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At least 109 records · Page 6Linked to original sources
USGS2002

Trends in late Maastrichtian calcareous nannofossil distribution patterns, Western North Atlantic margin

First and last occurrences of several Maastrichtian calcareous nannofossil species are shown to be diachronous across paleodepth and paleoenvironment using the graphic correlation method. Calcareous nannofossil assemblages examined from eleven cores from a deep- to shallow-water transect along the eastern United States Atlantic margin document that the first occurrence of Micula murus (Martini 1961) Bukry 1973 is diachronous, appearing 2.0 million years earlier in open ocean sites than in shallow marine sites. The first occurrence (FO) of Lithraphidites kennethii Perch-Nielsen 1984 is also nonsynchronous, appearing in the deep ocean before its FO in neritic waters. The last occurrence (LO) of L. praequadratus Roth 1978 is diachronous across paleodepth, going locally extinct first in deeper water. The LO of Watznaueria bybelliae Self-Trail 1999 is also diachronous, going locally extinct first in shallow-water settings. Ceratolithoides amplector Burnett 1997, C. pricei Burnett 1997, C. self-trailiae Burnett 1997, C. ultimus Burnett 1997, Cribrocorona gallica (Stradner 1963) Perch-Nielsen 1973. Micula praemurus (Bukry 1973) Stradner and Steinmetz 1984, Pseudomicula quadratus Perch-Nielsen et al. 1978, and Semihololithus spp. are present consistently in common to frequent abundances in ODP holes 1050C and 1052E on the Blake Nose, but they are rare or absent from neritic sections in Coastal Plain cores. It is apparent that these species flourished in an open ocean setting, suggesting that differences in assemblage abundance and diversity between deep ocean and nearshore areas were controlled by paleoceanographic factors. These species are not used for biostratigraphy, but may be useful indicators of open ocean conditions. The line of correlation (LOC) for nine Coastal Plain cores clearly defines the Cretaceous-Tertiary (K/T) boundary unconformity at the top of the Maastrichtian section (Peedee Formation) and the Campanian-Maastrichtian (C/M) unconformity at the base of the Maastrichtian section (Peedee/Donoho Creek formational contact). The K/T boundary unconformity is undulatory in nature; updip Maastrichtian sections have been stripped to a greater depth than the downdip sections. The uppermost Campanian, all of the lowermost Maastrichtian, and the basal upper Maastrichtian sediments are missing from the study area.

Micropaleontology↗
USGS2009

A new species of Pentadinium from Eastern Anatolia, Turkey, Pentadinium galileoi

The new gonyaulacoid dinoflagellate Pentadinium galileoi Sancay et al., sp. nov. from the Oligocene-Lower Miocene sediments of Eastern Anatolia has been identified. It is spherical, chordate with prominant discoidal cingulum and distally furcate apical, sulcal, and antapical processes. It has a type P(3???) archeopyle, and periarcheopyle is larger than endoarcheopyle. Tabulation is distinct and it has a formula of 1pr, 3-4',6???,6c,6???', 1p,1??????, Wall structure is granular in intraplate areas, and it has gonal spines at apex, posterior intercalary, and antapex. Processes at gonal positions may be on a variably developed antapical 'skirt' formed by extended septa (2-3 ??m), minute bifurcate spines intergonally and along cingulum at plate intersections. Periphragm and endophragm appressed except at cingular area and at septa. The size of the cysts ranges between 73-89??m with an avarage of 84??m.

Micropaleontology↗
USGS2009

Mid-Pliocene planktic foraminifer assemblage of the North Atlantic Ocean

The US Geological Survey Pliocene Research, Interpretation and Synoptic Mapping (PRISM) North Atlantic faunal data set provides a unique, temporally constrained perspective to document and evaluate the quantitative geographic distribution of key mid-Pliocene taxa. Planktic foraminifer census data from within the PRISM time slab (3.29 to 2.97 Ma) at thirteen sites in the North Atlantic Ocean have been analyzed. We have compiled Scanning Electron Micrographs for an atlas of mid-Pliocene assemblages from the North Atlantic with descriptions of each taxon to document the taxonomic concepts that accompany the PRISM data. In mid-Pliocene assemblages, the geographic distributions of extant taxa are similar to their present day distributions, although some are extended to the north. We use the distribution of extinct taxa to assess previous assumptions regarding environmental preferences.

