Pliocene-Pleistocene radiolarian events and magnetostratigraphic calibrations for the tropical Indian Ocean

Johnson, David A.; Schneider, David; Nigrini, Catherine A; Caulet, J.; Kent, Dennis V.

doi:10.1016/0377-8398(89)90031-5

Cited by 87 publications

(99 citation statements)

References 45 publications

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“…These assignments were checked using the nannofossil datums, the LAD of Reticulofenestra pseudoumbilica (NN16/ NN15) and the LAD of Phormostichoartus doliolum, (NN12/ NN11) (Spaulding, this volume). They are also concordant with the published ages of the radiolarian events, the LAD of Phormostichoartus doliolum, FAD of Amphirhopalum ypsilon, FAD of Spongaster tetras, and LAD of Solenosphaera omnitubus (Nigrini, this volume; Johnson and Nigrini, 1985;Johnson et al, 1989). The magnetostratigraphic results suggest that the sedimentation rate was higher in the Pliocene, especially during the late and middle Gilbert Chron (C2Ar and C3).…”

Section: Site 728supporting

confidence: 88%

“…As shown in Figure 4, these assignments are concordant with the horizons of the Pliocene radiolarian events (Nigrini, this volume), of which ages were paleomagnetically calibrated using DSDP and piston cores from the Equatorial Indian and Pacific Oceans (Johnson and Nigrini, 1985;Johnson et al, 1989). Polarity intervals of about or less than 10 5 yr were not clearly detected; as at Site 721, the Olduvai (C2), Kaena (C2A-1), and Mammoth (C2A-2) subchronozones were not observed in Hole 722A and 722B.…”

Section: Site 722supporting

confidence: 66%

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Magnetostratigraphy of Leg 117 Sediments from the Owen Ridge and the Oman Margin, Western Arabian Sea

Hayashida¹,

Bloemendal²

1991

Proceedings of the Ocean Drilling Program

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Magnetic measurements were made on discrete samples from the Neogene pelagic and hemipelagic sediments recovered during ODP Leg 117. Polarity zones, usually identified for uppermost 200 m, were correlated to the geomagnetic polarity time scale referring to biostratigraphic datums. Quality and resolution of the magnetostratigraphy was partly limited by the weak and relatively soft magnetic character of almost all intervals, and core disturbance by gas expansion at some Oman Margin sites. Clear polarity records of the Brunhes and Matuyama chrons (Cl to C2r) were observed at Sites 724 and 727 on the Oman continental margin. Extended reversal records of the Pliocene were found at Site 722 on the Owen Ridge and Site 728 on the Oman Margin, and correlated to the Gauss to Gilbert chrons (C2A to C3).

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Section: Site 728supporting

confidence: 88%

Section: Site 722supporting

confidence: 66%

Magnetostratigraphy of Leg 117 Sediments from the Owen Ridge and the Oman Margin, Western Arabian Sea

Hayashida¹,

Bloemendal²

1991

Proceedings of the Ocean Drilling Program

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“…The only two such events were the First Occurrence (FO) of Buccinosphaera invaginata, dated at 0.18 Ma [7], and the Last Occurrence (LO) of Stylatractus universus, dated at 0.42 Ma [8]. B. invaginata, a colonial, warm-water adapted species, is reported as very rare in modern sediments from the South Atlantic, reaching maximum abundances (however, up to only 1%), in the South Atlantic Central Gyre [9].…”

Section: Evidence Against Sources Of Error In the Sst Interpretationmentioning

confidence: 99%

A glacial warm water anomaly in the subantarctic Atlantic Ocean, near the Agulhas Retroflection

Cortese

Abelmann

Gersonde

2004

Earth and Planetary Science Letters

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ODP Site 1089 is optimally located in order to monitor the occurrence of maxima in Agulhas heat and salt spillage from the Indian to the Atlantic Ocean. Radiolarian-based paleotemperature transfer functions allowed to reconstruct the climatic history for the last 450 kyr at this location. A warm sea surface temperature anomaly during Marine Isotope Stage (MIS) 10 was recognized and traced to other oceanic records along the surface branch of the global thermohaline (THC) circulation system, and is particularly marked at locations where a strong interaction between oceanic and atmospheric overturning cells and fronts occurs. This anomaly is absent in the Vostok ice core deuterium, and in oceanic records from the Antarctic Zone. However, it is present in the deuterium excess record from the Vostok ice core, interpreted as reflecting the temperature at the moisture source site for the snow precipitated at Vostok Station. As atmospheric models predict a subtropical Indian source for such moisture, this provides the necessary teleconnection between East Antarctica and ODP Site 1089, as the subtropical Indian is also the source area of the Agulhas Current, the main climate agent at our study location.The presence of the MIS 10 anomaly in the d 13 C foraminiferal records from the same core supports its connection to oceanic mechanisms, linking stronger Agulhas spillover intensity to increased productivity in the study area. We suggest, in analogy to modern oceanographic observations, this to be a consequence of a shallow nutricline, induced by eddy mixing and baroclinic tide generation, which are in turn connected to the flow geometry, and intensity, of the Agulhas Current as it flows past the Agulhas Bank.We interpret the intensified inflow of Agulhas Current to the South Atlantic as responding to the switch between lower and higher amplitude in the insolation forcing in the Agulhas Current source area. This would result in higher SSTs in the Cape Basin during the glacial MIS 10, due to the release into the South Atlantic of the heat previously accumulating in the subtropical and equatorial Indian and Pacific Ocean. If our explanation for the MIS 10 anomaly in terms of an insolation variability switch is correct, we might expect that a future Agulhas SSST anomaly event will further delay the onset of next glacial age. In fact, the insolation forcing conditions for the Holocene (the current interglacial) are very similar to those present during MIS 11 (the interglacial preceding MIS 10), as both periods are characterized by a low insolation variability for the Agulhas Current source area. Natural climatic variability will force the Earth system in the same direction as the anthropogenic global warming trend, and will thus lead to even warmer than expected global temperatures in the near future. D

