Larger Foraminifera Research Articles

Late Cretaceous alveolinaceans (larger foraminifera) of the Caribbean palaeobioprovince and their stratigraphic distribution

Architectural analysis of the Late Cretaceous alveolinaceans of the Caribbean palaeobioprovince has made it possible to separate four genera: Praechubbina, Chubbinella gen. nov., Chubbina and Caribalveolina. The first three genera belong to the family Rhapydioninidae, while the fourth is placed in the family Alveolinidae. Two species, Praechubbina breviclaustra and P. oxchucensis sp. nov., represent the primitive genus Praechubbina, while the species cardenasensis and obesa, previously ascribed to this genus, must be reassigned respectively to Chubbinella gen. nov. and Caribalveolina. The species Chubbina jamaicensis, C. macgillavryi and C. fourcadei sp. nov. complete the inventory of Chubbina. The alveolinid genus Caribalveolina comprises two species, C. obesa and C. michaudi. Caribbean alveolinaceans include two successive assemblages. The lower assemblage is characterized by Praechubbina oxchucensis, P. brevisclaustra, Chubbinella cardenasensis and Caribalveolina obesa. The upper assemblage is represented by the genus Chubbina, with C. fourcadei, C. jamaicensis and C. macgillavryi, and Caribalveolina michaudi. The age of the lower assemblage is uncertain (probably Late Campanian–Early Maastrichtian), while the upper assemblage has been dated by strontium isotope stratigraphy as Late Maastrichtian. http://zoobank.org/urn:lsid:zoobank.org:pub:88A5CA4D-3D6F-42E9-BEE8-EF3F7B3BA85F

A TEST FOR THE POSSIBILITY OF PHOTOSYMBIOSIS IN EXTINCT FUSULINE FORAMINIFERA: SIZE AND SHAPE RELATED TO DEPTH OF HABITAT

ABSTRACT Late Paleozoic fusuline foraminifera are thought to have hosted photosymbionts, as do modern larger foraminifera, but the ancient host-symbiont relationship has never been demonstrated conclusively. Among modern larger foraminifera, deeper-dwelling species exhibit large surface-to-volume ratios in order to maximize the amount of sunlight that can be captured for use by photosymbionts. Shallower-dwelling species exhibit smaller surface-to-volume ratios in order to limit incoming sunlight, especially ultraviolet radiation. If modern symbiont-bearing foraminifera are appropriate analogues for fusulines, then deeper-dwelling fusulines ought to exhibit larger surface-to-volume ratios than shallower-dwelling ones. This prediction was tested by analyzing fusuline shells from the Virgilian (Upper Pennsylvanian) Oread, Lecompton and Deer Creek cyclothems in Kansas. Specimens from deeper-water “middle” limestones exhibit significantly larger surface-to-volume ratios than those from regressive “upper” limes...

Distribution of Foraminifera of the Poverty Continental Margin, New Zealand: Implications for Sediment Transport

ABSTRACT Foraminiferal assemblages were used to investigate the nature of sedimentation on the tectonically active Poverty continental margin (PCM) of New Zealand. Recent research around the world has been focused on understanding the sedimentary functioning of small mountainous rivers to the global sediment budget, and this study is part of a greater effort to define the processes that link sediment source and sink of such a system in New Zealand. Fifty-five surface samples from box, gravity, and multi-cores from the shelf and slope of the PCM were used to document the distribution of modern benthic foraminifera. Also, twenty samples from two gravity cores retrieved from Poverty Canyon, a hypothesized conduit of sediment to the deep ocean, were analyzed to evaluate the record of down-slope sediment transport. Seven biofacies, recognized by cluster analysis of benthic foraminiferal abundance data from surface and core samples, are strongly related to water depth and continental margin morphology: inner-shelf biofacies (26–43 m), shelf biofacies (~30–130 m) (this biofacies contained all samples from a canyon-head core taken at 359-m water depth), outer-shelf biofacies (60–250 m), upper-slope biofacies (230–350 m), shallow lower-slope biofacies (870–1255 m), Lachlan Anticline biofacies (40–63 m on the PCM shelf), and a mid-canyon thalweg biofacies from a core taken at 891-m water depth. Foraminiferal assemblages of the Lachlan Anticline biofacies are characterized by the largest foraminifera (mostly inner-and mid-shelf species), the most diverse assemblages, and the highest percentage of reworked planktonic tests in the dataset. Many planktonic and benthic specimens have probably been derived from the outcropping Miocene-Pliocene rock of the anticline. A high percentage of reworked (fossil) planktonic foraminifera at the mouth of Poverty Bay likely results from sediments shed from rapidly uplifting Plio-Pleistocene strata within the Waipaoa River drainage basin. Assemblages throughout the canyon-head (359 m) and mid-canyon (891 m) cores from Poverty Canyon contained higher percentages of shallower-water indicator taxa than other samples at similar depths outside the canyon, thus supporting the hypothesis that Poverty Canyon is channeling sediment from the shelf and upper slope to the deep ocean. However, different patterns of down-core distributions between the canyon head and mid-slope thalweg sites indicate that the nature of sedimentation varies down canyon. Abundances of shallower-water foraminifera suggest that shelf taxa are being supplied from a more consistent source to the canyon head, while shelf and upper-slope taxa are more variably supplied to the deeper-canyon thalweg. The effects of bioturbation appear to be greater in the canyon head.

