Contrasting vertical distributions of recent planktic foraminifera off Indonesia during the southeast monsoon: implications for paleoceanographic reconstructions

Planktic foraminifera are widely used in palaeoceanographic and paleoclimatic studies. The accuracy of such reconstructions depends on our understanding of the organisms’ ecology. Here we report on field observations of planktic foraminiferal abundances (>150 µm) from 5 depth intervals between 0–500 m water depth at 37 sites in the eastern tropical Indian Ocean. The total planktic foraminiferal assemblage comprises 29 morphospecies; with 11 morphospecies accounting for ~90 % of the total assemblage. Both species composition and dominance in the net samples are broadly consistent with the published data from the corresponding surface sediments. The abundance and vertical distribution of planktic foraminifera are low offshore west Sumatra, and increase towards offshore south Java and the Lesser Sunda Islands (LSI). Average living depth of Trilobatus trilobus, Globigerinoides ruber, and Globigerina bulloides increases eastward, while that of Neogloboquadrina dutertrei, Pulleniatina obliquiloculata, and Globorotalia menardii remains constant. We interpret the overall zonal and vertical distribution patterns in planktic foraminiferal abundances as a response to the contrasting upper water column conditions during the southeast monsoon, i.e., oligotrophic and stratified offshore Sumatra (non-upwelling) vs. eutrophic and well-mixed offshore Java-LSI (upwelling). Overall, the inferred habitat depths of selected planktic foraminifera species show a good agreement with those from sediment trap samples and from surface sedimentss off Sumatra, but not with those from surface sediments off Java-LSI. The discrepancy might stem from the different temporal coverage of these sample types. Our findings highlight the need to consider how foraminiferal assemblages and ecology vary on shorter timescales, i.e., from “snapshots” of the water column captured by plankton net to seasonal and interannual variability as recorded in sediment traps and how these changes are transferred and preserved in deep-sea sediments.

Sedimentological and paleontological analysis of the Lower Jurassic part of the Zatrnik Formation on the Pokljuka plateau, Slovenia

The uppermost Ladinian to Lower Jurassic Zatrnik Formation is the lithostratigraphic unit of the Mesozoic deeper marine Bled Basin. The uppermost part of the Zatrnik Formation and the transition into the overlying Ribnica Breccia was logged at the Zajamniki mountain pasture on the Pokljuka mountain plateau in the Julian Alps. The lowermost part the section belongs to the “classical” Zatrnik Formation and is dominated by beige micritic limestone and fine-grained calcarenite. Foraminifers Siphovalvulina, ?Everticyclammina, ?Mesoendothyra and ?Pseudopfenderina are present, indicating Early Jurassic age. The beige limestone is followed by light pink limestone of the uppermost Zatrnik Formation. Slumps are common in this interval, and crinoids are abundant. Alongside some species already present in beds lower in the succession, Meandrovoluta asiagoensis Fugagnoli & Rettori, Trocholina sp., Valvulinidae, small Textulariidae, Lagenida, and small ?Ophthalmidium alsooccur in this interval. Resedimented limestone predominates through the studied part of the Zatrnik Formation, indicating deposition on the slope or at the foot of the slope of the basin. The switch to crinoid-rich facies within the slumped interval of the Zatrnik Formation may reflect accelerated subsidence of the margins of the Julian Carbonate Platform in the Pliensbachian. The Zatrnik Formation is followed by the formation of the Pliensbachian (?) Ribnica Breccia. Impregnations of ferromanganese oxides, violet colour, and an increase in clay content are characteristic. The foraminiferal assemblage consists of Lenticulina, small elongated Lagenida, and epistominids. Individual beds of the Ribnica Breccia were deposited via debris flows. Enrichments in ferromanganese oxides point to slower sedimentation.

Living and dead foraminiferal assemblage from the supratidal sand Japsand, North Frisian Wadden Sea: distributional patterns and controlling factors

Supratidal sands are vitally important for coastal defence in the German Wadden Sea. They are less affected by human activities than other areas as they are located far off the mainland shore, touristical and commercial activities are generally prohibited. Therefore, supratidal sands are of high ecological interest. Nevertheless, the faunal inventory and distribution pattern of microorganisms on these sands were studied very little. The composition of living and dead foraminiferal assemblages was therefore investigated along a transect from the supratidal sand Japsand up to Hallig Hooge. Both assemblages were dominated by calcareous foraminifera of which Ammonia batava was the most abundant species. Elphidium selseyense and Elphidium williamsoni were also common in the living assemblage, but Elphidium williamsoni was comparably rare in the dead assemblage. The high proportions of Ammonia batava and Elphidium selseyense in the living assemblage arose from the reproduction season that differed between species. While Ammonia batava and Elphidium selseyense just finished their reproductive cycles, Elphidium williamsoni was just about to start. This was also confirmed by the size distribution patterns of the different species. The dead assemblage revealed 20 species that were not found in the living assemblage of which some were reworked from older sediments (e.g., Bucella frigida) and some were transported via tidal currents from other areas in the North Sea (e.g., Jadammina macrescens). The living foraminiferal faunas depicted close linkages between the open North Sea and the mainland. Key species revealing exchange between distant populations were Haynesina germanica, Ammonia batava and different Elphidium species. All these species share an opportunistic behaviour and are able to inhabit a variety of different environments; hence, they well may cope with changing environmental conditions. The benthic foraminiferal association from Japsand revealed that transport mechanisms via tides and currents play a major ecological role and strongly influence the faunal composition at this site.

