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At least 19 recordsLinked to original sources
USGS1990

A quantitative micropaleontologic method for shallow marine peleoclimatology: Application to Pliocene deposits of the western North Atlantic Ocean

A transfer function was developed to estimate summer and winter paleotemperatures for arctic to tropical regions of the western North Atlantic Ocean using fossil ostracode assemblages. Q-mode factor analysis was run on ostracode assemblages from 100 modern bottom sediment samples from continental shelves of North America, Greenland and the Caribbean using 59 ostracode taxa. Seven factors accounting for 80% of the variance define assemblages that correspond to frigid, subfrigid, cold temperate, mild temperate, warm temperate, subtropical and tropical climatic zones. Multiple regression of the factor matrix against observed February and August bottom temperatures yielded an astracode transfer function with an accuracy of about ??2??C. The transfer function was used to reconstruct middle Pliocene (3.5-3.0 Ma) shallow marine climates of the western North Atlantic during the marine transgression that deposited the Yorktown Formation (Virginia and North Carolina), the Duplin Formation (South and North Carolina) and the Pinecrest beds (Florida). Middle Pliocene paleowater temperatures in Virginia averaged 19??C in August and 13.5??C in February, about 5??C to 8??C warmer than at comparable depths off Virginia today. August and February water temperatures in North Carolina were 23??C and 13.4??C, in South Carolina about 23??C and 13.5??C and in southern Florida about 24.6??C and 15.4??C. Marine climates north of 35??N were warmer than today; south of 35??N, they were about the same or slightly cooler. Thermal gradients along the coast were generally not as steep as they are today. The North Atlantic transfer function can be applied to other shallow marine Pliocene and Pleistocene deposits of eastern North America. ?? 1990 Elsevier Science Publishers B.V.

Marine Micropaleontology↗
USGS1991

Neogene biostratigraphy and paleoenvironments of Enewetak Atoll, equatorial Pacific Ocean

Micropaleontologic analyses of Neogene sediments from Enewetak Atoll, Marshall Islands, provide data on the age of lagoonal deposits, stratigraphic disconformities and the paleoenvironmental and subsidence history of the atoll. Benthic foraminifers, planktic foraminifers, calcareous nannofossils and ostracodes were studied from six boreholes, the deepest penetrating 1605 feet below the lagoon floor into upper Oligocene strata. The Oligocene-Miocene boundary occurs at about 1200 ft below the lagoon floor. The early and middle Miocene is characterized by brief periods of deposition and numerous hiatuses. Ostracodes and benthic foraminifers indicate a shallow-marine reefal environment with occasional brackish water conditions. Upper Miocene and lower Pliocene deposits placed in calcareous nannofossil Zones NN9-15 and in planktic foraminifer Zones N16-19 contain species-rich benthic microfaunas which indicate alternating reefal and brackish water mangrove environments. The upper Pliocene contains at least two major depositional hiatuses that coincide with a major faunal turnover in benthic foraminiferal and ostracode assemblages. The Quaternary is characterized by benthic microfaunas similar to those of modern atoll lagoons and is punctuated by at least 11 disconformities which signify periods of low sea level. Atoll subsidence rates during the last 10 Ma averaged 30 to 40 m/m.y. ?? 1991 Elsevier Science Publishers B.V. All rights reserved.

Marine Micropaleontology↗
USGS1996

Diatom constraints on the position of the Antarctic Polar Front in the middle part of the Pliocene

The relative percentages of diatom taxa in 5 deep-sea cores (DSDP 266, ODP 699A, ODP 747A, ODP 751 A, and Eltanin Core 50-28) from the Southern Ocean are determined for an interval centered on 3.1 to 2.9 Ma in the middle part of the Pliocene. This climatically warm interval, which is being studied by the PRISM Project of the U.S. Geological Survey, coincides with a proposed interval of major deglaciation of East Antarctica. The maximum southerly position of the Antarctic Polar Front between 3.1 and 3.0 Ma is inferred from these diatom studies, the presence of calcareous nannofossils in the sediments, and sedimentologic and micropaleontologic information from the literature. It is suggested that the Antarctic Polar Front may have migrated by as much as 6 ° of latitude further to the south in the southeastern Atlantic and Indian Oceans during this Pliocene warm interval but probably lay close to its present day position in the southwest Atlantic and Drake Passage. Summer sea surface temperatures are inferred to have been no more than 3 °–4 °C warmer than present at latitudes between 55 ° and 60 °S.

