Orbitolinella depressa Henson, 1948: A porcelaneous, not an agglutinated larger benthic foraminifer

We examined uppermost Oligocene to lowermost Pliocene sections from four northeastern Gulf of Mexico boreholes for quantitative benthic foraminiferal faunal changes, stratigraphic ranges, paleobathymetry, organic carbon content, and planktonic foraminiferal relative abundances. The Eureka boreholes provide a depth transect in the De Soto Canyon area from the upper to lower bathyal zone: E68-136 (557m present depth, -600m paleodepth), E66-73 (857m present depth, 860-lOOOm paleodepth), E68-151A (1326m present depth, -1300m paleodepth), and E68-14 1A (1599m present depth, -1600m paleodepth). A number of taxa last appeared in the late Oligocene to early Miocene (Biochrons P22-N5) at E68-136; several of these disappearances constitute global last occurrences. A global benthic foraminiferal taxonomic turnover that began in the latest early Miocene in other parts of the ocean was restricted to the middle Miocene at E68-136 (Biochrons N9-N12), although faunal abundance changes began in late early Miocene Biochron N8. At middle bathyal borehole E66-73, ten taxa last occurred in Biochrons N8-N10, which is consistent with the timing of the taxonomic turnover in the Pacific and Atlantic. Depth-related faunal trends are examined and compared with previously published distributional data, resulting in revised paleobathymetric ranges of 12 taxa. Detailed age-paleodepth reconstructions reveal several stratigraphically and bathymetrically significant predominance biofacies in the northeast Gulf of Mexico: 1) Uvigerina pigmea dominated the middle-upper bathyal late Neogene; 2) Lenticulina spp. dominated the late Oligocenemiddle Miocene bathyal zone; 3) Oridorsalis spp., Gyroidinoides spp., and Globocassidulina subglobosa dominated the late Neogene lower bathyal zone; and 4) Uvigerina proboscidea was important in the late Neogene in the middle to upper bathyal zones. Four distinct bathymetric migrations are mapped, and 34 additional taxa are shown to have distinct paleobathymetric distributions. Planktonic foraminiferal biostratigraphic control allows us to evaluate the stratigraphic usefulness of benthic foraminiferal ranges. We revise the stratigraphic ranges of 12 bathyal benthic foraminiferal taxa, requiring re-correlation of the benthic foraminiferal zonal boundaries of Berggren and Miller (1989). INTRODUCTION Previous studies have shown that one of the largest benthic foraminiferal faunal changes of the Cenozoic occurred throughout the deep sea (>200m) in the late early to middle Miocene (Berggren 1972; Schnitker 1979, 1986; Woodruff and Douglas 1981; Boersma 1986; Thomas 1985, 1986a, 1886b, 1989, 1992; Woodruff 1985; Kurihara and Kennett 1986; Miller and Katz 1987; Thomas and Vincent 1987; Woodruff and Savin 1989; Miller et al. 1992; Thomas 1992; for an alternative view, see Boltovskoy and Boltovskoy 1988; Boltovskoy et al. 1992). These authors documented that major changes in taxonomic composition, percentages, and absolute abundances of benthic foraminifera began in the late early Miocene and culminated in the middle Miocene. Although this event has been well documented at open ocean locations, it remains poorly documented in marginal seas such as the Gulf of Mexico. The Eureka boreholes examined in this study (northeast Gulf of Mexico) yield faunal abundance changes and stratigraphic ranges that reflect this global middle Miocene benthic foraminiferal event. Benthic foraminiferal faunas have been recognized for their potential to assess paleobathymetry (e.g. Natland 1933; Bandy 1960). While Bandy (1960) promoted the concept that benthic foraminifera have distinct upper and lower depth limits, Streeter (1973) and Schnitker (1974) established that deep-water (>200m; bathyal-abyssal) benthic foraminifera are correlated to water mass properties that may vary independently of depth. Numerous subsequent studies have documented that deep-water benthic foraminiferal distributions are associated with physiochemical properties other than depth, and that depth alone does not control the vertical distribution of benthic foraminifera. For example, vertical distributions are correlated with water masses (e.g. Lohmann 1978; Corliss 1979; Schnitker 1979; Murray 1984; for Gulf of Mexico examples, see Pflum and 88? 86? 84? TEXT-FIGURE 1 Eureka bo ehole location map in the Gulf of Mexico. Contours are in meters. micropaleontology, vol. 39, no. 4, pp.367-403, plates 1-6, text-figures 1-32, tables 1-5, 1993 367 This content downloaded from 157.55.39.152 on Sat, 26 Nov 2016 04:11:28 UTC All use subject to http://about.jstor.org/terms M. E. Katz and K. G. Miller: Latest Oligocene to Earliest Pliocene benthicforaminiferal biofacies of the northeastern Gulf of Mexico TABLE 1 Age model parameters Datum Age (Ma) Depth (feet below sea level) E68-136 E66-73 E68-151 FO C. acutus & 5.

