ALBERT

Description: The site for CRP-3, 12 km east of Cape Roberts (77.006°S; 103.719°E)was selecte to overlap the lower Oligocene strata cored in nearby CRP-2/2A, and to sample the oldest strata in the Victoria Land Basin (VLB) for Paleogene climatic and tectonic history. As it transpired there was underlap of the order of 10s of metres. CRP-3 was cored from 3 to 939 mbsf (metres below the sea floor), with a core recovery of 97%. Coring took place from October 9 to November 19, 1999, on 2.0 to 2.2 m of sea ice and through 295 in of water. The Cenozoic strata cored were mostly g1acially influenced marine sediments of early Oligocene age, though they may be earliest Eocene near the base, where at 823 mbsf Devonian Beacon sandstone was encountered. Following CRP-1 and CRP-2/2A, CRP-3 completes the coring of 1500 m of strata on the western margin of the VLB. Core fractures and other physical properties, such as sonic velocity, density and magnetic susceptibility, were measured throughout the core. Down-hole logs for these and other properties were taken from 20 down to 900-919 mbsf. Also, vertical seismic profile data were gathered from shots offset both along strike and up dip from the hole. Sonic velocities in CRP-3 are close to 2.0 km/s in the upper 80 m, but become significantly faster below 95 mbsf, averaging 3.2+0.6 km/s to the bottom of the hole. An exception to this is an interval of dolerite conglomerate from 790 to c. 820 mbsf with a velocity of c. 4.5 km/s. Dip of the strata also increases down-hole from 10° in the upper 100 m to around 22° at the bottom. Over 3000 fractures were logged through the hole, and borehole televiewer imagery was obtained for most of the hole for orienting core and future stress field analysis. Two high-angle crush zones, interpreted as faults, were encountered at c. 260 and c. 540 mbsf, but no stratigraphic displacement could be recognised. A third fault zone is inferred from a low angle shear zone in the upper part of a coarse dolerite conglomerate from 790 to 805 mbsf. Temperature gradient was found to be 28.5°.km-1. Basement strata cored from 823 mbsf to the bottom of the hole are largely light-reddish brown medium-grained sandstone (quartz-cemented quartzarenite) with abundant well-defined parallel lamination. These features are comparable with the middle Devonian part of the Beacon Supergroup, possibly the Arena Sandstone. This interval also includes a body of intrusive rock from 901 to 920 mbsf. It has brecciated contacts and is highly altered but some tholeiitic affinity can be recognised in the trace element chemistry. Its age is unknown. Post-Beacon sedimentation began on deeply eroded quartzarenite with the deposition of a thin sandstone breccia and conglomerate, probably as terrestrial talus, followed by dolerite conglomerate and minor sandstone of probable fluvial origin to 790 mbsf. Sedimentation continued in a marine setting, initially sandstone and conglomerate, but above c. 330 mbsf the strata include mudstone and diamictite also. The older sandstone and conglomerate beds are seen as the products of rapid episodic sedimentation. They are interpreted by some as the product of glaciofluvial discharge into shallow coastal waters, and others as a result of sediment gravity flows, perhaps glacially sourced, into deeper water. The core above c. 330 mbsf has facies that allow the recognition of cyclic sequences similar to those in CRP-2A. Fourteen unconformity-bounded sequences have been recognised from 330 mbsf to the sea floor, and are interpreted in terms of glacial advance and retreat, and sea level fall and rise. Detailed lithological descriptions on a scale of 1 :20 are presented for the full length of the core, along with core box images, as a 300 page supplement to this issue. The strata cored by CRP-3 are for the most part poorly fossiliferous, perhaps as a consequence of high sedimentation rates. Nevertheless the upper 200 m includes several siliceous microfossil- and calcareous nannoplankton-bearing intervals. Siliceous microfossils, including diatoms, ebrideans, chrysophycean cysts and silicoflagellates are abundant and well-preserved in the upper 67 m - below this level samples are barren or poorly preserved, but contain residual floras that indicate assemblages were once rich. No siliceous microfossils were found below 193 mbsf. Calcareous nannofossil have a similar distribution but are generally well preserved. Foraminifera, marine and terrestrial palynomorphs, and marine macrofossils were found consistentlsy down to c. 330 mbsf and sporadically to 525 mbsf. The taxa suggest marine deposition in water depth of c. 50 to 120 m. Below 525 mbsf no microfossils were found, apart from mudstone with similar marine and terrestrial palynomorphs at 781 mbsf, and rare miospores in the conglomerate below 790 mbsf. The terrestrial miospore record, which include several species of Nothofagus and podocarpaceous conifers, suggest low diversity woody vegetation, implying a cold temperate to periglacial climate for