted at the Cranfield CO 2 -enhanced oil recovery (EOR) and sequestration site, Mississippi, U.S.A.. The program included extensive field geochemical monitoring, a detailed petrographic study, and an autoclave experiment under in situ reservoir conditions. Results show that mineral reactions in the Lower Tuscaloosa reservoir were minor during CO 2 injection. Brine chemistry remained largely unchanged, which contrasts with significant changes observed in other field tests. Field fluid sampling and laboratory experiments show consistently slow reactions. Carbon isotopic composition and CO 2 content in the gas phase reveal simple two-end-member mixing between injected and original formation gas. We conclude that the reservoir rock, which is composed mainly of minerals with low reactivity (average quartz 79.4%, chlorite 11.8%, kaolinite 3.1%, illite 1.3%, concretionary calcite and dolomite 1.5%, and feldspar 0.2%), is relatively unreactive to CO 2 . The significance of low reactivity is both positive, in that the reservoir is not impacted, and negative, in that mineral trapping is insignificant.

Mississippi↗
USGS1998

Near-surface structural model for deformation associated with the February 7, 1812, New Madrid, Missouri, earthquake

The February 7, 1812, New Madrid, Missouri, earthquake (M [moment magnitude] 8) was the third and final large-magnitude event to rock the northern Mississippi Embayment during the winter of 1811–1812. Although ground shaking was so strong that it rang church bells, stopped clocks, buckled pavement, and rocked buildings up and down the eastern seaboard, little coseismic surface deformation exists today in the New Madrid area. The fault(s) that ruptured during this event have remained enigmatic. We have integrated geomorphic data documenting differential surficial deformation (supplemented by historical accounts of surficial deformation and earthquake-induced Mississippi River waterfalls and rapids) with the interpretation of existing and recently acquired seismic reflection data, to develop a tectonic model of the near-surface structures in the New Madrid, Missouri, area. This model consists of two primary components: a north-northwest–trending thrust fault and a series of northeast-trending, strike-slip, tear faults. We conclude that the Reelfoot fault is a thrust fault that is at least 30 km long. We also infer that tear faults in the near surface partitioned the hanging wall into subparallel blocks that have undergone differential displacement during episodes of faulting. The northeast-trending tear faults bound an area documented to have been uplifted at least 0.5 m during the February 7, 1812, earthquake. These faults also appear to bound changes in the surface density of epicenters that are within the modern seismicity, which is occurring in the stepover zone of the left-stepping right-lateral strike-slip fault system of the modern New Madrid seismic zone.

Missouri↗
USGS2023

Microfossils and biostratigraphy of the Upper Cretaceous Coon Creek Formation Lagerstätte, Mississippi Embayment, USA

The Upper Cretaceous Coon Creek Formation type-locality in McNairy County, Tennessee, is an exceptional marine invertebrate Lagerstätte that was deposited in a nearshore reentrant into the ancestral continent of Appalachia. Extensive taxonomic analysis of the macrofauna has been done for over 100 years. However, documentation of the microfossil component at the type-locality has largely been ignored. This paper provides analysis of calcareous microfossils (benthic and planktonic foraminifera, calcareous nannofossils and ostracods) and palynomorphs (pollen, spores, algal remains and dinoflagellates) for detailed age control and information regarding environment of deposition. The Coon Creek type-locality is late Campanian (76.8–76.0 Ma) in age and was deposited in 35–60 m water depths. Calcareous nannofossil assemblages suggest that there was an influence of colder water through time, possibly by a connection to the northern Western Interior Seaway. The complex interplay between currents of the Gulf of Mexico and the Western Interior Seaway, upwelling and runoff influenced the palaeoenvironment. Increased influx of freshwater palynomorphs near the top of the section suggests placement proximal to the palaeoshoreline and that weathering increased through time. Changes in the dinoflagellate assemblage may be linked to a mosasaur mass mortality event and the presence of a harmful algal bloom.

Tennessee↗
USGS1983

Reworked Hantkenina speciments at Little Stave Creek, Alabama

The Eocene-Oligocene boundary in Mississippi and Alabama has been traditionally placed between the Shubuta Member of the Yazoo Formation and the overlying Red Bluff Formation (or its carbonate facies equivalent, the Bumpnose Formation). Consequently, the presence of Eocene planktonic foraminifers in the Red Bluff and Bumpnose has long been attributed to reworking. To test the validity of this hypothesis, samples were collected on both sides of the boundary from the upper "Shubuta" and Bumpnose units at Little Stave Creek, Alabama, and were examined for both calcareous nannofossil and planktonic foraminiferal content. The calcereous nannofossil assemblage, preserved in the matrix from inside handpicked specimens of Hantkenina from both units, was demonstrably older than the calcareous nannofossil assemblage from the surrounding sediment. Thus, at least some of the Hantkenina specimens in both the "Shubuta" and Bumpnose are indeed reworked, which not only confirms the original hypothesis regarding reworking within the Red Bluff and Bumpnose, but also indicates that the last occurrence of Hantkenina , the "Shubuta"-Bumpnose contact, and the Eocene-Oligocene boundary in the U.S. Gulf Coast may not be equivalent.