Benthic foraminifer palaeoecology of the Late Quaternary continental outer shelf of a landlocked marine basin in central Aegean Sea, Greece

High-resolution stratigraphy of Central and Southern Adriatic Quaternary deposits of sub-Milankovian climate change on Mediterranean circulation

An Eocene-Oligocene oxygen and carbon isotope history based on planktonic and benthic foraminifers from Deep Sea End_Page 523------------------------------ Drilling Project Leg 71 cores has been constructed for the Maurice Ewing Bank of the eastern Falkland Plateau, southwestern Atlantic Ocean. Specifically, the cores cover portions of the middle Eocene, upper Eocene, and lower Oligocene. Surface water isotopic temperatures postulated for the middle Eocene at Site 512 fluctuated within about four degrees but generally averaged about 9°C (48°F). Bottom isotopic temperatures at Site 512 (water depth = 1,846 m, 6,056 ft) were generally a degree lower than surface water temperatures. Surface water isotopic temperatures at Site 511 initially averaged about 11°C (52°F) during the late Eocene, but dropped to an average of 7°C (44.5°F) in the early Oligocene. Bottom isotopic temperatures at Site 511 (water depth = 2,589 m, 8,494 ft) generally record temperatures between 12.5°C (54.5°F) and 8°C (46.5°F), similar to the range in the surface water temperatures. During the early Oligocene, bottom isotopic temperatures dropped sharply and averaged about 2°C (35.5°F), very close to present-day values. Surface water isotopic temperature values also decreased to an average of about 7°C (44.5°F), leading to a significant divergence between surface and bottom water isotopic temperatures during the early Oligocene. Comp risons among Southern Ocean DSDP Sites 511, 512, and 277, and between these and other DSDP sites from central and northern latitudes (Sites 44, 167, 171, 292, 357, 398, 119, and 401) show that much of the Eocene was characterized by relatively warm temperatures until sometime in either the middle Eocene, late Eocene, or early Oligocene. At each site, conspicuous 18O enrichments occur in both the benthic and planktonic foraminifers over a relatively short period of time. Although a general trend toward a climatic deterioration is evident, the density of data points among the various studies is still too sparse to determine either a synchroneity or a time transgression between the major isotopic events. A close correlation could be made between the Site 511 oxygen isotope temperature curve and paleoclimatic trends derived independently from radiolarian studies. The sharp temperature drop and the divergence between bottom and surface water temperatures during the early Oligocene apparently reflect a major expansion of the Antarctic water mass. The migration of the boundary between the sub-Antarctic and Antarctic water masses over the site at this time would account in part for the sharp temperature changes. Sharp changes of this nature would not necessarily be noted in other geographic areas, particularly those to the north which have different oceanographic regimes. End_of_Article - Last_Page 524------------

