Benthic Extinction Event Research Articles

Extinction and recovery of benthic foraminifera across the Paleocene–Eocene Thermal Maximum at the Alamedilla section (Southern Spain)

A complete succession of lower bathyal–upper abyssal sediments was deposited across the Paleocene–Eocene Thermal Maximum (PETM) at Alamedilla (Betic Cordillera, Southern Spain), where the benthic foraminiferal turnover and extinction event associated with the negative carbon isotope excursion (CIE) across the PETM have been investigated. Detailed quantitative analyses of benthic foraminifera allowed us to distinguish assemblages with paleoecological and paleoenvironmental significance: pre-extinction fauna, extinction fauna, survival fauna (including disaster and opportunistic fauna) and recovery fauna. These assemblages have been associated with significant parts of the δ 13C curve for which a relative chronology has been established. The correlation between the benthic turnover, the δ 13C curve, the calcite and silicate mineral content, and sedimentation rates, allowed us to establish the sequence of events across the PETM. At Alamedilla, the benthic extinction event (BEE) affected ~ 37% of the species and it has been recorded over a 30-cm-thick interval that was deposited in c.a. 10 ky, suggesting a gradual but rapid pattern of extinction. The beginning of the BEE coincides with the onset of the CIE (+ 0 ky) and with an interval with abundant calcite, and it has been recorded under oxic conditions at the seafloor (as inferred from the benthic foraminiferal assemblages and the reddish colour of the sediments). We conclude that dissolution and dysoxia were not the cause of the extinctions, which were probably related to intense warming that occurred before the onset of the CIE. The BEE is immediately overlain by a survival interval dominated by agglutinated species (the Glomospira Acme). The low calcite content recorded within the survival interval may result from the interaction between dilution of the carbonate compounds by silicicate minerals (as inferred from the increased sedimentation rates), and the effects of carbonate dissolution triggered by the shoaling of the CCD. We suggest that Glomospira species (disaster fauna) may have bloomed opportunistically in areas with methane dissociation, in and around the North Atlantic. The disaster fauna was rapidly replaced by opportunistic taxa, which point to oxic and, possibly, oligotrophic conditions at the seafloor. The CCD gradually dropped during this interval, and calcite preservation improved towards the recovery interval, during which the δ 13C values and the calcite content recovered (c.a. + 71.25 to 94.23 ky) and stabilized (> 94.23 ky), coeval with a sharp decrease in sedimentation rates.

Recalibration of the Tethyan shallow-benthic zonation across the Paleocene-Eocene boundary: the Egyptian record

The Galala Mountains in Egypt provide an excellent platform-basin transect with deposits spanning the Paleocene/ Eocene (P/E) boundary. These interfingering deposits enable a recalibration between platform and open marine biostratigraphic schemes. We investigated 18 sections from a shallow-water carbonate platform margin, dominated by larger benthic foraminifera, to basinal marls with pelagic and deep marine biota. The Late Paleocene to Early Eocene development of larger foraminifera is well recorded in the Galala transect, in particular the Tethyan evolutionary event known as the larger foraminifera turnover (LFT). This turnover distinguishes Paleocene assemblages dominated by glomalveolinids, miscellanids and ranikothalids typical for shallow benthic Zone 4 (SBZ4) from those of SBZ5, dominated by alveolinids, nummulitids, and orbitolitids. Our data agree with previous studies that suggested that the larger foraminifera turnover (LFT) coincides with the Paleocene/ Eocene boundary, delineated by the carbon isotopic excursion (CIE) and that it correlates with the boundary between calcareous nannofossils subzones NP9a/b, the benthic extinction event in smaller benthic foraminifera and the boundary between planktic foraminifera Biozones P5/E1.