Marine Micropaleontology↗
USGS1992

High resolution late Pliocene sea-surface temperature record from the northeast Atlantic Ocean

Application of quantitative micropaleontologic methods of sea-surface temperature (SST) estimation to the planktic foraminiferal faunas at Hole 548 in the northeast Atlantic between 3.5 and 2.0 Ma provide a detailed record of Pliocene surface temperature changes during the onset of major Northern Hemisphere glaciation. SST estimates indicate a relatively warm interval of “enhanced interglacials (warm peaks)” between 3.2 and 2.8 Ma followed by steady cooling with a significant step-like change toward colder temperatures occurring about 2.4 Ma. This record compares well with faunal and SST records from other North Atlantic sites.

Marine Micropaleontology↗
USGS1995

Stratigraphic significance of siliceous microfossils collected during NAUTIPERC dives (off Peru, 5 °-6°S)

The geological evolution of the northern Peru convergent margin can be traced using samples collected during deep-sea dives of the submersible Nautile . In the Paita area (5°–6°S), the sedimentary sequence was intensively sampled along the main scarp of the middle slope area. It consists of Upper Miocene (7–9 Ma) to Pleistocene siltstone, sandstone and rare dolostone. The age distribution of these samples is the basis for a new geologic interpretation of the multichannel seismic line CDP3. Siliceous microfossils (both diatoms and radiolarians) show influence of both cold and temperature waters (local species mixed with upwelling ones). Diatom assemblages studied from the NP1-13 and NP1-15 dives bear a strong resemblance to assemblages from the Pisco Formation of southern Peru. Micropaleontological data from siliceous microfossils, provide evidence for two main unconformities, one is at the base of the Quaternary sequence and the other corresponds to a hiatus of 1 Myr, separating the Upper Miocene (7–8 Ma) sediments from uppermost Miocene (5–6 Ma) sediments. During the past 400 kyr, a wide rollover fold developed in the middle slope area associated with a major seaward dipping detachment fault. A catastrophic debris a valanche occurred as the results of an oversteepening of the landward flank of the rollover fold. The gravity failure of the slope, recognized by SeaBEAM and hydrosweep mapping, displaced enough material to produce a destructive tsunami which occurred 13.8 ± 2.7 kyr ago.

Pacific Ocean↗
USGS1976

Revised Miocene and Pliocene diatom biostratigraphy of Upper Newport Bay, Newport Beach, California

North Pacific diatom zones XXIII through IX of Schrader are recognizable in the middle Miocene to lower Pliocene stratigraphic section exposed around Upper Newport Bay in Newport Beach, California. Correlation with DSDP Site 173 and other stratigraphic sections in California allows the selection of diatom datums that are the most reliable for long-distance correlation. Individual diatom datums are proposed as markers for North Pacific diatom zones XXIII through IX. Correlations with DSDP Site 173 reveal a hiatus in the lower part of Core 15 that corresponds with a distinct lithologic and floral change in the core. Preliminary silicoflagellate data for the Upper Newport Bay stratigraphic section supports the diatom correlations. Correlation with calcareous nannofossil, radiolarian, and silicoflagellate zones at Upper Newport Bay and at DSDP Site 173 suggests that the boundary between North Pacific diatom zones XVII and XVI approximates the middle Miocene/upper Miocene boundary. The Miocene/Pliocene boundary is estimated to be in North Pacific diatom zone X. One new stratigraphically useful diatom species is described, Lithodesmium reynoldsii .

California↗
USGS1977

Paleoenvironmental analysis and correlation of a Cretaceous Islas Orcadas core from the Falkland Plateau, Southwest Atlantic

A comparison of Campanian-Maestrichtian cores from two localities on opposite sides of the Maurice Ewing Bank, at the eastern end of the east-west trending Falkland Plateau (Southwest Atlantic) reveals a significant change in faunal and floral assemblage characteristics across the Plateau. These changes are probably temperature dependent, and indicate that the Plateau served as an important barrier between water masses in the South Atlantic during late Cretaceous times.