Diagenetic Pattern in the Citarate Carbonate Rocks, Cilograng Area, Lebak Regency, Banten Province

DOI: 10.17014/ijog.v7i3.142The carbonate sequence overlies conformably the tuffaceous sandstone unit, and in turn is conformably underlain by the tuff-sandstone unit, both of which are members of the Citarate Formation. The Citarate carbonate rocks were deposited in an open platform back reef environment, which was temporarily drowned by local sea level rise. Regional Middle Miocene deformation formed NNE-WSW trend faults and E-W trend folds in the researched area. This paper discusses the nature of diagenetic alteration of the Citarate carbonate rocks based on petrographic analyses of twenty surface samples. Carbonate rocks from bottom to top comprise algae packstone, packstone-grainstone, coral-algae packstone, and foraminifer wackestone-packstone. Fragments of coral, coralline red algae, and large foraminifera are the dominant bioclasts in most of the observed samples, whereas echinoids and bivalves are less abundant; they are set in a recrystallized micrite matrix. Planktonic foraminifera are abundant only in few samples. Fragments of plagioclase, igneous volcanic rocks, pyroclastic rocks (tuff), and much less abundant quartz are commonly present in all the studied samples. A generalized diagenesis includes early marine cementation by fibrous aragonite, compaction, aragonite dissolution and/or neomorphism, precipitation of equant-grained calcite cement in a phreatic environment, dissolution to form moldic porosities, dolomitization, the formation of stylolites and fractures, and precipitation of late ferroan calcite during burial. Multiple carbonate cements occur as pore-filling phases, with ferroan calcite cementation taking place during later-stage burial. Secondary porosities were formed during different stages in diagenetic processes, such as dissolution, dolomitization, and stylolite and fracture formations. Although precipitation of nonferroan and ferroan calcite cement occluded porosities, porosity enhancement during early selective dolomitization might still be significant. Current observations also revealed the presence of intraparticle, micro-vuggy, and fracture porosities in different samples.

Morphological Abnormalities and Dwarfism in Maastrichtian Foraminifera from the Cárdenas Formation, Valles–San Luis Potosí Platform, Mexico: evidence of paleoenvironmental stress

