The Eocene–Oligocene transition at ODP Site 1263, Atlantic Ocean: decreases in nannoplankton size and abundance and correlation with benthic foraminiferal assemblages

Abstract. The biotic response of calcareous nannoplankton to environmental and climatic changes during the Eocene–Oligocene transition (~34.8–32.7 Ma) was investigated at high resolution at Ocean Drilling Program (ODP) Site 1263 (Walvis Ridge, South East Atlantic Ocean), and compared with a lower resolution benthic foraminiferal record. During this time interval, the global climate which had been warm during the Eocene, under high levels of atmospheric CO2 (pCO2), transitioned into the cooler climate of the Oligocene, with overall lower pCO2. At Site 1263, the absolute nannofossil abundance (coccoliths per gram of sediment; N g−1) and the mean coccolith size decreased distinctly across the E–O boundary (EOB; 33.89 Ma), mainly due to a sharp decline in abundance of large-sized Reticulofenestra and Dictyococcites, within ~53 kyr. Since carbonate dissolution did not vary much across the EOB, the decrease in abundance and size of nannofossils may highlight an overall decrease in their export production, which could have led to an increased ratio of organic to inorganic carbon (calcite) burial, as well as variations in the food availability for benthic foraminifers. The benthic foraminiferal assemblage data show the global decline in abundance of rectilinear species with complex apertures in the latest Eocene (~34.5 Ma), potentially reflecting changes in the food source, thus phytoplankton, followed by transient increased abundance of species indicative of seasonal delivery of food to the sea floor (Epistominella spp.; ~34.04–33.54 Ma), with a short peak in overall food delivery at the EOB (buliminid taxa; ~33.9 Ma). After Oi-1 (starting at ~33.4 Ma), a high abundance of Nuttallides umbonifera indicates the presence of more corrosive bottom waters, possibly combined with less food arriving at the sea floor. The most important signals in the planktonic and benthic communities, i.e. the marked decrease of large reticulofenestrids, extinctions of planktonic foraminifer species and more pronounced seasonal influx of organic matter, preceded the major expansion of the Antarctic ice sheet (Oi-1) by ~440 kyr. During Oi-1, our data show no major change in nannofossil abundance or assemblage composition occurred at Site 1263, although benthic foraminifera indicate more corrosive bottom waters following this event. Marine plankton thus showed high sensitivity to fast-changing conditions, possibly enhanced but pulsed nutrient supply, during the early onset of latest Eocene-earliest Oligocene climate change, or to a threshold in these changes (e.g. pCO2 decline, high-latitude cooling and ocean circulation).

Download Full-text

Microfossil evidence for trophic changes during the Eocene–Oligocene transition in the South Atlantic (ODP Site 1263, Walvis Ridge)

Climate of the Past ◽

10.5194/cp-11-1249-2015 ◽

2015 ◽

Vol 11 (9) ◽

pp. 1249-1270 ◽

Cited By ~ 7

Author(s):

M. Bordiga ◽

J. Henderiks ◽

F. Tori ◽

S. Monechi ◽

R. Fenero ◽

...

Keyword(s):

