Orbital control on carbonate-lignite cycles on sediment core KAP-107 in the Ptolemais Basin, northern Greece

Time control is essential for the reconstruction of geological processes. We use a combination of relative and absolute methods to establish the chronology and related paleoclimatic processes for Late Neogene lacustrine sediment from the Ptolemais Basin, northern Greece. We determined changes in magnetic polarity and correlated them to the global magnetic polarity time scale, which again is calibrated by radiometric methods, to provide a low-resolution age model for the Upper Miocene to Lower Pliocene (7 - 3 Ma). Sedimentary successions show rhythmic alterations of lignites, clays, and marls. Using photospetrometry we measured this variability at 1-cm resolution, and correlated the pattern to known changes in earth's orbital parameters, namely to eccentricity and precession. For 230-m long borehole KAP-107 from the Amynteon Sub-Basin we obtained a high-resolution age model that spans 2 myr from 5.1 to 3.1 Ma, with age control points at insolation maxima (20-kyr resolution). We recommend using photospectrometry as reliable tool to establish orbital-based chronologies and to reconstruct paleoclimate variability at high resolution.

Magnetostratigraphy of ODP Leg 107 holes

Apart from Site 650, core disturbance due to rotary drilling severely compromised the quality of the magnetostratigraphic data obtained from Leg 107 sediments. The correlation of polarity zones to the geomagnetic polarity time scale cannot be made solely on the basis of pattern fit. The proposed correlations are consistent between sites, and this consistency is constrained by the biostratigraphic datums. The resulting biomagnetostratigraphic correlations are reviewed in the synthesis section of this volume. The purpose of this paper is to document the magnetic stratigraphies, and present the preferred correlation to the geomagnetic reversal time scale. Four implications of the proposed correlations are: (1) The Mio-Pliocene boundary occurs in the lowest reversed interval of the Gilbert (Chron 3r) at about 4.9 Ma. (2) The thick pre-Pliocene lacustrine sequence recovered at Site 652 appears to have been deposited entirely within a single reversed polarity chron (Chron 3r). (3) The balatino-type gypsum recovered at Site 654 was also deposited entirely within this polarity chron (Chron 3r). (4) The Tortonian-Messinian boundary occurs within a normal polarity zone which is probably correlative to Chron 6 (Chron 3B) giving a boundary age of about 6.4 Ma.