Micropaleontology↗
USGS1980

Neogene diatoms from Petersburg, Virginia

Sixty-two diatom taxa have been identified from a diatomaceous sandy clay that crops out near the outlet of Wilcox Lake, Petersburg. Virginia. These diatoms are mostly cosmopolitan marine forms, but some species suggest deposition in brackish water that had a freshwater inflow. The regional stratigraphy, as well as the pelecypods and foraminifers, indicates that the beds may have been laid down in a lagoonal or estuarine environment. The diatom assemblage suggests that the deposit is of early Pliocene age, although previous biostratigraphic studies have considered it to be latest Miocene.

Virginia↗
USGS1979

Middle Miocene marine diatoms from the Hawthorn Formation within the Ridgeland Trough, South Carolina and Georgia

Diatomaceous sediments in outcrops of the Miocene Hawthorn Formation at Dawsons Landing in South Carolina and at Berrys Landing in Georgia, have yielded a total of 111 marine diatom taxa. Varving of the diatomaceous clay suggests that the diatoms were deposited in a restricted basin or lagoonal area that had oxygen-deficient bottom waters. The Middle Miocene diatom assemblage of the Hawthorn is correlative with that of approximately the upper half of Miocene Lithologic Unit 16 of the Choptank Formation in the Chesapeake Bay region of Maryland and with the Serravallian Stage.

Georgia, South Carolina↗
USGS1978

Marine diatom sequence in Miocene strata of the Chesapeake Bay region, Maryland

The Calvert and Choptank Formations exposed along the west shore of Chesapeake Bay in Maryland have been correlated with strata of early and middle Miocene age. The stratigraphic ranges of marine diatom marker species indicate a distinct diatom sequence in the deposits. A few diatoms that mark deep-sea Miocene deposits are found sparingly in these shallow neritic assemblages. Seven diatom zones based on well-recognized events in the diatom biostratigraphy are proposed for the mid-Atlantic region of the eastern United States. A suggested correlation of these zones is made with some of the deep-sea diatom zonations in the Atlantic and Pacific Ocean basins.

Maryland↗
USGS1990

Silicoflagellate and diatom biostratigraphy in successive Burdigalian transgressions, middle Atlantic coastal plain

The earliest Miocene strata on the Middle Atlantic Coastal Plain were deposited in two distinct marine transgressions separated by a hiatus in sedimentation of approximately one million years. The older unit (Bed 3A of the Calvert Formation and its correlatives) was deposited in a relatively restricted basin of middle Burdigalian (middle early Miocene) age. The younger unit (Bed 3B of the Calvert Formation and its correlatives) was deposited in a much more widespread basin of late Burdigalian (late early Miocene) age. The older deposit was completely overlapped by the younger deposit. These two beds of substantially differing geologic age are difficult, if not impossible, to distinguish solely by lithostratigraphy. They are, however, readily differentiated on the basis of their distinctive silicoflagellate and diatom assemblages.

Delaware, Maryland, New Jersey↗
USGS1984

Correlation of the middle eocene Kellogg Shale of northern California

The Kellogg Shale of northern California has traditionally been considered to be late Eocene in age on the basis of benthic foraminifer, radiolarian, and diatom correlations. The 30-m-thick Kellogg section exposed west of Byron, California, however, contains middle Eocene planktonic foraminifers (Zone P12), coccoliths (Subzones CP13c and CP14a), silicoflagellates (Dictyocha hexacantha Zone), and diatoms. Quantitative studies of the silicoflagellates and diatoms show a general cooling trend through the section which is consistent with paleoclimatic trends for this part of the middle Eocene (ca. 42-45 Ma) from elsewhere in the world. Seven new silicoflagellate taxa (Corbisema angularis, C. exilis, C. hastata miranda, C. inermis ballantina, C. regina, Dictyocha byronalis, Naviculopsis americana) and one new coccolithophorid species (Helicosphaera neolophota) are described.