During the early Maastrichtian an assemblage rich in large foraminifera, mostly composed of orbitoidal foraminifera, developed in the shallow-water deposits of the Cardenas Formation (Valles–San Luis Potosi Platform, Mexico). Among them, the most abundant is Lepidorbitoides minima, some of which display a morphologically abnormal test consisting of polyvalent forms, conical tests and budding, which could be induced by abrupt changes in environmental factors. The occurrence of the abnormalities preceded the demise of this species and of all the larger foraminiferal association in the upper part of the Gansserina gansseri Zone (early Maastrichtian). The abnormalities could be induced by environmental stress, probably related to interplay of different events such as increased terrigenous input and the transition to deeper facies due to Laramide tectonic instability before the K/P boundary. A late Maastrichtian community of dwarfed planktic foraminifera composed of Trinitella scotti Bronnimann, Plummerita reicheli Bronnimann, Rugoglobigerina cf. macrocephala Bronnimann, Rugoglobigerina hexacamerata Bronnimann, Heterohelix punctulata (Cushman), Pseudoguembelina costulata (Cushman), Pseudotextularia intermedia de Klasz, Globigerinelloides asperus Bolli, Guembelitria cretacea Cushman, Rugoglobigerina rugosa (Plummer), Rugotruncana sp., Globotruncanita stuarti (de Lapparent), and Globotruncana arca (Cushman) developed in the upper part of the sequence. This uncommon morphology could also be related to the highly stressed paleoenvironmental conditions related to global climatic change and local tectonic activity. Associated with this planktic assemblage is a deeper-water dwarfed benthic foraminiferal community composed of Gyroidinoides nitidus (Reuss), Coryphostoma incrassata (Reuss), Pseudouvigerina plummerae Cushman, P. cretacea Cushman, Bolivina cretosa Cushman, Planulina texana Cushman and Cibicides harperi (Sandidge).

Mangrove-bearing limestone from the Eocene Dammam Formation, Arabian Gulf: implications for the mangrove dispersal controversy

Fossil mangrove remains are found within the shallow carbonate strata of the Middle Eocene Dammam Formation of the Arabian Gulf. This formation is of wide distribution across most eastern parts of the Arabian Platform and represents the terminal stages of the Tethys Sea. The stand consists of well-preserved mangrove plant molds with the associated fossils of large foraminifera, gastropods, and barnacles. It forms part of carbonate ridges that circumscribe a present-day mangrove stand in Al-Khor estuary, NW Qatar. The two systems are comparable in many aspects in terms of sediment characterization and their faunal and flora contents. This finding supports the notion that mangrove ecosystems were common in the region at least since the Early Eocene and in alliance with the vicariance hypothesis, which states that earliest mangrove was restricted to the Tethys Sea.

An Upper Miocene siliciclastic-carbonate ramp: depositional architecture, facies distribution, and diagenetic history (Capo Vaticano area, southern Italy)

During the Late Miocene, the marginal areas of the Mediterranean Basin were characterized by the development of mixed siliciclastic-carbonate ramps. This paper deals with a temperate siliciclastic-carbonate ramp (late Tortonian–early Messinian in age) which crops out in the Capo Vaticano area, Southern Apennines (Italy). Carbonate components are mainly represented by calcitic skeletal fragments of coralline red algae, bryozoans, bivalves, and larger foraminifera, whereas corals, brachiopods, echinoderms, and planktonic foraminifera are subordinate. In the studied ramp, the depositional geometries of the main unit, the ‘Sabbie gialle ad Heterostegina’, show a gradual steepening from low/middle (dip about 2–5°) to steep slope settings (up to 25°). The microfacies observations, the quantitative analyses of the main biogenic components as well as the rhodolith shapes and growth forms allowed the differentiation between the middle and the outer ramp depositional setting and the refining of the stratigraphic framework. The middle ramp is characterized by coralline red algal debris packstone facies often associated with larger foraminiferal floatstone/packstone facies, while the outer ramp is characterized by rhodolith floatstone/rudstone facies. These facies pass basinward into typical open-marine deposits (planktonic foraminiferal facies). The taxonomic composition of the coralline red algal assemblage points to a temperate paleoclimate and emphasizes the Miocene Mediterranean phytogeographic patterns. The absence of non-skeletal grains (ooids and green algae), the paucity of Porites patch reefs, the rare occurrence of primary marine cementation, all confirm that the studied ramp was poorly lithified within a warm–temperate setting. The flat depositional profile of the ramp can be related to the absence or paucity of primary marine carbonate cements.