Perturbation at the sea floor during the Paleocene–Eocene Thermal Maximum: Evidence from benthic foraminifera at Contessa Road, Italy

Detailed analyses of the benthic foraminiferal assemblages extracted with the cold acetolyse method together with high resolution geochemical and mineralogical investigations across the Paleocene/Eocene (P/E) boundary of the classical succession at Contessa Road (western Tethys), allowed to recognize and document the Paleocene–Eocene Thermal Maximum (PETM) interval, the position of the Benthic Extinction Event (BEE) and the early recovery of benthic faunas in the aftermath of benthic foraminiferal extinction. The stratigraphical interval spanning the P/E boundary consists of dominantly pelagic limestones and two prominent marly beds. Benthic foraminifera indicate that these sediments were deposited at lower bathyal depth, not deeper than 1000–1500 m. The Carbon Isotope Excursion (CIE) interval is characterized by high barite abundance with a peak at the base of the same stratigraphic interval, indicating a complete, although condensed record of the early CIE. A succession of events and changes in the taxonomic structure of benthic foraminifera has been recognized that may be of use for supra-regional stratigraphic correlation across the P/E boundary interval. The composition of the benthic foraminiferal assemblages, dominated by infaunal taxa, indicates mesotrophic and changing conditions on the sea floor during the last ∼ 45 kyr of the Paleocene. The BEE occurs at the base of the CIE within the lower marly bed and it is recorded by the extinction of several deep-water cosmopolitan taxa. Then, the lysocline/CCD rose and severe carbonate dissolution occurred. Preservation deteriorated, the faunal density and simple diversity dropped to minimum values and a peak of Glomospira spp. has been observed. Stress-tolerant and opportunistic groups, represented mainly by bi-and triserial taxa, dominate the low-diversity post-extinction assemblages, indicating a benthic foraminiferal recovery under environmental unstable conditions, probably within a context of sustained food transfer to the bottom. A three-phase pattern of faunal recovery is recognizable. At first the lysocline/CCD started to descend and then recovered. Small-sized “ Bulimina”, Oridorsalis umbonatus, and Tappanina selmensis rapidly repopulated the severely stressed environment. Later on, Siphogenerinoides brevispinosa massively returns, dominating the assemblage together with other buliminids, Nuttallides truempyi, and Anomalinoides sp.1. Finally, a marked drop in abundance of S. brevispinosa is followed by a bloom of the opportunistic and recolonizer agglutinated Pseudobolivina that, for the first time, is recorded within the main CIE. A second interval of dissolution, but less severe than the previous one, has been recognized within the upper marly bed (uppermost part of the main CIE interval) and it is interpreted as a renewed, less pronounced shoaling of the lysocline/CCD that interrupted the recovery of benthic faunas. This further rise likely represents a response to persistent instability of ocean geochemistry in this sector of the Tethys before the end of the CIE. In the CIE recovery and post CIE intervals, the composition of the benthic foraminiferal assemblages suggests mesotrophic and unstable conditions at the sea floor. According to the geochemical proxy for redox conditions, the deposition of the PETM sediments at Contessa Road occurred in well-oxygenated waters, leading out a widespread oxygen depletion as major cause of the BEE. Changing oceanic productivity, carbonate corrosivity and global warming appear to have played a much more important role in the major benthic foraminiferal extinction at the P/E boundary.

Did the Late Paleocene thermal maximum affect the evolution of larger foraminifers? Evidence from calcareous plankton of the Campo Section (Pyrenees, Spain)