Ocean Circulation ◽

Global Climate ◽

Food Delivery ◽

Marine Phytoplankton ◽

Time Interval ◽

Foraminiferal Assemblage ◽

Sea Floor ◽

Walvis Ridge ◽

Bottom Waters ◽

Latest Eocene

Abstract. The biotic response of calcareous nannoplankton to environmental and climatic changes during the Eocene–Oligocene transition was investigated at a high resolution at Ocean Drilling Program (ODP) Site 1263 (Walvis Ridge, southeast Atlantic Ocean) and compared with a lower-resolution benthic foraminiferal record. During this time interval, global climate, which had been warm under high levels of atmospheric CO2 (pCO2) during the Eocene, transitioned into the cooler climate of the Oligocene, at overall lower pCO2. At Site 1263, the absolute nannofossil abundance (coccoliths per gram of sediment; N g−1) and the mean coccolith size decreased distinctly after the E–O boundary (EOB; 33.89 Ma), mainly due to a sharp decline in abundance of large-sized Reticulofenestra and Dictyococcites, occurring within a time span of ~ 47 kyr. Carbonate dissolution did not vary much across the EOB; thus, the decrease in abundance and size of nannofossils may reflect an overall decrease in their export production, which could have led to variations in the food availability for benthic foraminifers. The benthic foraminiferal assemblage data are consistent with a global decline in abundance of rectilinear species with complex apertures in the latest Eocene (~ 34.5 Ma), potentially reflecting changes in the food source, i.e., phytoplankton. This was followed by a transient increased abundance of species indicative of seasonal delivery of food to the sea floor (Epistominella spp.; ~ 33.9–33.4 Ma), with a short peak in overall food delivery at the EOB (buliminid taxa; ~ 33.8 Ma). Increased abundance of Nuttallides umbonifera (at ~ 33.3 Ma) indicates the presence of more corrosive bottom waters and possibly the combined arrival of less food at the sea floor after the second step of cooling (Step 2). The most important changes in the calcareous nannofossil and benthic communities occurred ~ 120 kyr after the EOB. There was no major change in nannofossil abundance or assemblage composition at Site 1263 after Step 2 although benthic foraminifera indicate more corrosive bottom waters during this time. During the onset of latest-Eocene–earliest-Oligocene climate change, marine phytoplankton thus showed high sensitivity to fast-changing conditions as well as to a possibly enhanced, pulsed nutrient supply and to the crossing of a climatic threshold (e.g., pCO2 decline, high-latitude cooling and changes in ocean circulation).

Download Full-text

Clay mineral distribution related to rift activity, sea-level changes and paleoceanography in the Cretaceous of the Atlantic Ocean

Clay Minerals ◽

10.1180/claymin.1993.028.1.07 ◽

1993 ◽

Vol 28 (1) ◽

pp. 61-84 ◽

Cited By ~ 51

Author(s):

M. Thiry ◽

T. Jacquin

Keyword(s):

Atlantic Ocean ◽

Sea Level ◽

Clay Minerals ◽

Clay Mineral ◽

Deep Sea ◽

Depositional Environments ◽

Sea Level Changes ◽

Sea Floor ◽

Deep Sea Sediments ◽

Bottom Waters

AbstractThe distribution of clay minerals from the N and S Atlantic Cretaceous deep-sea sediments is related to rifting, sea-floor spreading, sea-level variations and paleoceanography. Four main clay mineral suites were identified: two are inherited and indicative of ocean geodynamics, whereas the others result from transformation and authigenesis and are diagnostic of Cretaceous oceanic depositional environments. Illite and chlorite, together with interstratified illite-smectite and smectite occur above the sea-floor basalts and illustrate the contribution of volcanoclastic materials of basaltic origin to the sediments. Kaolinite, with variable amounts of illite, chlorite, smectite and interstratified minerals, indicates detrital inputs from continents near the platform margins. Kaolinite decreases upward in the series due to open marine environments and basin deepening. It may increase in volume during specific time intervals corresponding to periods of falling sea-level during which overall facies regression and erosion of the surrounding platforms occurred. Smectite is the most abundant clay mineral in the Cretaceous deep-sea sediments. Smectite-rich deposits correlate with periods of relatively low sedimentation rates. As paleoweathering profiles and basal deposits at the bottom of Cretaceous transgressive formations are mostly kaolinitic, smectite cannot have been inherited from the continents. Smectite is therefore believed to have formed in the ocean by transformation and recrystallization of detrital materials during early diagenesis. Because of the slow rate of silicate reactions, transformation of clay minerals requires a long residence time of the particles at the water/sediment interface; this explains the relationships between the observed increases in smectite with long-term sea-level rises that tend to starve the basinal settings of sedimentation. Palygorskite, along with dolomite, is relatively common in the N and S Atlantic Cretaceous sediments. It is not detrital because correlative shelf deposits are devoid of palygorskite. Palygorskite is diagnostic of Mg-rich environments and is indicative of the warm and hypersaline bottom waters of the Cretaceous Atlantic ocean.

Download Full-text

How volcanism impact on the variability of the South American Monsoon System and the associated Atlantic Subtropical Cell

10.5194/egusphere-egu2020-289 ◽

2020 ◽

Author(s):

Laura Sobral Verona ◽

Ilana Wainer ◽

Myriam Khodri

Keyword(s):