The trace fossil Nummipera eocenica from the Tatra Mountains, Poland: morphology and palaeoenvironmental implications

Jach, R., Machaniec, E. & Uchman, A. 2011: The trace fossil Nummipera eocenica from the Tatra Mountains, Poland: morphology and palaeoenvironmental implications. Lethaia, Vol. 45, pp. 342–355. The tubular trace fossil Nummipera eocenicaHölder 1989 occurs in a single stratigraphical horizon in Eocene nummulitic limestones of the Tatra Mountains, Poland. The wall of N. eocenica is built of Discocyclina and Nummulities (larger foraminifera) tests, very rarely of the Ditrupa (Polychaeta) tube fragments, bivalve shell fragments, echinoid spines and coralline algae. Morphotype are distinguished on the basis of wall composition and structure. Morphotype A is dominated by fusiform Discocyclina tests, which were preferentially selected by the trace makers for construction of a well-constructed and resistant wall. Morphotype B contains more robust tests of Nummulites, while morphotype C is dominated by saddle-shaped tests of Discocyclina. Nummipera eocenica was produced during a period of seafloor stabilization caused by a deepening. The succession of the morphotypes B, A reflects diminishing energy and increasing water depth. Probably morphotype C represents even lower energy environment than morphotype A. The trace fossil is interpreted as a domichnion, which wall was constructed for protection. The trace maker can be considered between polychaetes and crustaceans; however, comparisons to the closest recent analogues, the polychaete Diopatra cuprea or alpheid shrimps, are not satisfactory. □Bartonian, burrow, Carpathians, large foraminifera, trace fossils.

Maastrichtian facies succession and sea-level history of the Hossein-Abad, Neyriz area, Zagros Basin

The Maastrichtian shallow-water carbonate platform (Tarbur Formation) is described from outcrop in southwest Iran. It is characterised by eight microfacies types, which are dominated by larger foraminifera, rudist debris and dasycladacean algae. They are grouped into four distinct depositional settings: tidal flat, lagoon, barrier and open marine. The depositional settings include stromatolitic boundstone of tidal flat, peloidal dasycladacean miliolids wackestone and peloid bioclastic imperforate foraminifera wackestone of restricted lagoon, Omphalocyclus miliolids bioclast packstone–grainstone and miliolids intraclast bioclast packstone–grainstone of open lagoon, rudist bioclast grainstone of inner-platform shoals and rudist bioclast floatstone–rudstone and bioclastic wackestone of open-marine environments. The facies and faunal characters are typical of a ramp-like open shelf. The lack of reef-constructing organisms resulted in a gently dipping ramp morphology for the margin and slope. On the basis of facies analysis, three depositional sequences (third order) are defined.

New Paleocene large cassiduline foraminifera (Cassidinidae fam. nov., Miscellanacea) from Egypt and its phylogeny

Larger foraminifera of the Late Paleocene–Early Eocene lower slope to toe-of-slope deposits of the southern Galala, Egypt, are described. Sulcocassidina nakkadyi n. gen. et sp. (base) and Vacuolicassidella dakhlensis n. gen. et sp. (top) represent a phylogenetic line related to the family Cassidinidae (new family), superfamily Miscellanacea (new superfamily) in the latest Paleocene (shallow benthic zone 4) of the southern Galala, Egypt. In addition, Oscucassidella cassis n. gen. et sp., Pellatispiroides youssefi n. gen. et sp. and Chordcassidella ainshamsiana n. gen. et sp. are described and illustrated. Genus: Pomerolina n. gen. (Type species: Alveolina meandrina Carter, 1861, is newly erected and it belongs to Cassidinidae. In this family, the chambers are initially arranged streptospirally, whereas in later stages they are planispirally enrolled. Lateral chamberlets (retral process) are separated from the laminae by a passage and a marginal crest is added during growth.

Gradients and patterns of sclerobionts on experimentally deployed bivalve shells: Synopsis of bathymetric and temporal trends on a decadal time scale