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“…These two genera were well represented in Leg 115 material, but a number of the taxa occurred only sporadically. Consequently, the following events that were identified previously (Johnson et al, 1989) A number of other significant late Neogene events were not possible to identify, including the following:…”

Section: Radiolarian Eventsmentioning

confidence: 99%

“…The FO of Amphirhopalum ypsilon, at 3.8 Ma in the upper part of the Gilbert (Johnson et al, 1989), is identified between 31.0 and 34.0 mbsf in Hole 710A (Appendix B). Thus, the long intervals of reversed polarity in Core 115-710A-4H (Backman et al, in press, fig.…”

Section: Paleomagnetic Calibrations and Diachroneitymentioning

confidence: 99%

Radiolarian Biostratigraphy in the Central Indian Ocean, Leg 115

Johnson¹

1990

Proceedings of the Ocean Drilling Program

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Identifiable radiolarians of stratigraphic importance were recovered at eight of the sites drilled on Leg 115. The assemblages range in age from Holocene to middle Eocene (JDictyoprora mongolfieri Zone, about 48 Ma). Faunal preservation is particularly good in two stratigraphic intervals: the Holocene through upper Miocene (0-9 Ma), and the lowermost Oligocene to middle . Fluctuating rates of silica accumulation at these drill sites during the Cenozoic reflect changing tectonic and paleoceanographic conditions. In particular, the gradual closure of the Indonesian and Tethyan seaways and the northward migration of the Indian subcontinent severely restricted zonal circulation and silica accumulation in tropical latitudes during the late Oligocene through middle Miocene. By the late Miocene the Indian subcontinent had moved sufficiently north of the equator to allow trans-Indian zonal circulation patterns to become reestablished, and biosiliceous sedimentation resumed.The composition of the radiolarian assemblages in the tropical Indian Ocean is closely comparable with that of the "stratotype" sequences in the equatorial Pacific. However, there are some notable exceptions in Indian Ocean assemblages: (1) the scarcity of the genera Pterocanium and Spongaster in the Neogene; (2) the absence of the stratigraphically important Podocyrtis lineage, P. diamesa -* P. phyxis -» P. ampla, in the middle Eocene; and (3) the scarcity of taxa of the genus Dorcadospyris, with the exception of D. ateuchus.The succession of radiolarian events was tabulated for those stratigraphic intervals where the assemblages were well preserved. We identified 55 events in the middle Eocene to earliest Oligocene, and 31 events in the late Miocene to Holocene. The succession of events is closely comparable with that of the tropical Pacific. However, there are exceptions that appear to be real, rather than artifacts of sample preservation, mixing, and core disturbance. INTRODUCTION AND METHODSRadiolarians were recovered in eight of the sites occupied during Ocean Drilling Program (ODP) Leg 115 in the western Indian Ocean. The locations and water depths of these sites appear in Table 1.The upper portions of several of these sites were double-or triple-cored with the advanced hydraulic piston corer (APC). For purposes of this report, radiolarian biostratigraphy is reported only for a composite stratigraphic section at each site. There was insufficient time available to analyze all cores obtained from the duplicate-or triplicate-cored intervals.Within those stratigraphic intervals where radiolarian preservation was good, four samples per core were prepared and examined. Ordinarily, these samples were obtained from Sections 2, 4, 6, and the core catcher (CC). The sediment was prepared by means of standard techniques (Sanfilippo et al., 1985, p. 633) and was sieved at 63 /xm; two strewn slides were prepared for each sample.For each sample examined, qualitative estimates of radiolarian abundance (C = common; F = few; R = rare; + = very rare; -=...

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Pliocene-Pleistocene radiolarian events and magnetostratigraphic calibrations for the tropical Indian Ocean

Cited by 87 publications

References 45 publications

Magnetostratigraphy of Leg 117 Sediments from the Owen Ridge and the Oman Margin, Western Arabian Sea

Magnetostratigraphy of Leg 117 Sediments from the Owen Ridge and the Oman Margin, Western Arabian Sea

A glacial warm water anomaly in the subantarctic Atlantic Ocean, near the Agulhas Retroflection

Radiolarian Biostratigraphy in the Central Indian Ocean, Leg 115

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