the hinterland throughout the period recorded by CRP-3. Important components of the warmer Eocene flora, known from erratics in southern McMurdo Sound, are missing, through the dominance of smectite in clay from strata below 650 mbsf suggests that the landscape prior to the timne of deposition had experienced a more temperate weathering regime. Biostratigraphy for ihe upper part of CRP-3 is provided by diatoms and calcareous nannofossils. The first appearance of Cavitatus jouseanus at 48 mbsf suggests an age of arround 31 Ma for this horizon. The last appearance of Transverspontis pulcheroides at 114 mbsf in an interval of relatively high abundance indicates a reasonably sound age for this horizon at 32.5 ± 0.5 Ma. The absence of particular resistant diatoms that are older than 33 Ma supports an age that is younger than this for the upper 200 m of CRP-3. Marine palynomorphs, which occur sporadically down to 525 mbsf and in a single occurrence at 781 inbsf, have biostratigraphical potential once the many new species in this and other CRP cores are described, and F0 and LO datums established. The mudstone at 781 mbsf has a new clinocyst species, rare Lejeunecysta cysts and a variety of acritarchs and prasinophytes, a varied marine assemblage that is quite different from and presumably younger than the well known Transantarctic Flora of mid to late Eocene age. On this basis and for the moment we conclude that the oldest strata in CRP-3 are earliest Oligocene (or possibly latest Eocene) in age - c. 34 Ma. Over 1l00 samples were taken for magnetic studies. Four magnetozones were recognisd on the basis of NRM intensity and magnetic susceptibility, reflecting the change in sediment composition between quartz sand-dominated and dolerite-dominated. For this report there was time only to produce a magnetostratigraphy for the upper 350 m. This interval is largely of reversed polarity (5 normal intervals total 50 of the 350 m), in contrast to the dominantly normal polarities of CRP-2/2A, and is inferred to be Chron C12R. This extends from 30.9 to 33 Ma. consistent with the biostratigraphic datums from the upper part of CRP-3. The lower limit of reversed polarity has yet to be established. The short period normal events are of interest as they may represent cryptochrons or even polarity changes not recognised in the Geomagnetic Polarity Time Scale. Erosion of the adjacent Transantarctic Mountains through the Kirkpatrick Basalt (Jurassic tholeiitic flows) and dolerite-intruded Beacon Supergroup (Devonian-Triassic sandstone) into granitic basement beneath is recorded by petrographical studies of clast and sand grain assemblages from CRP-3. The clasts in the lower 30 m of the Cenozoic section are almost entirely dolerite apart from a few blocks from the Beacon Supergroup beneath. Above this, however, both dolerite and granitoids are ubiquitous, the latter indicating that erosion had reached down to granitic basement even as the first sediment was accumulating in the VLB. No clasts or sand grains of the McMurdo Volcanic Group were found, but rare silt-size brown volcanic glass occurs in smear slides through most of CRP-3, and is interpreted as distal air fall from alkaline volcanism in northern Victoria Land. Jurassic basalt occurs as clasts sporadically throughout the sequence: in the sand fraction they decline upwards in abundance. The influence of the Devonian Beacon Supergroup is most striking for the interval from 600 to 200 mbsf, where quartz grains, from 10 to 50% of them rounded, dominate the sand fraction. Laminae of coal granules from the overlying Permian coal measures in all but the upper 150 in of the CRP-3 sequence show that these also were being eroded actively at this time. CRP-3 core completed the stratigraphical sampling of the western margin of the VLB by not only coring the oldest strata (Seismic Unit V5) but also the basin floor beneath. This has several important tectonic implications: - most of the Kirkpatrick Basalt and the Beacon Supergroup with the sills of Ferrar Dolerite have been eroded by the time down-faulting displaced the Beacon to form the basin floor. - matching the Beacon strata at the bottom of CRP-3 with the equivalent strata in the adjacent mountains suggests c. 3000 m of down-to-the-east displacement across the Transantarctic Mountain Front as a consequence of rifting and subsequent tectonic activity. - the age of the oldest Cenozoic strata in CRP-3 (c. 34 Ma), which are also the oldest strata in this section of the VLB, most likely represents the initiation of the rift subsidence of this part of the West Antarctic Rift System. This age for the oldest VLB fill is much younger than previously supposed by several tens of millions of years, but is consistent with newly documented sea floor spreading data immediately north of the northern Victoria Land continental margin. These new data sets will drive a re-evaluation of the relationship between initiation of uplift of the Transantarctic Mountains (currently c.55 Ma) and VLB subsidence.