California↗
USGS1993

Quantitative analysis of Ostracoda and water masses around Japan: Application to Pliocene and Pleistocene paleoceanography

An ostracode data base consisting of 273 samples from coretops and comprising 226 species was developed for the seas around the Japanese Islands to determine zoogeographic patterns and for application to Pliocene and Pleistocene paleoceanography in the area. Quantitative analyses of the 59 most common taxa between 0 and 300m water depth indicate that ostracode associations are controlled by the main oceanic water masses around Japan and that bottom water temperature is a key factor influencing species distributions. Ostracodes from the following water masses were studied: warm Kuroshio Current, Tsushima Current (Tsugaru Current and Soya Current), Japan Sea intermediate water, Japan Sea proper water and cold Oyashio Current. In order to apply the modem coretop data base to fossil ostracode assemblages, the modem analog technique (MAT) using a squared chord distance (SCD) measure of dissimilarity was tested as a means of comparing fossil and modem assemblages. SCD values of 0.25 or less adequately identify modem analogs from the coretop data set at the local ecological level (i.e. within the same modern bay), while values of 0.25-0.5 identify modem analogs at the level of the zoogeographic province. The MAT method was tested against 3 Pliocene and 11 Pleistocene formations in Japan to examine the use of the MAT in paleoceanographic reconstruction.

Micropaleontology↗
USGS2022

Evolution and taxonomy of the Paleogene calcareous nannofossil genus Hornibrookina

The genus Hornibrookina consists of enigmatic calcareous nannofossils that first appeared shortly after the K-Pg mass extinction. Due to their relative paucity in most published sections, specimens of this genus have not been previously studied in detail and their paleobiogeographic preferences and evolutionary history have been poorly understood. Biostratigraphic and morphometric analyses of Hornibrookina specimens from outcrops and cores from the Atlantic Ocean, the North Sea, the Southern Ocean, the Indian Ocean, North America, South America, Africa, and New Zealand resulted in a comprehensive and detailed documentation of this group of calcareous nannofossils. Biostratigraphic ranges for each species are refined and a hypothetical evolutionary lineage for this genus is proposed. Two new species (Hornibrookina gracila and Hornibrookina indistincta), two new combinations (Hornibrookina elegans and Hornibrookina australis arca) and one new subspecies (Hornibrookina australis australis) are described. Morphometric analyses prove that Hornibrookina edwardsii and Hornibrookina teuriensis are distinctly different species with biostratigraphically useful ranges. Hornibrookina apellanizii is shown to be invalid.

Micropaleontology↗
USGS2022

Affinity of the benthic foraminifer Cassidulinoides parkeriana (Brady) for whale-falls: Evidence from off western Vancouver Island, British Columbia, Canada

A partial skeleton of a blue or fin whale, estimated to have been 16.5 m in length and thought to have been lying on the seafloor for less than 10 years, was observed at a depth of 1288 m off western Vancouver Island, British Columbia, Canada (48.68° N, 126.84° W). Four push cores were taken at the site, three (15-26 cm in length) directly under caudal vertebrae and one 18 cm long, considered a reference, 15 m away, in order to characterize changes in the benthic foraminiferal assemblage due to the whale-fall. A Q-mode cluster analysis identified four groupings, separating the surface and deeper samples of both the whale-fall and reference cores. The results of a metric multi-dimensional scaling plot and permutational multivariate analysis of variance test of the surface samples also suggest there was a significant difference between the whale-fall and reference core benthic foraminiferal faunas. No endemic species were recovered. Downcore samples below 6 cm in the whale-fall and reference cores were characterized by common Uvigerina peregrina , Pseudoparrella pacifica , Bolivina spissa , Bulimina striata , and Takayanagia delicata . In contrast, Cassidulinoides parkeriana , which typically is a minor component of benthic foraminiferal assemblages, dominated the upper 6 cm of the whale-fall cores, whereas the low oxygen-tolerant species T. delicata dominated the same interval in the reference core. The dramatic increase in abundance of C. parkeriana in the upper sediments below this whale-fall, as well as at the Torishima Seamount whale-fall site off Japan, indicate that it is an opportunistic species well adapted to taking advantage of unpredictable and highly localized tropic windfalls such as whale-falls. To our knowledge, this is the first benthic foraminiferal species shown to increase dramatically in abundance in the presence of a whale-fall. Additionally, modern fragments of whale bones occurring as deep as 12 to 15 cm downcore at the western Vancouver Island site demonstrate the effect of bioturbation by invertebrate scavengers that consume whale carcasses, indicating that detailed biostratigraphic records below whale-falls should be interpreted with caution.