Marine Micropaleontology↗
USGS1978

Correlation and zonation of miocene strata along the atlantic margin of North America using diatoms and silicoflagellates

Six Atlantic Miocene siliceous microfossil zones are proposed based on onshore and offshore samples from the United States Atlantic Margin. Diatoms and silicoflagellates are used to establish the zones. These zones are from oldest to youngest: 1. Zone I Actinoptychus heliopelta Concurrent Range Zone - Early Miocene 2. Zone II Delphineis ovata Partial Range Zone - late Early to early Middle Miocene 3. Zone III Delphineis ovata/Delphineis penelliptica Concurrent Range Zone - early Middle Miocene 4. Zone IV Delphineis penelliptica Partial Range Zone - Middle Miocene 5. Zone V Delphineis penelliptica/Coscinodiscus plicatus Concurrent Range Zone - Middle Miocene 6. Zone VI Coscinodiscus plicatus Partial Range Zone - Middle Miocene. The six zones are easily traced along the Southern and Middle Atlantic Seaboard, but the older three are found for the most part between Cape Hatteras and New Jersey. There is some suggestion of sea-level change during Zone IV. Using rare planktonic diatoms that are index species from other regions and the zonal markers established in this study, correlation can be made with the Standard Foraminiferal Zones, the North Pacific Diatom Zones and with DSDP core 391A in the Blake-Bahama Basin.

Marine Micropaleontology↗
USGS1980

Distribution of modern benthic foraminifers on the New Jersey Outer Continental Shelf

We used samples from 21 stations within a 600 km2 area of the New Jersey Outer Continental Shelf to assess the effects of a hydrodynamic environment on the distribution and redistribution of benthic foraminifers. These samples show that, although the predominant genera (Elphidium, Cibicides, and Saccammina) are the same as those reported by other investigators for this region, the environmental factors that control the generic distribution are more complex than were previously postulated. Generic distribution patterns derived from this study are correlated with the bottom topography and sediment distribution as well as the temperature, salinity, and dissolved oxygen concentrations of the bottom waters. The six predominant species observed in the samples (and their phenotypic variants) are cryophilic forms known to occur in the Virginian and Nova Scotian biogeographic provinces and in Arctic waters. Species distribution patterns also correlate well with bottom topography and hydrographic factors, but may be modified by seasonal fluctuations in test production and by redistribution of dead tests. At most stations, specimens of Elphidium subarcticum were attached to quartz grains. This phenomenon, which has not been reported before, probably is an adaptation to a high-energy environment. The distribution pattern of Elphidium subarcticum along with those of the sessile species Webbinella concava and Vasiglobulina n.sp. corroborate sedimentological evidence that the accumulation of modern sediments in the area is negligible.

New Jersey↗
USGS1981

Miocene biochronology and paleoceanography of the North Pacific

Biostratigraphic correlation based on microfossil datum levels, directly or indirectly tied to the paleomagnetic time scale, provides a high resolution time control for the Miocene in the equatorial and middle latitude North Pacific. Faunal changes and abundance fluctuations of planktic foraminiferal species combined with the oxygen Pacific. Faunal changes and abundance fluctuations of planktic foraminiferal species combined with the oxygen isotope record of foraminifers, reveal the paleoclimatic and paleoceanographic history. The planktic foraminiferal assemblage change in the early Miocene, extinction of Oligocene fauna and rise of a highly diverse Neogene fauna, appears to be related to increased water mass stratification in the world oceans presumably resulting from the establishment of circum-Antarctic circulation. An increase in the siliceous productivity in the eastern equatorial Pacific region between 20 and 18 Ma suggests that the vertical and horizontal circulation was intensified at that time. Climates cooled rapidly during the middle Miocene between 14 and 13 Ma suggesting the growth of a major east Antarctic ice sheet. Paleoclimatic conditions remained generally cool, although oscillating, during the late Miocene. In the late early to middle Miocene faunal provincialism developed between low and middle latitudes, and by late Miocene time a distinct provincialism similar to the present was established.

