AMS C-14 ages of coretops collected on RRS Charles Darwin cruise CD159, July 2004, N. Atlantic, for the NERC RAPID programme

Material and data were collected at 41 sites in the subpolar North Atlantic Ocean between Scotland and Newfoundland, during the RRS CharlesDarwin CD159 cruise in July 2004 (McCave, 2005). Sites were selected to reflect the major inputs of water that becomes the North Atlantic Deep Water (NADW); the Iceland-Scotland Overflow Water (ISOW), the Denmark Strait Overflow Water (DSOW) and the Labrador Sea Water (LSW). Areas cored were the south Iceland Rise, SE Greenland slope/rise and Eirik Drift, and the Labrador margin. A total of 29 box cores, 19 piston cores, 6 kasten cores, 9 short gravity cores and 20 CTD casts as well as 28 surface water samples were collected during the cruise. Here we present sediment core-top sample ages. The cores were sampled at 1 or 0.5 cm intervals and we used the top 1 or 2 cm, depending on availability of foraminifera in the samples. Sediment samples were disaggregated on an end-over-end wheel, wet sieved at >63 um, and dry sieved to 63-150 and >150 um. Accelerator Mass Spectrometer (AMS) radiocarbon dating was done for each core top based on between 900-1600 monospecific planktonic foraminifera (Globigerina bulloides or Neogloboquadrina pachyderma (sinistral)). All dates were of modern or late Holocene age except site RAPID-08-5B (9806 ± 38 uncorrected 14C years BP) and site RAPID-14-10B (11543 ± 40 uncorrected 14C years BP). The >150 um fraction was split until approximately 300 foraminifera remained and counted for number of lithic grains, benthic foraminifera, planktonic foraminifera and foraminifera fragments. In all but the shallowest sample (Greenland rise, 761m water depth) benthic foraminifera constituted less than 2% of the total >150 um fraction of the sample.

Planktonic foraminiferal stratigraphy, datum levels and ages of ODP Sites 184-1146 and 184-1148, South China Sea

Over 30 first and last occurrence (FO and LO, respectively) planktonic foraminifer datums were recognized from the Oligocene-Miocene section of Ocean Drilling Program (ODP) Site 1148. Most datum levels occur in similar order as, and are by correlation as probably synchronous with, their open-ocean records. Several datum levels represent local bioevents resulting from dissolution and Site 1148's unique paleoceanographic setting in the northern South China Sea. An age of 9.5-9.8 Ma is estimated for the local LO of Globoquadrina dehiscens (257 meters composite depth [mcd]), whereas the local LO of Globorotalia fohsi s.l. (301 mcd) is projected to be at ~13.0 Ma and the local FO of Globigerinatella insueta (367 mcd) is projected to be at ~18.0 Ma. The combined planktonic foraminifer and nannofossil results indicate that the Oligocene-Miocene section at Site 1148 is not complete. Unconformities up to 2-3 m.y. in duration, occurring at and before the Oligocene/Miocene boundary (OHS1, OHS2, OHS3, and OHS4 = MHS1), are associated with slump deposits between 457 and 495 mcd that signal tectonic instability during the transition from rifting to spreading in the South China Sea. Shorter unconformities of <0.5 m.y. duration that truncate the Miocene section were more likely to have been caused by sea-bottom erosion as well as dissolution. A total of 12 Miocene unconformities, MHS1 through MHS12, are mainly affected by dissolution and an elevated carbonate compensation depth (CCD) during Miocene third-order glaciations recorded in deep-sea positive oxygen isotope Mi glaciation events. Respectively, they fall at ~457 mcd (MHS1 = Mi-1), 407 mcd (MHS2 = Mi-1a), 385 mcd (MHS3 = Mi-1aa), 366 mcd (MHS4 = Mi-1b), 358 mcd (MHS5 = MLi-1), 333 mcd (MHS6 = Mi-2), 318 mcd (MHS7 = MSi-1), 308 mcd (MHS8 = Mi-3), 295 mcd (MHS9 = Mi-4), 288 mcd (MHS10 = Mi-5), 256 mcd (MHS11 = Mi-6), and 250 mcd (MHS12 = Mi-7). The correlation of these unconformities with Mi events indicates that some related driving mechanisms have been operating, causing deepwater circulation changes concomitantly in world oceans and in the marginal South China Sea.

Lithology and approximate sub-bottom depths and ages of the transition of soft to firm ooze and of firm ooze to chalk at DSDP Leg 89 and 90 Sites