Pacific Ocean, Vancouver Island↗
USGS2023

Multi-proxy record of ocean-climate variability during the last 2 millennia on the Mackenzie Shelf, Beaufort Sea

A 2,000 year-long oceanographic history, in sub-centennial resolution, from a Canadian Beaufort Sea continental shelf site (60meters water depth) near the Mackenzie River outlet is reconstructed from ostracode and foraminifera faunal assemblages, shell stable isotopes (delta 18O, delta 13C) and sediment biogenic silica. The chronology of three sediment cores making up the composite section was established using 137Cs and 210Pb dating for the most recent 150 years and combined with linear interpolation of radiocarbon dates from bivalve shells and foraminifera tests.Continuous centimeter-sampling of the multicore and high-resolution sampling of a gravity and piston core yielded a time-averaged faunal record of every approximately 40 years from 0 to 1850 CE and every approximately 24 years from 1850 to 2013 CE. Proxy records were consistent with temperature oscillations and related changes in organic carbon cycling associated with the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA). Abundance changes in dominant microfossil species, such as the ostracode Paracyprideis pseudopunctillata and agglutinated foraminifers Spiroplectammina biformis and S. earlandi, are used as indicators of less saline, and possibly corrosive/turbid bottom conditions associated with the MCA (approximately 800 to 1200 CE) and the most recent approximately 60 years (1950–2013). During these periods, pronounced fluctuations in these species suggest that prolonged seasonal sea-ice melting, changes in riverine inputs and sediment dynamics affected the benthic environment. Taxa analyzed for stable oxygen isotope composition of carbonates show the lowest delta 18O values during intervals within the MCA and the highest during the late LIA, which is consistent with a 1 degree to 2 degree C cooling of bottom waters. Faunal and isotopic changes during the cooler LIA (1300 to 1850 CE) are most apparent at approximately 1500 to 1850 CE and are particularly pronounced during 1850 to approximately 1900 CE, with an approximate 0.5 per mil increase in delta 18O values of carbonates from median values in the analyzed taxa. This very cold 50-year period suggests that enhanced summer sea ice suppressed productivity,which is indicated by low sediment biogenic silica values and lower delta 13C values in analyzed species. From 1900CE to present, declines in calcareous faunal assemblages and changes in dominant species (Cassidulina reniforme and P. pseudopunctillata) are associated with less hospitable bottom waters, indicated by a peak in agglutinated foraminifera from 1950 to 1990 CE.

Beaufort Sea, Mackenzie Shelf↗
USGS2024

First Occurrence of the nonindigenous Asian foraminifera Ammonia confertitesta in the Northeastern Pacific Ocean: Vancouver Island, British Columbia, Canada

Observations in 2022 of intertidal and subtidal foraminiferal faunas at four localities along the central-eastern side of Vancouver Island, British Columbia, Canada, and molecular analyses have documented the first occurrence of the nonindigenous Asian species Ammonia confertitesta Zheng in the northwestern Pacific Ocean. The species was present at three of these localities: Davis Lagoon south of Ladysmith (4% in the lagoon and 49% on the beach) and 0.6% in Nanaimo Harbor. The vector of introduction is thought to be the release of ballast water and associated sediment. These releases probably occurred in the Port of Vancouver, which were then transported by means of the cyclonic circulation across the Strait of Georgia, or from local anchorages close to the sampling sites. The timing of the introduction is impossible to determine because no stratigraphic record is presently available. However, foraminiferal studies in the late 1980s near the Port of Vancouver that recovered calcareous taxa did not report the presence of this species, nor was it found at 33 sites sampled from 1997 to 1999 throughout the Strait of Georgia.

