Early Pleistocene climate changes in the central Mediterranean region as inferred from integrated pollen and planktonic foraminiferal stable isotope analyses

Abstract

International audienceVegetation inherited from a Pliocene subtropical climate evolved through obliquity oscillations and global cooling leading to modern conditions. An integrated, highly time-resolved record of pollen and stable isotopes (δ18O and δ13C of Globigerina bulloides) was obtained to understand vegetation responses to Early Pleistocene climate changes. Continental and marine responses are compared in the Central Mediterranean region with a particular consideration of environmental changes during anoxic events. Pollen data illustrate vegetation dynamics as follows: [1] development of mesothermic elements (warm and humid conditions); [2] expansion of mid- and high-altitude elements (cooler but still humid conditions); and [3] strengthening of steppe and herb elements (cooler and dry conditions). These successions correlate with precession. δ18O variations recorded by Globigerina bulloides define two cycles (MIS 43-40) related to obliquity. At northern low- to mid-latitudes, the pollen signal records temperature and wetness changes related to precession even during global climate changes induced by obliquity. This may result in unexpected increasing wetness during glacial periods, which has to be considered specific to the Central and Eastern Mediterranean region. Lastly, an analysis of anoxic events reveals that enhanced runoff is indicated by increasing frequency of the riparian trees Liquidambar and Zelkova

Refining upon the climatic background of the Early Pleistocene hominid settlement in western Europe: Barranco León and Fuente Nueva-3 (Guadix-Baza Basin, SE Spain)

“…For the time between 1.25 and 1.55 Ma, such warm and humid periods are roughly contemporaneous with the precessional amplitude maxima (eccentricity), as suggested by Joannin et al (2007) for the time period from MIS 40 to 43. Whereas oxygen isotope composition mainly follows obliquity, these latter warm moister periods can be correlated with precession minima and insolation maxima.…”

“…Enhanced summer dryness and warmth during precession minima in the western Mediterranean is linked with enhanced west African monsoons (Baldi et al, 2004), while net precipitation over the Mediterranean basin should increase during precession minima and winter precipitation should be favored by stronger land/sea temperature contrasts over the Mediterranean Sea in autumn (Tuenter et al, 2003;Meijer and Tuenter, 2007). Together with the well-calibrated environmental reconstructions of Joannin et al (2007) for the late Early Pleistocene of Santa Lucia (southern Italy), such data should make it possible to identify the particular periods with warm and humid conditions and better constrain the chronology of Barranco Le on D and Fuente Nueva-3 within the range given by the biostratigraphy and numerical dating.…”

“…These authors also reviewed other sites in southern Europe, such as Stirone (northern Italy), Pietrafitta (central Italy), Camerota (southern Italy), Bernasso and Nogaret (southern France), and Bobila Ordis (northeastern Spain), where phases of Carya abundance appear in the middle of interglacial periods, under a humid climate. In a more recent study in the Crotone area (southern Italy), Joannin et al (2007) identified three interglacial-related forest phases: deciduous forest, subtropical-humid forest, and altitudinal coniferous forest. This last step constitutes a transition toward a fourth step, which is glacial-related open vegetation.…”

“…According to the detailed late Early Pleistocene environmental reconstruction by Joannin et al (2007), the vegetation dynamics is separated into three main steps: 1) development of mesothermic elements, mainly Olea (warm and humid conditions correlated with MIS 43 and 42); 2) expansion of mid-and high-altitude elements (temperate but still humid conditions correlated with MIS 42e41); and 3) strengthening of steppe and herb elements (cooler, dry conditions correlated with MIS 40). The existence of such cold periods during the earliest Pleistocene in southern Europe is well attested by the temperature reconstructions for the period comprised between 2.11 and 2.46 Ma (Klotz et al, 2006), with estimated MAT up to 6.4 C lower when compared to the presentday climate.…”

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

“…Numerous studies across the Mediterranean postulate a climatic control on cyclical alternations in marine and terrestrial successions, invoking a linkage with the changeable variations in the Earth's orbital parameters (e.g. Postma & Drinia,1993;Weltje & De Boer, 1993;Kroon et al, 1998;Van Vugt et al, 1998;Wehausen & Brumsack, 1999;Foucault & Mélières 2000;Lourens et al, 2001;Joannin et al, 2007;amongst others). Therefore, it is likely that the sediments of Cyprus should provide a relatively intact archive of past climatic variability, likely to be recognizable on orbital timescales.…”