Two wells drilled along the margin of Enewetak Atoll penetrated approximately 1000 m of upper Eocene, Oligocene, and lower Miocene carbonates. Strontium isotope stratigraphy indicates relatively continuous deposition of carbonate from 40 Ma to 20 Ma. Depositional environments show a gradual basinward progradation of facies with slope carbonates passing upward into fore-reef, reef, back-reef, and lagoonal carbonates. Slope strata contain wackestones and packstones with submarine-cemented lithoclasts, coral, coralline algae fragments, benthic rotaline forams, planktonic forams, and echinoderm fragments. Fore-reef strata are dominantly packstones and boundstones containing large pieces of coral, abundant benthic forams, coralline algae fragments, stromatoporoids( ), and minor planktonic forams. Reef and near-reef sediments include coralgal boundstones and grainstones with abundant benthic forams. Halimeda and miliolid forams are common in lagoonward parts of the back reef. Sponge borings, geopetal structures, and fractures are common in reef and fore-reef strata. Lagoonal strata are wackestones and packstones with common mollusks, coral, coralline algae, and benthic forams (rotaline and miliolid). Diagenesis has extensively altered strata near the atoll margin. Aragonite dissolution and calcite cements (radiaxial and cloudy prismatic) are abundant in fore-reef, reef, and some back-reef strata. Petrographic and geochemical data indicate aragonite dissolution and calcite cementation in seawater at burialmore » depths of 100 to 300 m. Dolomite occurs in slope and deeply buried reefal carbonates. Most dolomitization occurred at burial depths of more than 1000 m in cool marine waters circulating through the atoll. lagoonal strata are not significantly altered by marine diagenesis and still contain abundant primary aragonite and magnesium calcite.« less

Lower Miocene through upper Pleistocene benthic foraminifer assemblage records from Ocean Drilling Program Site 751 on the Southern Kerguelen Plateau (57°44'S, water depth 1634 m) were combined with benthic and planktonic foraminifer oxygen and carbon isotope records and high-resolution CaCO3 data from the same site. Implications for the Neogene productivity and paleoceanography of the southern Indian Ocean are discussed. We used distinctive features of the Miocene δ 18 θ and δ13C curves for stratigraphic correlation. Coinciding with a lower middle Miocene hiatus from 14.2 to 13.4 Ma, there was a rapid increase in benthic δ18θ values by 1.2%c. This distinct increase occurs in middle Miocene benthic foraminifer oxygen isotope curves from all oceans. No major change, however, in benthic foraminifer faunal composition occurred in this period of growth of the Antarctic ice cap and cooling of deep ocean waters (14.9-14.2 Ma). A drastic change in benthic foraminifer faunas coincided with a hiatus from 8.4 to 5.9 Ma. Shortly after this hiatus, in the latest Miocene, the CaCO3 content of the sediments dropped from 75% to 0%. From that time ( 5.8 Ma) through the early Pliocene, Site 751 has been situated beneath a high biogenic siliceous productivity zone. Carbonate contents of upper Pliocene and Pleistocene sediments vary between 20% and 70%. The benthic foraminifer faunas in the uppermost Pliocene and lower Pleistocene reflect strong bottom current conditions, in contrast to those in the upper Pleistocene, which indicate calm sedimentation and high food supply. High δ13C values of planktonic foraminifers compared with low values of benthic foraminifers suggest high primary productivity in the late Pleistocene. The changes in productivity were probably a result of latitudinal migration and meandering of the Polar Frontal Zone.

