(Table 2) Organic residue at DSDP Hole 76-534A

The kind, sedimentation rate, and diagenesis of organic particles delivered to the North Atlantic seafloor during the Middle Jurassic-Early Cretaceous were responsible for the presence of carbonaceous sediments in Hole 534A. Organic-rich black clays formed from the rapid supply of organic matter; this organic matter was composed of either abundant, well-preserved, and poorly sorted particles of land plants deposited in clays and silty clays within terrigenous turbiditic sequences (tracheal facies) or abundant amorphous debris (xenomorphic facies) generated through the digestive tracts of marine zooplankton and sedimented as fecal pellets. Evidence for the fecal-pellet origin of xenomorphic debris is illustrated. Black clays were also produced in sediments containing less organic matter as a result of the black color of carbonized particles composing all or most of the residues (micrinitic facies). Slowly sedimented hematitic Aptian clays contain very little carbonized, organic debris that survived diagenetic oxidation. In the red calcareous clay sequence of the Late Jurassic, larger amounts of this oxidized debris turned several clay layers black or blackish red. Carbonized debris also dominates the residues recovered in interbedded black and green Albian clays. Carbonization of organic matter in these sediments either turned them black or provided the diagenetic environment for reduced iron. Carbonized debris is also appreciable in burrow-mottled black-green Kimmeridgian clay. The study of Hole 534A organic matter indicates that during the middle Callovian there was a rapid supply of terrigenous organic matter, followed by a late Callovian episode of rapidly supplied xenomorphic debris deposited as fecal pellets. The Late Jurassic-Berriasian was a time of slower sedimentation of organic matter, primarily of a marine dinoflagellate flora in a poorly preserved xenomorphic facies variously affected by diagenetic oxidation. Several intervals of carbonized tracheal tissue in the Oxfordian and Kimmeridgian suggest episodes of oxidized terrigenous matter. The same sequence of Callovian organic events is evident in much of the Early Cretaceous

(Table 1) Biomass and total standing crop of major wet sedge tundra species at five sites at Alexandra Fiord in 1981 and 2005

The global climate is changing rapidly and Arctic regions are showing responses to recent warming. Responses of tundra ecosystems to climate change have been examined primarily through short-term experimental manipulations, with few studies of long-term ambient change. We investigated changes in above- and belowground biomass of wet sedge tundra to the warming climate of the Canadian High Arctic over the past 25 years. Aboveground standing crop was harvested from five sedge meadow sites and belowground biomass was sampled from one of the sites in the early 1980s and in 2005 using the same methods. Aboveground biomass was on average 158% greater in 2005 than in the early 1980s. The belowground biomass was also much greater in 2005: root biomass increased by 67% and rhizome biomass by 139% since the early 1980s. Dominant species from each functional group (graminoids, shrubs and forbs) showed significant increases in aboveground biomass. Responsive species included the dominant sedge species Carex aquatilis stans, C. membranacea, and Eriophorum angustifolium, as well as the dwarf shrub Salix arctica and the forb Polygonum viviparum. However, diversity measures were not different between the sample years. The greater biomass correlated strongly with increased annual and summer temperatures over the same time period, and was significantly greater than the annual variation in biomass measured in 1980-1983. Increased decomposition and mineralization rates, stimulated by warmer soils, were likely a major cause of the elevated productivity, as no differences in the mass of litter were found between sample periods. Our results are corroborated by published short-term experimental studies, conducted in other wet sedge tundra communities which link warming and fertilization with elevated decomposition, mineralization and tundra productivity. We believe that this is the first study to show responses in High Arctic wet sedge tundra to recent climate change.

(Table 1) Percentage of non-opaque heavy minerals, heavy residue, magnetite, and opaque heavy minerals, DSDP Sites 58-445 and 58-446

Heavy-mineral analyses were made for 39 samples, 27 from DSDP Site 445 and 12 from Site 446. About one-fourth of the samples were so loose that they were easily disaggregated in water. The amount of heavy residue and the magnetite content of the heavy fraction were very high, 0.2 to 44 per cent and (on the average) more than 20 per cent, respectively. Among the non-opaque heavy minerals, common hornblende (0 to 80%) and augite (0 to 98%) are most abundant. Pale-green and bluish-green amphiboles (around 10%) and the epidote group (a few to 48%) are next in abundance. Euhedral apatite and biotite and irregularly shaped chromite are not abundant, but are present throughout the sequence. Hacksaw structure is developed in pale-green amphibole and augite. At Site 445, a fair amount of chlorite and a few glauconite(?) grains are present from Core 445-81 downward. The content of common hornblende and opaque minerals also changes from Core 445-81 downward. A geological boundary may exist between Cores 445-77 and 445-81. Source rocks of the sediments at both sites were basaltic volcanic rocks (possibly alkali suite), schists, and ultramafic rocks. The degree of lithification and amount of heavy residue, and the content of magnetite, non-opaque heavy minerals (excluding mafic minerals), and mafic minerals in the cores were compared with Eocene, Oligocene, and Miocene sandstones of southwest Japan. In many respects, the sediments at Sites 445 and 446 are quite different from those of southwest Japan. From the early Eocene to the early Miocene, the area of these sites belonged to a different geologic province than southwest Japan.

Compositions of paleosols from the Salarevo Formation, Sukhona River valley (Severnaya Dvina basin)

Paleosols crop out in the Sukhona River valley as several members up to 10 m thick embedded into the Salarevo Formation sediments. Principal characteristics of the paleosols include a dense network of root channels, indications of eluvial gley alteration, redistribution and formation of secondary carbonates represented by several generations, and formation of block-prismatic soil structure with specific clayey films at structural jointing faces. The paleosols are divided into a number of genetically interrelated horizons (from top to bottom): presumably organogenic accumulation (AElg), eluvial gley horizon (Elg), illuvial horizons (B1 and B2), illuvial gley horizon (Bg), and transitional horizons (ElBg and BElg). The paleosols formed under conditions of a semiarid climate with sharp seasonal or secular and multisecular oscillations of atmospheric precipitation. Such soils point to specific ecological environments existed in the northern semiarid belt of the Earth before the greatest (in Phanerozoic) biospheric crisis at the Permian-Triassic boundary.