The larger foraminifer turnover (LFT), which marks the base of the Ilerdian stage, may be related to the Late Paleocene Thermal Maximum (LPTM), or be at least nearly coeval with that climatic event. Thus, the impact of the LPTM may have been greater than hitherto realised, having also affected mid-latitude shallow-marine biota. This conclusion has been reached after a re-study of the calcareous plankton of the uppermost Paleocene and lowermost Eocene interval of the Campo section in the central southern Pyrenees. Campo is an important reference section because it contains larger foraminifers, planktic foraminifers and calcareous nannofossils, and their co-occurrence was used to intercalibrate their respective zonal schemes. Previous studies at Campo placed the onset of planktic foraminiferal Zone P5 near the base of the Ilerdian, and the calcareous nannofossil NP9/NP10 chronal boundary (sensu Bybell, L.M., Self-Trail, J.M., 1995. Evolutionary, biostratigraphic and taxonomic study of calcareous nannofossils from a continuous Paleocene/Eocene boundary section in New Jersey. US Geol. Surv. Prof. Pap. 1554, pp. 1–36) not less than 150 m above the Ilerdian lower limit. By these estimates, the LPTM (known to have occurred in the middle part of Zone P5 and just before the NP9/NP10 boundary) would be an event much younger than the LFT. However, our reexamination of planktic foraminifers suggests that the base of the Ilerdian is probably situated at the middle of Zone P5 (a possibility proposed by Hillebrandt in 1965, but denied by later authors). For instance, Morozovella occlusa has been found for the first time in the Campo section. Its Last Appearance Datum (LAD), which in the Pyrenees was approximately coeval with that of Morozovella velascoensis (event used to place the top of Zone P5), has been identified in beds situated less than 70 m above the base of the Ilerdian. Such thickness represents a time span of a similar magnitude as the one which separated the LPTM and the LAD of M. occlusa in the deep-water hemipelagic succession of the Basque Basin, in the western Pyrenees. Autochthonous calcareous nannofossils are neither abundant nor well preserved in most of the studied interval, with Rhomboaster bramlettei (the marker of the base of Zone NP10) being extremely rare in lower and middle Ilerdian beds, a fact that makes it very difficult to fix the position of the NP9/NP10 boundary in the Campo section. However, the bases of zones NP9 and NP11 have been located, and they support the zonation with planktic foraminifers. These new data suggest that the LFT and the LPTM may have been coeval or nearly so, a possibility reinforced by correlation with sections of the Basque Basin. Specialists of larger benthic foraminifers can easily delineate the LFT in shallow water carbonate successions of the Tethys domain, and they propose to place the Paleocene/Eocene boundary at the base of the Ilerdian stage. On the other hand, the deep benthic extinction event (BEE) is a major global biotic turnover in the bathyal and abyssal realms, while the ∂13C excursion (CIE) is an excellent tool for correlation between marine and terrestrial records. Therefore, the synchrony or near synchrony postulated here between the LFT, BEE and CIE (all of them probably related to the LPTM) would argue strongly in favour of these events as the criterion to officially redefine the Paleocene/Eocene boundary.

Benthic extinction event and global warming at the end of Paleocene and in the early Eocene

Benthic extinction event and global warming at the end of Paleocene and in the early Eocene

Paleocene to Early Eocene paleoceanography of the Middle East: The δ13C and δ18O isotopes from foraminiferal calcite

Paleocene to early Eocene benthic foraminiferal δ13C and δ18O records from southern Tethyan sections at Ben Gurion, Israel (paleodepth 500–700 m), and Gebel Aweina, Egypt (paleodepth 150–200 m), show generally similar trends but 1–3‰ more negative values than coeval deep‐sea isotopic records. In both Tethyan sections a negative δ13C excursion of 2.5–3‰ marks the benthic extinction event in the latest Paleocene. For at least 1 m.y. after this event, δ13C values were 1.5–2‰ more negative on the shelf than at upper bathyal depths, reflecting a deepening of the oxygen minimum zone, possibly related to an increase or spatial shift in upwelling. Benthic δ18O records indicate a 2–4°C temperature gradient between the shelf and upper bathyal depths. Temperature‐salinity reconstructions suggest that upwelling was a dominant mechanism for surface water formation in this part of the southern Tethys during the late Paleocene.

A benthic foraminiferal record of Paleocene sea level and trophic/redox conditions at Gebel Aweina, Egypt