Some modifications for Biostratigraphic Scheme of Paleocene deposits of the Northern Ukraine as result of examination of foraminifera assemblages of the Dnieper-Donets Depression and Ukrainian Shield are proposed. In the Northern Ukraine section sediments of Psolian regional stage (regiostage) contain the most representative assemblages of planktonic and benthic foraminifera. Two planktonic foraminifers’ zones Subbotina trivialis – Globoconusa daubjergensis – Globanomalina compressa and Praemurica inconstans established earlier by M.V. Jartseva (1972) characterize the Psolian regiostage. Subbotina trivialis – Globoconusa daubjergensis – Globanomalina compressa zone corresponding to Eoglobigerina taurica and Globoconusa daubjergensis zones of the Belokamenskian regiostage of the Southern Ukraine is correlated with Danian zone P1 Eoglobigerina edita of tropical planktonic foraminiferal biochronological zonation. Praemurica inconstans zone of the Northern Ukraine corresponds to south Ukraine zone of the same name and is correlated with zone P2 Praemurica uncinata of Danian too. Benthic foraminifers’ assemblages from Psolian deposits have been distinguished as Cibicides lectus zone corresponding to Anomalina danica s. l. and Pyramidina crassa interregional zones of Danian and Zelandian of the south Russia and adjacent regions. Reviewed in the article biostratigraphical characteristics of local stratigraphic units of Psolian regiostage: the Sumy Suite of the Dnieper-Donets Depression (zones Subbotina trivialis – Globoconusa daubjergensis – Globanomalina compressa, beds with Cibicidoides lectus, beds with Cibicidoides favorabilis of the central part of the Depression; Anomalina danica zone, Ceratolamarckina tuberculata local zone, beds with Parasubbotina pseudobulloides and beds with Globoconusa kozlowskii of the north-eastern part of the Depression), Strata of quartz-glauconitic sands of the Konka-Yalyn Depression (beds with Parasubbotina pseudobulloides, beds with Cibicidoides lectus), the Luzanovka Beds (beds with Parasubbotina pseudobulloides, beds with Globoconusa daubjergensis, beds with Elphidiella prima) and the Polesje Beds (beds with Parasubbotina pseudobulloides, beds with Cibicidoides lectus), the Rajgorod Suite (assemblage with Anomalina danica) of the Ukrainian Shield. Correlation of these Suites, Beds and Strata are given. The Merlian regiostage of the Northern Ukraine contains not numerous foraminifers. Benthic foraminifers’ associations from the Merlian and Irzhavets Suites of the Dnieper-Donets Depression have been distinguished as assemblage with Bolivinopsis spectabilis. Sediment containing this assemblage is of Thanetian age by dinocysts. Findings of sporadic planktonic foraminifers in the Merlian deposits do not contradict this.

Foraminifera indicate Neogene evolution of Yongle Atoll from Xisha Islands in the South China Sea

This paper reports the fauna and distribution of large‐sized benthic foraminifers (LsBFs; defined as benthic foraminifers >0.5 mm in size) from surface sediments collected around Tahiti, French Polynesia, as well as from the Pleistocene deposits drilled off the Tiarei area, Tahiti, during Integrated Ocean Drilling Program (IODP) Expedition 310. At least 6 and 22 genera of living and dead tests of LsBFs, respectively, were identified from modern surface sediments. Foraminiferal abundance in surface sediments depends mainly on the water depth and substratum type. The taxonomic composition of dead LsBF assemblages varies with depositional environments and water depths. Back‐reef lagoon assemblages are dominated by Schlumbergerina alveoliniformis, whereas fore‐reef slope and shelf assemblages are dominated by Amphistegina spp. The relative abundance of Amphistegina lessonii decreases with increasing water depth. On the shelf, A. lessonii is replaced by Amphistegina bicirculata and Planostegina sp. Pleistocene samples consisting mainly of volcaniclastic sandstone/siltstone and skeletal grainstone contained very small numbers and low species diversity of fossil LsBFs. Amphistegina lobifera, Heterostegina depressa, and Eponides repandus were commonly found in the Pleistocene samples. The taxonomic compositions showed little variation within holes. The Pleistocene assemblages were compositionally similar to those found in modern fore‐reef slope environments of <30 m depth. Combined results of coral U/Th ages and paleoenvironmental interpretations from in situ corals and LsBFs indicate that the Pleistocene sequence in the Tiarei area was deposited in a fore‐reef slope environment during Marine Isotope Stage 3.