Mid-Late Holocene Paleoenvironmental and Sea Level Reconstruction on the Al Lith Red Sea Coast, Saudi Arabia

Late Quaternary paleoenvironments are of particular interest to understand how the Earth System’s climate will respond to the undramatic changes during this period, compared with the broader glacial-interglacial variations. In this study, a shallow sediment core (2.84 m long) retrieved from the Red Sea coastal zone in northern Ghubbat al Mahasin, south of Al-Lith, Saudi Arabia, is used to reconstruct the mid-Late Holocene paleoenvironments and sea level based on a multiproxy approach. Remote sensing data, sedimentary facies, benthic foraminiferal assemblages, δ18O and δ13C stable isotopes, elemental composition and 14C dating were utilized. The stratigraphy of the core shows three distinctive depositional units. The basal pre 6000 year BP unit consists of unfossiliferous fine to medium sand sharply overlain by black carbonaceous mud and peat, suggesting deposition in a coastal/flood plain under a warm and humid climate. The middle unit (6000-3700 year BP) records the start and end of the marine transgression in this area. It consists of gray argillaceous sand containing bivalve and gastropod shell fragments and a benthic foraminiferal assemblage attesting a lagoonal or quiet shallow marine environment. The upper unit (<3700 year BP) consists of unfossiliferous yellowish-brown argillaceous fine-grained sands deposited on an intertidal flat. Both middle-and upper-units stack in a regressive shallowing upward pattern although they may be separated by a hiatus. The overall regressive facies and the stable isotopic data are consistent with a late Holocene sea-level fall and a change to a more arid climate.

The foraminiferal record in the Holocene evolution of the Mecklenburg Bay (south-western Baltic Sea)

Foraminiferal assemblages were analyzed in a 620-cm long core retrieved from the central part of the Mecklenburg Bay (MB, south-western Baltic Sea) to aid in the reconstruction of environmental changes occurring in the area during the Holocene and to complement a set of previously investigated palaeoenvironmental proxies. A total of five foraminifera-based stratigraphic units were identified, including an initial 80-cm thick layer devoid of foraminifera. The next two units featured an increasing abundance of the foraminiferal assemblage dominated by the calcareous Ammonia group species. Nearly all the calcareous foraminifera found in the core were decalcified. Following the maximum abundance within the 470–410 cm layer, the foraminiferal abundance declined sharply and the assemblage’s dominance structure changed to domination of the agglutinated foraminiferal species, Eggerelloides scaber, which continued up to the top of the core and marked a pronounced shift in environmental conditions (shallower depth, lower salinity, more dynamic sedimentation conditions). The foraminifera-based stratigraphy of the core proved to be complementary to that emerging from previous analyses of diatoms and sediment geochemistry.

Biostratigraphy and paleoenvironment of Maastrichtian foraminiferal assemblages from a succession located NW of Tuxtla Gutiérrez, Chiapas (SE Mexico)

During the Maastrichtian, two lithostratigraphic units were deposited in the central Chiapas region; the Ocozocoautla and Angostura formations. The first unit crops out northwest of the city of Tuxtla Gutiérrez in central Chiapas. It is a complex lithological unit mainly composed of siliciclastic rocks interbedded with limestone. Overlying it, the Angostura limestone is recognized. This study focuses on a taxonomic study of the larger benthic and planktic foraminifera from both formations in order to assign age and to infer the paleoenviroment. The Ocozocoautla Formation includes an association of benthic as well as significant planktic foraminifera. Based on the microfossils stratigraphic distribution, two biozones were defined: the Pseudorbitoides rutteni–Ayalaina rutteni Assemblage Zone of earliest Maastrichtian and the upper part of the Gansserina gansseri Interval Zone of early Maastrichtian. The Angostura Formation contains dasycladacean algae and larger foraminifera considered as important age markers in shallow-water environments. Two foraminiferal interval zones were defined, Praechubbina breviclaustra Interval Zone of early late Maastrichtian and Chubbina jamaicensis Total Range Zone of late to latest Maastrichian age. The microfacies (grainstone, wackestone–packstone, wackestone) as well as the foraminiferal assemblage enable the paleoenvironment to be reconstructed, suggesting a deposit that developed in an open-water marine setting with moderate to high energy, characterized by benthic and planktic foraminifera in the Ocozocoautla Formation, while in the Angostura Formation a shallow-water marine protected environment is inferred. The paleobiogeographical distribution of the assemblage from both the Ocozocoautla and Angostura formations mostly contains endemic benthic foraminifera of the Caribbean Province and other few Tethysian forms of the Angostura Formation.