Alabama↗
USGS2012

Transmissivity of the Upper Floridan aquifer in Florida and parts of Georgia, South Carolina, and Alabama

The Floridan aquifer system (FAS) covers an area of approximately 100,000 square miles in Florida and parts of Georgia, South Carolina, Alabama, and Mississippi. Groundwater wells for water supply were first drilled in the late 1800s and by the year 2000, the FAS was the primary source of drinking water for about 10 million people. One of the methods for assessing groundwater availability is the development of regional or subregional groundwater flow models of the aquifer system that can be used to develop water budgets spatially and temporally, as well as evaluate the groundwater resource change over time. Understanding the distribution of transmissivity within the FAS is critical to the development of groundwater flow models. The map presented herein differs from previously published maps of the FAS in that it is based on interpolation of 1,487 values of transmissivity. The transmissivity values in the dataset range from 8 to 9,000,000 feet squared per day (ft 2 /d) with the majority of the values ranging from 10,000 to 100,000 ft 2 /d. The wide range in transmissivity (6 orders of magnitude) is typical of carbonate rock aquifers, which are characterized by a wide range in karstification. Commonly, the range in transmissivity is greatest in areas where groundwater flow creates conduits in facies that dissolve more readily or areas of high porosity units that have interconnected vugs, with diameters greater than 0.1 foot. These are also areas where transmissivity is largest. Additionally, first magnitude springsheds and springs are shown because in these springshed areas, the estimates of transmissivity from interpolation may underestimate the actual range in transmissivity. Also shown is an area within the Gulf Trough in Georgia where high yielding wells are unlikely to be developed in the Upper Floridan aquifer. The interpolated transmissivity ranges shown on this map reflect the geologic structure and karstified areas. Transmissivity is large in the areas where the system is unconfined, such as west-central Florida and southwest Georgia just northwest of the Gulf Trough. Transmissivity is small along the Gulf Trough and Southwest Georgia Embayment (referred to as Apalachicola Embayment in some reports). Transmissivity is also small in the thin, updip part of the system near its northern boundary. Another area of large transmissivity coincides with the Southeast Georgia Embayment.

Alabama, Florida, Georgia, South Carolina↗
USGS1970

Comparative hydrogeology: An example of its use

As a start toward needed classifications of hydrogeologic settings, a type of setting is described. The setting includes areas where soluble materials are exposed to considerable recharge from precipitation and where both the topographic relief and permeability are inappreciable. Typical areas of this setting are (1) the Black Belt of the Coastal Plain of Alabama and Mississippi, underlain by chalk of the Selma Group, and (2) a 25-sq-mi area near Harrisburg, Cabarrus County, North Carolina, underlain by gabbro in the Piedmont province. Hydrologic conditions that may be inferred and that are easily discernible from this type of setting include: excessive evapotranspiration, low water-table gradient, water table near land surface, thin soils, ground-water movement being almost inappreciable, and the zone of movement being almost limited to a thin zone that includes the contact between the soil and rock, inappreciable ground-water discharge to streams leading, in turn, to a low base flow in streams, low drainage density, and subsurface water relatively high in dissolved mineral matter. Evaluation of the hydrogeologic setting described leads inductively into the undeveloped field of comparative hydrology, which represents a quick useful means of discerning the significance of processes and principles in particular environments. The setting reveals the significance of solution by subsurface water in developing some plains. Comparative hydrology, using the described setting and typical karst settings as examples, allows an advanced analysis of some pertinent factors.

Alabama, Mississippi, North Carolina↗
USGS1995

Water-quality and lake-stage data for Wisconsin lakes, water year 1994

The U.S. Geological Survey (USGS), in cooperation with local and other agencies, collects data at selected lakes throughout Wisconsin. These data, accumulated over many yes rs, provide a data base for developing an improved understanding of the water quality of lakes\ To make these data available to interested parties outside the USGS, the data are published annually in this report series. The location of surface water-quality and lake-stage stations in Wisconsin for water year 1994 are shown in figure 1. A water year is the 12-month period from October 1 through September 30. It is designated by the calendar year in which it ends and which includes 9 of the 12 months. Thus the period October 1, 1993 through September 30, 1994, is called "water year 1994." The purpose of this report is to provide information about the physical, che-nical, and biological characteristics of Wisconsin lakes. Data that have been collected at specific lakes, and information to aid in the interpretation of those data, are included in this report. Data collected includes measurements of lake stage and in-lake water quality. Graphs of Secchi depths, and total-phosphorus and chlorophyll-a concentrations versus time are included for lakes with two or more years of data. Descriptive information for each lake includes location of the lake, drainage area of the lake's watershed, period for which data are available, revisions to previously published records, and pertinent remarks. Additional data, such as streamflow and water quality in tributary and outlet streams of some of the lakes, are published in two other volunres: "Water Resources Data-Wisconsin, 1994, St. Lawrence River Basin" (Volume 1) and "Water Resources Data-Wisconsin, 1994, Upper Mississippi River Basin" (Volume 2).

Wisconsin↗
USGS2019

The Zn–Pb mineralization of Florida Canyon, an evaporite-related Mississippi Valley-type deposit in Bongará district, northern Peru

The Florida Canyon evaporite-related Zn–Pb sulfide deposit, in northern Peru, is one of the largest Mississippi Valley-type (MVT) deposits in South America. Triassic carbonate and former evaporite-bearing rocks of the Pucará Group host the ore bodies that comprise two different styles: (i) predominantly stratabound ore associated with hydrocarbon-rich porous dolostones and evaporite dissolution breccias; and (ii) high-grade ore associated with evaporite breccias representing diapiric injections along faults. A dome structure that controls the location of the ore deposit was defined by drillhole spatial data; the dome likely resulted from halokinetic processes during Andean deformation. NNE-trending steeply dipping secondary faults linked to major NW structures appear to control the distribution of ore grades in the deposit. Mineralization post-dated hydrocarbon migration and accumulation. Strontium, carbon, and oxygen data isotopic signatures allow distinction between pre-and syn-mineralization carbonate stages. The sulfur isotopic composition of sulfides in the deposit suggests they precipitated as the result of mixing of a metal-rich fluid with resident hydrogen sulfide in the dome. Local thermochemical sulfate reduction (TSR) may have contributed to the reduced sulfur budget during mineralization.

Economic Geology↗