Carbon Isotope Excursion Interval Research Articles

Secondary controls on the stratigraphic signature of the carbon isotope excursion marking the Paleocene-Eocene thermal maximum at Ocean Drilling Program Site 1135

The negative carbon isotope excursion (CIE) associated with an ancient global warming event referred to as the Paleocene Eocene thermal maximum (PETM, ca. 56 Ma) is commonly observed to have a smaller magnitude in marine records than in terrestrial records. This disparity has been attributed to secondary mechanisms that either attenuate or amplify the CIE magnitude in marine and terrestrial records, respectively. Here we investigate the effects of carbonate diagenesis and sediment mixing on the stratigraphic signature of the CIE in a PETM record recovered at Ocean Drilling Program (ODP) Site 1135 in the southern Indian Ocean. Comparison of parallel planktic foraminifer δ13C records constructed with two different analytical techniques – conventional gas source mass spectrometry (GSMS) measurements of individual whole shells versus in-situ microanalyses on subdomains inside individual foraminifer shells using secondary ion mass spectrometry (SIMS) – shows that both the δ13CGSMS and δ13CSIMS records capture the CIE. However, the δ13CSIMS records yield excursion magnitudes (acarininids = 5.3‰, morozovellids = 3.9‰) that are ~1.6‰ larger than in the whole-shell δ13CGSMS records. Patterns of intrashell δ13C variation delineated by the in-situ SIMS microanalyses indicate that the smaller CIE magnitude registered by δ13CGSMS records is chiefly due to incorporation of diagenetic calcite overgrowths by GSMS analyses of whole foraminifer shells. We also find that many foraminifer shells are infilled with fine-fraction carbonate (nannofossils) and posit that incorporation of non-CIE nannofossils into these infillings further bias whole-shell GSMS δ13C measurements toward more positive values over the CIE interval. We propose that 5.3‰ is the best estimate of the CIE in this deep-sea record, a near match to the average CIE magnitude published for terrestrial PETM records.

Cretaceous southern high latitude benthic foraminiferal assemblages during OAE 2 at IODP Site U1516, Mentelle Basin, Indian Ocean

At Site U1516 (Mentelle Basin, southeast Indian Ocean, offshore western Australia), the International Ocean Discovery Program (IODP) Expedition 369 recovered an almost complete pelagic record of the Upper Cretaceous, including the Oceanic Anoxic Event 2 (OAE 2). To better understand paleoenvironmental changes across OAE 2, 32 samples were analysed for benthic foraminiferal abundance data that represent one of the few benthic foraminiferal datasets spanning the OAE 2 in the southern high latitudes.The OAE 2 interval at Site U1516 is characterized by an interval of low CaCO3 content that contains a prominent positive Carbon Isotope Excursion (CIE). The record of the OAE 2 can be subdivided in pre OAE 2, pre max-CIE, low CaCO3, and post low CaCO3 intervals. Through the Cenomanian–Turonian boundary, we document an extreme decline in benthic foraminifera during OAE 2, that is followed by a profound repopulation event in the post low CaCO3 interval.Benthic foraminiferal assemblages indicate an outer neritic to upper bathyal depositional environment. During the pre OAE 2 and pre max-CIE intervals, calcareous deep-water gavelinellids, lingulogavelinellids and gyroidinids are dominant. In the low-carbonate interval, the microfossil record documents a substantial increase in radiolaria and foraminifera are almost absent as only three out of nine samples contain benthic foraminifera. Changes in benthic foraminiferal assemblage composition are documented in the initial low CaCO3 interval, underlying the maximum CIE and associated interferences. Comparison of the pre- and post-CIE benthic foraminiferal assemblages highlights a distinct repopulation event during the post max- CIE interval mainly represented by the conspicuous increase in abundance of agglutinated taxa and Conorboides. Compared to other southern high latitude records, the dataset collected at Site U1516 represents one of the most complete benthic foraminiferal records across the OAE 2 that registers the Late Cretaceous environmental changes in the Southern Hemisphere.

