Larger Foraminiferal Assemblages Research Articles

EOCENE STALKED CRINOIDS IN THE GENUS <em>ISSELICRINUS</em> (ECHINODERMATA, CRINOIDEA, ISOCRINIDA) FROM NORTHEASTERN ITALY

Long fragments of isocrinid stalks belonging to the stalked crinoid genus Isselicrinus (Isocrinida, Isselicrininae) were found at Cambrigar, near Ferrara di Monte Baldo (Verona province, northeastern Italy) in the strata called “Harpactocarcinus punctulatus and Pentacrinus diaboli horizon”, traditionally ascribed to the lower Eocene (Ypresian). Morphometric analysis of this material allowed us to identify two distinct species filtering their food at different levels of the water column. The first species, characterized by a mostly pentagonal stalk section, is ascribable to Isselicrinus diaboli (Bayan), a taxon frequently cited from the lower Eocene of northeastern Italy but until now poorly known. The other species has a marked star-shaped stalk section presenting a combination of pedomorphic characters and is ascribed to the new taxon Isselicrinus baldoensis n. sp. A detailed analysis of numerous columnals and pluricolumnals of Isselicrinus diaboli from the type-locality of San Pancrazio near Mossano (Berici Hills, Vicenza province, northeastern Italy) allowed us to propose a revised and more complete diagnosis of this taxon. The particular burial conditions and the ecology of these two species are discussed as well as a reappraisal of the age of the “Harpactocarcinus punctulatus and Pentacrinus diaboli horizon”. Based on new calcareous nannofossil data, and confirmed by the larger foraminiferal assemblages, the isocrinids from Cambrigar are firmly assigned to the Lutetian (middle Eocene). Calcareous nannofossils identified in the matrix of historical hand specimens from the classical locality of San Pancrazio indicate a similar age.

Eocene larger foraminiferal biostratigraphy, depositional history and paleogeography of the Sylhet Limestone of the Mikir Hills of Assam, NE India: Implications for an Open Tethys

This study presents results of integrated larger foraminiferal biostratigraphy, lithofacies and stable carbon isotope (13 C org) analysis carried out in the Sylhet Limestone of Dillai Parbat Limestone Mine succession, Karbi Anglong District, Assam. Larger foraminiferal assemblages assign a middle Eocene age to the studied succession of Sylhet Limestone. The Shallow Benthic Zone (SBZ) 13 and SBZ 16-18 and a barren interval in between is recognized in the studied part of the Sylhet Limestone. The SBZ 13 Zone (early Lutetian) is represented by fossiliferous limestone at the base of the section and is inferred to have been deposited in a subtidal environment. The overlying barren interval lies in the arenaceous interval and was likely deposited in a subtidal channel sand shoaling bars. The upper part of the section ismarked by SBZ16-18 (late Lutetian to Bartonian) and was deposited in subtidal channel sand inner neritic zone environments, followed by intertidal marl to subtidal limestone. The organic carbon stable isotopic data reveals a sharp negative excursion at about 34-35m of the succession, which may be correlated with Middle Eocene Climatic Optimum (MECO) and/or vegetation types. This and earlier studies from India and elsewhere indicate that during the middle Eocene, the Neo-Tethys Sea was open and connected through the East and West coasts of India, Northeast India, western Himalaya, and most of the Middle East and southeast Europe. This vast area produced enormous amount of petroleum.

