North-central Gulf Coast Research Articles

Woodland-period fisheries on the north-central coast of the Gulf of Mexico

ABSTRACT Despite the prevalence of Woodland-period middens on the Gulf of Mexico’s northern coast, Woodland fisheries remain poorly known. Vertebrate and invertebrate assemblages from Plash Island (1BA134; cal AD 325–640) and Bayou St. John (1BA21; cal AD 650–1040) suggest this period was more than a prelude to Mississippian farming. Much of the coastal Woodland economy centered on reliable, productive estuarine resources, particularly molluscs and fishes that provided communities with multiple options in a resilient strategy employed for at least 700 years. A nuanced interpretation of coastal life as an array of flexible, managed responses to a dynamic estuarine environment is more plausible than a model that postulates seasonal abandonment of a productive coastal territory and valuable gear. We posit a more parsimonious interpretation: residents of Woodland fishing villages on the north-central Gulf coast skillfully and flexibly managed the opportunities and challenges of complex multi-season, year-round fisheries.

Utilizing Crowd-Sourced Rainfall and Flood Impact Information to Improve the Analysis of the North Central Gulf Coast Flood Event of April 2014

Utilizing Crowd-Sourced Rainfall and Flood Impact Information to Improve the Analysis of the North Central Gulf Coast Flood Event of April 2014

Hurricane frequency and landfall distribution for coastal wetlands of the Gulf coast, USA

The regularity and severity of tropical storms are major determinants controlling ecosystem structure and succession for coastal ecosystems. Hurricane landfall rates vary greatly with high and low frequency for given coastal stretches of the southeastern United States. Site-specific meteorological data of hurricane wind speeds and direction, however, are only available for select populated cities of relatively sparse distribution and inland from the coast. A spatial simulation model of hurricane circulation, HURASIM, was applied to reconstruct chronologies of hurricane wind speeds and vectors for northern Gulf coast locations derived from historical tracking data of North Atlantic tropical storms dating back to 1851. Contrasts of storm frequencies showed that tropical storm incidence is nearly double for Florida coastal ecosystems than the westernmost stretches of Texas coastline. Finer-scale spatial simulations for the north-central Gulf coast exhibited sub-regional differences in storm strength and frequency with coastal position and latitude. The overall pattern of storm incidence in the Gulf basin indicates that the disturbance regime of coastal areas varies greatly along the coast, inland from the coast, and temporally over the period of record. Field and modeling studies of coastal ecosystems will benefit from this retrospective analysis of hurricane incidence and intensity both on a local or regional basis.

Spatiotemporal Patterns and Return Periods of Tropical Storm and Hurricane Strikes from Texas to Maine

AbstractThe authors analyze 105 yr (1901–2005) of tropical cyclone strikes at 45 coastal locations from Brownsville, Texas, to Eastport, Maine, with the primary objective of examining spatiotemporal patterns of storm activity. Interpretation of the data suggests that geographically, three focal points for activity are evident: south Florida, the Outer Banks of North Carolina, and the north-central Gulf Coast. Temporally, clusters of hyperactivity are evident in south Florida from the 1920s through the 1950s and then again during the most recent years. North Carolina was a region of enhanced activity in the 1950s and again in the 1990s. A more consistent rate of occurrence was found along the north-central Gulf Coast; the last two years, however, were active in this region. Return periods of tropical storm strength systems or greater range from a frequency of once every 2 yr along the Outer Banks of North Carolina, every three years on average in southeast Texas, southeastern Louisiana, and southern Florida, and about once every 10–15 yr in northern New England. Hurricane return periods range from 5 yr in southern Florida to 105+ years at several sheltered portions of the coastline (e.g., near Cedar Key, Florida, Georgia, and the northeastern seaboard), where some locations experienced only one strike, or no strikes through the entire period of record. Severe hurricane (category 3–5) return periods range from once every 15 yr in South Florida to 105+ in New England.