We quantitatively analyzed benthic foraminiferal assemblages in order to reveal biotic and paleoenvironmental trends in the Paleocene section of Gebel Aweina, Egypt, on the southern Tethyan shelf. The first correspondence axis ranks taxa along an empirically derived bathymetric gradient, with neritic taxa (e.g., Discorbis duwi and Haplophragmoides walteri) opposed to bathyal taxa (e.g., Nuttallides truempyi and Gavelinella beccari(/ormis). The estimated paleodepth, as reflected by the various assemblages, was mostly ~ 200 m, but varied between ~ 50 m (P3a, NP4) and ~ 300 m (P4, N P8). The resultant four relative sea-level cycles appear to be at least of regional extent and may in part be eustatically controlled. The second correspondence axis reflects trends in trophic and redox development. Low-food, high-oxygen conditions prevailed during Biochrons Plc-P3b (NP4 NP5) and late P4 (NP8), when assemblages were mostly dominated by Cibicidoides spp. Most oligotrophic conditions coincided with maximum paleodepth. Intermediate trophic levels were established during middle P4 (NP6) and early P5 (NP9). From the level of the latest Paleocene benthic extinction event (BEE; middle P5 and NP9) onwards until Biochron P6a (NP10), assemblages dominated by buliminids marked increased trophic levels and reduced ventilation, probably resulting from enhanced surface productivity. Enhanced surface productivity along the southern Tethyan margin started during Biochron P4, and, at least on some shelves, intensified after the BEE. Increasing productivity during the latest Paleocene contrasts with global trends. This may be expected during climatic warming and an expanding trophic resource continuum, leading to regionally intensified eutrophy and oligotrophy. High productivity through upwelling along the southern Tethyan provides support for GCM predictions of intense wind-stress in this region during the warm late to latest Paleocene. © 1998 Elsevier Science B.V.

High-resolution iridium, δ13C, δ18O, foraminifera and nannofossil profiles across the latest Paleocene benthic extinction event at Zumaya, Spain

In the expanded upper Paleocene-lower Eocene section (≈ 30 m of Zone P5 sediments) at Zumaya, northern Spain, the highest occurrence of many late Paleocene deep-sea benthic foraminifera species (≈ 40% extinction), coincides with a transition from marl to calcite-free clay. Our high-resolution studies (chemical elements, δ 13 C, δ 18 O, calcareous nannofossils, planktic and benthic foraminifera) show that below the marl-clay transition there is a 40–50 cm thick interval (corresponding to 10–20 kyr) containing a detailed record of a gradual succession of faunal and geochemical events culminating in the benthic extinctions. Planktic foraminiferal and nannofossil changes (e.g., the onset of demise in Fasciculithus genus) occur a few meters below the marl-clay transition. In the limestone 50 cm below the base of the clay, a prominent glauconite maximum indicates that sea-floor oxygenation suddenly decreased. Glauconite continues to be common until the onset of clay deposition. A whole-rock negative δ 13 C shift (1.6‰), most likely reflecting an original sea-water trend, is gradually developed over the 40 cm of greenish brown marls immediately below the clay. At the base of these marls there is a small, significant iridium anomaly of 133 ppt Ir compared with an average background of 38 ppt. In the marls the demise of the Fasciculithus species accelerates, Gavelinella beccariiformis becomes extinct, and the abundance of Acarinina species begins to increase. The superjacent 4 m of clay is devoid of original calcite in its lower part and has a low calcareous content higher up. At calcareous levels in the clay an unusual planktic foraminifera fauna occurs, dominated by Acarinina species. When marl deposition returns, δ 13 C gradually increases and then stabilizes at values about 0.5‰ lower than before the isotopic excursion. The δ 13 C excursion spans in total 5 m, probably corresponding to 200–400 kyr. The fasciculiths disappear shortly after the stabilization of δ 13 C. Here we also present a whole-rock δ 13 C profile through the entire Paleocene section at Zumaya. The profile is very similar to previous profiles registered in well preserved deep-sea material, suggesting that whole-rock δ 13 C at Zumaya can be used for correlation. The origin of the Ir anomaly ≈ 40 cm below the benthic extinction event is enigmatic. It may be impact-related; however, the clearly gradual sequence of environmental events in the 50 cm below the dissolution clay, are more readily reconciled with changing oceanic circulation and palaeogeographic change, possibly in connection with volcanism, than with an instantaneous impact. The small Ir anomaly may reflect such volcanism, sea-water precipitates, or a small impact event, possibly unrelated to the palaeoenvironmental change.