Eocene resedimented limestone deposits from the Osa Peninsula, Costa Rica: slope-apron accumulation in a volcanic forearc environment

Eocene limestones from the Osa Peninsula of southern Costa Rica were deposited in a slope-apron environment in an active volcanic forearc setting. Larger foraminiferal assemblages from clasts and beds record two main resedimented carbonate microfacies: a dominant Eoconuloides–Helicostegina–Eulinderina facies from the middle Eocene (Lutetian) and a subordinate Lepidocyclina tobleri panamensis–Lepidocyclina (Nephrolepidina) chaperi facies from the upper Eocene (uppermost Bartonian–Priabonian). Both facies consist of abundant shallow-marine benthic carbonate, volcaniclastic, and planktic materials that were re-deposited by gravity flows into a deeper-marine forearc basin. The accessory volcaniclastic grain assemblages are bimodal in composition, comprising differentiated rock and ejecta fragments derived from explosive arc volcanism in addition to basaltic grain contributions from the volcanic forearc basement. The source of the carbonate materials was likely the Fila de Cal carbonate platform presently located in the adjoining arc-ward region of the Fila Costena thrust belt. Strong biostratigraphic correlations with platform carbonate and other similar forearc successions bearing resedimented limestones reveal not only a provenance from carbonate environments within the arc but they also record coeval events of resedimentation along a continuous deep-marine forearc slope. The sedimentary sequence was deformed as result of coeval basaltic activity and fault tectonics. There is no evidence of accumulation by accretionary processes in the carbonate deposits studied. The findings indicate that the basement of the Osa Peninsula and its sedimentary cover probably formed part of the Costa Rican forearc that was uplifted and deformed in response to basaltic volcanic activity and subsequent Cocos Ridge subduction.

Palaeogene marine stratigraphy in China

Palaeogene deposits are widespread in China and are potential sequences for locating stage boundaries. Most strata are non-marine origin, but marine sediments are well exposed in Tibet, the Tarim Basin of Xinjiang, and the continental margin of East China Sea. Among them, the Tibetan Tethys can be recognized as a dominant marine area, including the Indian-margin strata of the northern Tethys Himalaya and Asian-margin strata of the Gangdese forearc basin. Continuous sequences are preserved in the Gamba–Tingri Basin of the north margin of the Indian Plate, where the Palaeogene sequence is divided into the Jidula, Zongpu, Zhepure and Zongpubei formations. Here, the marine sequence ranges from Danian to middle Priabonian (66–35 ma), and the stage boundaries are identified mostly by larger foraminiferal assemblages. The Paleocene/Eocene boundary is found between the Zongpu and Zhepure formations. The uppermost marine beds are from the top of the Zongpubei Formation (~35 ma), marking the end of Indian and Asian collision. In addition, the marine beds crop out along both sides of the Yarlong Zangbo Suture, where they show a deeper marine facies, yielding rich radiolarian fossils of Paleocene and Eocene. The Tarim Basin of Xinjiang is another important area of marine deposition. Here, marine Palaeogene strata are well exposed in the Southwest Tarim Depression and Kuqa Depression. They comprise mostly neritic and coastal lagoon facies of the Tethyan realm. Palaeontological evidence suggests that the Paleocene/Eocene boundary here is in middle of the Qimugen Formation. The Tarim Basin was largely drained by Late Oligocene. To the east, the marine offshore Palaeogene strata are widespread in the North Taiwan and East Zhejiang depressions of the continental shelf basin of East China Sea. Abundant fossils including foraminifera, calcareous nannofossils, ostracods, pollen and bivalves occur in the marine environment. Biostratigraphically, the sequence is well correlated with the international planktonic foraminiferal and nannofossil zonations.

Middle–Late Eocene Nummulites (N. burdigalensis group) from Gebel Hafit, along the United Arab Emirates and Oman borders, Arabian Peninsula