Leg 90 recovered approximately 3705 m of core at eight sites lying at middle bathyal depths (1000-2200 m) (Sites 587 to 594) in a traverse from subtropical to subantarctic latitudes in the southwest Pacific region, chiefly on Lord Howe Rise in the Tasman Sea. This chapter summarizes some preliminary lithostratigraphic results of the leg and includes data from Site 586, drilled during DSDP Leg 89 on the Ontong-Java Plateau that forms the northern equatorial point of the latitudinal traverse. The lithofacies consist almost exclusively of continuous sections of very pure (>95% CaCO3) pelagic calcareous sediment, typically foraminifer-bearing nannofossil ooze (or chalk) and nannofossil ooze (or chalk), which is mainly of Neogene age but extends back into the Eocene at Sites 588, 592, and 593. Only at Site 594 off southeastern New Zealand is there local development of hemipelagic sediments and several late Neogene unconformities. Increased contents of foraminifers in Leg 90 sediments, notably in the Quaternary interval, correspond to periods of enhanced winnowing by bottom currents. Significant changes in the rates of sediment accumulation and in the character and intensity of sediment bioturbation within and between sites probably reflect changes in calcareous biogenic productivity as a result of fundamental paleoceanographic events in the region during the Neogene. Burial lithification is expressed by a decrease in sediment porosity from about 70 to 45% with depth. Concomitantly, microfossil preservation slowly deteriorates as a result of selective dissolution or recrystallization of some skeletons and the progressive appearance of secondary calcite overgrowths, first about discoasters and sphenoliths, and ultimately on portions of coccoliths. The ooze/chalk transition occurs at about 270 m sub-bottom depth at each of the northern sites (Sites 586 to 592) but is delayed until about twice this depth at the two southern sites (Sites 593 and 594). A possible explanation for this difference between geographic areas is the paucity of discoasters and sphenoliths at the southern sites; these nannofossil elements provide ideal nucleation sites for calcite overgrowths. Toward the bottom of some holes, dissolution seams and flasers appear in recrystallized chalks. The very minor terrigenous fraction of the sediment consists of silt- through clay-sized quartz, feldspar, mica, and clay minerals (smectite, illite, kaolinite, and chlorite), supplied as eolian dust from the Australian continent and by wind and ocean currents from erosion on South Island, New Zealand. Changes in the mass accumulation rates of terrigenous sediment and in clay mineral assemblages through time are related to various external controls, such as the continued northward drift of the Indo-Australian Plate, the development of Antarctic ice sheets, the increased desertification of the Australian continent after 14 m.y. ago, and the progressive increase in tectonic relief of New Zealand through the late Cenozoic. Disseminated glass shards and (altered) tephra layers occur in Leg 90 cores. They were derived from major silicic eruptions in North Island, New Zealand, and from basic to intermediate explosive volcanism along the Melanesian island chains. The tephrostratigraphic record suggests episodes of increased volcanicity in the southwest Pacific centered near 17, 13, 10, 5 and 1 m.y. ago, especially in the middle and early late Miocene. In addition, submarine basaltic volcanism was widespread in the southeast Tasman Sea around the Eocene/Oligocene boundary, possibly related to the propagation of the Southeast Indian Ridge through western New Zealand as a continental rift system.

(Table 2) Radiocarbon ages of lake sediments from Boresø, East Greenland

This chapter provides a review of proxy data from a variety of natural archives sampled in the Wollaston Forland region, central Northeast Greenland. The data are used to describe long-term environmental and climatic changes. The focus is on reconstructing the Holocene conditions particularly in the Zackenberg area. In addition, this chapter provides an overview of the archaeological evidence for prehistoric occupation of the region. The Zackenberg area has been covered by the Greenland Ice Sheet several times during the Quaternary. At the Last Glacial Maximum (LGM, about 22,000 years BP), temperatures were much lower than at present, and only very hardy organisms may have survived in the region, even if ice-free areas existed. Marked warming at around 11,700 years BP led to ice recession, and the Zackenberg area was deglaciated in the early Holocene, prior to 10,100 years BP. Rapid early Holocene land emergence was replaced by a slight transgression in the late Holocene. During the Holocene, summer solar insolation decreased in the north. Following deglaciation of the region, summer temperatures probably peaked in the early to mid-Holocene, as indicated by the occurrence of a southern beetle species. However, the timing for the onset of the Holocene thermal maximum is rather poorly constrained because of delayed immigration of key plant species. During the thermal maximum, the mean July temperature was at least 2-3°C higher than at present. Evidence for declining summer temperatures is seen at around 5500, 4500 and 3500 years BP. The cooling culminated during the Little Ice Age that peaked about 100-200 years ago. The first plants that immigrated to the region were herbs and mosses. The first dwarf shrubs arrived in Northeast Greenland prior to 10,400 years BP, and dwarf birch arrived around 8800 years BP. The first people arrived about 4500 years BP, but the region was depopulated several times before the last people disappeared some time after 1823 AD, perhaps as a consequence of poor hunting conditions during the peak of the Little Ice Age.

(Table 2) Radiocarbon ages of bottom sediments from the North Atlantic

Late Quaternary paleoceanology of the North Allantic has been studied on the base of radiolaria data.

Granulometry, calcium carbonate content and radiocarbon ages of soil profiles obtained in Quinghai Province, northeast Tibet

Colluvial deposits consisting of silts and loams were detected in several climatologically different areas of NE Tibet (3200-3700 m a.s.l.). Layering, distinct organic content and low content of coarse matter as well as location in the relief revealed an origin from low-energy slope erosion (hillwash). Underlying and intercalated paleosols were classified as Chernozems, Phaeozems, Regosols and Fluvisols. Fifteen radiocarbon datings predominant on charcoal from both colluvial layers and paleosols yielded ages between 8988 ± 66 and 3512 ± 56 uncal BP. Natural or anthropogenic factors could have been the triggers of the erosional processes derived. It remains unclear which reason was mainly responsible, due to controversial paleoclimatic and geomorphic records as well as insufficient archaeological knowledge from this region. Determinations of charcoal and fossil wood revealed the Holocene occurrence of tree species (spruce, juniper) for areas which nowadays have no trees or only few forest islands. Thus large areas of NE Tibet which are at present steppes and alpine pastures were forested in the past.