Light regulation of benthic sulfate reduction rates mediated by seagrass (Thalassia testudinum) metabolism

The effects of light reduction on community metabolism and sediment sulfate reduction rates (SRR) were assessed experimentally in a shallow (, 2.0 m) seagrass (Thalassia testudinum) meadow along Florida's north-central Gulf coast. Nine experimental plots (1.5 m 3 1.5 m) were shaded differentially to achieve a 0-90% gradient in light reduction within the seagrass meadow. Gross primary production and net community production (NCP), estimated with in situ benthic chamber incubations, decreased with increasing light reduction. The compensation irradiance for community metabolism, i.e., the shading level at which NCP shifted from net autotrophic to net heterotrophic, was determined to be 52.5% of the incoming irradiance at canopy height in the seagrass bed (308.7 m Em 22 s 21 PAR at noon). Sediment SRR, determined with the use of a 35 S-SO4 22 radiotracer technique, increased quickly (within 5 d) and markedly with increased shade, i.e., simulated light reduction. SRR increased 50-fold when shading exceeded the light compensation point for the seagrass community, rendering the community net heterotrophic. Five days after restoring ambient light conditions, SRR had decreased sharply for all shading treatments. The observed decrease in NCP, coincident with the increase in the SRR with light reduction, suggests that light reduction has an indirect influence on sediment SRR mediated through its effect on seagrass metabolism.

Biology, Habitat Preference, and Larval Description of Cicindela cursitans Leconte (Coleoptera: Carabidae: Cicindelinae)

Cicindela cursitans LeConte is a small, flightless tiger beetle with a widely scattered distribution in the Great Plains, the Ohio Valley, and the north-central Gulf Coast region. Many aspects of the life history of C. cursitans are poorly known, and the larval stages have remained undescribed until now. We designed experiments to determine specific habitat preference, female oviposition preference, and daily activity cycles of the adults. In addition, we describe the entire pre-adult life history. Adults are most numerous on moist clay soils with sparse to patchy vegetation, but they may also occur in tall-grass prairies. Females oviposit strictly in moist soils consisting of fine particles. Adults are both diurnal and crepuscular, and presumably spend the nighttime hours hiding among vegetation. Larvae occur in the same habitats as the adults and are typically clustered near the bases of plants. The larvae are the smallest of any tiger beetle species described in North America (body length of first instars ¼ 2.6‐3.2 mm, second instars ¼ 5.4‐6.7 mm, third instars ¼ 8.4‐10.1 mm) and most similar in morphology to Cicindela debilis Bates. Knowledge of the life history and habitats used by this species will allow a better understanding of its distribution and abundance, and its association with prairie habitats. This information as well as low dispersal rates may make this species useful for assessment of habitat quality and restoration success. Cicindela cursitans LeConte is a small flightless tiger beetle. At less than 1 cm in length, adults are among the smallest species in North America (Graves and Brzoska 1991). It is also among the more poorly known species, despite having been first described by LeConte in 1857 (LeConte 1857). The species is associated with bunchgrass prairies near rivers (Tinerella and Rider 2000; M. L. Brust, pers. obs.); however, its pre-adult life history remains very poorly known. It is a summer-active species in the adult stage and is most numerous in June and July (Graves and Pearson 1973; Knisley et al. 1987; Larochelle and Lariviere 2001). Because of its small size and general resemblance to ants it is easily overlooked (Graves and Brzoska 1991), and its North American distribution is probably underestimated (Graves and Pearson 1973; Graves

Abundance and Sizes of Bay Scallops in Heterogeneous Habitats Along the Gulf Coast of Florida

Southern bay scallops (Argopecten irradians concentricus) form the basis of a recreational fishery along Florida's Gulf Coast. Recent declines in scallop abundances have led to significant harvest restrictions. As a way to gain insight into influences on scallop abundances and size, surveys of bay scallops and coastal habitats were conducted in two relatively undisturbed, shallow estuaries along the north-central Gulf Coast of Florida. Scallop abundances did not vary significantly between years or between locations kilometers apart. Shell heights did vary significantly between years at locations kilometers apart; however, these differences were not consistently related to differences in chlorophyll concentrations in the water column or distributions of benthic habitat classes. At the 100-m scale within locations, scallops were not proportionally distributed across the major habitat classes (i.e., Syringodium filiforme, Thalassia testudinum, mixed seagrass assemblage, other seagrasses, and areas of no/low seagrass cover). In general, proportionately more scallops were observed in association with S. filiforme, T. testudinum, and mixed seagrass habitats. Bay scallops collected from S. filiforme and areas of no/low grass cover were consistently 1-3 mm larger than those collected from T. testudinum and mixed seagrass assemblages. These results suggest the importance of S. filiforme and T. testudinum as habitats for bay scallops. The results also point to the need for further investigation into possible functional differences among seagrass species that may influence the ecology of bay scallops at a small spatial scale and the need for closer examination of scallop movement that may allow for active habitat selection. The work presented here, plus further efforts to elucidate the drivers of small-scale differences in scallop abundances and sizes, will benefit managers who seek to enhance scallop fisheries or protect and restore coastal habitats.