A Middle–Late Eocene diagnostic larger foraminiferal assemblage is described and illustrated from carbonates of the uppermost Dammam Formation, on both sides of Gebel Hafit anticline in the Northern Oman Mountains in the United Arab Emirates. The Middle Eocene carbonates yielded Nummulites obesus d'Archiac, 1852, N. ismaili Boukhary, Hamdan & Bahr n. sp., N. papazzonii Boukhary, Hamdan & Bahr n. sp. and N. kenawyi Boukhary, Hamdan & Bahr n. sp. (a species of the N. burdigalensis group). In addition, N. cf. boussaci Rozlozsnik, 1924, N. cf. lorioli De La Harpe, 1879, N. hottingeri Schaub, 1981, N. strougoi Boukhary, Hamdan & Bahr n. sp. (of the N. partschi group), N. ansaryi Boukhary, Hamdan & Bahr n. sp. (of the N. gizehensis group), N. cf. praebullatus Schaub, 1981, N. cizancourti Sander, 1962 (of the group of N. fabianii), N. cf. stamineus Nuttall, 1927 (of the N. discorbinus group), N. maculatus Nuttall, 1926 (of the N. laevigatus group) and Assilina gigantea De La Harpe, 1926 are recorded. On the top of the sequence, an assemblage with N. hottingeri Schaub, 1981, which was assigned by Schaub 1981 to the Biarritzian ( = Bartonian), was found associated with N. ptukhiani, Silvestriella tetraedra (Gümbel, 1870) and Pellatispira madaraszi (Hantken, 1875); these findings suggest that this association should be assigned to the Priabonian stage, confirming for the sampled succession of a Late Eocene age for sediments deposited in an inner-shelf environment, which was possibly related to the eustatic fall of sea level at the end of the Priabonian. http://zoobank.org/2EBD2891-293F-465A-AE1C-F419F0CDB970

Oligocene larger foraminifera from United Arab Emirates, Oman and Western Desert of Egypt

An early Oligocene (Rupelian) diagnostic larger foraminiferal assemblage is described and illustrated from marls and limestones of the Asmari Formation, at Jabals Hafit and Malaqet in the UAE. An equivalent assemblage is identified in the mudstones of the Tahwah Formation, Wadi Suq, Oman. Although Nummulites intermedius (D'Archiac 1846) and N. fichteli are fully synonymous (e.g. Roveda 1970; Schaub 1981; Sirel 2003), in this study both species are biometrically differentiated, distinct and both names are valid. N. fichteli Michelotti 1841, N. intermedius (D'Archiac 1846) and N. emiratus n. sp., which are index for the early Oligocene (Rupelian), and they are replacing each others competitively and environmentally. The presence of Blondeauina bouillei n.gen., N. emiratus n.sp., N. intermedius, N. fichteli, Planoperculina complanata (Defrance 1822) and Austrotrillina asmariensis Adams 1968 ascribed the section of the Asmari Formation to the early Oligocene (Rupelian). The studied marls and limestones were deposited in outer and inner shelf environments, respectively. The Asmari Formation in the area studied consists mainly of marl in its lower portion and reefal limestone in its upper part, indicating a major marine regression. The Tahwah Formation in Oman is composed of bioturbated silty and muddy marls and is a facies equivalent to the Asmari Formation marls. The Asmari Formation facies change probably relates to a mid-Oligocene fall in global sea level. In this study, the Dabaa Formation, a subsurface unit of late Eocene–Oligocene marine shales in the north Western Desert of Egypt, was chosen to correlate with the Oligocene of Emirates and Oman. The Dabaa Formation comprises Spiroclypeus ornatus (Henson 1937) and Eulepidina dilatata (Michelotti 1861). The environment of deposition was inner shelf to littoral, which become estuarine towards the top in many areas. This Oligocene Dabaa sequence is correlatable with Wadi El Arish sequence recently discovered by Kuss and Boukhary (2008) from Risan Aneiza, Northern Sinai, Egypt.

Rhodolith-rich lithofacies of the Porto Badisco Calcarenites (upper Chattian, Salento, southern Italy)