Barium, SiO2 (excess), and P2O5 as proxies of biological productivity in the Middle East during the Palaeocene and the latest Palaeocene benthic extinction event

ABSTRACTThe distribution of barium and other elements related to biological productivity has been studied in two Palaeocene sections from the Middle East. In the bathyal Ben Gurion section, Israel, Ba* (= Ba/Al2O3× 15%) concentrations are low, in the range 0.04% to 0.3% in the lower Palaeocene, and very high, 1% to 2%, throughout most of the upper Palaeocene. In the neritic Gebel Aweina section in Egypt Ba* values are low, < 0.1%, throughout the entire Palaeocene. The Ba* enrichments at Ben Gurion and their correlations with increases in P2O5 and opaline silica, and local and global δ13C maxima, indicate that upwelling and high productivity were important in this region during the late Palaeocene. The absence of Ba* enrichments in the shallower Gebel Aweina section probably reflects the strong depth dependence of biobarium deposition.In the uppermost Palaeocene, at the level where the global benthic extinction event is registered, Ba* concentrations in the Ben Gurion section increase to anomalous 6%. which suggests that upwelling and possibly wind strengths intensified during this event. The results speak against deep‐water formation in this region since downwelling and not upwelling is required.

Globanomalina luxorensis, a Tethyan Biostratigraphic Marker of Latest Paleocene Global Events

The lowest common occurrence (LCO) of the planktonic foraminifera Globanomalina luxorensis marks the level of the latest Paleocene global benthic extinction event (BEE) and associated negative 613C excursion in various bathyal and neritic successions in the Mediterranean region. Below the BEE level, G. luxorensis is extremely rare and subordinate in abundance relative to its precursor G. chapmani. From this level onwards, G. luxorensis generally constitutes a large proportion of the planktonic assemblage (up to 10%). We propose to adopt the LCO of G. luxorensis as a marker for the level of the BEE in Tethyan continental margin deposits. It appears particularly useful for pinpointing the level of the BEE in neritic successions, where the benthic turnover is less pronounced. In combination, the BEE, the LCO of G. luxorensis, and the 613C excursion, provide a powerful and accurate means of correlating a unique horizon through varioarus marine environments. This makes this level very suitable to serve as a baseline for redefinition of the Paleocene/Eocene boundary.

Latest Paleocene benthic extinction event on the southern Tethyan shelf (Egypt): Foraminiferal stable isotopic (δ13C, δ18O) records

Research Article| April 01, 1996 Latest Paleocene benthic extinction event on the southern Tethyan shelf (Egypt): Foraminiferal stable isotopic (δ13C, δ18O) records B. Schmitz; B. Schmitz 1Department of Marine Geology, Earth Sciences Centre, S-413 81 Göteborg, Sweden Search for other works by this author on: GSW Google Scholar R. P. Speijer; R. P. Speijer 1Department of Marine Geology, Earth Sciences Centre, S-413 81 Göteborg, Sweden Search for other works by this author on: GSW Google Scholar M.-P. Aubry M.-P. Aubry 2Institut des Sciences de l'Evolution, Université Montpellier II, Case 061, F-34095 Montpellier Cedex 5, France Search for other works by this author on: GSW Google Scholar Author and Article Information B. Schmitz 1Department of Marine Geology, Earth Sciences Centre, S-413 81 Göteborg, Sweden R. P. Speijer 1Department of Marine Geology, Earth Sciences Centre, S-413 81 Göteborg, Sweden M.-P. Aubry 2Institut des Sciences de l'Evolution, Université Montpellier II, Case 061, F-34095 Montpellier Cedex 5, France Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1996) 24 (4): 347–350. https://doi.org/10.1130/0091-7613(1996)024<0347:LPBEEO>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation B. Schmitz, R. P. Speijer, M.-P. Aubry; Latest Paleocene benthic extinction event on the southern Tethyan shelf (Egypt): Foraminiferal stable isotopic (δ13C, δ18O) records. Geology 1996;; 24 (4): 347–350. doi: https://doi.org/10.1130/0091-7613(1996)024<0347:LPBEEO>2.3.CO;2 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 SocietyGeology Search Advanced Search Abstract The dramatic global extinction of 35%–50% of benthic foraminifera species in the deep sea in the latest Paleocene and associated negative excursions in δ13C and δ18O may be related to spreading of warm, saline bottom water from subtropical Tethyan shallow regions over the sea floor worldwide. Our study of neritic sections in Egypt shows that in the southern shallow Tethys, a prominent long-term change in bottom-water chemistry, sedimentation, and benthic foraminifera fauna was initiated at the time when the deep-sea benthic extinction event (BEE) took place. Bottom-water δ13C values on the Tethyan shelf show a sudden 3.0‰ negative shift at this event; however, contrary to the deep sea, in which the δ13C excursion was of short duration, Tethyan δ13C values did not fully return to preboundary values, but remained depressed by ∼1.5‰ for at least 1 m.y. The δ13C values at the Egyptian shelf during the BEE are much lower than would be expected if this was a source region for global deep water. The δ18O values indicate no significant change in bottom-water salinity or temperature at the BEE. The long-lasting environmental changes that began on the Egyptian shelf at the BEE may be related to, for example, gateway reorganization along the Tethyan seaway. Paleogeographic changes possibly also triggered a change in the loci of global deep-water formation; however, these loci must be sought in another part of the Tethys. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Stable (δ13C, δ18O) and strontium () isotopes through the Paleocene at Gebel Aweina, eastern Tethyan region