Bivalve shells deployed experimentally in a variety of environments of deposition (EODs) and over a wide range of depths from 15 to 570 m in the Bahamas and Gulf of Mexico were assessed for encrusting and endolithic bionts (sclerobionts sensu Taylor and Wilson, 2002) that accumulated over 1-, 2-, 8- and 12/13-year intervals. Data include percent coverage and, when possible, identification to generic- or species-level taxonomic categories. Data were binned into two further categories based on guilds and whether or not sclerobionts were judged to be preservable. Each study site shows substantial variability in both percent coverage and species richness/composition, which we attribute to partial burial of different individuals or parts of arrays. Average values of taxonomic richness, guild number, and percent coverage, for a given EOD represent a combination of exposed and buried shells as would be typical of a time-averaged fossil assemblage; maximally covered shells give the potential coverage for each site. In both study areas there are characteristic patterns in terms of overall percentage of shells covered by sclerobionts, numbers and extent of coverage by different guilds as well as by different taxa. For most EODs, there is a progressive, though non-linear increase in both species richness and areal coverage through the twelve years; exceptions are in the 30 m site in the Bahamas, and Parker Bank and Flower Garden sites in the Gulf of Mexico, which show a significant decline in areal coverage (though not in richness). This effect may result from differences in sediment cover over time. These sites showed a tendency to have many or all experimental bags completely sediment covered in the later sampling. Cluster analysis and non-metric multidimensional scaling (NMDS) of various shell substrate species at all EODs from the Bahamas and Gulf of Mexico reveal discrete groupings that are related to both depth (light?) gradient and other factors, such as variations in sedimentation and salinity. Similar numbers of guilds are found at various EODs although the specific guild types represented differ. In general, highest average richness values are recorded for carbonate 70–90 m wall and deep reef sites (69 to 70 taxa) and lowest are for the EFG brine pool (no sclerobionts other than bacterial films after 12/13 years) and deeper dysphotic to subphotic sites (max values: 25 taxa); surprisingly, shallow water sites (< 30 m) yield only moderate diversities of 40–50 taxa. This results in part from the fact that certain encrusters, especially the foraminifer Gypsina and coralline algae tend to overgrow others and dominate space, in addition to burial effects. Certain taxa (notably the serpulid Pseudovermilia) are ubiquitous, while other taxa (e.g. larger foraminifera, vermetid gastropods and many bryozoans) are largely restricted to shallower depths. A combination of species richness, average coverage and key taxa permits discrimination of groups of EODs and potentially, in tandem with other evidence, of depth gradients.

Basin architecture and growth folding of the NW Zagros early foreland basin during the Late Cretaceous and early Tertiary

Abstract: We present and use the chronostratigraphy of 13 field logs and detailed mapping to constrain the evolution of the early Zagros foreland basin, in NW Iran. Large foraminifera, calcareous nannofossil, palynological and 87 Sr/ 86 Sr analysis supplied ages indicating a Campanian–early Eocene age of the basin infill, which is characterizd by a diachronous, southwestward migrating, shallowing upwards, mixed clastic–carbonate succession. Growth synclines and local palaeoslope variations indicate syndepositional folding from Maastrichtian to Eocene time and suggest forelandward migration of the deformation front. We also illustrate the basin architecture with a synthetic stratigraphic transect. From internal to external areas, time lines cross the formation boundaries from continental Kashkan red beds to Taleh Zang mixed clastic–carbonate platforms, Amiran slope deposits and basinal Gurpi–Pabdeh shales and marls. The foreland basin depocentres show a progressive migration from the Campanian to Eocene ( c . 83–52.7 Ma), with rates of c . 2.4 mm a −1 during the early–middle Palaeocene ( c . 65.5–58.7 Ma) increasing to c . 6 mm a −1 during the late Palaeocene–earliest Eocene ( c . 58.7–52.8 Ma). Coeval subsidence remained at c . 0.27 mm a −1 during the first 12.7 Ma and decreased to c . 0.16 mm a −1 during the last 4.2 Ma of basin filling. Finally, we integrate our results with published large-scale maps and discuss their implications in the context of the Zagros orogeny. Supplementary material: Tables with dating results are available at http://www.geolsoc.org.uk/SUP18439 .

Lithofacies Attributes of a Transgressive Carbonate System : The Middle Eocence Seeb Formation, Al Khoud Area, Muscat, Oman

The Seeb Formation (Middle Eocene) is an about 600 m thick transgressive carbonate succession deposited in the Batina and Muscat coastal region of Oman. The formation consists of five informal, but distinct units, and their stacking architecture suggests a deepening-upward, shallow marine depositional setting. Unit I is characterized by cross-bedded, sandy, bioclastic packstones to grainstones deposited in a high energy beach-to-intertidal environment. Unit II consists of indistinctly bedded, nodular, bioclastic (mainly larger foraminifera) packstones and wackestones deposited in a logoonal lagoonal environment. Unit III is defined by medium to thickly bedded, bioclastic packestones to grainstones and subordinate, laterally confined conglomerates. Prominent sedimentary structures in Unit III include hummocky and swaly cross-stratificiation, erosional surfaces, dewatering-induced deformations and laterally amalgamating beds. This unit represents sub-tidal sand shoals deposited in a storm-dominated shelf (between the fair-weather wave-base and storm-base). Unit IV is extensively burrowed, nodular, bioclastic wackestone to rudstone which is similar to Unit II in many aspects. Unit IV was deposited on the basinward side of the Unit III sand shoals below the reach of the storm-generated waves and currents. The uppermost Unit V is characterized by poorly-cemented bioclastic (large foraminiferal) rudstones with clay and silt-size quartz matrix. Bioclasts are generally intact with no apparent reworking. Deposition of Unit V is also envisaged as a low-energy, outershelf environment.

