Chemical composition of bottom sediments from the Deryugin Basin, Sea of Okhotsk

This paper reports data including new analyses of contents of Ni, Co, V, Mo, Fe, Mn, Zn, Ba, Sc, Y, Cd, Rb, Cs, and W in bottom sediments of the Deryugin Basin. Features of chemical element distribution in the bottom area were identified and zones of maximum accumulation of major and trace elements were allocated. A correlation between the elements was shown.

Chemical composition of bottom sediments along the Transpacific section

Distribution of Fe, Mn, Ti, Cu, Ni, Co, V, Cr, Mo, As in bottom sediments of a section from the Hawaiian Islands to the coast of Mexico. In the surface layer and isochronic layers of sediments from biogenic-terrigenous sediments of the Mexico coast to pelagic red clays of the Northeast Basin contents of all studied elements increase, and more sharply for mobile ones - Mn, Mo, Cu, Ni, Co, As. In near Hawaii sediments rich in coarsely fragmented volcanic-terrigenous and pyroclastic material of basalt composition enriched in Ti, Fe, Cr, V, P contents of these elements in surface sediments and in sediment mass increase and contents of Mn, Mo, Ni, Co, Cu, As (for the same reason) decrease compared to red clays. An area of hemipelagic and transition sediments is identified; these sediments have much higher contents of Mn, Fe, Cu, Ni, Mo, As, (Ba) than red clays and similar sediments of the Northwest Pacific Ocean. This is due to hydrothermal activity in the tectonically active zone at the northern extension of the East Pacific Rise. Similar character of distribution of the elements in the surface layer and in the isochrone layers of bottom sediments along the most part of the section is shown. Similarity between distribution of the elements in sediments of the western and the eastern parts of the Transpacific section is established.

CPI, d13C, Corg and diploptene from ODP Hole 169-1034B varved sediments

Saanich Inlet has been a highly productive fjord since the last glaciation. During ODP Leg 169S, nearly 70 m of Holocene sediments were recovered from Hole 1034 at the center of the inlet. The younger sediments are laminated, anaerobic, and rich in organic material (1-2.5 wt.% Corg), whereas the older sediments below 70 mbsf are non-laminated, aerobic, with glacio-marine characteristics and have a significantly lower organic matter content. This difference is also reflected in the changes of interstitial fluids, and in biomarker compositions and their carbon isotope signals. The bacterially-derived hopanoid 17alpha(H),21beta(H)-hop-22(29)-ene (diploptene) occurs in Saanich Inlet sediments throughout the Holocene but is not present in Pleistocene glacio-marine sediments. Its concentration increases after ~6000 years BP up to present time to about 70 µg/g Corg, whereas terrigenous biomarkers such as the n-alkane C31 are low throughout the Holocene (<51 µg/g Corg) and even slightly decrease to 36 µg/g Corg at the most recent time. The increasing concentrations of diploptene in sediments younger than ~6000 years BP separate a recent period of higher primary productivity, stronger anoxic bottom waters, and higher bacterial activity from an older period with lesser activity, heretofore undifferentiated. Carbon isotopic compositions of diploptene in the Holocene are between ~31.5 and ~39.6 per mil PDB after ~6000 years BP. These differences in the carbon isotopic record of diploptene probably reflect changes in microbial community structure of bacteria living at the oxic-anoxic interface of the overlying water column. The heavier isotope values are consistent with the activity of nitrifying bacteria and the lighter isotope values with that of aerobic methanotrophic bacteria. Therefore, intermediate delta13C values probably represent mixtures between the populations. In contrast, carbon isotopic compositions of n-C31 are roughly constant at ~31.4 ± 1.1 per mil PDB throughout the Holocene, indicating a uniform input from cuticular waxes of higher plants. Prior to ~6000 years BP, diploptene enriched in 13C of up to -26.3 per mil PDB is indicative of cyanobacteria living in the photic zone and suggests a period of lower primary productivity, more oxygenated bottom waters, and hence lower bacterial activity during the earliest Holocene.

