Digital surface model, hillshade and Lambertian reflectance model of the rock glaciers Oelgrube and Aeusseres Hochebenkar (Oetztal Alps, Tyrol, Austria)

With full-waveform (FWF) lidar systems becoming increasingly available from different commercial manufacturers, the possibility for extracting physical parameters of the scanned surfaces in an area-wide sense, as addendum to their geometric representation, has risen as well. The mentioned FWF systems digitize the temporal profiles of the transmitted laser pulse and of its backscattered echoes, allowing for a reliable determination of the target distance to the instrument and of physical target quantities by means of radiometric calibration, one of such quantities being the diffuse Lambertian reflectance. The delineation of glaciers is a time-consuming task, commonly performed manually by experts and involving field trips as well as image interpretation of orthophotos, digital terrain models and shaded reliefs. In this study, the diffuse Lambertian reflectance was compared to the glacier outlines mapped by experts. We start the presentation with the workflow for analysis of FWF data, their direct georeferencing and the calculation of the diffuse Lambertian reflectance by radiometric calibration; this workflow is illustrated for a large FWF lidar campaign in the Ötztal Alps (Tyrol, Austria), operated with an Optech ALTM 3100 system. The geometric performance of the presented procedure was evaluated by means of a relative and an absolute accuracy assessment using strip differences and orthophotos, resp. The diffuse Lambertian reflectance was evaluated at two rock glaciers within the mentioned lidar campaign. This feature showed good performance for the delineation of the rock glacier boundaries, especially at their lower parts.

Physics, geochemistry and bulk sedimentology on cores from the Peru Basin

Empirical relationships between physical properties determined non-destructively by core logging devices and calibrated by carbonate and opal measurements determined on discrete samples allow extraction of carbonate and opal records from the non-destructive measurements in biogenic settings. Contents of detrital material can be calculated as a residual. For carbonate and opal the correlation coefficients (r) are 0.954 and ?0.916 for sediment density, ?0.816 and 0.845 for compressional-wave velocity, 0.908 and ?0.942 for acoustic impedance, and 0.886 and ?0.865 for sediment color (lightness). Carbonate contents increase in concert with increasing density and acoustic impedance, decreasing velocity and lighter sediment color. The opposite is true for opal. The advantages of deriving the sediment composition quantitatively from core logging are: (i) sampling resolution is increased significantly, (ii) non-destructive data can be gathered rapidly, and (iii) laboratory work on discrete samples can be reduced. Applied to paleoceanographic problems, this method offers the opportunity of precise stratigraphic correlations and of studying processes related to biogenic sedimentation in more detail. Density is most promising because it is most strongly affected by changes in composition.

Geochemistry and physics on sediment cores from the Peru Basin

We studied preservation/dissolution cycles and paleoproductivity in eight sediment cores from the Peru Basin south of the highly productive surface waters of the eastern equatorial Pacific. Stratigraphy is based on stable oxygen isotopes and on combined magnetostratigraphy and biostratigraphy. Sediment cores which span the last 8 m.y., were retrieved during cruise 79 with RV SONNE close to the carbonate compensation depth (CCD). In general, sediments show Pacific-type carbonate cycles. We interpret a pronounced carbonate peak between 6 and 7 Ma as the result of a western and northern extension of the highly productive Peru Current. Decreased carbonate contents from the late Miocene to the late Pliocene might be associated with a slow contraction of the latitudinal extent of the high-productivity belt north of the study areas. During the Pliocene, carbonate variations showed 400 kyr cycles indicating the growth and decay of ice sheets, which should have been associated with pulsations of the Antarctic ice cap. An abrupt collapse of the carbonate system occurred at 2.4 Ma. Higher frequency variations of the carbonate record indicate the major increase of the northern hemisphere glaciation. During the Quaternary, carbonate fluxes are high during glacials and low during interglacials. Large amplitude variations with long broad minima and maxima, associated with small migrations of the lysocline and the CCD (< 200 m), are indicative of the preservation/dissolution history in the Peru Basin. During the early Pleistocene, climatic forcing by the 41 kyr obliquity cycle is not observed in the carbonate record. During the last 800 kyr, variability in the carbonate record was dominated by the 100 kyr eccentricity cycle. Fluxes of biogenic material (calcium carbonate, organic carbon, opal, and barium) were greatest during glacials, which imply higher productivity and export production of the Peru Current during cold climatic periods. Dissolution was greatest during interglacials as inferred from the relatively poor preservation of planktonic foraminifera and from the low accumulation rate of carbonate. After the Mid-Brunhes Event (400 ka), we observe a plateaulike shift to enhanced dissolution and to intensified productivity.