Chemical and isotope compositions of sediments from DSDP Hole 86-576A and Core LL44-GPC-3

A record of changes in Pb and Sr isotopic composition of two cores (DSDP 86-576A and LL44- GPC-3) from the red clay region of the central North Pacific has been determined for the past 60-65 million years. The isotope records of the eolian silicate fraction of the red clays reflect the change in source area as the core sites migrated under different wind systems. The Sr isotope compositions of eolian silicate material are consistent with Asian loess and North American arc volcanism that has been recognized from mineralogical studies. The silicate-bound eolian Pb isotopic compositions similarly reflect Asian loess and arc volcanism. The isotope records of three ferromanganese crusts from similar locations in the central Pacific are similar to the eolian component of red clays, but offset to less radiogenic values. This may be due to two mechanisms: (1) Pb that can be removed from eolian material by seawater is much less radiogenic, or less likely (2) hydrothermal Pb can be transported further away from venting sites through particle exchange with seawater, despite hydrothermal venting acting as a net sink of oceanic Pb. The temporal changes in Pb isotopes in the ferromanganese crusts, bulk red clays and eolian silicates are similar although offset from each other suggesting that eolian deposition is an important source of Pb to seawater and to ferromanganese crusts. This contrasts with the Atlantic and Southern Ocean where more intense deep water flow leads to isotopic gradients in FeMn crusts that do not reflect surface water conditions immediately above the crust. A mechanism is proposed which accounts for Pacific deepwater Pb being isotopically influenced by eolian deposition.

Standard meteorological measurements on board of POLARSTERN during expedition ANT-IV (PS08, 4 cruises, south summer 1985/86) in the Atlantic and Weddell Sea, Antarctica

During the fourth Antarctic voyage ANT-IV of the research icebreaker POLARSTERN standard meteorological measurements have been performed. The measurements include 3-hourly synoptic observations as well as daily upper air soundings. The measurements started on September 6 1985 at Bremerhaven and were terminated at April 28 1986 in Punta Arenas. The 3-hourly synoptic observations are performed following the instructions of the FM 13 ships code defined by the World Meteorological Organization (WMO). The datasets include automatic measurements such as mean ship's speed, wind velocity, wind direction, air temperature, water temperature as well as visual observations such as total cloud amount, present weather, clouds, height and period of swell waves, ice classification. The visual observation are not performed during night time. For the upper air soundings VAISALA RS80 radiosondes, carried by helium-filled balloons (TOTEX 350 - 1500) were used. Data reception and evaluation were carried out by a MicroCora System (VAISALA). The upper air soundings include profile measurements of pressure, temperature, relative humidity and wind vector. Usually the soundings started at the heliport (10 m above sea level) and terminated between 15 and 37 km. The height of the measurements was calculated by applying the barometric formula. The wind vector was determined with the aid of the OMEGA navigation system.

(Table 3) Age-related trends of desert pavement properties in the Transantarctic Mountains

Compared to mid-latitude deserts, the properties, formation and evolution of desert pavements and the underlying vesicular layer in Antarctica are poorly understood. This study examines the desert pavements and the vesicular layer from seven soil chronosequences in the Transantarctic Mountains that have developed on two contrasting parent materials: sandstone-dolerite and granite-gneiss. The pavement density commonly ranges from 63 to 92% with a median value of 80% and does not vary significantly with time of exposure or parent material composition. The dominant size range of clasts decreases with time of exposure, ranging from 16-64 mm on Holocene and late Quaternary surfaces to 8-16 mm on surfaces of middle Quaternary and older age. The proportion of clasts with ventifaction increases progressively through time from 20% on drifts of Holocene and late Quaternary age to 35% on Miocene-aged drifts. Desert varnish forms rapidly, especially on dolerite clasts, with nearly 100% cover on surfaces of early Quaternary and older age. Macropitting occurs only on clasts that have been exposed since the Miocene. A pavement development index, based on predominant clast-size class, pavement density, and the proportion of clasts with ventifaction, varnish, and pits, readily differentiated pavements according to relative age. From these findings we judge that desert pavements initially form from a surficial concentration of boulders during till deposition followed by a short period of deflation and a longer period of progressive chemical and physical weathering of surface clasts. The vesicular layer that underlies the desert pavement averages 4 cm in thickness and is enriched in silt, which is contributed primarily by weathering rather than eolian deposition. A comparison is made between desert pavement properties in mid-latitude deserts and Antarctic deserts.