Radiolarian biostratigraphy in sediments of ODP Site 202-1237

Site 1237 is located on Nazca Ridge ~140 km off the coast of Peru and thus within the offshore region of the Peru-Chile Current. A total of 83 samples were used to provide an initial radiolarian biostratigraphic framework for Site 1237; radiolarians are present to Sample 202-1237B-19H-2, 58-60 cm (186.45 meters composite depth [mcd]) and are of good to fair abundance and preservation. Site 1237 is influenced by both subtropical and northward-transported southern latitude waters, has 55 ash layers within the uppermost 166 m, and has minimal to gross reworking. Shipboard paleomagnetic results showed that the upper 200 m spanned the last 12 m.y., and in the upper 100 mcd, the paleomagnetic inclination pattern could be directly correlated to the geomagnetic polarity timescale (GPTS). Tropical biostratigraphy was used to establish the zonal boundaries for Site 1237, and the paleomagnetic and radiolarian stratigraphy were well correlated.

Silicoflagellate abundances in sediments of ODP Leg 207 sites

The Ocean Drilling Program (ODP) drilled at five sites in the western Atlantic Ocean during Leg 207. The objective of the drilling was to recover samples from the shallow buried Cretaceous and Paleocene sediments on the Demerara Rise off Suriname, South America. These sediments are being studied for a number of paleoceanographic studies of the low-latitude Atlantic off the coast of Suriname (this volume). For this report two sites, Sites 1257 and 1258, were selected for silicoflagellate study because shipboard results suggested these two sites as the only ones with siliceous microfossils of Paleocene-Eocene age. The Demarara Rise is a predominant submarine plateau located off the coast of Suriname and French Guyana. This plateau stretches 380 km along the coast and is 220 km wide. The depth to seafloor along the depth transect drilled during ODP Leg 207 ranges from 1000 to 4500 m, but most of the remainder of the plateau lies in shallow water of 700 m. Much of this area is covered with 2-3 km of sediments. The Demerara Rise is built on rifted Precambrian continental crust. The plateau was one of the last places to be in contact with West Africa during the opening of the Atlantic Ocean (see Shipboard Scientific Party, 2004). Site 1257 (9°27'N, 54°20'W; water depth = 2951 m) is located on a terrace on the northwestern Demerara Rise ~400 km from Suriname. This is the second deepest water depth location drilled during Leg 207. Sediments from this area range in age from Miocene to Albian. This area is part of the transform fault that separated from Central America and western Africa. Three holes were drilled at Site 1257. Site 1258 (9°26'N, 54°43'W; water depth = 3192 m) is located on the western slope of the Demerara Rise ~380 km north of Suriname. This site is the distal and deepest site of the paleoceanographic depth transect drilled across Demerara Rise during Leg 207. The area is located on a ridge of Paleocene sediments cropping out on the seafloor. Three holes were drilled at Site 1258, but only one is studied.

Chronology and annual proxy data of Lago Grande di Monticchio sediments

We present new annual sedimentological proxies and sub-annual element scanner data from the Lago Grande di Monticchio (MON) sediment record for the sequence 76-112 thousand years before present (ka). They are combined with the previously published decadal to centennial resolved pollen assemblage in order to provide a comprehensive reconstruction of six major abrupt stadial spells (MON 1-6) in the central Mediterranean during early phase of the last glaciation. These climatic oscillations are defined by intervals of thicker varves and high Ti-counts and coincide with episodes of forest depletion interpreted as Mediterranean stadial conditions (cold winter/dry summer). Our chronology, labelled as MON-2014, has been updated for the study interval by tephrochronology and repeated and more precise varve counts and is independent from ice-core and speleothem chronologies. The high-resolution Monticchio data then have been compared in detail with the Greenland ice-core d18O record (NorthGRIP) and the northern Alps speleothem d18Ocalcite data (NALPS). Based on visual inspection of major changes in the proxy data, MON 2-6 are suggested to correlate with Greenland stadials (GS) 25-20. MON 1 (Woillard event), the first and shortest cooling spell in the Mediterranean after a long phase of stable interglacial conditions, has no counterpart in the Greenland ice core, but coincides with the lowest isotope values at the end of the gradual decrease in d18Oice in NorthGRIP during the second half of the Greenland interstadial (GI) 25. MON 3 is the least pronounced cold spell and shows gradual transitions, whereas its NorthGRIP counterpart GS 24 is characterized by sharp changes in the isotope records. MON 2 and MON 4 are the longest most and pronounced oscillations in the MON sediments in good agreement with their counterparts identified in the ice and spelethem records. The length of MON 4 (correlating with GS 22) supports the duration of stadial proposed by the NALPS timescales and suggests ca 500 yr longer duration than calculated by the ice-core chronologies GICC05modelext and AICC2012. Absolute dating of the cold spells provided by the MON-2014 chronology shows good agreement among the MON-2014, the GICC05modelext and the NALPS timescales for the period between 112 and 100 ka. In contrast, the MON-2014 varve chronology dates the oscillations MON 4 to MON 6 (92-76 ka) ca. 3,500 years older than the most likely corresponding stadials GS 22 to GS 20 by the other chronologies.

