Organic-rich layers in the Metochia section (Gavdos, Greece): evidence for a single mechanism of sapropel formation during the past 10 My

Schenau, Sjoerd; Antonarakou, Assimina; Hilgen, F.J.; Lourens, Lucas Joost; Nijenhuis, Ivar A; Weijden, C. H. Van der; Zachariasse, Willem-Jan

doi:10.1016/s0025-3227(98)00086-3

Cited by 72 publications

(47 citation statements)

References 66 publications

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“…Overall, we infer that WAM variability led to recurrent GSPs back to 8 Ma (Figure 5g), with GSPs forming 400-kyr and 100-kyr clusters that attest to the impact of eccentricity modulation of precession (and hence of insolation) on monsoon variability [63], [82], [83], [85], [86] (Figure 5a,e,f). A less regular sapropel pattern after 0.9 Ma [63], [66] suggests that GSPs were somewhat less frequent after development of large polar ice caps during the Mid-Pleistocene Transition (Figure 5a,f,g).…”

Section: Resultsmentioning

confidence: 74%

“…Enhanced WAM (as opposed to EAM) precipitation during GSPs also provides an explanation for enhanced pedogenic activity [81] and dampening of dust production [66] throughout the Sahara during periods of sapropel formation. Such a prominent role of the WAM as the main driver of GSPs explains the accumulation of sapropels back to 10 Ma, under the same scenario of enhanced monsoonal discharge during local summer insolation maxima [63], [82], [83], well before the earliest clear evidence for a river connecting the East African tropical regions with the Mediterranean Sea across Egypt sometime between the latest Miocene (ca 6 Ma [79]) and the early Pliocene (4–5 Ma [84]). …”

Section: Resultsmentioning

confidence: 99%

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Dynamics of Green Sahara Periods and Their Role in Hominin Evolution

2013

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Astronomically forced insolation changes have driven monsoon dynamics and recurrent humid episodes in North Africa, resulting in green Sahara Periods (GSPs) with savannah expansion throughout most of the desert. Despite their potential for expanding the area of prime hominin habitats and favouring out-of-Africa dispersals, GSPs have not been incorporated into the narrative of hominin evolution due to poor knowledge of their timing, dynamics and landscape composition at evolutionary timescales. We present a compilation of continental and marine paleoenvironmental records from within and around North Africa, which enables identification of over 230 GSPs within the last 8 million years. By combining the main climatological determinants of woody cover in tropical Africa with paleoenvironmental and paleoclimatic data for representative (Holocene and Eemian) GSPs, we estimate precipitation regimes and habitat distributions during GSPs. Their chronology is consistent with the ages of Saharan archeological and fossil hominin sites. Each GSP took 2–3 kyr to develop, peaked over 4–8 kyr, biogeographically connected the African tropics to African and Eurasian mid latitudes, and ended within 2–3 kyr, which resulted in rapid habitat fragmentation. We argue that the well-dated succession of GSPs presented here may have played an important role in migration and evolution of hominins.

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Section: Resultsmentioning

confidence: 74%

Section: Resultsmentioning

confidence: 99%

Dynamics of Green Sahara Periods and Their Role in Hominin Evolution

2013

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“…This chronology was compared with computed astronomical curves for the past variations in the Earth's orbit and spinaxis to determine phase relations between the sapropel cycles and the astronomical cycles: individual sapropels correspond to precession minima=summer insolation maxima, and small-scale and large-scale sapropel clusters to 100,000 and 400,000 years eccentricity maxima (Hilgen, 1991), while alternating thin-thick sapropels reflect precession=obliquity interference (Lourens et al, 1996). Further research showed that the sapropels are the equivalent of greycoloured CaCO 3 -poor marl beds in the basic carbonate cycles of the Pliocene Trubi Formation of southern Italy while a multidisciplinary study of three 9.5-Ma-old sapropels revealed that the basic mechanism of cycle formation remained essentially the same over the last 10 million years (Schenau et al, 1999). Pliocene-Pleistocene phase relations between sedimentary and orbital cycles can therefore be applied to astronomically calibrate (older) sedimentary cycles like those in the Gibliscemi sections .…”

Section: Astronomical Calibration and Age Modelmentioning

confidence: 92%

Integrated stratigraphy and astronomical calibration of the Serravallian/Tortonian boundary section at Monte Gibliscemi (Sicily, Italy)

