Distribution, stratigraphic position and age of ash layer “L”, in the Panama Basin region

Ninkovich, Dragoslav; Shackleton, Nicholas J

doi:10.1016/0012-821x(75)90156-9

Cited by 174 publications

(76 citation statements)

References 19 publications

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“…Therefore, in addition to the averaged LR04 curve, we also looked at two marine sequences covering this period. One dataset is the composite record (referred to as S05) of Eastern Equatorial Pacific sites: V19-30 (0-341 kyr bp) 51 , V19-28 (341-430 kyr bp) 52 , V19-25 (430-460 kyr bp) (N. J. Shackleton, unpublished data), ODP 677 (460-1,809 kyr bp) 24 and ODP 846 (1,812-2,600 kyr bp) 53 . The other dataset is a new well-resolved record U1308 (ref.…”

Section: Discussionmentioning

confidence: 99%

A simple rule to determine which insolation cycles lead to interglacials

Tzedakis

Crucifix

Mitsui

et al. 2017

Nature

131

148

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The Milanković astronomical theory of ice ages 1 posits that quasiperiodic expansions and contractions of Northern Hemisphere ice sheets are driven by variations in Earth's orbital geometry and axial inclination that influence the amount of summer insolation received at northern high latitudes. Astronomical periodicities of obliquity (41,000-year (41-kyr) cycles) and precession (23-and 19-kyr cycles) were found to be embedded in records of changing ice volume and climate 2 ; however, in addition to these cycles, climate variance in the Middle and Late Pleistocene was dominated by a 100-kyr cycle 2 , which was not predicted by the original theory. The development of improved chronologies 3 and advances in demarcating interglacial boundaries 4 have shown that the onset of interglacials over the past 600 kyr occurred near the maximum in boreal summer insolation, with perihelion (when Earth is nearest to the Sun) at the northern summer solstice. Mean daily insolation on 21 June at 65° N is often used as a predictor of glacial changes, because it represents maximum values at a sensitive time of the year at a critical latitude for ice-sheets. However, the data in Fig. 1 reveal that not all insolation maxima led to interglacials: some prominent insolation peaks are associated with incomplete deglaciations-that is, interstadials (for example, Marine Isotope sub-Stages (MIS) 6e and 9a)-and some prominent interglacials are associated with moderate insolation maxima, most notably MIS 11c (ref. 5). It is, in fact, difficult to decide which insolation maxima would lead to interglacials by using only this insolation curve. An additional complication is that deglaciations occurred approximately every 41 kyr (the so-called '41-kyr world') up until about one million years before present (1 Myr bp), but have been less frequent since then (the so-called '100-kyr world' , but see below). Therefore, any comprehensive explanation of how astronomical forcing translates into the sequence of Quaternary ice ages needs to account for the occurrence of interglacials at different frequencies.Several numerical models [6][7][8][9][10][11][12][13][14][15][16] have reproduced the pattern, and in some cases much of the timing, of glacial-interglacial cycles over part or all of the Quaternary. Although each of these has pointed at some of the ingredients involved in a comprehensive explanation, some include large numbers of tunable parameters, none is fully successful over the past million years, and few offer a consistent and simple rule that accounts for the whole Quaternary sequence. Here we ask whether the onset of interglacials over the course of the Quaternary can be predicted from simple combinations of astronomical parameters (that is, without any knowledge of atmospheric CO 2 concentration, dust or other climate data). We determine the parameters of such a model in a statistical way, which allows us to discuss whether a simple model can successfully accommodate the observed sequence and to assess how tightly the succession of ice ages is...

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Section: Discussionmentioning

confidence: 99%

A simple rule to determine which insolation cycles lead to interglacials

Tzedakis

Crucifix

Mitsui

et al. 2017

Nature

131

148

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“…We have throughout assumed that no phase lag existed between insolation and GRAPE density and that high density (high percentage of CaCO 3 ) is associated with high Northern Hemisphere summer insolation. This phase relationship may be approximately valid for the most recent past; in the Pacific Ocean, a low percentage of CaCO 3 is associated with interglacial-to-glacial transitions and good carbonate preservation with glacial-to-interglacial transitions (e.g., Ninkovich and Shackleton, 1975;Keir and Berger, 1985;Le and Shackleton, 1992). Whether this phase relationship is appropriate to the equatorial high productivity belt in the eastern Pacific Ocean, and whether the same phase relationship is appropriate for the older part of the record, is not yet known.…”

Section: Tuning Methodsmentioning

confidence: 98%

A New Late Neogene Time Scale: Application to Leg 138 Sites

Shackleton¹,

Crowhurst²,

Hagelberg³

et al. 1995

Proceedings of the Ocean Drilling Program, 138 Scientific Results

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225

240

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The sediments recovered during Leg 138 provide a remarkable opportunity to improve the geological time scale of the late Neogene. We have developed new time scales in the following steps. First, we constructed age models on the basis of shipboard magnetostratigraphy and biostratigraphy, using the time scale of Berggren, Kent, and Flynn (1985). Second, we refined these age models using shipboard GRAPE density measurements to provide more accurate correlation points. Third, we calibrated a time scale for the past 6 m.y. by matching the high-frequency GRAPE density variations to the orbital insolation record of Berger and Loutre (1991); we also took into account δ 18 θ records, where they were available. Fourth, we generated a new seafloor anomaly time scale using our astronomical calibration of C3A.n (t) at 5.875 Ma and an age of 9.639 Ma for C5n.ln (t) that is based on a new radiometric calibration (Baksi, 1992). Fifth, we recalibrated the records older than 6 Ma to this new scale. Finally, we reconsidered the 6-to 10-Ma interval and found that this could also be partially tuned astronomically.

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“…Several investigators have successfully correlated deep sea tephra layers with source volcanic rocks on land (Ninkovich, 1968;Ninkovich & Shackleton, 1975;Keller et al, 1978). Although deep sea tephra is several hundred or more km from the source volcanic rocks, it is correctable using diagnostic features of volcanic ash.…”

Section: Tephra Correlationmentioning

confidence: 99%

Petrography and Geochemistry of Volcanic Glass: Leg 57, Deep Sea Drilling Project

Fujioka¹,

Furuta²,

Arai³

1980

Initial Reports of the Deep Sea Drilling Project

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About 200 volcanic ash layers were recovered during DSDP Leg 57. The volcanic glass in some of these layers was investigated petrographically and chemically in this study. Volcanic glass is mainly rhyolitic and/or rhyodacitic in chemical composition, and its refractive index ranges from 1.496 to 1.529. Some volcanic ash layers consist of multiple grains of different chemical compositions. All the volcanic glass belongs to the tholeiitic and the calc-alkalic volcanic rock series, in SiO->-

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Distribution, stratigraphic position and age of ash layer “L”, in the Panama Basin region

Cited by 174 publications

References 19 publications

A simple rule to determine which insolation cycles lead to interglacials

A simple rule to determine which insolation cycles lead to interglacials

A New Late Neogene Time Scale: Application to Leg 138 Sites

Petrography and Geochemistry of Volcanic Glass: Leg 57, Deep Sea Drilling Project

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