Compositional analysis of glazed earthenwares from eighteenth-century sites on the northern Gulf Coast

Compositional classification of colonial-era ceramics using neutron activation analysis has heretofore focused primarily on majolicas from Spain and Mexico. In order to expand the chemical database to include 18th-century French ceramics, 186 sherds from Old Mobile and nearby sites on the north-central Gulf Coast have been analyzed, including faience blanche, faience brune, Mexican majolicas, and several types of coarse earthenwares. Quantitative analysis of 23 elements provides a basis for distinguishing French and Spanish-colonial earthenwares, as well as suggesting some preliminary chemical groupings of French faience.

Waning Miocene subduction and arc volcanism in Baja California: the San Luis Gonzaga volcanic field

Subduction of the Guadalupe–Magdalena microplate beneath Baja California ended in the middle Miocene, and the last volcanic events in the frontal arc extinguished along the present-day eastern margin of the Baja California peninsula. The San Luis Gonzaga area in the north-central Gulf coast contains one of the younger arc-related volcanic centers in northern Baja California. The volcanic succession contains three sequences. The basal sequence (Group 1) is composed of stratified pyroclastic deposits, up to 500 m thick, and subordinate lava flows. The near-vent facies crop out in tilted fault blocks along the present shoreline, whereas the distal facies are exposed across ∼12 km toward the west and includes epiclastic deposits and at least three ash flow tuffs. This sequence is internally concordant and overlies smooth paleosurface developed on granitic basement, and pinches out across the Gulf escarpment. The Potrero Andesite (Group 2) is a series of dacite to basaltic-andesite lava flows from a shield volcano located ∼15 km west of today's coastline; similar source vents also occurs further south of the San Luis Gonzaga area. A sequence of dacite domes (Group 3) intrudes the near-vent facies of Group 1 and contains subordinate volcanic breccia and minor lava flows that overlie Group 1 sequence. Cross-cutting relationships and the abundance of volcanic breccia associated with the domes suggest that these domes were emplaced as semi-rigid intrusions (spines) with low explosive activity. The San Luis Gonzaga volcanic suite ranges in composition from basaltic andesite to dacite with predominant plagioclase and pyroxene and variable amounts of hornblende. Trace-element patterns indicate calc-alkaline to mildly alkaline magmas with high Ba and low Nb contents. Incompatible-element ratios and mineralogical characteristics suggest different magma batches and/or different amount of crustal assimilation for the three sequences that produced contrasting eruptive styles. A pink dacitic tuff that lies in the upper portion of Group 1 yielded an 40Ar/ 39Ar age of 17.2±0.3 Ma. The most precise of three ages from the andesitic sheet flows of Group 2 is 15.4±0.5 Ma. The dacite domes of Group 3 represent the end of Miocene arc activity, but they are strongly altered and no reliable ages were obtained. These data fall within the range of isotopic ages reported for arc lavas (21 to 16 Ma) from the discontinuous series of isolated volcanic fields in northern Baja California. This contrasts with the continuous and more voluminous arc-volcanism in southern Baja California that started earlier (25 Ma) and ended later (11 Ma). These space–time patterns of arc volcanism reflect the geometry of the subducted Farallon slab and the history of its breakup as the Rivera triple junction migrated to the south.

Evidence and Effects of Wrench Faulting, North Central Gulf Coast Region: ABSTRACT

Evidence and Effects of Wrench Faulting, North Central Gulf Coast Region: ABSTRACT

Depositional Systems of Lower Tuscaloosa Formation (Cretaceous), North-Central Gulf Coast Basin: ABSTRACT

The lower Tuscaloosa Formation in east-central Louisiana and southwestern Mississippi consists of a southward-thickening wedge of coarse to fine-grained sandstones and shales. The Lower Cretaceous carbonate-shelf margin is a natural boundary separating the updip fluvial depositional system from the downdip deltaic depositional system. The lower Tuscaloosa Formation thickens from a minimum thickness of 120 ft (37 m) updip to a penetrated thickness of 2,800 ft (850 m) downdip. The tectonic setting is one of regional uplift to the north, local uplifts within the alluvial valley, and growth faulting south of the Lower Cretaceous shelf margin. Based on analyses of core, lithologic logs, and a series of sandstone isolith maps constructed from electric logs, the lower Tuscaloosa is interpreted to have been deposited in 3 major depositional systems: (1) a fluvial system, (2) a deltaic system, and (3) a barrier-island system. Seven subenvironments of these depositional systems include: (1) fluvial channels, (2) floodplains, (3) deltaic distributary channels, (4) distributary natural levees, (5) crevasse splays, (6) shallow-marine bays, and (7) accretion ridges. The deltaic depositional system is composed of several fluvial-dominated, wave-influenced deltas. The distribution of deltaic depositional subenvironments was influenced by the tectonics of the basin and by the near-shore wave energy. This type of delta persisted throughout most of the lower Tuscaloosa deposition. End_of_Article - Last_Page 515------------

