The late Pleistocene record of productivity fluctuations in the eastern equatorial Pacific Ocean

Adelseck, Charles G.; Anderson, Thomas F.

doi:10.1130/0091-7613(1978)6<388:tlprop>2.0.co;2

Cited by 66 publications

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“…Cyclic fluctuations in carbonate content of Pleistocene sediments have offered an excellent fine-scale stratigraphic tool allowing correlations across the entire equatorial Indo-Pacific (Arrhenius, 1952;Olausson, 1960;Oba, 1969;Hays et al, 1969;Thompson and Saito, 1974;Luz and Shackleton, 1975;Ninkovich and Shackleton, 1975;Thompson, 1976;Adelseck, 1977;Valencia, 1977;Adelseck and Anderson, 1978;Thompson and Sciarrillo, 1978;Mayer, 1979;Volat et al, 1980). The mechanisms governing these carbonate fluctuations in ocean geochemistry, however, are still largely unknown.…”

Section: Introductionmentioning

confidence: 99%

Neogene Carbonate Stratigraphy of Hess Rise (Central North Pacific), and Paleoceanographic Implications

Vincent¹

1981

Initial Reports of the Deep Sea Drilling Project

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A detailed Neogene carbonate stratigraphy obtained from Hess Rise, in the temperate zone of the North Pacific, allows a cross-latitudinal correlation of carbonate fluctuations throughout the Pacific. The correlations are based on paleomagnetically dated biostratigraphic events.The carbonate record at Site 310, on Central Hess Rise, at a water depth of about 3500 meters, was obtained with a sampling interval representing time intervals of roughly 20,000 years in the Plio-Pleistocene, 30,000 years in the uppermost Miocene younger than about 6.2 m.y., and 140,000 years in the remainder of the upper Miocene and the middle Miocene. This record allows identification at Site 310 of specific carbonate events recognized throughout the equatorial Pacific, showing the ocean-wide nature of these events. The carbonate records compared with Site 310 are based on (time-) sampling intervals similar to those of Site 310. The comparison records are all located in the high-productivity belt of the equatorial Pacific, from depths near 2000 meters in the Panama Basin (DSDP Sites 157 and 158) to depths near 4500 meters, not far above the CCD (various piston cores). Specific carbonate events were not detected in the Plio-Pleistocene carbonate record at Site 466, on southern Hess Rise. This record was obtained with a sampling interval equivalent to a time span of about 60,000 years. This site, located at a water depth of about 2700 meters, has a Plio-Pleistocene sedimentary history similar to that at nearby Site 310, with approximately the same accumulation rate.Long-term cycles are superimposed on the short-term carbonate fluctuations in the equatorial Pacific sequences. The periodicity of these cycles, although not regular, is on the order of 0.5 m.y. for the upper Pleistocene, and on the order of 1 to 1.5 m.y. for the lower Pleistocene, Pliocene, and Miocene. Some of these long-term cycles are apparent in the carbonate stratigraphy at Site 310, especially in the Pleistocene and Miocene, but are not seen in the Pliocene. In Cores V24-59 and RC12-66, the Gauss includes the interval with the lowest calcium carbonate content of the entire Neogene, and sediment in this sequence accumulated more slowly than before or after. In contrast, at both Sites 310 and 157, this sequence accumulated at an average rate higher than overlying and underlying sediments. At Site 310, it contains the highest CaCO 3 average concentration of the entire Neogene.At Sites 310 and 466, there is an overall correlation between lower carbonate content and poorer foraminifer preservation in the Pleistocene, but no such correlation exists in the Pliocene and upper Miocene."Dissolution spikes" were found to be associated with climatic deterioration (marked by a distinct 18O enrichment in benthic foraminifers) and with a lightening in the benthic carbon-isotope record. They appear to be of global significance. These excursions provide chemostratigraphic signals of utmost importance for chronostratigraphic correlations. This does not imply, however, that carbona...