Vancouver Island↗
USGS1981

Paleoclimatic implications of Late Pleistocene marine ostracodes from the St. Lawrence lowlands.

Using modern zoogeographic data and inferred temperature ranges for Champlain Sea ostracode species, bottom water paleotemperatures were estimated for three phases of deposition of this inland sea. The temporal distribution of these and other environmentally diagnostic species in Champlain Sea deposits reveals a significant local climatic change in the Champlain Valley from frigid/subfrigid to cold-temperate marine conditions about 11 000 to 10 600 yr BP. Oceanographic changes in the Champlain Sea are correlated with major deglaciation events recorded in the North Atlantic.-from Author

Micropaleontology↗
USGS1985

Elemental X-ray mapping of agglutinated foraminifer tests: A non- destructive technique for determining compositional characteristics.

The composition of agglutinated foraminiferal tests vary remarkably in response to local substrate characteristics, physiochemical properties of the water column and species- dependant selectivity of test components. We have employed a technique that combines a scanning electron microscope with an energy dispersive X-ray spectrometer system to identify major and minor elemental constituents of agglutinated foraminiferal walls. As a sample is bombarded with a beam of high energy electrons, X-rays are generated that are characteristic of the elements present. As a result, X- ray density maps can be produced for each of several elements present in the tests of agglutinated foraminifers.

Micropaleontology↗
USGS1988

Radiolarian biostratigraphy of siliceous Eocene deposits in central California

Abundant Eocene siliceous deposits in California are located in the San Joaquin and Sacramento valleys. The white shales to buff mudstones are characterized by radiolarians, diatoms, and silicoflagellates. Taxonomic descriptions and abundance data of key radiolarian species in existing monographs have limited biostratigraphic and paleoenvironmental interpretation. The California fauna is similar to faunas from the Norwegian Sea, Russian Platform, and southern oceans of Antarctica. Eocene faunas from the equatorial Pacific Ocean and Caribbean Sea differ considerably in diversity. In this study, the taxonomy and biostratigraphic information of species comprising more than 2% of the population are evaluated. Two radiolarian zones are erected for the middle Eocene of California, the Podocyrtis fasciata and Calocyclas semipolita Zones. Paleoenvironmental information suggests that some differences in the fauna may be environmentally controlled due to deposition in submarine canyons. -Authors

Micropaleontology↗
USGS1987

The ubiquitous ostracode Darwinula stevensoni (Brady and Robertson, 1870), redescription of the species and lectotype designation.

Darwinula stevensoni (Brady and Robertson 1870) is the type species of Darwinula, the ubiquitous living and fossil nonmarine nominate genus of the Darwinulidae and the Darwinulacea. To date, the additional families Darwinuloididae (fossil), Microdarwinulidae (living and fossil), Panxianidae (fossil), and Suchonellidae (fossil) have been referred to the Darwinulacea. A type specimen for D. stevensoni has not been previously designated. In order to stabilize the species, a lectotype is selected from the type series in the Brady collection at The Hancock Museum, Newcastle upon Tyne. The species is redescribed and reillustrated based on the study of the carapace of a paralectotype and also of valves and appendages of specimens from both England and the United States. Living species of Darwinula have a cosmopolitan distribution in fresh and brackish water. Fossil Darwinulacea, documented in the Carboniferous, serve as indicators of continental Paleozoic to Holocene deposits. - Author

Micropaleontology↗