Atlantic Ocean ◽

Ocean Circulation ◽

Global Climate ◽

Volcanic Eruptions ◽

The South ◽

Climatic Feature ◽

Monsoon System ◽

Convergence Zones ◽

The Tropics ◽

Subtropical Cell

Large volcanic eruptions can affect the global climate through changes in atmospheric and ocean circulation. Understanding the influence of volcanic eruptions on the hydroclimate over monsoon regions is of great scientific and social importance. The South America Monsoon System (SAMS) is the most important climatic feature of the continent. Both the Intertropical and the South Atlantic wind convergence zones (ITCZ and SACZ, respectively) are fundamental components of the SAMS. They show variations on a broad range of scales, dependent on complex multi-system interactions with the adjacent Atlantic Ocean and teleconnections. Also driven by the winds, the Atlantic Subtropical Cell (STC) is the link between the subduction zone in the subtropical gyre with the tropics. Hence, the STC influence equatorial sea surface temperature variability on interannual to decadal scales in the tropical Atlantic Ocean. In order to improve our understanding of the responses of the ocean-atmosphere system to the volcanic forcing, we aim to identify the dominant mechanisms of seasonal-to-interdecadal variability of the SAMS and the Atlantic STC after large Pinatubo-like (1991) and Tambora-like (1815) eruptions relying on the VolMIP model intercomparison project experiments.

Download Full-text

An Atlas of Phanerozoic Paleogeographic Maps: The Seas Come In and the Seas Go Out

Annual Review of Earth and Planetary Sciences ◽

10.1146/annurev-earth-081320-064052 ◽

2021 ◽

Vol 49 (1) ◽

Author(s):

Christopher R. Scotese

Keyword(s):

Ocean Circulation ◽

Land Surface ◽

Plate Tectonics ◽

Global Climate ◽

Annual Review ◽

Publication Date ◽

Time Interval ◽

Mountain Building ◽

The Past ◽

Evolution Of Life

Paleogeography is the study of the changing surface of Earth through time. Driven by plate tectonics, the configuration of the continents and ocean basins has been in constant flux. Plate tectonics pushes the land surface upward or pulls it apart, causing its collapse. All the while, the unrelenting forces of climate and weather slowly reduce mountains to sand and mud and redistribute these sediments to the sea. This article reviews the changing paleogeography of the past 600 million years. It describes the broad patterns of Phanerozoic paleogeography as well as many of the specific paleogeographic events that have shaped the modern continents and ocean basins. The focus is on the changing latitudinal distribution of the continents, fluctuations in sea level, the opening and closing of oceanic seaways, mountain building, and how these paleogeographic changes have affected global climate, ocean circulation, and the evolution of life. This review presents an atlas of 114 paleogeographic maps that illustrate how Earth's surface has evolved during the past 600 million years. During that time interval, Earth has witnessed the formation and breakup of two supercontinents: Pannotia and Pangea. The continents have been transformed from low-lying flooded platforms to high-standing land areas crisscrossed by the scars of past continental collisions. Oceans have opened and closed, and then opened again in a seemingly never-ending cycle. ▪ The changing configuration of the continents and ocean basins during the past 750 million years is illustrated in 114 paleogeographic maps. ▪ These maps describe how the surface of Earth has been continually modified by mountain building and erosion. ▪ The changing paleogeography has affected global climate, ocean circulation, and the evolution of life. ▪ The data and methods used to produce the maps are described in detail. Expected final online publication date for the Annual Review of Earth and Planetary Sciences, Volume 49 is May 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Download Full-text

Antarctic Climate History and Global Climate Changes

10.1093/oxfordhb/9780190699420.013.18 ◽

2017 ◽

Author(s):

Pontus Lurcock ◽

Fabio Florindo

Keyword(s):

Ocean Circulation ◽

Climate Changes ◽

Numerical Models ◽

Global Climate ◽

Sediment Cores ◽

Ice Sheets ◽

Global Ocean ◽

Climate History ◽

Global Climate Changes ◽

Planetary Albedo

Antarctic climate changes have been reconstructed from ice and sediment cores and numerical models (which also predict future changes). Major ice sheets first appeared 34 million years ago (Ma) and fluctuated throughout the Oligocene, with an overall cooling trend. Ice volume more than doubled at the Oligocene-Miocene boundary. Fluctuating Miocene temperatures peaked at 17–14 Ma, followed by dramatic cooling. Cooling continued through the Pliocene and Pleistocene, with another major glacial expansion at 3–2 Ma. Several interacting drivers control Antarctic climate. On timescales of 10,000–100,000 years, insolation varies with orbital cycles, causing periodic climate variations. Opening of Southern Ocean gateways produced a circumpolar current that thermally isolated Antarctica. Declining atmospheric CO2 triggered Cenozoic glaciation. Antarctic glaciations affect global climate by lowering sea level, intensifying atmospheric circulation, and increasing planetary albedo. Ice sheets interact with ocean water, forming water masses that play a key role in global ocean circulation.