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Section: Introductionmentioning

confidence: 99%

Neogene Carbonate Stratigraphy of Hess Rise (Central North Pacific), and Paleoceanographic Implications

Vincent¹

1981

Initial Reports of the Deep Sea Drilling Project

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“…This, combined with a drop in fertility, led to a decrease in sedimentation rates. However, Adelseck and Anderson (1978) suggest that the lysocline in the eastern equatorial Pacific has remained within a few hundred meters of its present depth (3200 m) for the past 370,000 y. The depths of our sites are close to this depth (2750 m).…”

Section: Pelagic Oozesmentioning

confidence: 86%

Sediment Lithostratigraphy of the Galapagos Hydrothermal Mounds

Borella¹

1983

Initial Reports of the Deep Sea Drilling Project

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The hydrothermal sediments in the Galapagos mounds area are localized and essentially restricted to the mounds. Hydrothermal nontronites are interbedded with pelagic sediment, which indicates that hydrothermal activity is episodic. The nontronites are thickest on the mounds, thinning away from them rapidly and extending no more than 50 to 60 meters from a mound in any direction. The nontronites also are confined vertically to within the upper one-half to two-thirds of the cores. Manganese-oxide crust fragments are more localized than are the nontronites and do not form any continuous layer.The lack of pelagic sediments on the mounds, the presence of nontronitic mottled zones adjacent to hydrothermal sediment layers (both vertically and laterally), the decrease of siliceous fossil content, and the presence of mostly gradational boundaries between nontronite and pelagic sediment layers suggest that hydrothermal solutions are continually invading and cannibalizing the host pelagic sediment. Replacement and dissolution of pelagic sediment along with direct precipitation of hydrothermal sediments account for the distribution of sediments on a mound.A "relict" brown oxidized surface layer is found at 7 meters sub-bottom and can be correlated from hole to hole. I suggest that this layer is the prominent regional acoustic reflector reported by Lonsdale (1977). The combination of low carbonate accumulation and enrichment of diagenetic Fe and Mn in this zone is probably responsible for altering the acoustic impedance.

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“…1a, b). This site was selected because of (i) its position within the equatorial "cold tongue", west of the East Pacific Rise in the open ocean, which makes it less prone to continental influence compared to sites east of the East Pacific Rise (Mix et al, 1995); (ii) the good preservation of foraminifera (Jakob et al, 2016(Jakob et al, , 2017 despite the fact that the present-day water depth at Site 849 is close to the lysocline (Adelseck and Anderson, 1978;Berger et al, 1982); and (iii) the high sedimentation rates (2.7 cm kyr −1 for our study interval; Jakob et al, 2017) with continuous sedimentation (Mayer et al, 1992).…”

Section: Odp Site 849mentioning

confidence: 99%

Thermocline state change in the eastern equatorial Pacific during the late Pliocene/early Pleistocene intensification of Northern Hemisphere glaciation

et al. 2018

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Abstract. The late Pliocene/early Pleistocene intensification of Northern Hemisphere glaciation (iNHG) ∼ 2.5 million years ago (marine isotope stages, MIS, 100-96) stands out as an important tipping point in Earth's climate history, which strongly influenced oceanographic and climatic patterns including trade wind and upwelling strength in the eastern equatorial Pacific (EEP). The thermocline depth in the EEP, in turn, plays a pivotal role in the Earth's climate system: small changes in its depth associated with short-term climate phenomena such as the El Niño-Southern Oscillation can affect surface-water properties and the ocean-atmosphere exchange. However, thermocline dynamics in the EEP during the iNHG still remain unclear. While numerous studies have suggested a link between a thermocline shoaling in the EEP and Northern Hemisphere ice growth, other studies have indicated a stable thermocline depth during the iNHG; consequently, a causal relationship between thermocline dynamics and ice-sheet growth has been excluded. In light of these contradictory views, we have generated geochemical (planktic foraminiferal δ 18 O, δ 13 C and Mg / Ca), sedimentological (sand accumulation rates) and faunal (abundance data of thermocline-dwelling foraminifera) records for Ocean Drilling Program Site 849 located in the central region of the EEP. Our records span the interval from ∼ 2.75 to 2.4 Ma (MIS G7-95), which is critical for understanding thermocline dynamics during the final phase of the iNHG. Our new records document a thermocline shoaling from ∼ 2.64 to 2.55 Ma (MIS G2-101) and a relatively shallow thermocline from ∼ 2.55 Ma onwards . This indicates a state change in thermocline depth at Site 849 shortly before the final phase of the iNHG. Ultimately, our data support the hypothesis that (sub-)tropical thermocline shoaling may have contributed to the development of large Northern Hemisphere ice sheets.

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The late Pleistocene record of productivity fluctuations in the eastern equatorial Pacific Ocean

Cited by 66 publications

References 0 publications

Neogene Carbonate Stratigraphy of Hess Rise (Central North Pacific), and Paleoceanographic Implications

Neogene Carbonate Stratigraphy of Hess Rise (Central North Pacific), and Paleoceanographic Implications

Sediment Lithostratigraphy of the Galapagos Hydrothermal Mounds

Thermocline state change in the eastern equatorial Pacific during the late Pliocene/early Pleistocene intensification of Northern Hemisphere glaciation

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