Abstract Stable ( δ 13 C, δ 18 O) and strontium ( 87 Sr 86 Sr ) isotopic records have been established through the Paleocene section at Gebel Aweina, in the Eastern Desert, Egypt. The section has been formed in a shelf-upper bathyal environment and, spans the interval from planktonic foraminiferal Zones P1d to P6a or P6b. Integrated evaluation of isotopic results and scanning electron microscope observations suggest that, strontium and whole-rock δ 13 C records reflect primarily original isotopic trends, whereas δ 18 O and foraminiferal δ 13 C values have been severely affected by diagenesis. The whole-rock δ 13 C record exhibits a continuous increase of 4‰ from the early Paleocene to middle late Paleocene. The increase is followed by a stepwise δ 13 C decrease of the same magnitude through the late late Paleocene and onwards. The gross trends of this δ 13 C record have earlier been registered in many coeval deep-sea sections, but there are also some significant disparities. At Aweina, for example, the Paleocene carbon isotopic changes have a higher amplitude. In the deep sea, the mid-to-late Paleocene δ 13 C increase has been interpreted to reflect high biological productivity and/or changes in the global carbon mass balance. The δ 13 C decrease in the upper part of the Aweina section can be identified as the Paleocene-Eocene transitional long-term (> 10 3 kyr) negative δ 13 C shift, which may reflect a major reorganisation in global oceanic circulation patterns. The well-known latest Paleocene, deep-sea, benthic foraminiferal extinction event has been found in the upper part of the Aweina section, and coincides with a distinct and rapid δ 13 C decrease of 1.5‰ The benthic extinction event and the associated δ 13 C anomaly thus represent important stratigraphic markers also in more shallow environments. The Gebel Aweina δ 13 C record shows considerably lower values compared to the global δ 13 C record during early and early late Paleocene and in the latest Paleocene. In the early late Paleocene (foraminiferal Zones P3a to the base of P4) the Aweina δ 13 C values increase rapidly by 1.5‰, and converge with the global record; thereafter the two records covary up to the benthic extinction event, after which they diverge. The convergence between the records may reflect sea-level rise and more open water-mass exchange between the eastern Tethys and the world ocean. The similarity of pilot δ 13 C records from Greece and Tunisia with the Aweina record support this interpretation. Diagenetic processes, however, cannot be ruled out, and further studies are required to determine the significance of the 13 C depletions in the eastern Tethyan sediments. The 87 Sr 86 Sr ratios through the Paleocene at Gebel Aweina are remarkably invariable close to a value of 0.7077. This is the same trend that has been reported in some earlier detailed studies conducted on well-preserved calcitic material from the Paleocene, indicating original Sr-isotopic signatures at Gebel Aweina. The homogeneity of Sr-isotopic ratios throughout the Paleocene contrasts with the prominent changes observed in the carbon isotope record, indicating a decoupling of the mechanisms regulating the mass fluxes of these elements. The invariable Sr-isotopic ratios suggest stable conditions as regards to relative changes in mass fluxes of riverine and/or hydrothermal Sr during the Paleocene.