The Upper Cretaceous foraminiferal record of IODP Site U1512 (Great Australian Bight, Indian Ocean)

<p>Site U1512 was drilled during Expedition 369 of the International Ocean Discovery Program (IODP), which is located in the Great Australian Bight, southern Indian Ocean. It provides exceptional insights into the benthic foraminiferal biostratigraphy and paleoecology of a high southern latitude restricted marginal marine basin during the Late Cretaceous hot greenhouse climate and the rifting between Australia and Antarctica. The sedimentary sequence recovered at Site U1512 presents a rare record of a deep water agglutinated foraminifera (DWAF) community from the Southern High Latitudes. The Cretaceous record at Site U1512 covers the lower Turonian through Santonian (nannofossil zones UC8b to UC12/CC10b to CC16, <em>H. helvetica</em> to <em>Marginotruncana</em> spp. - <em>Planoheterohelix papula</em> - <em>Globotruncana linneana</em> planktonic foraminifera zones). Diverse benthic foraminiferal assemblages yield many new taxa that are yet to be described.</p><p>Agglutinated forms dominate the assemblage in most intervals. In lower to mid Turonian and Santonian strata, calcareous benthic as well as planktonic foraminifera are frequent. Abundant radiolaria are recovered from the mid Turonian, and they increase up-section and exceed 50% of the microfossil assemblage. We documented a diverse benthic foraminiferal assemblage consisting of 162 taxa (110 agglutinated and 52 calcareous). The most common taxa of the DWAF assemblage are tubular (i.e., <em>Kalamopsis grzybowskii,</em> <em>Bathysiphon</em> spp.) and planispiral forms (i.e., <em>Ammodiscus</em> spp., <em>Haplophragmoides</em> spp., <em>Buzasina</em> sp., <em>Labrospira</em> spp.).</p><p>The Turonian strata yield highly abundant <em>Bulbobaculites problematicus</em> and <em>Spiroplectammina navarroana</em>. The presence of the agglutinated foraminiferal marker taxa <em>Uvigerinammina jankoi</em> and <em>Bulbobaculites problematicus</em> provides a tie-point to the Tethyan DWAF biozonation of Geroch and Nowak (1984). The composition of foraminiferal assemblages and the increase in radiolaria abundance suggest unstable environmental conditions at Site U1512 during the early Turonian through Santonian. These characteristics refer to changes in bathymetry associated with changing ocean chemistry. Results of quantitative analyses of the benthic foraminiferal assemblages indicate a restricted paleoenvironmental regime, dictated by changes in paleobathymetry, unstable patterns in ocean circulation, and the discharge of a nearby river delta system.</p><p>References: Geroch, S., Nowak, K., 1984. Proposal of zonation for the Late Tithonian – late Eocene. based upon arenaceous Foraminifera from the Outer Carpathians, Poland, 225-239, In: Oertli, H.J. (Ed.), Benthos ´83; 2nd international 915 Symposium on Benthic Foraminifera, Pau (France) April 11-15, 1983, Elf Aquitaine, ESO REP and TOTAL CFP, Pau and Bordeaux.</p><p> </p>

Assessing the rate of post-depositional change within the 2004 Indian Ocean tsunami deposit: implications for long-term records of paleotsunamis

<p>Foraminifera are commonly used to examine patterns of tsunami inundation occurring over centennial to millennial timescales. However, the impacts of post-depositional change on geologic reconstructions is unknown. In tropical environments, the taphonomic character (i.e. test surface condition) of a foraminifer can deteriorate, rendering them unidentifiable, and in the worst case, dissolve them entirely. Here, we investigate the rates and extent of post-depositional change associated with the foraminiferal assemblages found within the 2004 Indian Ocean Tsunami (IOT) deposit over a 15-year time interval in Aceh, Indonesia from 2007 to 2019. </p><p>The IOT deposit consisted of a 13-18cm thick, medium-fine sand unit that sharply overlays a muddy sand contact. During the 15-year time series analysis, the IOT deposit remained a consistent thickness and maintained easily recognizable stratigraphical contacts between the overlying soil layer and the underlying mud layer. The overlying soil layer increased in thickness from 2cm in 2007 to 6cm in 2019 and resulted in roots bioturbating the IOT deposit. Calcareous taxa dominated the IOT deposit assemblage, where hyaline taxa accounted for 62% of the assemblage, porcelaneous taxa for 34% of the assemblage and agglutinated taxa for 4% of the assemblage. The concentration of calcareous foraminifera within the tsunami deposit decreased by 5% from 2007 to 2019. This trend is attributable to the high abundance of delicate porcelaneous tests, which are more susceptible to post-depositional processes than the more robust hyaline tests. The taphonomic character of the foraminiferal assemblage became more corraded (dissolved, abraded and/or pitted) over the 15-year period. The relative abundance of corraded individuals within the foraminiferal assemblage increased by 4% in the IOT deposit, to reach a relative abundance of 50% by 2019 compared to 46% in 2007. Our results indicate that there is minimal change occurring within the deposit and presents good evidence that microfossils can be used as reliable indictors of tsunami origin and to identify characteristics of a tsunami deposit. While it is minimal, we recommend that post-depositional change should still be considered, especially with regards to the more delicate porcelaneous tests and over longer taphonomic timescales.</p>