Geochemical evidence from the Kioto Carbonate Platform (Tibet) reveals enhanced terrigenous input and deoxygenation during the early Toarcian

The early Toarcian , as registered in a variety of sedimentary archives, was characterized by an abrupt negative carbon-isotope excursion (CIE) typically superimposed on a long-term positive trend, and was accompanied by significant climatic and environmental changes. However, the changes in continental weathering influx and oceanic deoxygenation in shallow waters and their possible role in causing carbonate-platform crises in low latitudes remains poorly constrained. Here, we present carbonate content and carbonate-hosted elements for the Pliensbachian–Toarcian transitional interval from the Kioto Carbonate Platform (KCP) in the Tibetan Himalaya. The most water-insoluble elements (e.g. Ti, Sc, Th and total rare earth elements) show an obvious increase starting at the Pliensbachian–Toarcian boundary, followed by a weak increase or relatively high-level values during the negative phase of the T-OAE CIE, suggesting that the enhanced terrigenous input can be linked to rapid global warming during this time interval. The Mn, Ce and Ce anomaly start to increase immediately following the rise in abundance of the water-insoluble elements, followed in turn by enhanced values over the interval of the negative CIE. These observations indicate that the deoxygenation process and development of manganous (suboxic) conditions occurred in shallow water during this time interval and were likely linked to enhanced continental weathering and nutrient input, favoring both primary productivity and oxygen consumption. Stratigraphically higher, the water-insoluble elements show a gradual decreasing trend parallel with elevated values of redox proxies during the recovery phase of the CIE, suggesting decline in continental weathering intensity and a corresponding second deoxygenation in shallow waters. In this instance, deoxygenation might have been caused by a slackening of ocean circulation and/or enhanced recycling of bioessential nutrients. The coupled relationship between biotic changes, carbonate content and geochemical data suggest that: (1) the onset of enhanced terrigenous influx and deoxygenation in shallow waters likely led to slight deterioration to the KCP around Pliensbachian–Toarcian boundary time, and (2) the drastically enhanced terrigenous flux and deoxygenation likely played a pivotal role in the more severe crisis for benthic carbonate producers during the negative phase of the CIE. • Continental weathering proxies start to rise at Pl–To boundary, followed by high values in the negative T-OAE CIE interval. • Redox proxies increase immediately following weathering proxy rise, followed by enhanced values in the T-OAE CIE interval. • Relationship between proxies of continental weathering and redox suggests a deoxygenation driven by enhanced primary productivity. • Enhanced continental weathering and deoxygenation could have triggered the carbonate-platform crises before and during the T-OAE CIE. • A decline in continental weathering intensity and corresponding deoxygenation occurred in the recovery T-OAE CIE interval.

Integrated sedimentary, biotic, and paleoredox dynamics from multiple localities in southern Laurentia during the late Silurian (Ludfordian) extinction event

The Silurian was a time of major climatic transition punctuated by multiple biotic crises and global carbon cycle perturbations. The most severe of these biotic events was the late Silurian (Ludfordian) Lau/Kozlowskii extinction event (LKE) and the associated Lau carbon isotope excursion (CIE). Although the extinction event and Lau CIE are globally documented, the only records thus far of local and global marine paleoredox conditions through this interval are from a single region in Scandinavia. Here we examine four sections along a bathymetric transect of mixed carbonate-siliciclastic sediments from western Tennessee, USA. A novel approach using a multi-proxy dataset combining high-resolution geochemical data and microfacies analyses from multiple localities explores the possibilities of local/regional-scale redox heterogeneities during a time of widespread environmental upheaval on a global scale. Paired positive excursions recorded in carbonate carbon isotopes and carbonate-associated sulfate sulfur isotopes support recent work from carbonate and siliciclastic successions from Scandinavia, suggesting a global enhancement of organic carbon and pyrite burial driven by an expansion of euxinic (anoxic and sulfidic water column) conditions in the oceans during the mid-Ludfordian. Furthermore, positive excursions in organic carbon isotopes and pyrite sulfur isotopes reflect the global changes in redox. Stratigraphic trends in I/Ca ratios imply a local expansion of low-oxygen conditions, with low, but non-zero values during the rising limb and peak of the CIE. The fossil assemblages vary across the shelf and through the CIE interval. Stratigraphic changes in fossil assemblages and I/Ca are closely associated with local and global changes in oxygenation and sea level during the mid-Ludfordian. The collective data indicate significant biotic reorganization in response to changes in marine redox conditions and in conjunction with sea-level variation during the LKE interval, but detailed macroscopic biodiversity is currently unconstrained for this region.

