Astronomic timescale for the Pliocene Atlantic δ¹⁸O and dust flux records of Ocean Drilling Program Site 659

Abstract

Abstract. High-resolution benthic oxygen isotope and dust flux records from Ocean Drilling Program site 659 have been analyzed to extend the astronomically calibrated isotope timescale for the Atlantic from 2.85 Ma back to 5 Ma. Spectral analysis of the o 1 BO record indicates that the 41-kyr period of Earth's orbital obliquity dominates the Pliocene record. This is shown to be true regardless of fundamental changes in the Earth's climate during the Pliocene. However, the cycles of Sahelian aridity fluctuations indicate a shift in spectral character near 3 Ma. From the early Pliocene to 3 Ma, the periodicities were dominantly precessional (19 and 23 kyr) and remained strong until1.5 Ma. Subsequent to 3 Ma, the variance at the obliquity period (41 kyr) increased. The timescale tuned to precession suggests that the Pliocene was longer than previously estimated by more than 0.5 m.y. The tuned ages for the magnetic boundaries Gauss/Gilbert and Top Cochiti are about 6-8% older than the ages of the conventional timescale. A major phase of Pliocene northern hemisphere ice growth occurred between 3.15 Ma and 2.5Ma. This was marked by a gradual increase in glacial Atlantic o 1 BO values of 1o/oo and an increase in amplitude variations by up to 1.5o/oo, much larger than in the Pacific deepwater record (site 846). The first maxima occured in cold stages G6-96 between 2.7 Ma and 2.45 Ma. Prior to 3 Ma, the isotope record is characterized by predominantly low amplitude fluctuations(< 0.7o/oo.). When obliquity forcing was at its minimum between 4.15 and 3.6 Ma and during the Kaena interval, o 18 0 amplitude fluctuations were minimal. From 4.9 to 4.3 Ma, the o 18 0 values decreased by about 0.5o/oo, reaching a long-term minimum at 4.15 Ma, suggesting higher deepwater temperatures or a deglaciation. Deepwater cooling and/or an increase in ice volume is indicated by a series of short-term o 1 BO fluctuations between 3.8 and 3.6 Ma.

The middle Pleistocene transition: characteristics, mechanisms, and implications for long-term changes in atmospheric pCO2

“…Dwyer et al (1995) Changes in other components of the climate system indicate differing sensitivities to the changes in global ice volume and deep-water temperature that occurred during the MPT. The onset of the MPT was accompanied by decreases in sea surface temperatures (SSTs) in the North Atlantic (Ruddiman et al, 1989) and tropical-ocean upwelling regions (Schefus et al, 2004;Liu and Herbert, 2004;McClymont and Rossel-Mele, 2005) and by an increase in African (Tiedemann et al, 1994) and Asian aridity and monsoonal intensity (Clemens et al, 1996;Williams et al, 1997;Sun et al, 2006). The low-frequency component of North Atlantic SSTs and proxies of Asian and African monsoon and aridity also appeared at this time.…”

“…10c). In this Dd 13 C (AÀP) record, the change to more depleted glacial d 13 C values seen in the Site 607 record at (Tiedemann et al, 1994), (c) Flux of terrigenous (eolian) sediments in ODP Site 722 (Clemens et al, 1996), (d) Stacked record of normalized mean grain size of quartz (MGSQ) from loess sequences on the Chinese Loess Plateau (Sun et al, 2006), (e) Percent biogenic silica from Lake Baikal, south-central Siberia (Williams et al, 1997). Broad light-gray vertical bar shows timing of the MPT (Fig.…”

“…The percent and flux of eolian sediments to adjacent oceans is a proxy for aridity of the source area (Tiedemann et al, 1994;deMenocal, 1995;Clemens et al, 1996), whereas monsoon wind strength can be estimated from the grain size of wind-blown lithogenic sediments deposited in the oceans and on the loess plateau of China (Clemens et al, 1996;Sun et al, 2006). Lastly, Williams et al (1997) interpret the sedimentary record of biogenic silica in Lake Baikal, south-central Siberia, as a proxy for temperature, with high biogenic silica percentages associated with warmer waters in the lake.…”

The meridional temperature gradient in the eastern North Atlantic during MIS 11 and its link to the ocean–atmosphere system

“…The pelagic sediments off NW Africa clearly reflect the glacialinterglacial pattern due to changes in wind-driven terrigenous input (Tiedemann et al, 1994;Pflaumann et al, 1998). Because glacial times were characterised by a reduced intensity of the West African monsoon and enhancement of the trade wind strength, the glacial sediment intervals contain sufficiently more of an eolian fraction in comparison to the interglacial sections (Tjallingii et al, 2008).…”

Eastern Mediterranean foraminiferal palaeoecological response to Mid-Late Pliocene climatic regime: A preliminary note.

“…According to Hilgen (1991), individual sapropels in the eastern Mediterranean can be correlated with minima of the precessional cycle. Other studies support the precessional cycle as the dominant factor influencing the lower to upper Pliocene climatic evolution (Tiedemann et al 1994). In the absence of high resolution stratigraphic control, we can only speculate as to the precise nature of astronomical forcing behind the brown-white marl cycles studied herein.…”