Late Pliocene-Early Pleistocene Nannofossil Stratigraphy in North-Central Gulf Coast: ABSTRACT

The early Pleistocene deposits of southeastern Louisiana consist of basal regressive sandstone overlain by a thick marine transgressive shale unit to which various informal names have been applied. This early Pleistocene shale has an areal extent of more than 20,000 sq mi and ranges in thickness from 100 ft in updip areas to several thousand feet in the continental shelf. This study was based on sidewall cores from 4 wells drilled more than 60 mi offshore from the coastline in the southern part of the Ship Shoal area, Terrebonne Parish, Louisiana. Samples also were examined from piston cores taken in the Atlantic and Pacific Oceans and the distribution of pertinent calcareous nannofossils in these samples was compared with distributions in the Louisiana sections. End_Page 1836------------------------------ Thirty-two species of calcareous nannofossils from 20 genera have been identified from the late Pliocene and early Pleistocene strata of the Louisiana continental shelf. Of these 32 species, 2 are restricted sufficiently to be useful as stratigraphic criteria. The significant occurrences are, the extinction of Discoaster brouweri Tan Sin Hok and the first appearance of Gephyrocapsa caribbeanica Boudreaux and Hay and these 2 species may be used to define the base of the early Pleistocene marine shale in the north-central Gulf Coast. Other results include: (1) delineation of a phylogenetic series extending from Coccolithus doronicoides Black and Barnes in the middle Pliocene section to Emiliania huxleyi (Lohmann) in the Holocene, (2) recognition of the co-occurrence of Ceratolithus cris atus (Kamptner) and Ceratolithus rugosus Bukry and Bramlette in the earliest Pleistocene sediments, (3) extension of the geologic range of Gephyrocapsa protohuxleyi McIntyre and Cricolithus jonesi Cohen back to the early Pleistocene, and (4) the first reported fossil record of Homozygosphaera wettsteini (Kamptner) and Calyptrosphaera oblonga Lohmann. End_of_Article - Last_Page 1837------------

Depositional Systems of Lower Wilcox Group, North-Central Gulf Coast Basin: ABSTRACT

The lower Wilcox Group (Eocene) of Louisiana, End_Page 1826------------------------------ Mississippi, and Alabama consists of deposits of four principal depositional systems: (1) the Holly Springs delta system which is volumetrically the largest system; (2) the Pendleton bay-lagoon system which extends into eastern Texas; (3) a restricted shelf system east of the delta system; and (4) an unnamed fluvial system which crops out along the flanks of the northward-trending Mississippi trough. Sandstone isolith maps outline the geometry of the delta mass and show at least three lobe complexes separated by mud-rich interdeltaic subembayments. Detailed facies maps, on which information derived primarily from electric logs is used, allows recognition of seven principal component facies of the delta system: (1) bar-finger sand facies; (2) interdistributary bay mud-salt facies; (3) distributary channel sand facies; (4) prodelta mud facies; (5) distributary mouth bar-delta front sand facies; (6) interdistributary deltaic plain sand-mud-lignite facies; and (7) destructional phase sand-mud-lignite facies. Two principal types of delta lobes differentiated by their areal geometry, internal facies relations, and distributary channel development, can be recognized in the Holly Springs delta system. Bird-foot lobes were constructed where distributaries prograded over thick prodelta mud sequences; thinner, more lobate shoal-water delta lobes formed on shallow, sandy shelves or on foundered plains of older deltas. A distinct correlation between depositional environment and the production of oil exists in the Holly Springs and Rockdale delta systems, which comprise the lower Wilcox of southeast Texas. Sand units associated with facies of the distal margins of individual delta lobes or with the destructional units are the most prolific reservoirs, and production is therefore centered along the flanks of the major lobe complexes where maximum delta destruction and interfingering with marine mud occurred. End_of_Article - Last_Page 1827------------