Effects of size-dependent sediment mixing on deep-sea records of the Paleocene-Eocene Thermal Maximum

Abstract Stratigraphic features of the carbon isotope excursion (CIE) marking the Paleocene-Eocene Thermal Maximum (PETM; ca. 55.8 Ma) are used to study ocean-climate change and carbon cycling during this ancient global warming event. Yet discrepancies in its timing and amplitude exist between bulk-carbonate and planktic-foraminifera δ13C records. Here we examine these disparities through the lens of δ13C compositions of size-segregated planktic shells across the pre-CIE to CIE transition in the iconic PETM section of Ocean Drilling Program Site 690 in the Weddell Sea. Our results show that the stratigraphic position of the CIE onset is dependent upon shell size, which we attribute to preferential mixing of smaller shells with pre-CIE δ13C values up into the overlying CIE interval. Hence, the transitory loss of size-dependent δ13C signatures in photosymbiotic planktic foraminifera is a taphonomic artifact, not a geochemical signal of symbiont “bleaching” during the PETM. Our results also indicate that many salient features of the Site 690 bulk-carbonate δ13C record are aberrations caused by size-dependent sediment mixing, and as such, should not be viewed as primary signals of ocean-climate change during what is arguably one of the best ancient analogs for future ocean-climate change.

The wider context of the Lower Jurassic Toarcian oceanic anoxic event in Yorkshire coastal outcrops, UK

The Toarcian Oceanic Anoxic Event (T-OAE, ∼183Ma) was characterized by enhanced carbon burial, a prominent negative carbon-isotope excursion (CIE) in marine carbonate and organic matter, and numerous geochemical anomalies. A precursor excursion has also been documented at the Pliensbachian/Toarcian boundary, but its possible causes are less constrained. The T-OAE is intensively studied in the Cleveland Basin, Yorkshire, UK, whose sedimentary deposits have been litho-, bio- and chemostratigraphically characterised. Here, we present new elemental data produced by hand-held X-ray fluorescence analysis to test the expression of redox-sensitive trace metals and detrital elements across the upper Pliensbachian to mid-Toarcian of the Cleveland Basin. Detrital elemental concentrations (Al, Si, Ti, Zr) are used as proxies for siliciclastic grain content and thus, sea-level change, which match previous sequence stratigraphic interpretations from the Cleveland Basin. The timescale of the event is debated, though our new elemental proxies of relative sea level change show evidence for a cyclicity of 350cm that may be indicative of ∼405 kyr eccentricity cycles in Yorkshire. Trends in total organic carbon and redox-sensitive elements (S, Fe, Mo, As) confirm scenarios of widespread ocean deoxygenation across the T-OAE. The correlation of comparable trends in Mo across the T-OAE in Yorkshire and the Paris Basin suggests a similar oceanic drawdown of this element accompanying widespread anoxia in the two basins. Data from Yorkshire point to a transgressive trend at the time of the Mo drawdown, which contradicts the “basin restriction” model for the euxinic conditions that characterise the CIE interval.

Chronology of the Early Toarcian environmental crisis in the Lorraine Sub-Basin (NE Paris Basin)

Early Toarcian (Jurassic; ∼183 Ma) sediments recorded profound environmental changes, including mass extinction, global warming, marine transgression as well as widespread bottom water anoxia and organic matter accumulation on the Western Tethyan shelf. Enhanced organic matter accumulation was accompanied by a positive carbon isotope excursion (CIE) in pelagic carbonate, which marks the Toarcian Oceanic Anoxic Event. These environmental changes were accompanied by a major perturbation of the global carbon cycle, expressed by negative CIE, interrupting the positive trend. The duration of the carbon cycle perturbation is still debated, with estimates for the negative CIE range from ∼200 to ∼600 kyr. Here we present ultra high-resolution (<1 kyr) measurements of magnetic susceptibility and sediment color from a marine section located in the Lorraine Sub-Basin (NE Paris Basin) documenting Milankovitch-controlled fluctuations in depositional conditions that occurred superimposed onto the overall sea level evolution. Differences in the wavelength of the sedimentary cycles indicate variable sediment accumulation rates that mainly resulted from rapid sea level fluctuations. The most pronounced sea level rise that took place within the uppermost tenuicostatum zone resulted in a strong condensation of the basal Schistes Carton formation. Strong condensation can explain the discrepancy between durations previously calculated for the CIE placed at this stratigraphic interval. Our data support durations of ∼900 kyr and ∼600 kyr for the positive and negative CIE, respectively. The cyclostratigraphy-based timescale further proposes a duration of >555 kyr for the tenuicostatum zone and 1310 kyr for the serpentinum zone. The durations of the elegantulum and falciferum subzones can be estimated to ∼790 kyr and ∼520 kyr, respectively. A change in the orbital response from eccentricity- to obliquity-forcing, evident from other locations, is well-expressed in the Lorraine Sub-Basin and occurred within the CIE interval. The strong impact of the obliquity component in post-event deposits hints to processes most effective at high latitudes, such as the waxing and waning of polar ice. Paleogeographic features of the Western Tethyan shelf supported the tele-connection of higher to lower latitude processes via water exchange through the Viking Corridor.