Download Full-text

Assessing reconstruction techniques of the Atlantic Ocean circulation variability during the last millennium

Climate Dynamics ◽

10.1007/s00382-016-3111-x ◽

2016 ◽

Vol 48 (3-4) ◽

pp. 799-819 ◽

Cited By ~ 7

Author(s):

Eduardo Moreno-Chamarro ◽

Pablo Ortega ◽

Fidel González-Rouco ◽

Marisa Montoya

Keyword(s):

Atlantic Ocean ◽

Ocean Circulation ◽

Last Millennium

Download Full-text

Dynamic Downscaling of the Impact of Climate Change on the Ocean Circulation in the Galápagos Archipelago

Advances in Meteorology ◽

10.1155/2013/837432 ◽

2013 ◽

Vol 2013 ◽

pp. 1-18 ◽

Cited By ~ 7

Author(s):

Yanyun Liu ◽

Lian Xie ◽

John M. Morrison ◽

Daniel Kamykowski

Keyword(s):

Climate Change ◽

Ocean Circulation ◽

Global Climate Change ◽

Climate Model ◽

Global Climate ◽

Ocean Model ◽

Reanalysis Dataset ◽

Equatorial Undercurrent ◽

Galapagos Archipelago ◽

The Impact

The regional impact of global climate change on the ocean circulation around the Galápagos Archipelago is studied using the Hybrid Coordinate Ocean Model (HYCOM) configured for a four-level nested domain system. The modeling system is validated and calibrated using daily atmospheric forcing derived from the NCEP/NCAR reanalysis dataset from 1951 to 2007. The potential impact of future anthropogenic global warming (AGW) in the Galápagos region is examined using the calibrated HYCOM with forcing derived from the IPCC-AR4 climate model. Results show that although the oceanic variability in the entire Galápagos region is significantly affected by global climate change, the degree of such effects is inhomogeneous across the region. The upwelling region to the west of the Isabella Island shows relatively slower warming trends compared to the eastern Galápagos region. Diagnostic analysis suggests that the variability in the western Galápagos upwelling region is affected mainly by equatorial undercurrent (EUC) and Panama currents, while the central/east Galápagos is predominantly affected by both Peru and EUC currents. The inhomogeneous responses in different regions of the Galápagos Archipelago to future AGW can be explained by the incoherent changes of the various current systems in the Galápagos region as a result of global climate change.

Download Full-text

A Near-Uniform Basin-Wide Sea Level Fluctuation of the Mediterranean Sea

Journal of Physical Oceanography ◽

10.1175/jpo3016.1 ◽

2007 ◽

Vol 37 (2) ◽

pp. 338-358 ◽

Cited By ~ 56

Author(s):

Ichiro Fukumori ◽

Dimitris Menemenlis ◽

Tong Lee

Keyword(s):

Atlantic Ocean ◽

Mediterranean Sea ◽

Sea Level ◽

Ocean Circulation ◽

Large Scale ◽

Circulation Model ◽

Level Fluctuation ◽

Strait Of Gibraltar ◽

Sea Level Fluctuation ◽

The Mediterranean

Abstract A new basin-wide oscillation of the Mediterranean Sea is identified and analyzed using sea level observations from the Ocean Topography Experiment (TOPEX)/Poseidon satellite altimeter and a numerical ocean circulation model. More than 50% of the large-scale, nontidal, and non-pressure-driven variance of sea level can be attributed to this oscillation, which is nearly uniform in phase and amplitude across the entire basin. The oscillation has periods ranging from 10 days to several years and has a magnitude as large as 10 cm. The model suggests that the fluctuations are driven by winds at the Strait of Gibraltar and its neighboring region, including the Alboran Sea and a part of the Atlantic Ocean immediately to the west of the strait. Winds in this region force a net mass flux through the Strait of Gibraltar to which the Mediterranean Sea adjusts almost uniformly across its entire basin with depth-independent pressure perturbations. The wind-driven response can be explained in part by wind setup; a near-stationary balance is established between the along-strait wind in this forcing region and the sea level difference between the Mediterranean Sea and the Atlantic Ocean. The amplitude of this basin-wide wind-driven sea level fluctuation is inversely proportional to the setup region’s depth but is insensitive to its width including that of Gibraltar Strait. The wind-driven fluctuation is coherent with atmospheric pressure over the basin and contributes to the apparent deviation of the Mediterranean Sea from an inverse barometer response.