This study describes the rhodolith-rich lithofacies of the Porto Badisco Calcarenites, an upper Chattian rhodalgal/larger foraminiferaldominated unit exposed in the southern part of the Apulia Carbonate Platform (Salento Peninsula, Italy). The lensoid rhodolith-rich lithosome at the base of the studied section is made of rhodolith rudstone and floatstone which infill a channel-like depression inherited from the substrate. Changes in the texture of the rhodolith facies and in the inner structure of the rhodoliths reflect variations in submarine current velocity across the section of the channel. Inherited topography controlled both the locus and the mode of rhodolith accumulation. The rhodolith lithosome is bounded by a flat surface above which rhodoliths are notably absent and beds are tabular. This implies that rhodolith accumulation ended as soon as substrate topography was completely levelled off. The taxonomic composition of the red algal and larger foraminiferal assemblages suggests that the rhodolith-rich unit deposited in the oligophotic zone. The abundance of tropical genera among the coralline algae (Lithoporella and Sporolithon) and the high diversity of larger foraminiferal assemblages indicate that the deposition of the Porto Badisco Calcarenites took place in the warm waters of the tropical to subtropical zone

Rapid subsidence of the Kikai Seamount inferred from drowned Pleistocene coral limestone: Implication for subduction of the Amami Plateau, northern Philippine Sea

Carbonate rock cores drilled on the Kikai Seamount, northern Philippine Sea are examined for better understanding of tectonic history of the northern Philippine Sea. The Kikai Seamount, the summit of which is at 1960 m water depth, is an isolated high on the northwestern part of the Amami Plateau formed by subduction-related arc volcanism, and is situated close to the axis of the Ryukyu Trench in front of the Ryukyu Arc, SW Japan. The seamount is capped with shallow-water carbonates such as coral rudstone. Detailed examinations of lithology, larger foraminiferal assemblages, and Sr isotope composition reveal that the core material comprises Miocene carbonates unconformably overlain by Early Pleistocene carbonates. It indicates rapid subsidence of the Kikai Seamount since the Early Pleistocene. The most probable cause of rapid subsidence is collision and subduction of the Amami Plateau laden with the Kikai Seamount. The rapid subsidence may have started when the western corner of the plateau reached the Ryukyu Trench and began subduction beneath the Ryukyu Arc. The onset of the subsidence is likely to be controlled by a motion change in the Philippine Sea Plate. The latest change in subduction direction from north to northwestward into northwestward to west has been believed to have occurred at 1-2 Ma during latest Pliocene to Early Pleistocene time. The change of direction resulted in the shift from oblique into right-angle subduction of the plate beneath the Ryukyu Arc and also the onset of the collision and subduction of the Amami Plateau.

Latitudinal changes in larger benthic foraminiferal assemblages in shallow‐water reef sediments along the Ryukyu Islands, Japan

Abstract The taxonomic diversity of hermatypic corals decreases with increasing latitude, which correlates with sea‐surface temperatures. However, little is known about latitudinal changes in the taxonomic diversity and biogeographic patterns of larger benthic foraminifera, although their physiological requirements are similar to those of hermatypic corals because of their symbiotic relationships with microalgae. The present study examined how the abundance and taxonomic composition of larger foraminiferal assemblages in shallow‐water reef sediments change with latitude along the Ryukyu Islands (Ryukyus), which are located near the northern limit of coral‐reef distributions in the western Pacific Ocean. Three islands from different latitudes in the Ryukyus were selected to investigate latitudinal changes in larger foraminiferal assemblages: Ishigaki Island (24°20′N, 124°10′E), Kudaka Island (26°09′N, 127°54′E) and Tane‐ga‐shima Island (30°20′N, 131°E). Four sediment samples were taken at each of three topographic sites (beach, shallow lagoon and reef crest) on the reef flat of each island. Foraminiferal tests of a 2.0‐ to 0.5‐mm size fraction were selected, identified and counted. The variations in foraminiferal abundance in reef sediments from three latitudinally different islands exhibit two contrasting trends along reef flats: a shoreward decrease on Ishigaki and Tane‐ga‐shima Islands and a shoreward increase on Kudaka Island. A total of 25, 24 and 13 foraminiferal taxa were identified in Ishigaki, Kudaka and Tane‐ga‐shima Islands, respectively. Baculogypsina sphaerulata, Neorotalia calcar and Amphistegina spp. were dominant (i.e. >3% of foraminiferal assemblages) in the three islands. Calcarina gaudichaudii and Calcarina hispida were common on Ishigaki and Kudaka Islands but were absent on Tane‐ga‐shima Island. Larger foraminiferal assemblages from three different reef‐flat environments on Ishigaki Island can be distinguished, whereas those from the three environments on Kudaka and Tane‐ga‐shima Islands are similar in composition. These latitudinal changes in larger foraminiferal assemblages in reef sediments may possibly be caused by variations in the topography of reef flats, distributions and standing crops of living foraminifers on reef flats, and the northern limit of some calcarinid species in the northern Ryukyus.