Pacing of the Toarcian Oceanic Anoxic Event (Early Jurassic) from astronomical correlation of marine sections

The Early Toarcian Oceanic Anoxic Event (OAE) in the Early Jurassic Period is associated with a major negative carbon isotope excursion (CIE), mass extinction, marine transgression and global warming. The Toarcian OAE is thought to have been caused by flood basalt magmatism, and may have been a trigger for mass extinction. However, these proposed causes of the Toarcian OAE and associated biotic crisis are not adequately resolved by a precise chronology. The duration of the Toarcian OAE has been estimated to be anywhere from ~0.12 to ~0.9Myr, most recently 0.74 to 3.26Myr from U–Pb dating. The CIE associated with the Toarcian OAE has a similar pattern at numerous localities, and there is evidence that the marine carbon isotope variations recorded astronomical forcing signals. Here we estimate a duration of ~620kyr for the main negative CIE, ~860kyr for the polymorphum zone and >1.58Myr for the levisoni zone based on 405-kyr astronomical eccentricity tuning of the marine section at Peniche (Portugal). This 405-kyr tuned series provides a ~2.5Myr continuous high-resolution chronology through the Early Toarcian. There are 6, or possibly 7 short eccentricity cycles in the main CIE interval at Peniche. To confirm this astronomically based estimate, we analyzed three other sections at Yorkshire (UK), Dotternhausen (Germany), and Valdorbia (Italy) from marine carbon isotopic series. These four stratigraphic sections from Early Jurassic western Tethys record the Toarcian OAE with ~6 prominent carbon isotope cycles in the CIE that span a 600±100kyr duration. The Peniche 405-kyr tuned series indicates that the pre- and post-CIE intervals experienced strong precession–eccentricity-forced climate change, whereas the CIE interval is marked by dominant obliquity forcing. These dramatic and abrupt changes in astronomical response in the carbon isotopes point to fundamental shifting in the Early Toarcian paleoclimate system that was directly linked to the global carbon cycle.

Carbon isotope stratigraphy and depositional oxia through Cenomanian/Turonian boundary sequences (Upper Cretaceous) in New Zealand

Stratigraphic sections across the Cenomanian/Turonian boundary (C/T boundary) are identified in New Zealand and were deposited in southern high latitudes of the palaeo-Pacific. Lithological evidence for Cretaceous Oceanic Anoxic Event 2 (OAE2), which preceded and spanned the C/T boundary, is lacking in these sections. The correlative interval is identified, however, from a positive 2‰ carbon isotope excursion (CIE) and from clustered highest occurrences of Cenomanian-restricted dinoflagellate taxa together with the lowest occurrence of Turonian Heterosphaeridium difficile. A zone lacking benthic macrofossils encompasses the CIE. In some sections, this interval is also characterized by distinctive red mudstone beds; the thickest such red bed (6–18m thick) may overlap or just overlie the main part of the CIE interval. Shelly macrobenthos, notably inoceramid bivalves, disappeared >500kyr prior to the CIE. This suggests that environmental deterioration associated with OAE2 may have preceded the inferred volcanic trigger that has been identified from other regions. Strong intermediate water depth oxia during OAE2, which contrasts with oceanic anoxic conditions that occurred elsewhere on the globe, apparently prevailed during the later phase of OAE2 in the southernmost Pacific. New data from New Zealand indicate that causal mechanism(s) of OAE2 may be complex.

Mid-Ludfordian coeval carbon isotope, natural gamma ray and magnetic susceptibility excursions in the Mielnik IG-1 borehole (Eastern Poland)—Dustiness as a possible link between global climate and the Silurian carbon isotope record

