Porcelaneous Foraminifers Research Articles

A new species of the larger porcelaneous foraminifer Borelis provides novel insights into Neogene to Recent western Pacific palaeobiogeographical dispersal patterns

Only three species of alveolinoidean larger foraminifera occur in present-day tropical shallow-water marine settings. Alveolinella quoyi thrives in the Central Indo-Pacific and Eastern Indo-Pacific, Borelis pulchra in the Central and Eastern Indo-Pacific and in the central Atlantic, whereas Borelis schlumbergeri inhabits the Indo-Pacific Ocean. The northernmost record is that of Alveolinella quoyi from the shallow-water settings in Okinawa (central Ryukyu Islands, Japan). A new porcelaneous larger foraminiferal species, Borelis matsudai sp. nov. (Alveolinoidea, Borelinae), is established herein, based on specimens discovered in present-day shallow-water sediments from Sekisei Lagoon, southern Ryukyu Islands (Japan). This is the northernmost record of the genus in the western Indo-Pacific Warm Pool. The architectural characters of this species suggest its phylogenetic relationship with the Borelis pulchra group. A comprehensive literature survey of fossil and modern records of Borelis pulchra over the past 30 million years shows that the Middle Miocene constriction of the Indonesian Seaway and the Late Miocene–Early Pliocene restriction of the Indonesian Throughflow impacted the species-level dispersal of this species in the Indo-Australian Archipelago. Driven by the Kuroshio dispersal route Borelis matsudai sp. nov. likely appeared in the southern and central Ryukyu Islands at least from the Chibanian (Middle Pleistocene). This species represents a marginal part of a population in significant contact with its ancestor (B. pulchra), which is widespread southward since the Oligocene (Philippines). With ongoing global warming possible occurrences of Borelis matsudai sp. nov. in the northern Ryukyu Islands, where it has not yet been found, are expected. The Sekisei Lagoon represents, therefore, a biogeographical stepping stone relay station in northward migration of the shallow-water benthic organisms along the Kuroshio dispersal route.

Recognition of upper Triassic temperate foraminiferal assemblages: Insights from the Khodz Group (NW Caucasus, Russia)

A more than 300 m thick succession of thick-bedded pink to grey limestone of the Norian – Rhaetian Khodz Group in the NW Caucasus serves to document the development of a temperate carbonate ramp during the final stages of the Cimmerian orogeny. Limestone samples were collected on the west side of Mt. Kolokolnia. The lower part of the Khodz Group contains bioclastic packstone microfacies composed largely of heterotrophic organisms: bryozoans, brachiopods, echinoderms, bivalves, small benthic foraminifers, juvenile ammonoids, agglutinated worm tubes, gastropods, ostracods and sponges. The upper part is comprised of layers of wackestone with frequent evidences of short episodes of emersion. Sponge spicules locally predominate; very few coral fragments also occur. Foraminiferal assemblages of the Khodz Group contain a high proportion of involutinids, including Licispirella violae (Blau), L. iranica (Senowbari-Daryan, Rashidi & Torabi), Coronaserra deminuta (Blau), Coronipora sp., ?Kristantollmanna bicarinata (Blau), Frentzenella perforata Rigaud, Blau, Martini & Rettori, ?Involutina turgida Kristan, ?Trocholina turris Frentzen, and T. ex gr. intermedia/umbo Frentzen, together with porcelaneous foraminifers such as Galeanella tollmanni (Kristan), and Decapoalina schaeferae (Zaninetti, Altiner, Dager & Ducret), which are typical reef dwellers in tropical platforms. Such faunal and foraminiferal association points to a shallow (photic zone) marine depositional environment. Trocholinids are among the most successful survivors of the end-Triassic crisis. The rich occurrence of diversified trocholinids in temperate Triassic seas at high latitudes within the western Eastern Laurasia palaeobiogeographic province suggests that: 1) temperate areas may have played an important role as refugia for marine life during this major biotic event, and 2) the importance of ocean acidification in the selective extinction of marine organisms is overestimated.