Recently, Late Cretaceous strata ranging from the Cenomanian to the late Maastrichtian were found in the Subsilesian Unit of Moravian Carpathians. The stratigraphic assignment is based upon planktonic and benthic foraminifer biostratigraphy. Planktonic foraminifer markers: Marginotruncana pseudolinneiana Pess., Globotruncanella petaloidea (Gand.), Laeviheterohelix dentata (Sten.), Rugoglobigerina pennyi (Brön.) and benthic foraminifer markers: Plectorecurvoides irregularis Geroch, Bulbobaculites problematicus (Neagu), Uvigerinammina jankoi Majzon, Conotrochammina sp. etc. are briefly discussed and figured. In Campanian–Maastrichtian marls also articulated specimens of inoceramid bivalves Platyceramus sp. indeterminable to specific level were found. They are related to giant inoceramids known from the Coniacian–Campanian of the Euramerican biogeographical region and North Pacific Province. Folded inoceramid valves evidences slumping of sediment during the early diagenesis, prior to formation of carbonate concretions that include the shells. Both lithology and composition of foraminifer assemblages show trend from eutrophic black clays of the Cenomanian, through greenish silty clays of the Turonian–Coniacian, towards greygreen mottled and more oligotrophic variegated marls and clays of the Campanian–Maastrichtian. Cenomanian taphocoenosis consists of agglutinated taxa dominated by Rhizammina, Hyperammina, Kalamopsis and Adercotryma. Calcareous benthic foraminifers are extremely rare, planktonics are missing. Benthic foraminifer density (specimens per 1 g of rock) is about 9. Turonian–Coniacian taphocoenosis contains, besides agglutinated taxa, also some calcareous taxa including few planktonics. Campanian–Maastrichtian taphocoenoses comprise agglutinated and calcareous benthics indicating bathyal habitat (Marssonella, Spiroplectammina, Recurvoides, Gyroidinoides). Benthic foraminifer density reaches the value 643. At the same time the planktonic foraminifers represent 94 % of taphocoenosis.

Purpose. Development of a zonal biostratigraphic scheme by benthic foraminifers from Maastrichtian deposits of the Northern outskirts of Donbas, by using the studied sections of the region as an example. Methodology. Microfaunistic analysis was used in the processing of the material. Shells were removed from 150-200 g rocks by the standard methodology in Franke chambers and studied, using the MBS-9 microscope. Results. The biostratigraphic division of the Maastrichtian deposits of the Northern outskirts of the Donbas by benthic foraminifers, previously proposed by the author for the Upper Cretaceous deposits of this territory, is presented. An analysis of the four Early Maastrichtian and two Late Maastrichtian foraminiferal complexes made it possible to distinguish three zones of foraminifers. In the Lower Maastrichtian, the following zones were identified – Neoflabellina retuculata (lower), Brotzenella complanata (upper), in the Upper Maastrichtian – Hanzawaia ekblomi (with lower subzone Cuneus minutus). The Neoflabellina retuculata zone has been defined by the characteristic species Neoflabellina reticulata, Orbignyna sacheri, Heterostomella bullata, Cibicidoides bembix, Osangularia navarroana, Bolivina decurrens, B. incrassata incrassata, Pseudovigerina cristata. The Brotzenella complanata zone is characterized by the following species: Brotzenella complanata, Spiroplectammina suturalis, Gaudryina pyramidata, Cibicidoides bembix, Eponides peracutus, Bolivina incrassata crassa, Pseudovigerina cristata. Species Hanzawaia ekblomi, Anomalinoides pinguis, Praebulimina imbricata, Cuneus minutus are characteristic of the Hanzawaia ekblomi zone. Correspondence of the foraminiferous zones to macrophaunistic is given: Neoflabellina retuculata to the subzone Belemnella licharewi / B. lanceolata, Brotzenella complanata – subzones of Belemnella lanceolata and Belemnella sumensis of the Acanthoscaphites tridens zone of the outskirts of Donbas, the lower part of the Hanzawaia ekblomi zone – the Belemnitella junior / Spyridoceramus tegulatus zone of platform Ukraine. According to the current stratigraphic schemes of Ukraine, the correspondence of the Maastrichtian foraminiferal zones to the local stratigraphic subdivisions of the Northern outskirts of Donbas is indicated. The paleontological characteristics of the Konoplyanivska (two subsuites) and Kamyanobridska suites, which according to the age corresponds to the Lower Maastrichtian deposits, were supplemented with new data. A comparison of the studied foraminifers with species of the Boreal province of the International Stratigraphic Scale was carried out, general species are indicated. Scientific novelty. "The stratigraphic scheme of the Upper Cretaceous deposits of the Northern outskirts of Donbas" is supplemented with new data. Practical significance. The biostratigraphic division of the Maastrichtian deposits of the Northern outskirts of the Donbas by benthic foraminifers can be used for interregional correlation, as well as for detailed mapping of this region.