Marine Micropaleontology↗
USGS1981

Late Miocene biogeography and paleoclimatology of the central North Atlantic

Quantitative analyses of planktonic foraminiferal assemblages from Deep Sea Drilling Project (DSDP) Holes 334 and 410 demonstrate that subpolar and subtropical faunal provinces existed in the North Atlantic during the late Miocene. Climatic oscillations are clearly recorded in Hole 410 by variations in abundance of the Neogloboquadrina subpolar assemblage. These climatic oscillations have a period of about 1 m.y. Higher frequency oscillations with a periodicity of one to several hundred thousand years are evident from about 6.5 to 7.5 m.y. and are probably present throughout the entire late Miocene. A revised age of 7.0 m.y. is proposed for the first occurrence of the calcareous nannofossil Amaurolithus primus (the Amaurolithus datum).

Marine Micropaleontology↗
USGS1981

Miocene benthic foraminiferal isotope records: A synthesis

18 O/ 16 0 and 13 C/ 12 C ratios of Miocene benthic foraminifera from a number of Atlantic, Pacific and Indian Ocean DSDP sites (71, 77B, 206, 208, 238, 279, 289, 296, 329, 357 and 366A) have been compiled. These provide a rather detailed history of Miocene deep water especially in the Pacific Ocean. Bottom-water temperatures rose during the early Miocene and then declined rapidly during the middle Miocene. This decline was accompanied by an increase in Antarctic glaciation. Late Miocene bottom temperatures and Antarctic ice volumes are inferred to be similar to today's, but exhibited some fluctuation. The early Miocene ocean was less thermally stratified at intermediate and abyssal depths while the late Miocene deep ocean had a thermal structure generally similar to the modern ocean. Foraminiferal carbon isotope ratios at most of the sites varied quasi-sympathetically throughout the Miocene. These variations must reflect comparable variations in the mean 13 C/ 12 C of marine HCO 3 . However, the causes of such variations are not yet clear.

Marine Micropaleontology↗
USGS1982

North Pacific Late Miocene correlations using microfossils, stable isotopes, percent CaCO3, and magnetostratigraphy

A multidisciplinary approach to stratigraphy based on magnetostratigraphy, stable isotopes, percent CaCO 3 and microfossils provides a framework for paleoclimatic and paleoceanographic reconstruction of the equatorial and North Pacific. A high-resolution biochronologic time scale has been achieved through integration of diatom, radiolaria, coccolith and planktic foraminifer datum levels with direct or indirect correlations to the paleomagnetic time scale. Over 70 datum levels have been identified between 12.5 and 5 Ma from low and middle latitudes resulting in an unprecedented time control. This high-resolution biostratigraphic control combined with stable-isotopic and percent CaCO 3 analyses permits identification of regional as well as global paleoceanographic events.

Marine Micropaleontology↗
USGS1983

Bathyal ostracodes from the Florida-Hatteras slope, the Straits of Florida, and the Blake Plateau

Epibathyal ostracodes from the Florida-Hatteras slope, the Blake Plateau and the Straits of Florida were studied to determine the relationship of numerous genera and species to bottom-water environmental conditions such as dissolved oxygen and bottom-water temperatures. From a total of 100 samples, 44 samples evenly distributed between 200 and 1100 m water depth and having an average of 325 specimens were examined in detail. Using occurrence data from the adjacent continental shelf, carapace preservation, Rose Bengal staining and population data, indigenous death assemblages were distinguished from transported or reworked fossil specimens. The percent of transported specimens varied as follows: Blake Plateau less than 1%; Straits of Florida 10–60%; Florida-Hatteras slope 1–15%. Indigenous death assemblages contained between 10 and 61 species per sample, averaging 33.3 species. Krithe, Argilloecia and Pseudocythere occur in greater than 90% of the samples and usually constitute 10 to 30% of each. Trachyleberidea, Bairdoppilata, Saida, Paranesidea, Ambocythere, Bythocypris, Cytherella, Bradleya, Henryhowella , and Polycopidae occur in 45 to 80% of the samples in varying percentages. The upper depth limits of 39 taxa occur at or just below the thermocline suggesting a relationship to temperature. Australoecia, Quasibuntonia, Cytheropteron, Ruggieriella, Saida, Ambocythere, Trachyleberidea, Macrocypris, Krithe, “Thalassocythere” , and Cytherella are most common or restricted to the O 2 minimum zone. Conversely, Anchistrocheles, Bradleya, Henryhowella , and Rockallia are most common below 750 m in well oxygenated water with temperatures below 8°C. The results show that: (1) ostracodes display a narrow depth zonation controlled by dissolved oxygen and water temperature; (2) species diversity is very high for a bathyal zone; (3) ostracodes can be used to identify the source of sediment that has been transported downslope; and (4) some taxa are useful in recognizing low oxygenated water in Cenozoic deposits.