Automicrite in a ‘nummulite bank’ from the Monte Saraceno (Southern Italy): evidence for synsedimentary cementation

AbstractFollowing introduction of the term ‘nummulite bank’, there has been debate regarding interpretation of these types of deposits as autochthonous (automicrite) or allochthonous (detrital micrite). These banks are made up of large foraminifera and ill‐defined fine‐grained components. The fine‐grained components consist mainly of micrites. The recognition of automicrite has deep implications for the synsedimentary cementation and stabilization of the bank. In order to distinguish between automicrite and detrital micrite, the nanomorphology, geochemistry and organic matter remains in the microfacies of a nummulite bank in the Middle Eocene of Monte Saraceno (Gargano, Southern Italy) were analysed. Optical and scanning electron microscope investigations showed that the micrites have been recrystallized to aggrading microsparite. Epifluorescence observations on selected micrite/microsparite areas with peloidal texture revealed the presence of organic matter. Scanning electron microscope analyses on epifluorescent micrites showed that the microbial peloids have smaller crystal sizes than those in organic matter‐depleted areas. The geochemical characterization of extracted organic matter, performed through the functional group analyses by Fourier transform‐infrared spectroscopy, shows strong prevalence of the aromatic fraction over the aliphatic and carboxylic ones. These characteristics of organic compounds indicate both their thermal maturation and their likely derivation from degradation of bacterial communities. The local presence of peloidal anti‐gravity textures, bright epifluorescence and organic molecules in clotted peloidal areas suggest that the metabolic activity of microbial communities could have induced precipitation of these micrites and, consequently, the syndepositional cementation of the nummulite bank. This type of cementation can rapidly stabilize sediments and promote the depositional bank geometry.

Los Andes Fueguinos: el registro micropaleontologico de los mayores acontecimientos paleooceanograficos australes del Campaniano al Mioceno.

The succession of microfossil assemblages in the almost complete marine Late Cretaceous-Miocene stratigraphic column found in the Fuegian Andes, the orogenic margin of the Austral Basin, reveals a close relationship with the local tectonic events, the Atlantic transgressions-regressions on the Patagonian Platform, and the most relevant paleoceanographic global events. The Fuegian upper Campanian-lower Eocene sequence, dominated by flysch-type assemblages of agglutinated foraminifers and poorly oxygenated waters of fairly limited depth, is coherent with silled basins in a recently proposed cortical stretching period. The Maastrichtian (Policarpo Formation) has a cosmopolitan agglutinated foraminiferal assemblage contrasting with the coeval austral endemic calcareous assemblages of Patagonia. In the Paleocene/Eocene transition the assemblages of calcareous microfossils, of restricted distribution, exhibit the greatest Cenozoic turnover from a cosmopolitan Midway-type assemblage (La Barca Formation) to a strongly endemic Early Eocene assemblage (Punta Noguera Formation), with the oldest records of the Fuegian-Patagonian Cenozoic most typical genera. The Early Paleogene has no record of philothermic taxa such as larger foraminifera or morozovelids planktonic foraminifera, and only a short-lived bryozoan limestone (Rio Bueno Formation) and the low percentage of the ostracod family Hemicytheridae insinuated a warm period. The upper middle-uppermost Eocene sequence (La Despedida Group) starts with a transgression recorded in the Austral Basin (Leticia, Man Aike, Rio Turbio formations and Boltovskoyella beds), and in the Colorado Basin. This transgression is coeval with a temperature peak of 42 Ma, bringing a Fuegian retrograde fauna and a foraminiferal assemblage with large-sized nodosarids, which were replaced throughout the Late Eocene (Cerro Colorado Formation) by typical Antarctic genera that reflect the falling global temperature, culminating in the Tenuitella insolita Zone with abundant Chiloguembelina, a local effect of the global environmental fluctuations. The Eocene/Oligocene boundary and the Oi-1 seem to be represented by an unconformity and/or the Tchat Chii Conglomerate. In the earliest Oligocene (Maria Cristina beds) foredeep environments below the LCC and deep water foraminifer indicators appear, contrasting with coeval global high δ18O values and a Late Eocene-Early Oligocene withdrawal in the Patagonian Platform, which suggest that the coeval deepening recorded in the Fuegian Andes is due only to tectonic causes that facilitated the incursion of Antarctic waters into the basin. The latest Oligocene-Early Miocene global warm anomaly corresponds to a constriction period of the Drake Passage; in the Fuegian Andes lysocline conditions dominate, and a generalized transgression occurs including an Antarctic corrosive water current, which penetrates in the Patagonian Platform; on both regions, there are minor discontinuities coincident with the Mi-1, and an extended unconformity is found prior to the mid Miocene transgressive pulse coeval with the Neogene optimum.