<p>The definition of reference conditions has a major role for the understanding of the present-day and paleoecological quality status on transitional environments. The estuarine quality paradox and the paucity of unimpacted sites make the definition of reference conditions a challenging task. In this context, the integration of biological indicators with stratigraphic data is essential, as the vertical stacking pattern of facies composing the shallow subsurface of modern coastal plains reflects changes in physical-chemical parameters which, in turn, affect (paleo-)biotic communities.</p><p>In the Po coastal plain (N Italy), the mid to late Holocene back-barrier succession of the Mezzano Lowland and the adjacent present-day Bellocchio Lagoon offer a unique example of pristine paralic system for comparing reference conditions defined in fossil and modern settings, respectively. Benthic foraminifers and ostracods from the Mezzano succession allowed us to investigate vertical (i.e., temporal) and lateral (i.e., spatial) changes in (paleo-)environmental conditions, in analogy to the lateral variations recorded at the Bellocchio Lagoon.</p><p>Both sites present subtidal channel sands almost barren in autochthonous meiofauna and fine-grained lagoon sediments with abundant benthic foraminifers and ostracods mostly represented by euryhaline taxa recording the highest diversity. Intertidal muddy deposits are also recorded, including mud flat clays with abundant oligotypic assemblages dominated by highly-confined benthic foraminifers. In the present study, we demonstrate that changes in modern benthic foraminifer assemblages diversity and composition often interpreted as perturbations of ecological conditions in response to anthropogenic pressures also occur under natural state, as confirmed by paleoenvironmental conditions recorded by ostracods. This reflects the effects of authogenic processes at short time and geographic scales.</p>

Recent benthic foraminifers as indicators of the sedimentary dynamics of the Tina Mayor and Tina Menor estuaries (S Bay of Biscay, N Spain)

Paleo-depths reconstruction of the last 550,000 years based on the transfer function on recent and Quaternary benthic foraminifers of the East Corsica margin

Data on the distribution of radiolarians and planktonic and benthic foraminifers are obtained for the first time from the Alan-Kyr Section (Coniacian–Campanian), in the central regions of the Crimean Mountains. Radiolarian biostrata, previously established from Ak-Kaya Mountain (central regions of the Crimean Mountains) were traced: Alievium praegallowayi–Crucella plana (upper Coniacian–lower Santonian), Alievium gallowayi–Crucella espartoensis (upper Santonian without the topmost part), and Dictyocephalus (Dictyocryphalus) (?) legumen–Spongosaturninus parvulus (upper part of the upper Santonian). Radiolarians from the Santonian–Campanian boundary beds of the Crimean Mountains are studied for the first time, and Prunobrachium sp. ex gr. crassum–Diacanthocapsa acanthica Beds (uppermost Santonian–lower Campanian) are recognized. Bolivinoides strigillatus Beds (upper Santonian) and Stensioeina pommerana–Anomalinoides (?) insignis Beds (upper part of the upper Santonian–lower part of the lower Campanian) are recognized. Eouvigerina aspera denticulocarinata Beds (middle and upper parts of the lower Campanian) and Angulogavelinella gracilis Beds (upper part of the upper Campanian are recognized on the basis of benthic foraminifers. These beds correspond to the synchronous biostrata of the East European Platform and Mangyshlak. Marginotruncana coronata-Concavatotruncana concavata Beds (Coniacian–upper Santonian), Globotruncanita elevata Beds (terminal Santonian), and Globotruncana arca Beds (lower Campanian) are recognized on the basis of planktonic foraminifers. Radiolarian and planktonic and benthic foraminiferal data agree with one another. The position of the Santonian–Campanian boundary in the Alan-Kyr Section, which is located stratigraphically above the levels of the latest occurrence of Concavatotruncana concavata and representatives of the genus Marginotruncana, is refined, i.e., at the level of the first appearance of Globotruncana arca. A gap in the Middle Campanian–lower part of the upper Campanian is established on the basis of planktonic and benthic foraminifers. The Santonian–Campanian beds of the Alan-Kyr Section, on the basis of planktonic foraminifers and radiolarians, positively correlate with synchronous beds of the Crimean-Caucasian region, and beyond. Benthic foraminifers suggest a connection with the basins of the East European Platform.