DEPTH COENOCLINES AND ENVIRONMENTAL CONSIDERATIONS OF WESTERN PACIFIC LARGER FORAMINIFERA

Research Article| January 01, 2004 DEPTH COENOCLINES AND ENVIRONMENTAL CONSIDERATIONS OF WESTERN PACIFIC LARGER FORAMINIFERA Johann Hohenegger Johann Hohenegger 1 Institut für Paläontologie, Universität Wien, Althanstrasse 14, 1090 Wien, Österreich (Austria) 1E-mail: johann.hohenegger@univie.ac.at Search for other works by this author on: GSW Google Scholar Journal of Foraminiferal Research (2004) 34 (1): 9–33. https://doi.org/10.2113/0340009 Article history received: 15 Oct 2002 accepted: 13 Feb 2003 first online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Johann Hohenegger; DEPTH COENOCLINES AND ENVIRONMENTAL CONSIDERATIONS OF WESTERN PACIFIC LARGER FORAMINIFERA. Journal of Foraminiferal Research 2004;; 34 (1): 9–33. doi: https://doi.org/10.2113/0340009 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyJournal of Foraminiferal Research Search Advanced Search Abstract Symbiont-bearing benthic foraminifera are restricted to the euphotic zone of tropical and warm-temperate seas. Species distribution is correlated with depth, and the continuous alteration of community structures represents a coenocline. Since depth is a composite environmental gradient, the coenocline of larger foraminifera is not stable but alters with changes in primary limiting factors: temperature, light, water movement, substrate, and nutrients.Temperature determines geographic distribution and affects the depth distribution of larger foraminifera by the development of a shallow thermocline that truncates the distribution of shallower species and excludes species adapted to the deepest euphotic zone. Within these constraints, light is the most important primary factor because larger foraminifera are at least partly dependent upon photosynthesis by their algal endosymbionts for growth and calcification. The microalgae show distinct intervals along the light gradient and the foraminiferal host develops various strategies for regulating light intensity. First, well-structured environments in shallow waters allow shelter against irradiation by protecting in shadow areas. Second, wall and test structures enable regulation of light penetration. A range of mechanisms allows species to resist the highest energies in the breaker zone of the reef edge and crest, where foraminifera attach to inorganic or organic hard substrates. Concentrations of dissolved and particulate organic matter in the water column, as well as sediments or other inorganic particles, influence depth distributions by changing water transparency and, therefore, photosynthesis. Permanent or episodic elevations of concentrations therefore compress the coenocline upward. Species adapted to hard substrates must compete for the reduced space, while species living in the deepest euphotic zone are at a disadvantage because they are insufficiently motile to surmount large depth differences. Changing light transparencies due to nutrient input and different hydrodynamic conditions alter relations between the light coenocline and water depth. Thus, paleodepth interpretations based on larger foraminiferal assemblages should be based not only on foraminiferal taxa and ecology, but also on environmental evidence for climate, terrigeneous influence, water transparency, and hydrodynamic conditions based on sedimentology, geochemistry, and associated fossil biota. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Oxygen and carbon isotopic variation in co-existing larger foraminifera from a reef flat at Akajima, Okinawa, Japan