Components, facies and ramps: Redefining Upper Oligocene shallow water carbonates using coralline red algae and larger foraminifera (Venetian area, northeast Italy)

Chattian mixed carbonate-siliciclastic deposits from two palaeogeographic units of Southern Alps, the Lessini Shelf and Venetian foreland basin of northeast Italy, are studied with respect to facies distributions and controlling ecological factors on dominant biogenic components. These ramp depositional systems are located in the western Southern Alps on the Lessini Shelf, and in the eastern Southern Alps in the Venetian foreland basin. The successions show an extensive geographic distribution of at least 150 km × 40 km at the southern margin of the Southern Alps. Palaeoenvironments are inferred following microfacies characteristics and floral and faunal indicators, especially those of coralline red algae and larger foraminifera. An inner- to middle homoclinal ramp morphology is reconstructed based on facies distributions and taxonomic and coralline algal growth-form proxy data. The distribution along depositional strike shows variation from thinner, carbonate dominated sequence in the west (Monti Berici and Monti Lessini) to a more variable, mixed carbonate-siliciclastic dominated environment to the east (Vittorio Veneto, Alpago). Facies character and occurrence are controlled by local hydrodynamic conditions and varying water turbidity of the studied ramp depositional system. The general facies succession shows a transgressive sequence from the proximal inner- to proximal middle ramp. A shoal belt of trough cross-bedded sandstones occurs in a proximal inner ramp position in all of the studied areas. In a gentle-dipping homoclinal ramp, most benthic organisms inhabited the relatively quite environments off these shoals in a distal inner ramp setting. Basinward environments (proximal middle ramp) constitute areas of maximal carbonate production and consist primarily of larger foraminiferal facies and rhodolith pavements. Larger foraminifera, represented by two larger foraminiferal assemblages, are most diversified in the shallower settings (near the fair-weather wave base, distal inner/proximal middle ramp), whereas coralline algae predominate in deeper areas (proximal middle ramp) constructing extensive rhodolith pavements. Rhodolith pavements are distinguished with respect to rhodolith shape, size, growth-forms and coralline algal taxonomic composition. Larger foraminifera are interpreted with respect to shell structures, shell architectures and comparable Recent counterparts. The analysed benthic communities thrived in a mesotrophic regime within trophic gradients constrained by fluvial influence. Coralline algal dominance and a moderately diverse larger foraminiferal assemblage suggest a tropical/warm temperate transition. The considerable stability imposed on sediments by the rhodolith pavement must also have significantly contributed to the maintenance of a middle ramp profile bulge. This study will contribute to a better understanding of Oligocene carbonates which have received less attention than their Eocene or Miocene counterparts.

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.