Palaeoenvironmental changes in the Khuran Estuary of SE coastal Iran during the last two millennia, based on the analysis of a sediment core

Late Holocene palaeoenvironments of the northern Strait of Hormoz and the palaeohydrology of the SE Zagros were reconstructed using multi-proxy analysis (e.g. magnetic susceptibility (MS), grain size analysis, total organic matter %, CaCO3%, C/N ratio, and foraminiferal assemblage) of a radiocarbon-dated sediment core (KHU) from the Khuran Estuary. High sedimentation rate (1.23 cm yr−1) and elevated grain size, MS, C/N ratio, as well as the abundance of porcelaneous foraminifers (Quinqueloculina sp.), revealed that during the first three centuries CE, sediments settled in a relatively high accommodation space with strong tidal currents and raised terrigenous sediment input from the SE Zagros. About four centuries later, the gradual disappearance of porcelaneous taxa and the dominance of agglutinated and hyaline ones, besides the increasing C/N ratio, indicated that geomorphological conditions became favourable for mangroves. MS reduction and negative correlation between MS and grain size showed that during this period the relative proportion of terrigenous particles in sediment decreased which, in turn, confirms a reduction of river discharge. Afterwards, the abundance of mud aggregates, low C/N ratio and a dramatic reduction of foraminifers showed that a < 1 m thick sediment unit representing a relatively long period (1.4 cal kyr BP onwards; sedimentation rate: 0.06 cm yr−1) was deposited within a high marsh environment being mostly above mean high water. Generally, correlations between proxy records of the core KHU with Zagros lakes and other archives from African lakes and Greenland re-inforce the reconstruction of atmospheric teleconnection between the North Atlantic and the interior of West Asia during the late Holocene.

Tarburina zagrosianan. gen., n. sp., a new larger benthic porcelaneous foraminifer from the late Maastrichtian of Iran

A new larger benthic porcelaneous foraminifer of soritid affinity is described as Tarburina zagrosiana n. gen., n. sp. from the late Maastrichtian of the Tarbur Formation, Zagros Zone, SW Iran. It occurs in foraminiferal–dasycladalean wackestones and packstones, in association with Loftusia ssp., dicyclinids/cuneolinids, Neobalkhania bignoti Cherchi & Schroeder, Gyroconulina columellifera Schroeder & Darmoian, Spirolina ? farsiana Schlagintweit & Rashidi, Broeckina cf. dufrenoyi (d9Archiac), other benthic foraminifers, and dasycladalean algae. Due to its elongate test and marginal chamber subdivision by aligned vertical partitions, Tarburina n. gen. can be compared with representatives of the Praerhapydionininae. The interio-marginal slit-like foramina/aperture of Tarburina represents an outstanding feature in complex porcelaneous taxa. The monospecific genus Tarburina is considered a Maastrichtian newcomer within the Late Cretaceous Global Community Maturation cycle of larger benthic foraminifera. A biostratigraphic and palaeobiogeographical restriction seems possible, as reported for many other Late Cretaceous larger benthic foraminifera.

AGGLUTINATED OR PORCELANEOUS TESTS: WHERE TO DRAW THE LINE?

The simple, tubular foraminifer Glutameandrata vallieri n. gen., n. sp. is formally described from Spring Creek, one of the most fossiliferous Late Triassic localities of North America (Martin Bridge Formation, Wallowa terrane, Oregon, USA). Uncoiled in the final stage, this new benthic form displays an initial meandrospiroid arrangement, a coiling mode typically observed in coeval porcelaneous foraminifers. Yet, we demonstrate through a comparative study of diagenetic results that the wall of G. vallieri n. gen., n. sp. is, in fact, finely agglutinated. Agglutinated meandrospiroid foraminifers, here encompassed by the family Glutameandratidae n. fam., are sporadically but continuously observed in Triassic-Recent rocks. Their potential phylogenetic relationships and their significance to define the relative taxonomic importance of wall characteristics versus coiling mode are discussed. For over a century, optical differences in the wall appearance of agglutinated and porcelaneous foraminifers have been used for taxonomic distinction, with moderate success in the fossil record. Parameters and processes controlling these optical differences remain partly unclear and the exact boundary between these two types of walls is still indefinite. Calcite-cemented calc-agglutinated tests and porcelaneous agglutinating tests only differ in fine details of the microstructure and composition of the wall, related to differences in the wall morphogenesis. With diagenesis, these details are progressively obliterated, often hindering correct taxonomic assignments. We here provide criteria allowing the distinction between porcelaneous and calcareous agglutinated tests in the fossil, up to a high level of thermal maturation. The walls of porcelaneous and agglutinated foraminifers are not equally affected by diagenetic effects and subtle structural differences in the wall outline persist up to a significant level of test alteration.