Florida↗
USGS1983

Biochronology and paleoclimatic implications of Middle Eocene to Oligocene planktic foraminiferal faunas

Planktic foraminiferal assemblages have been analyzed quantitatively in six DSDP sites in the Atlantic (Site 363), Pacific (Sites 292, 77B, 277), and Indian Ocean (Sites 219, 253) in order to determine the nature of the faunal turnover during Middle Eocene to Oligocene time. Biostratigraphic ranges of taxa and abundance distributions of dominant species are presented and illustrate striking similarities in faunal assemblages of low latitude regions in the Atlantic, Pacific and Indian oceans. A high resolution biochronology, based on dominant faunal characteristics and 55 datum events, permits correlation between all three oceans with a high degree of precision. Population studies provide a view of the global impact of the paleoclimatic and paleoceanographic changes occurring during Middle Eocene to Oligocene time. Planktic foraminiferal assemblage changes indicate a general cooling trend between Middle Eocene to Oligocene time, consistent with previously published oxygen isotope data. Major faunal changes, indicating cooling episodes, occur, however, at discrete intervals: in the Middle Eocene 44-43 Ma (P13), the Middle/Late Eocene boundary 41-40 Ma (P14/P15), the Late Eocene 39-38 Ma (P15/P16), the Eocene/Oligocene boundary 37-36 Ma (P18), and the Late Oligocene 31-29 Ma (P20/P21). With the exception of the E/0 boundary, faunal changes occur abruptly during short stratigraphic intervals, and are characterized by major species extinctions and first appearances. The Eocene/Oligocene boundary cooling is marked primarily by increasing abundances of cool water species. This suggests that the E/0 boundary cooling, which marks a major event in the oxygen isotope record affected planktic faunas less than during other cooling episodes. Planktic foraminiferal faunas indicate that the E/0 boundary event is part of a continued cooling trend which began during the Middle Eocene. Two hiatus intervals are recognized in low and high latitude sections at the Middle/Late Eocene boundary and in the Late Eocene (P15/P16). These hiatuses suggest that vigorous bottom water circulation began developing in the Middle Eocene, consistent with the onset of the faunal cooling trend, and well before the development of the psychrosphere at the E/0 boundary.

Marine Micropaleontology↗
USGS1983

Latest Oligocene through early middle Miocene diatom biostratigraphy of the eastern tropical Pacific

Study of DSDP Sites 71, 77, and 495 has allowed the development of a refined diatom biostratigraphy for the latest Oligocene through early middle Miocene of the eastern tropical Pacific which is well correlated to the low-latitude zonations for planktonic foraminifers, coccoliths, and radiolarians. Six zones and 7 subzones are proposed, and correlation with high-latitude diatoms zonations for the North Pacific, the Norwegian Sea, and the Southern Ocean is suggested by the discovery of selected diatoms in these tropical sediments which were previously thought to be restricted to high latitudes. Six new species and one new variety of diatoms which are stratigraphically useful are proposed: Actinocyclus hajosiae , n. sp., A. radionovae , n. sp., Coscinodiscus blysmos , n. sp., C. praenodulifer , n. sp., Craspedodiscus rydei , n. sp., Thalassiosira bukryi , n. sp., and Coscinodiscus lewisianus var. robustus n. var.

Marine Micropaleontology↗