Sonic and gamma-ray astrochronology: Cycle to cycle calibration of Atlantic climatic records to Mediterranean sapropels and astronomical oscillations

An astronomical polarity timescale for the late middle Miocene based on cyclic continental sequences

“…Such conditions are linked to high‐amplitude precession minima, which occur at times of eccentricity maxima. This phase relation is consistent with the interpretation of cyclic patterns observed in Pliocene marine sediments from drill holes located in the Gulf of Cadiz [ Sierro et al , 2000]. They found that prolonged periods of relatively dry climate conditions occurred during 400‐kyr eccentricity minima and punctuated wet episodes during eccentricity maxima.…”

Obliquity forcing of low-latitude climate

“…Furthermore, in the late Pliocene and Pleistocene, phase relations suggest that the obliquity influence on sapropel formation and North African aridity did not proceed indirectly via ice driven responses but more directly via summer insolation (Lourens et al, 1996(Lourens et al, , 2010. In addition, colour changes associated with carbonate dilution cycles in north-western Africa and Spain reveal precession-obliquity interference patterns similar to those found in Mediterranean sapropels (Hilgen et al, 2000;Sierro et al, 2000). Also, others have ruled out global ice volume as a primary forcing mechanism for the occurrence of obliquityrelated variability in Indian monsoon strength as inferred from sediment records of the Arabian Sea (Clemens et al, 1991;Clemens and Prell, 2003).…”

“…For instance, dust flux records from both the (sub)tropical Atlantic and the Arabian Sea concur with obliquity-paced global climate cycles, suggesting a close link between changes in low-latitude aridity and glacial variability (Bloemendal and deMenocal, 1989;deMenocal et al, 1993;Tiedemann et al, 1994;deMenocal, 1995). Several other proxy studies, however, find lowlatitude obliquity signals at times when glacial cycles were much smaller or even absent (Lourens et al, 1996(Lourens et al, , 2001Hilgen et al, 1995Hilgen et al, , 2000Sierro et al, 2000). In particular, obliquity-controlled interference patterns in Mediterranean sapropels are present not only in the Pleistocene (Lourens et al, 1996) but also in the warmer Pliocene and Miocene (Hilgen et al, 1995Zeeden et al, 2014).…”

“…2; Reichart, 1996;Leuschner and Sirocko, 2003) as well as the P -1 2 T curve (Lourens et al, 2001). Hence, the widely applied 65 • N 21 June insolation curve (Tiedemann et al, 1994;Hilgen et al, 1995;Lourens et al, 1996Lourens et al, , 2001Hilgen et al, 2000;Sierro et al, 2000) needs to be reconsidered in favour of SITIG. SITIG instead of 65 • N 21 June insolation relies on a physical basis as described by the analysis presented here rather than pattern matching, and explains the obliquity influence on tropical climate independent of glacial-interglacial variability.…”

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“…MOW millennial to long-term variability and its effects on thermohaline circulation is an active and prolific line of research at present. It has been inferred that the rate of deepwater formation reached its highest level in the Mediterranean during glacial stages, when contribution of NADW was at a minimum and Antarctic Bottom Water (AABW) at a maximum, but there are still many questions to resolve in this regard (e.g., Duplessy et al, 1988;Abrantes, 1988;Caralp, 1988Caralp, , 1992Sarnthein et al, 1994;Schönfeld, 1997Schönfeld, , 2002Cayre et al, 1999;Flower et al, 2000;Sierro et al, 2000Sierro et al, , 2005Shackleton et al, 2000;Schönfeld and Zahn, 2000;Cacho et al, 2000Cacho et al, , 2001Moreno et al, 2002;Schönfeld et al, 2003;Slater, 2003;Löwemark et al, 2004;Raymo et al, 2004;Voelker et al, 2006;Llave et al, 2006;Lebreiro et al, 2009;Lebreiro, 2010;Voelker and Lebreiro, 2010; among others).…”