Pressure, tilt, temperature and conductivity monitoring within the Immerged Santorini Caldera during Jul 2012 - Sep 2013

Bottom pressure, tilt and seawater physical-properties were monitored for a year using two instruments within the immerged Santorini caldera (Greece). Piggy-backed on the CALDERA2012 cruise, this geodetic experiment was designed to monitor evolution of the 2011-2012 Santorini unrest. Conducted during a quiescent period, it allowed us to study oceanographic and atmospheric signal in our data series. We observe periodic oceanographic signals associated with tides, and seiches that are likely linked to both the caldera and Cretan basin geometries. In winter, the caldera witnesses sudden cooling events that tilt an instrument towards the Southeast, indicating cold-water influx likely originating from the north-western passage between Thirasia and Oia. We do not obtain evidence of long-term vertical seafloor deformation from the pressure signal, although it may be masked by instrumental drift. However, tilt data suggests a local seafloor tilt event ~1 year after the end of the unrest period which could be consistent with inflation under or near Nea Kameni. Seafloor geodetic data recorded at the bottom of the Santorini caldera illustrates that the oceanographic signature is an important part of the signal, which needs to be considered for monitoring volcanic or geological seafloor deformation in shallow-water and/or nearshore areas.

Paleomagnetism of ODP Leg 115 sediments

Ocean Drilling Program Leg 115 was designed to study Neogene sedimentation history in the western Indian Ocean Basin as well as the Cenozoic evolution of the Reunion hotspot. We describe the paleomagnetic analysis of the sediments recovered on this leg, focusing on the sites that provided the most readily interpretable data: Sites 706, 709, 710, and 711. Sediments from Site 706 show no reversals but appear to give a reliable reversed polarity primary direction, judged on the basis of the demagnetization behavior of individual samples as well as from the results of a fold test formulated by comparing the two holes drilled at this site. Magnetic polarity stratigraphy in sediments from Site 709 can be deduced in two limited sections of Pliocene-Pleistocene and Oligocene-Miocene age. Sediments recovered at Site 710 (and, to a lesser extent, Site 711) render a relatively continuous magnetic polarity stratigraphy that spans most of the Neogene and adds significantly to the body of data available to address problems in Miocene geochronology. In addition to these magnetostratigraphic results, the paleomagnetism of these sediments can be used to determine paleolatitude. Using the most reliable inclination measurements from Sites 706, 710, and 711, we compared paleomagnetic estimates of paleolatitude with estimates derived from a hotspot-based absolute plate motion model. Our data, which covers the interval since 33 Ma, shows that paleolatitudes calculated with the geocentric axial dipole assumption are in general accord with the hotspot predictions. However, a correction for the long-term nondipole field brings the paleomagnetic results into even better agreement with plate motions that are based on the fixity of African hotspots.

Parameters of the Earths orbit for the last 5 Million years in 1 kyr resolution

New values for the astronomical parameters of the Earth's orbit and rotation (eccentricity, obliquity and precession) are proposed for paleoclimatic research related to the Late Miocene, the Pliocene and the Quaternary. They have been obtained from a numerical solution of the Lagrangian system of the planetary point masses and from an analytical solution of the Poisson equations of the Earth-Moon system. The analytical expansion developed in this paper allows the direct determination of the main frequencies with their phase and amplitude. Numerical and analytical comparisons with the former astronomical solution BER78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated. The corresponding insolation values have also been computed and compared to the former ones. This analysis leads to the conclusion that the new values are expected to be reliable over the last 5 Ma in the time domain and at least over the last 10 Ma in the frequency domain.