Accumulation rates of sediments and main sedimentary components in ODP Leg 121 holes on Broken Ridge

Broken Ridge, in the eastern Indian Ocean,is overlain by about 1600 m of middle Cretaceous to Pleistocene tuffaceous and carbonate sediments that record the oceanographic history of southern hemisphere mid-to high-latitude regions. Prior to about 42 Ma, Broken Ridge formed the northern part of the broad Kerguelen-Broken Ridge Plateau. During the middle Eocene, this feature was split by the newly forming Southeast Indian Ocean Ridge; since then, Broken Ridge has drifted north from about 55° to 31°S. The lower part of the sedimentary section is characterized by Turonian to Santonian tuffs that contain abundant glauconite and some carbonate. The tuffs record a large but apparently local volcanic input that characterized the central part of Broken Ridge into the early Tertiary. Maestrichtian shallow-water(several hundred to 1000 m depth) limestones and cherts accumulated at some of the highest rates ever documented from the open ocean, 4 to 5 g/cm**2/kyr. A complete (with all biostratigraphic zones) Cretaceous-Tertiary boundary section was recovered from site 752. The first 1.5 m.y. of the Tertiary is characterized by an order-of-magnitude reduction in the flux of biogenic sediments, indicating a period of sharply reduced biological productivity at 55°S, following which the carbonate and silica sedimentation rates almost reach the previous high values of the latest Cretaceous. We recovered a complete section through the Paleocene that contains all major fossil groups and is more than 300 m thick, perhaps the best pelagic Paleocene section encountered in ocean drilling. About 42 Ma, Broken Ridge was uplifted 2500 m in response to the intra-plateau rifting event; subsequent erosion and deposition has resulted in a prominent Eocene angular unconformity atop the ridge. An Oligocene disconformity characterized by a widespread pebble layer probably represents the 30 Ma sea-level fall. The Neogene pelagic ooze on Broken Ridge has been winnowed, and thus its grain size provides a direct physical record of the energy of the southern hemisphere drift current in the Indian Ocean for the past 30 m.y.

Diversity of abyssal agglutinated foraminifera from Cenomanian to Santonian sediments of the North Atlantic

Benthic foraminiferal assemblages of distinctive taxonomic composition occur at the top of benthic fossil-free black shales which correspond to the anoxic event at the Cenomanian/Turonian boundary in the North Atlantic abyssal DSDP/ODP sites 386, 398, 603 and 641. These assemblages consist of minute, thin-walled agglutinated foraminifera with low specific diversity of 2 to 4 species, variable abundance and dominance of few taxa (Haplophragmoides, Rhizammina and Glomospira). The species are inferred to be opportunistic, able to survive in low-oxygen environments and to be pioneers recolonizing the seafloor after cessation of bottom-water anoxia. Most species are characterized by test morphologies with high surface/volume ratios and single-layered wall structures, with loosely agglutinated grains, and small amounts of organic cement for agglutination. These features are best observed in material from ODP Hole 641A which has exceptional foraminiferai preservation because of its shallow burial depth. The successive appearance of benthic foraminifera after the anoxic event is probably controlled by the continuous reoccurrence of more oxygenated bottom- and interstitial-water conditions. With the final development of oxic bottom-water conditions in the Turonian, a rapid radiation of deep-water agglutinated foraminifera occurred in the North Atlantic.