Download Full-text

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

10.5194/egusphere-egu21-7844 ◽

2021 ◽

Author(s):

Erik Wolfgring ◽

Michael A. Kaminski ◽

Anna Waśkowska ◽

Maria Rose Petrizzo ◽

Eun Young Lee ◽

...

Keyword(s):

Indian Ocean ◽

Ocean Circulation ◽

Planktonic Foraminifera ◽

Late Eocene ◽

Foraminiferal Assemblage ◽

Benthic Foraminiferal Assemblage ◽

International Ocean Discovery Program ◽

Foraminiferal Record ◽

Great Australian Bight ◽

Microfossil Assemblage

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, H. helvetica to Marginotruncana spp. - Planoheterohelix papula - Globotruncana linneana planktonic foraminifera zones). Diverse benthic foraminiferal assemblages yield many new taxa that are yet to be described.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., Kalamopsis grzybowskii, Bathysiphon spp.) and planispiral forms (i.e., Ammodiscus spp., Haplophragmoides spp., Buzasina sp., Labrospira spp.).The Turonian strata yield highly abundant Bulbobaculites problematicus and Spiroplectammina navarroana. The presence of the agglutinated foraminiferal marker taxa Uvigerinammina jankoi and Bulbobaculites problematicus 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.References: Geroch, S., Nowak, K., 1984. Proposal of zonation for the Late Tithonian &#8211; late Eocene. based upon arenaceous Foraminifera from the Outer Carpathians, Poland, 225-239, In: Oertli, H.J. (Ed.), Benthos &#180;83; 2nd international 915 Symposium on Benthic Foraminifera, Pau (France) April 11-15, 1983, Elf Aquitaine, ESO REP and TOTAL CFP, Pau and Bordeaux.&#160;

Download Full-text

Early season mesopelagic carbon remineralization and transfer efficiency in the naturally iron-fertilized Kerguelen area

Biogeosciences Discussions ◽

10.5194/bgd-11-9035-2014 ◽

2014 ◽

Vol 11 (6) ◽

pp. 9035-9069 ◽

Cited By ~ 9

Author(s):

S. H. M. Jacquet ◽

F. Dehairs ◽

A. J. Cavagna ◽

F. Planchon ◽

L. Monin ◽

...

Keyword(s):

Carbon Sequestration ◽

Polar Front ◽

Carbon Export ◽

Major Barrier ◽

Early Season ◽

Sea Floor ◽

Carbon Transfer ◽

Carbon Remineralization ◽

Bottom Waters ◽

Transfer Potential

Abstract. We report on the zonal variability of mesopelagic particulate organic carbon) remineralization and deep carbon transfer potential during the Kerguelen Ocean and Plateau compared Study 2 expedition (KEOPS 2; October–November 2011) in an area of the Polar Front supporting recurrent massive blooms from natural Fe fertilization. Mesopelagic carbon remineralization was assessed using the excess, non-lithogenic particulate barium (Baxs) inventories in mesopelagic waters and compared with surface primary and export productions. Results for this early season study are compared with results obtained earlier (2005; KEOPS 1) for the same area during summer. For the Kerguelen plateau (A3 site) we observe a similar functioning of the mesopelagic ecosystem during both seasons (spring and summer), with less that 30% of carbon exported from the upper 150 m being remineralized in the mesopelagic column (150–400 m). For deeper stations (> 2000 m) located on the margin, inside a Polar Front meander, as well as in the vicinity of the Polar Front, east of Kerguelen, remineralization in the upper 400 m in general represents > 30% of carbon export, but when considering the upper 800 m, in some cases, the entire flux of exported carbon is remineralized. It appears that above the plateau (A3 site) mesopelagic remineralization is not a major barrier to the transfer of organic matter to the sea-floor (close to 500 m). There the efficiency of carbon sequestration into the bottom waters (> 400 m) reached up to 87% of the carbon exported from the upper 150 m. In contrast, at the deeper locations mesopelagic remineralization clearly limits the sequestration of carbon to depths > 400 m. For sites at the margin of the plateau (station E-4W) and the Polar front (station F-L), mesopelagic remineralization even exceeds upper 150 m export, resulting in a null sequestration efficiency to depths > 800 m. In the Polar Front meander, where successive stations form a time series, the capacity of the meander to transfer carbon to depth > 800 m is highly variable (0 to 73 %). The highest carbon transfer efficiencies in the meander are furthermore coupled to intense and complete deep (> 800 m) remineralization, resulting again in a close to zero deep (> 2000 m) carbon sequestration efficiency there.

Download Full-text