Rajkanella hottingerinaformis n. gen., n. sp., a new larger benthic foraminifer from the middle-upper Cenomanian of Kosovo

A new larger benthic porcelaneous foraminifer of soritid affinity is described as Rajkanella hottingerinaformis n. gen., n. sp. from the middle-upper Cenomanian of Kosovo. It occurs in foraminiferal packstones and grainstones, in association with cuneolinids, rhapidionids, chrysalidinids, and other benthic foraminifers. Due to its general morphology and superficial chamber subdivision by exoskeletal elements, Rajkanella n. gen. can be compared with the early Paleogene genus Hottingerina Drobne, 1975, from which it mainly differs in its apertural features, ornamented test, and coiled adult stage. Further differences to coeval Pseudorhapydionina De Castro, 1971, Pseudorhipidionina De Castro, 1971, and to other comparable genera, are discussed. The discovery of Rajkanella hottingerinaformis in the middle-upper Cenomanian is a further witness of the significant radiation and blooming of increasingly complex porcelaneous foraminifers in inner platform, shallow-water depositional settings during that period.

Broeckina gassoensis sp. nov., a larger foraminiferal index fossil for the middle Coniacian shallow-water deposits of the Pyrenean Basin (NE Spain)

The Upper Cretaceous shallow-water carbonates of the Pyrenean Basin (NE Spain) host rich and diverse larger foraminiferal associations which witness the recovery of this group of protozoans after the dramatic extinction of the Cenomanian–Turonian boundary interval. In this paper a new, large discoidal porcelaneous foraminifer, Broeckina gassoensis sp. nov., is described from the middle Coniacian shallow-water deposits of the Collada Gassó Formation, in the Bóixols Thrust Sheet. This is the first complex porcelaneous larger foraminifer of the Late Cretaceous global community maturation cycle recorded in the Pyrenean bioprovince. It differs from the late Santonian–early Campanian B. dufrenoyi for its smaller size in A and B generations and the less developed endoskeleton, which shows short septula. Broeckina gassoensis sp. nov. has been widely employed as a stratigraphic marker in the regional geological literature, under the name of “Broeckina”, but its age was so far controversial. Its middle Coniacian age (lowermost part of the Peroniceras tridorsatum ammonite zone), established in this paper by strontium isotope stratigraphy, indicates that it took about 5 My after the Cenomanian–Turonian boundary crisis to re-evolve the complex test architecture of larger foraminifera, which is functional to their relation with photosymbiotic algae and K-strategy.

Reduced seasonality of Holocene climate and pervasive mixing of Holocene marine section: Northeastern Gulf of Mexico shelf

The large porcelaneous foraminifers Cyclorbiculina compressa, Parasorites orbitolitoides , and Peneroplis proteus are conspicuous in death assemblages from Holocene marine sediments of the Alabama and Florida panhandle shelf. The species inhabited the northeastern Gulf of Mexico in the Holocene (ca. 6.4–1.9 ka) but do not live in the region today. These foraminifers require warm, clear waters, and thus are important paleoclimatic and paleoenvironmental indicators. They apparently were derived from sublittoral seagrass habitats and indicate reduced seasonality in the region during the middle to late Holocene. In addition, a mixed foraminiferal fauna, a hydrodynamically reworked macrofaunal assemblage, and stratigraphic disorder in foraminiferal 14 C dates indicate extensive reworking of the entire Holocene marine transgressive package. Evidence that mollusks are indigenous but large foraminifers are transported supports the generalization that out-of-habitat transport of macrofauna is negligible in most marine settings.