The maximum age of Hawaiian terrestrial lineages: geological constraints from Kōko Seamount

AbstractAim To determine if Kōko Seamount submerged below sea level before Kure Island and Pearl and Hermes Reef formed, resulting in a period in which there were no extant islands. A period with no islands would eliminate prior terrestrial and shallow marine biotas that could migrate from island to island and require a restart of colonization from distant shores to populate the younger islands of the Hawaiian volcanic chain.Location Emperor Seamount Chain, north‐central Pacific Ocean.Methods We estimate subsidence rates for Kōko Seamount using ages determined from fossil large foraminifera and Sr‐isotopes, and maximum depths using palaeodepth estimates based on coralline algae. These data are combined with palaeolatitude changes as the Pacific Plate moved northwards, sea level variations, and sea surface temperature variations at the seamount through time to reconstruct the time and causes of submergence.Results Rounded carbonate clasts include three facies: zooxanthelate corals, bioclastic packstones to rudstones, and rhodolith floatstones. Two rudstones contain relatively deep‐water, coralline algal rhodoliths and large foraminifera indicative of Aquitanian (20.4–20 Ma) and Burdigalian (20–16 Ma) stages of the Early Miocene, consistent with Sr‐isotope ages of algae and one sample of large foraminifera. Corals grew on Kōko Seamount from c. 50 to 27.1 ± 0.4 Ma, the youngest Sr‐isotope age of a coral sample. These shallow, warm‐water coral reefs came under increasing stress as the volcano subsided at 0.012 ± 0.003 mm yr−1, and migrated northwards, and as global climate cooled. The summit submerged and shallow coral reef growth ceased before 29 Ma, probably around 33 Ma. The volcano continued its slow subsidence, and deep‐water carbonates accumulated until they too were unable to keep pace, dying out at c. 16 Ma.Main conclusions The final submergence of the summit of Kōko Seamount by about 33 Ma confirms that biota on older Hawaiian–Emperor Islands could not have migrated from island to island along the entire chain to eventually colonize the present Hawaiian Islands. There was a period between at least 33 and 29 Ma in which no islands existed, and distant colonization had to repopulate the younger portion of the Hawaiian chain, which began to emerge between about 29 and 23 Ma.

Symbiosis drove cellular evolution

Anthropocentric cultural bias led to conceptualizations of evolution as a tree with branches leading to a crown of vertebrates and higher plants. Gradually refined over the years it became part of common scientific culture to think of eukaryotic evolution as process by which cells, limited by surface to volume ratios and other factors, became specialized, leading to multi-cellularity and eventually to the crowned tree. Knowledge of other pathways of cellular evolution is available, but not broadly recognized. Molecular systematics, genetic analyses and ultrastructural comparisons have changed our outlook on evolution and the diversity of life. The discovery of a huge (average size 2.1 cm) unicellular, new, exceptionally complex, dinoflagellate-hosting soritid foraminiferan from the Heron-Wistori Channel, (GBR Australia) gave impetus to re-explore some old ideas on cellular evolution and place them in a contemporary context. In particular, it caused change in perspective of the evolution of the collective group known as larger foraminifera (LF). They exemplify the power by which symbiosis drove the evolution of a predisposed and malleable group of organisms. The factors that underlay foraminiferan predisposition to symbioses with algae are discussed. Each of the evolutionary lines of LF has developed, in its own way, amazing structural adaptations making them extremely complex giant cells.

Mineralogical characteristics and mineral economics of Sanu and Gotan SMS grade limestone deposits of Rajasthan

Two large, chemically similar, SMS grade limestone deposits occur in Sanu area of Jaisalmer and Gotan area of Nagaur, Rajasthan. The Sanu deposit belongs to Khuiala Formation of Tertiary sequence of lower Eocene age, while Gotan deposit belongs to Bilara Group of Marwar Supergroup of late Neoproterozoic to early Cambrian. These deposits are being developed and utilised as flux in the steel plants of India. The Sanu limestone of Jaisalmer is more suitable compared to Gotan and other limestone deposits of the country due to its superior and favourable physical properties. Mineralogically, it consists of fine-grained, sub-rounded to rounded grains of calcite mainly replacing tests of the larger foraminifera. While, the Gotan limestone is composed of fine to coarse-grained, angular to sub-rounded grains of calcite. In Sanu area, about 54% of the limestone produced is being generated as −30 mm grit during the process of sizing for SMS grade. This lower size of limestone is suitable for making cement but due to non-avaibility of rail transport facility from Sanu to Jaisalmer for a distance of about 60 km, it remains unutilised as mineral reject.