scholarly journals New composite bio- and isotope stratigraphies spanning the Middle Eocene Climatic Optimum at tropical ODP Site 865 in the Pacific Ocean

2020 ◽  
Vol 39 (2) ◽  
pp. 117-138
Author(s):  
Kirsty M. Edgar ◽  
Steven M. Bohaty ◽  
Helen K. Coxall ◽  
Paul R. Bown ◽  
Sietske J. Batenburg ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Middle Eocene ◽  
Calcareous Nannofossils ◽  
Ocean Drilling Program ◽  
Planktic Foraminifera ◽  
The Pacific ◽  
Composite Section ◽  
Study Interval ◽  
Climatic Optimum ◽  
Calcareous Microfossils

Abstract. The Middle Eocene Climatic Optimum (MECO) at ca. 40 Ma is one of the largest of the transient Eocene global warming events. However, it is relatively poorly known from tropical settings since few sites span the entirety of the MECO event and/or host calcareous microfossils, which are the dominant proxy carrier for palaeoceanographic reconstructions. Ocean Drilling Program (ODP) Pacific Ocean Site 865 in the low-latitude North Pacific (Allison Guyot) has the potential to provide a useful tropical MECO reference, but detailed stratigraphic and chronological constraints needed to evaluate its completeness were previously lacking. We have addressed this deficit by generating new high-resolution biostratigraphic, stable isotope, and X-ray fluorescence (XRF) records spanning the MECO interval (∼38.0–43.0 Ma) in two holes drilled at Site 865. XRF-derived strontium ∕ calcium (Sr∕Ca) and barium ∕ strontium (Ba∕Sr) ratios and Fe count records allow correlation between holes and reveal pronounced rhythmicity, enabling us to develop the first composite section for Holes 865B and 865C and a preliminary cyclostratigraphy for the MECO. Using this new framework, the sedimentary record is interpreted to be continuous across the event, as identified by a pronounced transient benthic foraminiferal δ18O shift of ∼0.8 ‰. Calcareous microfossil biostratigraphic events from widely used zonation schemes are recognized, with generally good agreement between the two holes, highlighting the robustness of the new composite section and allowing us to identify planktic foraminiferal Zones E10–E15 and calcareous nannofossil Zones NP15–18. However, discrepancies in the relative position and ordering of several primary and secondary bioevents with respect to published schemes are noted. Specifically, the stratigraphic highest occurrences of planktic foraminifera, Acarinina bullbrooki, Guembelitrioides nuttalli, and Morozovella aragonensis, and calcareous nannofossils, Chiasmolithus solitus and Sphenolithus furcatolithoides, and the lowest occurrence of Reticulofenestra reticulata all appear higher in the section than would be predicted relative to other bioevents. We also note conspicuous reworking of older microfossils (from planktic foraminiferal Zones E5–E9 and E13) into younger sediments (planktic foraminiferal Zones E14–15) within our study interval consistent with reworking above the MECO interval. Regardless of reworking, the high-quality XRF records enable decimetre-scale correlation between holes and highlight the potential of Site 865 for constraining tropical environmental and biotic changes, not just across the MECO but also throughout the Palaeocene and early-to-middle Eocene interval.

‘Bleaching’ of Photosymbionts in Planktic Foraminifera During the Middle Eocene Climatic Optimum

2014 ◽  
Vol 13 ◽  
pp. 141-141
Author(s):  
Kirsty M. Edgar ◽  
Stephen M. Bohaty ◽  
Samantha J. Gibbs ◽  
Philip F. Sexton ◽  
Richard D. Norris ◽  
...  
Keyword(s):  
Middle Eocene ◽  
Planktic Foraminifera ◽  
Climatic Optimum

Abyssal benthic foraminifera in the eastern equatorial Pacific (IODP EXP 320) during the middle Eocene

2013 ◽  
Vol 87 (6) ◽  
pp. 1160-1185 ◽  
Author(s):  
Hiroyuki Takata ◽  
Ritsuo Nomura ◽  
Akira Tsujimoto ◽  
Boo-Keun Khim ◽  
Ik Kyo Chung
Keyword(s):  
Water Depth ◽  
Benthic Foraminifera ◽  
Middle Eocene ◽  
Accumulation Rate ◽  
Equatorial Pacific ◽  
Equatorial Pacific Ocean ◽  
Ocean Drilling Program ◽  
Integrated Ocean Drilling Program ◽  
Eastern Equatorial Pacific ◽  
Study Interval