The graptolite-bearing upper Silurian succession of the Mielnik IG-1 borehole (eastern Poland) represents a periplatform setting on a neritic carbonate platform located on the palaeocontinent of Baltica and records widely recorded positive mid-Ludfordian Carbon Isotope Excursion (CIE). The initial increase of δ13C values occurs in the uppermost part of the Neocucullograptus kozlowskii Zone whereas pronounced increase and maximal values (+6.74‰) are noted in the N. kozlowskii–Pseudomonoclimacis latilobus interzone (Pristiograptus dubius bloom interval). The thickness–time relation in the section indicates that the main, initial shift in carbon isotope ratio (of 2.7‰) occurred over a very short time, estimated to be around 4000years, and is coeval with a rapid initiation of deposition of rock-forming, silt-sized detrital dolomite and quartz. The CIE decline is interpreted as steeper than in inner shelf sections, and is coincident with a flooding event in the Ps. latilobus–Slovinograptus balticus Zone; whereas the end of the excursion is coeval with the next flooding surface marked by the Ps. Latilobus–Uncinatograptus acer graptolite assemblage. Combined SGR (Spectral Gamma Ray), facies, and faunal records during the CIE suggest prolonged sea-level lowstand conditions. The abundant detrital material (‘dolomite siltstone facies’), occurring exclusively in the CIE interval, is noted in microfacies as well as in the geophysics record—as pronounced negative excursions in total natural gamma ray and magnetic susceptibility, both resulting from dilution by diamagnetic and low-radioactivity minerals. The perfectly sorted, vertically equally-sized silt material contains unique, constant and low diversified grain assemblage (euhedral dolomite, quartz, minute ooids)—suggesting its provenance exclusively from the shallower and/or emerged parts of the carbonate platform interior. The spot findings of graptolites and nautiloids along with delicate parallel lamination of sediments indicates relatively deep environment, with absence of traction processes. These features, along with the lack of dolomite detritus in accompanying redeposited carbonates, suggest its derivation by wind. With regard to the earlier noted presence of aeolian detritus in the middle Ludfordian, we suggest dustiness as a plausible driving force of the CIE. In the hypothesis proposed, bioavailable Fe-bearing dust inflow in concert with antiestuarine circulation on shelfs, caused nutrient (N:P ratio) disturbances, resulting in methanogenesis in surface layer of the seas. The surface layer methanogenesis should resulting in bathymetric gradient of isotope fractionation, what is consistent with the CIE record. Coincidence of sea-level lowstand, low-latitude aridity, and gustiness of the global climate, are in accordance with the hypothetical short-lived glaciation in mid-Ludfordian time.

Carbonate saturation dynamics during the Paleocene–Eocene thermal maximum: Bathyal constraints from ODP sites 689 and 690 in the Weddell Sea (South Atlantic)

Spatiotemporal patterns of carbonate dissolution provide a critical constraint on carbon input during an ancient (~55.5Ma) global warming event known as the Paleocene–Eocene thermal maximum (PETM), yet the magnitude of lysocline shoaling in the Southern Ocean is poorly constrained due to limited spatial coverage in the circum-Antarctic region. This shortcoming is partially addressed by comparing patterns of carbonate sedimentation at the Site 690 PETM reference section to those herein reconstructed for nearby Site 689. Biochemostratigraphic correlation of the two records reveals that the first ~36ka of the carbon isotope excursion (CIE) signaling PETM conditions is captured by the Site 689 section, while the remainder of the CIE interval and nearly all of the CIE recovery are missing due to a coring gap. A relatively expanded stratigraphy and higher carbonate content at mid-bathyal Site 689 indicate that dissolution was less severe than at Site 690. Thus, the bathymetric transect delimited by these two PETM records indicates that the lysocline shoaled above Site 689 (~1,100m) while the calcite compensation depth remained below Site 690 (~1,900m) in the Weddell Sea region. The ensuing recovery of carbonate sedimentation conforms to a bathymetric trend best explained by gradual lysocline deepening as negative feedback mechanisms neutralized ocean acidification. Further, biochemostratigraphic evidence indicates the tail end of the CIE recovery interval at both sites has been truncated by a hiatus most likely related to vigorous production and advection of intermediate waters.

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.

Palaeoenvironmental turnover across the Palaeocene/Eocene boundary at the Stratotype section in Dababiya (Egypt) based on benthic foraminifera

AbstractThe Global Stratotype Section and Point for the Palaeocene/Eocene (P/E) boundary was defined at Dababiya Quarry (Egypt) at the base of the carbon isotope excursion (CIE). We present the first detailed analysis of Palaeocene–Eocene benthic foraminifera from Dababiya, in order to infer the palaeoenvironmental turnover across the P/E boundary. At Dababiya, the CIE coincides with a major turnover in foraminiferal assemblages; the last occurrence of Angulogavelinella avnimelechi, at the base of the CIE, may be correlated to the main phase of extinction of deep‐sea benthic foraminifera. Benthic foraminifera indicate that stressful conditions such as oxygen deficiency, carbonate dissolution, and changes in food supply, persisted at the sea floor over most of the CIE interval. The main phase of recovery of benthic foraminifera is recorded c. 250 cm above the P/E boundary, and it may be linked to increased productivity and oxygenation at the sea floor.