Description: Aimed at year-round recording of the chemical aerosol composition in central Antarctica, an unattended operating aerosol sampler was successfully deployed at the EPICA deep drilling site in Dronning Maud Land (Kohnen Station). Analyses of teflon/nylon filter packs consecutively collected over bi-weekly intervals during the February 2003 to December 2005 period allowed to evaluate seasonal concentration variations of methane sulphonate (MS), Cl-, NO3-, non-sea salt (nss-)SO4**2- and Na+, while NH4+ and mineral dust related ion results remained below detection limits. For MS and nss-SO4**2 distinct late summer maxima around 44 and 200 ng/m**3, respectively, were found, while (total) NO3- showed a broad November maximum of about 52 ng m**-3. In contrast, the highest concentrations of Na+ with peak values of up to 160 ng/m**3 were observed during the winter half year. The seasonality of these species broadly coincided with long-term observations at the coastal Neumayer Station, including surprisingly comparable NO3- levels. However, the biogenic sulphur and sea salt concentrations were lower at Kohnen by typically a factor of 2-3 and 10, respectively. The arrival of sea ice derived sea salt particles at Kohnen could not clearly detected, since even during mid-winter the nss-SO4**2- to Na+ ratio was generally too high to unambiguously identify a sulphur depleted sea salt SO4**2- fraction.

Description: Under the framework of the ANDRILL Southern McMurdo Sound (SMS) Project successful downhole experiments were conducted in the 1138.54 metre (m)-deep AND-2A borehole. Wireline logs successfully recorded were: magnetic susceptibility, spectral gamma ray, sonic velocity, borehole televiewer, neutron porosity, density, calliper, geochemistry, temperature and dipmeter. A resistivity tool and its backup both failed to operate, thus resistivity data were not collected. Due to hole conditions, logs were collected in several passes from the total depth at ~1138 metres below sea floor (mbsf) to ~230 mbsf, except for some intervals that were either inaccessible due to bridging or were shielded by the drill string. Furthermore, a Vertical Seismic Profile (VSP) was created from ~1000 mbsf up to the sea floor. The first hydraulic fracturing stress measurements in Antarctica were conducted in the interval 1000-1138 mbsf. This extensive data set will allow the SMS Science Team to reach some of the ambitious objectives of the SMS Project. Valuable contributions can be expected for the following topics: cyclicity and climate change, heat flux and fluid flow, seismic stratigraphy in the Victoria Land Basin, and structure and state of the modern crustal stress field.

Description: Here we present an improvement of paleotemperature reconstructions for the Southern Ocean by combining new diatom data from the Pacific sector with published Atlantic and Indian sector reference data. The statistical analysis of 336 surface sediment samples recovered from a wide area of Southern Ocean environments defines a supra-regional reference data set for quantitative summer sea surface temperature (SSST) estimations. In situ temperature measurements covering the time span from approx. 1900 to 1991 were used as reference instead of more recent time series of satellite-derived data, possibly biased by ocean warming. Different transfer function (TF) models for the Imbrie and Kipp Method (IKM), the Modern Analog Technique (MAT), Weighted Averaging (WA), and Weighted Averaging Partial Least Squares (WAPLS) were tested. Best performance for IKM was obtained using the D336 set with 29 diatom taxa and three factors, resulting in root mean square error of prediction (RMSEP) of 0.833 °C for SSST. MAT estimates were best with six analogs resulting in lowest RMSEP of 0.812 °C. WAPLS applied to D336 resulted in a RMSEP of 0.782 °C. WA performed less well, expressed by a RMSEP of 0.974 °C. Furthermore, two subsets for the Atlantic (D151) and the Pacific sectors (D107) were applied with IKM to test for advantages of localized TFs. IKM-D151 and IKM-D107 performed comparably good as IKM-D336, with RMSEP of 0.71 °C and 0.68 °C, respectively. Application of the augmented reference data sets on two Pleistocene sediment records from the Atlantic (PS1768-8) and Pacific (PS58/271-1) sectors led to best performance of IKM with D336, expressed by high overall communalities (〉 0.75) and fewer (PS1768-8) to no (PS58/271-1) no-analogs, compared to the regional data sets, proving IKM-D336 to deal better with higher assemblage variability. SSST estimates for both cores exhibit similar glacial/interglacial patterns for all four applied D336-based TF methods, with best concordance between IKM and WAPLS.