Deep sea benthic foraminiferal record from the Haymana Basin (Turkey): changes in abundance patterns and diversity across Cretaceous-Paleogene boundary

<p>In order to reveal the response of benthic foraminifera to Cretaceous-Paleogene (K/Pg) boundary event, a high-resolution benthic foraminiferal study was carried out from a land-based Haymana section which is biostratigraphically complete, and once located in the northern branch of the Tethyan Ocean. To this end, 25 samples collected from deep marine succession of the Haymana Basin were quantitatively assessed along with the utilization of quantification of species, morphogroup analysis and diversity indices to establish remarkable changes in biofacies which resulted from the boundary event.</p><p>Depositional environment is inferred as upper bathyal (200-600 m) throughout the studied section based on foraminiferal associations. Bathymetric marker species include mainly bi- to triserial forms in Maastrichtian, which favor this interval. Calcareous taxa including <em>Bolivinoides draco</em>,  <em>Eouvigerina subsculptura</em>, <em>Nonionellina</em> sp. 1, <em>Pseudouvigerina</em> <em>plummerae</em>, <em>Pyramidina</em> <em>minuta</em>, as well as species belonging to <em>Gyroidinoides</em>, <em>Laevidentalina</em>, <em>Lagena</em>, <em>Lenticulina</em>, <em>Pullenia</em>, and <em>Sitella</em> are together forming 30% of the whole assemblage in this study, which are also attributed as Shallow Bathyal Assemblage of Widmark and Speijer (1997b) from the upper bathyal environment. Accompanied agglutinated taxa are consisting of <em>Clavuinoides</em> <em>trilatera</em>, <em>Arenobulimina</em> sp., as well as species of <em>Dorothia</em>, <em>Gaudryina</em>, <em>Verneuilina</em>, and <em>Heterostomella</em>, which are reported from low and mid-latitude Slope Deep Water biofacies of Kuhnt et al. (1989). There was probably no paleobathymetric change in the Danian, as it is concluded from the structure of the faunal assemblage. Besides, calcareous taxa are found to be more abundant with respect to agglutinated taxa within the whole section, offering deposition over Carbonate Compensation Depth (CCD) level.</p><p>With this study, <em>Eouvigerina</em> <em>subsculptura</em> Acme Zone is newly offered for the uppermost Maastrichtian, and also aligned with <em>Bolivinoides draco</em> Zone, since it is existing as very abundant in all samples. Besides, <em>Angulogavelinella</em> <em>avnimelechi</em>-<em>Anomalinoides rubiginosus</em> Interval Zone (BB1) is assigned for the lowermost Danian section based on marker Paleocene species.</p><p>Based on this benthic foraminiferal record, a highly diverse foraminiferal assemblage is observed in the Maastrichtian, then it is replaced with a poor to moderate diversity assemblage in the Danian. This finding is presented by diversity indices (Fisher alpha, Shannon H and Berger Parker). Presence of diverse morphogroups together in the upper Maastrichtian section along with taxa preferring high nutrient levels including <em>E. Subsculptura</em> (11-23%), <em>Sliteria varsoviensis</em> (0-6%), <em>Praebulimina reussi</em> (2-9%), <em>Heterostomella</em> spp. (4-11%) and <em>Sitella</em> spp. (1-13%) suggests meso- to eutrophic conditions in this section. A sudden change in the faunal composition right after the K/Pg boundary offers depleted food flux into the bottom of the basin. Infaunal morpogroups decline after the boundary in the Danian section, whereas epifaunal morphogroups including mostly opportunistic <em>Cibicidoides</em> spp. (17%), increased in number in this section. The timing of this record is coinciding with the worldwide primary productivity collapse and planktonic foraminiferal mass extinction during the K/Pg boundary event.</p><p>Keywords: K/Pg boundary, deep sea benthic foraminifera, quantitative assessment, paleoenvironment, Haymana Basin</p>