The larger foraminiferal assemblage on the reef flat at Akajima (Ryukyu Island Arc) is comprised of Marginopora kudakajimaensis, Amphisorus hemprichii, Sorites orbiculus, Peneroplis planatus, Heterostegina depressa, Neorotalia calcar, Calcarina gaudichaudii, Baculogypsina sphaerulata and Amphistegina lessonii. The oxygen and carbon isotopic variations in several specimens of each species, living under similar conditions, were examined. Symbiosis had little to no effect on oxygen isotopic composition of the bulk carbonate of the analysed species. The isotopic analysis along the ontogenetic stages indicates near-equilibrium precipitation of oxygen isotopes in the early life stages and, therefore, the initial chambers should be microsampled in isotopic analyses for a better estimate of palaeotemperature. The order of depletion of δ 13C parallels the order of accretion of calcium carbonate by the foraminiferal species. A poor correlation between δ 18O and δ 13C and a large variation in δ 18O and δ 13C with size of the shell are the characteristic features of the symbiont-bearing benthic foraminifera inhabiting reef flat environments. In a deeper water species oxygen isotopic values vary little with size of the shell.

Neogene Foraminiferida from GSQ Sandy Cape 1–3R bore, Queensland: A biostratigraphic appraisal

A stratigraphic borehole was drilled on the northern end of Fraser Island near the outer part of the southeastern Queensland continental shelf. This bore encountered about 300 m of late Tertiary marine sediments, lying beneath 125 m of Quaternary marine and aeolian sands and above a thin deposit of late Oligocene marine sands. Planktic and larger foraminiferal assemblages (e.g. species of Operculina, Lepidocyclina, Miogypsina, Cycloclypeus, Flosculinella, Austrotrillina, and Archaias) have been used to correlate the Sandy Cape 1–3R Neogene section with the biostratigraphy of the offshore Capricorn Basin. A regional erosional unconformity, previously detected as a seismic reflector, has been dated by this work and related to the stratigraphy of the shelf.

Stratigraphic Correlation of Planktonic and Larger Foraminiferal Zones: ABSTRACT

A very few areas of the sedimentary basins of the world are characterized by marine facies of clastic and non-clastic origin, which are rich in planktonic and larger foraminiferal assemblages. Pakistan is one of the countries where the Tertiary marine deposits (Paleocene to Miocene) are represented by both clastic and nonclastic facies characterized by stratigraphically restricted planktonic and larger foraminiferal species, which provide the basis for the interregional biostratigraphic correlation. The marine clastic deposits of Paleocene to Miocene age in the Lower Indus and Baluchistan basins of Pakistan are rich in the planktonic assemblages. On the basis of the stratigraphically restricted species, 22 planktonic foraminiferal zones were delineated to mark the stratigraphic boundary of the various European stages (Kureshy, 1977). The non-clastic marine deposits of Paleocene to early Miocene age in the Lower Indus and Upper Indus basins of Pakistan, which are interbedded with clastic deposits, are rich in larger foraminifera. On the basis of the stratigraphically restricted species, ten biostratigraphic zones of the larger foraminifera are designated (Kureshy, 1978). These assemblages are cosmopolitan in occurrence of identical geological ages. The planktonic foraminiferal zones are more widespread and have close resemblance to the Caribbean region, as compared to larger foraminiferal zones. The larger foraminifera of Pakistan have no resemblance to the Caribbean region; however, they closely resemble Middle East and Indo-Pacific regions. The End_Page 1170------------------------------ planktonic and larger foraminiferal zones are correlated, and datum planes are designated. These zones are correlated to Blow (1969) and van der Vlerk (1927) Letter Stage Classification for interregional correlation. End_of_Article - Last_Page 1171------------

The Eocene succession of Garo Hills, Assam, India

SUMMARYBased on the distribution of several stratigraphically important species three distinct larger foraminiferal zones are recognized in the Middle-Upper Eocene succession of Garo Hills, Assam, India. A comparison of these zones with larger foraminiferal assemblages from other Middle-Upper Eocene successions in the Indian region is attempted and observations are made on the demarcation of the Middle and Upper Eocene boundary and the classification of the Upper Eocene succession in this region.