We report on the faunal transition of benthic foraminifera during the middle Eocene at Site U1333 (4862 m water depth, 3,560–3,720 m paleo-water depth) of Integrated Ocean Drilling Program Expedition 320 in the eastern equatorial Pacific Ocean. During the period ∼41.5–40.7 Ma, which includes carbonate accumulation event 3 (CAE-3), the benthic foraminiferal accumulation rate (BFAR) increased gradually and then it declined rapidly. In contrast, BFAR was considerably lower during ∼40.7–39.4 Ma, corresponding to the middle Eocene climatic optimum (MECO), and then it increased during ∼39.3–38.4 Ma, including CAE-4. Diversity (E [S200]) was slightly lower in the upper part of the study interval than in the lower part. The most common benthic foraminifera were Nuttallides truempyi, Oridorsalis umbonatus, and Gyroidinoides spp. in association with Globocassidulina globosa and Cibicidoides grimsdalei during the period studied. Quadrimorphina profunda occurred abundantly with N. truempyi, O. umbonatus, and G. globosa during ∼39.4–38.4 Ma, including CAE-4, although this species was also relatively common in the lower part of the study interval. Virgulinopsis navarroanus and Fursenkoina sp. A, morphologically infaunal taxa, were common during ∼38.8–38.4 Ma, corresponding to the late stage of CAE-4. Based on Q-mode cluster analysis, four sample clusters were recognized and their stratigraphic distributions were generally discriminated in the lower and upper parts of the study interval. Thus, there was only a small faunal transition in the abyssal eastern equatorial Pacific during the middle to late-middle Eocene. The faunal transition recognized in this study may be related to recovery processes following intense carbonate corrosiveness in the eastern equatorial Pacific during MECO.

scholarly journals Early Palaeogene planktic foraminiferal and carbon isotope stratigraphy, Hole 762C, Exmouth Plateau, northwest Australian margin

2002 ◽  
Vol 21 (1) ◽  
pp. 29-42 ◽  
Author(s):  
Haidi J. L. Hancock ◽  
George C. Chaproniere ◽  
Gerald R. Dickens ◽  
Robert A. Henderson
Keyword(s):  
Carbon Isotope ◽  
Middle Eocene ◽  
Petroleum Exploration ◽  
Ocean Drilling Program ◽  
Planktic Foraminifera ◽  
Exmouth Plateau ◽  
Carbon Isotopic ◽  
Important Region ◽  
Sequential Samples ◽  
Early Paleocene

Abstract. Although the northwest margin of Australia is an important region for petroleum exploration and palaeoceanographic investigations, its Palaeogene stratigraphy is poorly documented, especially in terms of a foraminiferal biozonation. Early Palaeogene cores from 502.96 to 307.80 m below sea floor at Ocean Drilling Program Site 762 on the Exmouth Plateau were examined in this study for their planktic foraminiferal assemblages and the carbon isotopic compositions of Subbotina spp. Planktic foraminifera are generally well preserved and belong to 74 species and 17 genera. In spite of a mid-latitudinal palaeolatitude (c. 40°S) the sequence, deposited between the early Paleocene and Middle Eocene, contains all planktic foraminiferal Zones P1c through P10 of the current global scheme for tropical locations, except for Subzone P4b. Most zones are well defined by the datums of primary marker species except P3a and P9, which have boundaries that probably occur in core gaps, and the P9 zonal boundaries are defined by secondary marker species. Overall, variations in δ13C based on sequential samples of Subbotina are similar in pattern and magnitude to global summary isotope curves spanning the early Palaeogene. However, the prominent δ13C excursion that characterizes the Palaeocene/Eocene transition is mostly missing and appears to lie in a core gap. The planktic foraminiferal zonation, linked with that based on nannofossils, a recalibrated magnetostratigraphy and carbon isotope records, provides a robust temporal framework for the Early Palaeogene of the northwest margin of Australia.

scholarly journals The Nazca Drift System – palaeoceanographic significance of a giant sleeping on the SE Pacific Ocean floor

2021 ◽  
pp. 1-15
Author(s):  
Gérôme Calvès ◽  
Alan Mix ◽  
Liviu Giosan ◽  
Peter D. Clift ◽  
Stéphane Brusset ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Deep Water ◽  
Bottom Current ◽  
Ocean Drilling Program ◽  
Nazca Plate ◽  
Ocean Drilling ◽  
The Pacific ◽  
The Pacific Ocean ◽  
Nazca Ridge ◽  
Sea Currents