Hilgen

Krijgsman²,

Raffi

et al. 2000

Marine Micropaleontology

118

148

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Results are presented of an integrated stratigraphic (calcareous plankton biostratigraphy, cyclostratigraphy and magnetostratigraphy) study of the Serravallian=Tortonian (S=T) boundary section of Monte Gibliscemi (Sicily, Italy). Astronomical calibration of the sedimentary cycles provides absolute ages for calcareous plankton bio-events in the interval between 9.8 and 12.1 Ma. The first occurrence (FO) of Neogloboquadrina acostaensis, usually taken to delimit the S=T boundary, is dated astronomically at 11.781 Ma, pre-dating the migratory arrival of the species at low latitudes in the Atlantic by almost 2 million years. In contrast to delayed low-latitude arrival of N. acostaensis, Paragloborotalia mayeri shows a delayed low-latitude extinction of slightly more than 0.7 million years with respect to the Mediterranean (last occurrence (LO) at 10.49 Ma at Ceara Rise; LO at 11.205 Ma in the Mediterranean). The Discoaster hamatus FO, dated at 10.150 Ma, is clearly delayed with respect to the open ocean. The ages of D. kugleri first and last common occurrence (FCO and LCO), Catinaster coalitus FO, Coccolithus miopelagicus last (regular) occurrence (L(R)O) and the D. hamatus=neohamatus cross-over, however, are in good to excellent agreement with astronomically tuned ages for the same events at Ceara Rise (tropical Atlantic), suggesting that both independently established timescales are consistent with one another. The lack of a reliable magnetostratigraphy hampers a direct comparison with the geomagnetic polarity timescale of Cande and Kent (1995; CK95), but ages of calcareous nannofossil events suggests that CK95 is significantly younger over the studied time interval. Approximate astronomical ages for the polarity reversals were obtained by exporting astronomical ages of selected nannofossil events from Ceara Rise (and the Mediterranean) to eastern equatorial Pacific ODP Leg 138 Site 845, which has a reliable magnetostratigraphy.Our data from the Rio Mazzapiedi-Castellania section reveal that the base of the Tortonian stratotype corresponds almost exactly with the first regular occurrence (FRO) of N. acostaensis s.s. as defined in the present study, dated at 10.554 Ma. An extrapolated age of 11.8 Ma calculated for the top of the Serravallian stratotype indicates that there is a gap between the top of the Serravallian and the base of the Tortonian stratotype, potentially rendering all bio-events in the interval between 11.8 and 10.554 Ma suitable for delimiting the S=T boundary. Despite the tectonic deformation and the lack of a magnetostratigraphy, Gibliscemi remains a candidate to define the S=T boundary by means of the Tortonian global boundary stratotype section and point (GSSP). © 2000 Elsevier Science B.V. All rights reserved.Ł Corresponding author. E-mail: fhilgen@geo.uu.nl 0377-8398/00/$ -see front matter © 2000 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 7 -8 3 9 8 ( 0 0 ) 0 0 0 0 8 -6 182 F.J. Hilgen et al. / Marine Micropaleontology 38 (2000)

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“…On astronomical time-scales, the eastern Mediterranean oceanography was repeatedly affected by monsoon [25,48]. However, with regard to the overall similarity of the palaeogeography with the present-day, there might have been a marked influence of the Atlantic domain on eastern Mediterranean climate via atmospheric teleconnections and ocean circulation patterns [28-31, 44, 49].…”

Section: Geological Contextmentioning

confidence: 99%

“…Growth rates were ~4 mm/year and similar to massive Porites from modern high-latitude reefs [22], which reflects the position of Crete at the northern margin of the Late Miocene reef belt [23], and the warmer than present Late Miocene greenhouse climate [2]. Although the Late Miocene palaeoceanography and palaeoclimatic evolution of the Mediterranean is well known on geological time-scales [7,24,25], little information exists with regard to the subannual and interannual climate variability. For the eastern Mediterranean and Middle East, the Arctic Oscillation/North Atlantic Oscillation (AO/NAO), the Northern Hemisphere's dominant mode of atmospheric variability [26,27], exerts not only a major impact on the present-day interannual climate variability, but has also played a critical role during the Holocene and Last interglacial [28][29][30][31].…”

Section: Introductionmentioning

confidence: 99%