Abstract The evolution and resulting morphology of a contourite drift system in the SE Pacific oceanic basin is investigated in detail using seismic imaging and an age-calibrated borehole section. The Nazca Drift System covers an area of 204 500 km2 and stands above the abyssal basins of Peru and Chile. The drift is spread along the Nazca Ridge in water depths between 2090 and 5330 m. The Nazca Drift System was drilled at Ocean Drilling Program Site 1237. This deep-water drift overlies faulted oceanic crust and onlaps associated volcanic highs. Its thickness ranges from 104 to 375 m. The seismic sheet facies observed are associated with bottom current processes. The main lithologies are pelagic carbonates reflecting the distal position relative to South America and water depth above the carbonate compensation depth during Oligocene time. The Nazca Drift System developed under the influence of bottom currents sourced from the Circumpolar Deep Water and Pacific Central Water, and is the largest yet identified abyssal drift system of the Pacific Ocean, ranking third in all abyssal contourite drift systems globally. Subduction since late Miocene time and the excess of sediments and water associated with the Nazca Drift System may have contributed to the Andean orogeny and associated metallogenesis. The Nazca Drift System records the evolution in interactions between deep-sea currents and the eastward motion of the Nazca Plate through erosive surfaces and sediment remobilization.

Microfossil evidence for the EECO and MECO events in the Eocene sediments of the Isle of Wight, UK.

2021 ◽  
Author(s):  
Malcolm Hart ◽  
Pritpal Mangat ◽  
Meriel Fitzpatrick
Keyword(s):  
Middle Eocene ◽  
Warm Water ◽  
Calcareous Nannofossils ◽  
Isle Of Wight ◽  
North West ◽  
Early Eocene Climatic Optimum ◽  
Levels Of Detail ◽  
Climatic Optimum ◽  
South East England ◽  
London Clay

<p>The Paleogene section of Whitecliff Bay (Isle of Wight) is one of the most complete onshore successions in North West Europe (see Curry, 1965, 1966). The microfossil assemblages have been investigated by many micropaleontologists and the succession of foraminifera, ostracods, calcareous nannofossils, pteropods, diatoms, charophytes and dinocysts have been described in varying levels of detail. The planktic foraminiferal datum (Wright, 1972; Murray et al., 1989) in the Lower Eocene and the occurrence of larger foraminifera in the mid-Eocene provide evidence of incursions of warm water taxa that may be recording the presence of the Early Eocene Climatic Optimum (EECO) and the Middle Eocene Climatic Optimum (MECO) although these occurrences could equally be caused by changes in palaeogeography, glacio-eustasy and the general depositional environment.</p><p>Over a period of over 40 years samples have been collected from both the cliff succession and, at times of lowered sediment levels, on the foreshore which can often provide 100% exposure of the succession. Preservation of microfossil assemblages in samples is always better when collected from the foreshore while the cliff succession often records no calcareous (e.g., foraminifera) or siliceous microfossils (e.g., diatoms).</p><p>Both EECO and MECO are recorded as being brief, transient events while the palaeontological variations look to be of an altogether longer duration. Stable isotope data are limited (Dawber et al., 2011) and, at the present time, do not provide precise confirmation of isotope excursions precisely synchronous with the palaeontological distributions. Nevertheless, the evidence of northward migration by warm-water taxa is quite distinctive and worthy of still further investigation. In the case of MECO, the presence of Nummulites spp., Alveolina fusiformis and corals is certainly suggestive of warm-water migration into the northern confines of the Anglo-Paris-Belgian Basin.</p><p>Curry, D., 1965. The Palaeogene Beds of South-East England. Proceedings of the Geologists’ Association, 76(2), 151‒173.</p><p>Curry, D., 1966. Problems of correlation in the Anglo-Paris-Basin. Proceedings of the Geologists’ Association, 77(4), 437‒467.</p><p>Dawber, C.F., Tripati, A.K., Gale, A.S., MacNiocaill, C., Hesselbo, S.P., 2011. Glacioeustasy during the middle Eocene? Insights from the stratigraphy of the Hampshire Basin, UK. Palaeogeography, Palaeoclimatology, Palaeoecology, 300, 84–100.</p><p>Wright, C.A., 1972.  The recognition of a planktonic foraminiferid datum in the London Clay of the Hampshire Basin. Proceedings of the Geologists’ Association, 83, 413‒419.</p><p>Murray, J.W., Curry, D., Haynes, J.R., King, C.,1989. Palaeogene. In: Jenkins, D.G., Murray, J.W. (eds), Stratigraphical Atlas of Fossil Foraminifera [2<sup>nd</sup> Edition] (eds), British Micropalaeontological Series, Ellis Horwood Ltd, Chichester, 490‒536.</p>

scholarly journals Symbiont 'bleaching' in planktic foraminifera during the Middle Eocene Climatic Optimum

Geology ◽  
2012 ◽  
Vol 41 (1) ◽  
pp. 15-18 ◽  
Author(s):  
K. M. Edgar ◽  
S. M. Bohaty ◽  
S. J. Gibbs ◽  
P. F. Sexton ◽  
R. D. Norris ◽  
...  
Keyword(s):  
Middle Eocene ◽  
Planktic Foraminifera ◽  
Climatic Optimum
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