Subdivisions of the sediment column, carbon and calcium carbonate at DSDP Hole 64-480

We analyzed 580 integrated scrape-samples from HPC Site 480 for organic and carbonate carbon. Once precise dating is available, these will provide a high-resolution framework for understanding late Quaternary Oceanographic and climatic fluctuations in this region. Organic carbon ranges mostly within a narrow band of 1.8 to 3.5% C. Calcium carbonate varies from undetectable to over 20%, with an average of only about 5%. Source of carbonate are mostly benthic and planktonic foraminifers, although some sections are dominated by diagenetic carbonate, shelly hash, or nannofossils. Detrital sources are low in carbonate. We divided the sequence into 17 calcium carbonate (CC) zones to separate pulses, low and median values. The CC-Zones show various second-order patterns of cyclicity, asymmetry, and events. Laminated zones have lowest uniform values, but a perfect correlation between carbonate content and homogeneous or laminated facies was not found. Maximum values tend to be located near the transition of these two sediment types, showing that accumulation of carbonate is favored during times of breakdown of stable Oceanographic conditions.

Quaternary carbonate record of ODP Hole 115-709A

The CaCO3 content in Quaternary deep-sea sediments from Pacific and Atlantic oceans have been suggested to respond differently to glacial/interglacial cycles; CaCO3 contents are highest during glacials in the Pacific but highest during interglacials in the Atlantic Ocean. It is not yet clear as to whether a Pacific or an Atlantic pattern of CaCO3 fluctuations dominates the Indian Ocean. We have analyzed the Ocean Drilling Program (ODP) Site 709A from the western equatorial Indian Ocean for the last 1370 ka to determine the relationships between percentages and fluxes of CaCO3 and Quaternary paleoclimatic changes. We also analyzed the coarse (>25 µm) and fine (<25 µm) fractions of CaCO3 in an attempt at estimating the influence of differences in productivity of foraminifera and calcareous nannofossils in shaping the CaCO3 record. Carbon isotopes and Ba/Al ratios were used as indices of productivity. Percentages and fluxes of CaCO3 in the total sediment and <25 µm fraction do not show any clear relationships to glacial/interglacial cycles derived from d18O of the planktonic foraminifera Globigerinoides ruber. This indicates that CaCO3 fluctuations at this site do not show either a Pacific or an Atlantic pattern of CaCO3 fluctuations. Fluxes of CaCO3 (0.38 to 2.46 g/cm**2/ ka) in total sediment and Ba/Al ratios (0.58 to 3.93 g/cm**2/ka) show six-fold variability through the last 1370 ka, which points out that productivity changes are significant at this site. Fluxes of the fine CaCO3 component demonstrate a 26-fold change (0.02 to 0.52 g/cm**2/ka), whereas the coarse CaCO3 component exhibit eight-fold change (0.13 to 1.07 g/cm**2/ka). This suggests that productivity variations of calcareous nannofossils are greater in comparison with the foraminifera. On the other hand, mean values of coarse CaCO3 fluxes are higher compared to those of fine CaCO3, which reveals that the foraminifera contribute more to the bulk CaCO3 flux than the calcareous nannofossils in the equatorial Indian Ocean.

Neptunian dikes and their fillings in carbonates of the Warstein area (northeastern Rhenish massif)

Neptunian dikes and cavities as weil as their fillings are described from Middle to Upper Devonian carbonates of the Warstein area. The genesis of the pre-Upper Carboniferous dikes is due to pre-orogenic synsedimentary tensional movements. Lifting, subsidence and tilting caused joints and cracks, which are enlarged to dikes and cavities on submarine conditions. The post-Upper Carboniferous dikes are based on the orogenesis during Upper Carboniferous time, causing numerous tectonical divisional planes in the sediments. Along these planes a far-reaching karstification took place since mesozoic time. According to their size the cavities are subdivided into macro-, mega- and microdikes. With the exception of one macrodike all the others are limited to the massive limestone. Megadikes especially occur in Upper Devonian cephalopod limestone and in the Erdbach limestone, microdikes can be found in all carbonatic rocks. The dikes follow pre-orogenic, tectonical and sedimentary divisional planes and are orientated to ac-, bc- as well as bedding planes and diagonal directions. The fillings happened down from above either in a solitary event or repeatedly in long-lived dikes during a span of several ten millions of years. More seldom the fillings took place laterally or upside from beneath. The dikes contain - without regard to autochthonous conodont faunas - older and/or younger mixed faunas, too. Occasionally they were used as life district by a trilobite fauna adapted to the dikes. The dikes represent sedimentary pitfalls and conserve sediments eroded in other places. Therefore, by aid of the fillings, it can be demonstrated, that stratigraphic gaps are not absolutely due to primary interruptions of sedimentation, but were caused by reworking. Some dikes contain the distal offsets of slides and suspension streams. Relations between condensation and development of dikes could not be derived in the Warstein area. However, an increase of the frequency of dikes towards east to the eastern margin of the Warstein carbonate platform could be pointed out. This margin is a slope, persisting more than 10 millions of years, between a block and a basin. Evidently cracks and dikes, which were caused by settlements, slides and earth quakes, occured there frequently. The Warstein dikes and cavities, caused by karstification, are filled with terrestrial Lower Cretaceous, marine Upper Cretaceous and terrestrial Pleistocene to Holocene sediments. Tertiary sediments could not be detected.

Carbonate, organic carbon and nitrogen, bitumen and rock-eval pyrolysis at DSDP Leg 79 Holes

The lipids and kerogens of 15 sediment samples from Site 547 (ranging from Pleistocene to Early Jurassic/Triassic) and 4 from Site 545 (Cretaceous) have been analyzed. A strong terrestrial contribution of organic matter was found, and significant autochthonous inputs were also present, especially at Site 545. Both strongly reduced and highly oxidized sediments have been found in the Cenozoic and Jurassic samples of Site 547. On the contrary, all the Cretaceous sections of Sites 547 and 545 are anoxic. Sediments from anoxic paleoenvironments are immature and have a high content of sterenes, diasterenes, steradienes, hopenes, and ßß hopanes. Samples from oxic paleoenvironments are mainly mature and their content of hopenes and steriod structures is below the detection level. Nevertheless, their hopane distributions have the immature ßß homologs as the predominant molecular markers. For Site 545 the most abundant molecular markers are ring A monoaromatic steranes, and their presence is attributed to microbial and chemical transformations during early diagenesis.

Neogen carbonate and stable isotope record of ODP Hole 120-751A

Lower Miocene through upper Pleistocene benthic foraminifer assemblage records from Ocean Drilling Program Site 751 on the Southern Kerguelen Plateau (57°44'S, water depth 1634 m) were combined with benthic and planktonic foraminifer oxygen and carbon isotope records and high-resolution CaCO3 data from the same site. Implications for the Neogene productivity and paleoceanography of the southern Indian Ocean are discussed. We used distinctive features of the Miocene d18O and d13C curves for stratigraphic correlation. Coinciding with a lower middle Miocene hiatus from 14.2 to 13.4 Ma, there was a rapid increase in benthic d18O values by 1.2 per mil. This distinct increase occurs in middle Miocene benthic foraminifer oxygen isotope curves from all oceans. No major change, however, in benthic foraminifer faunal composition occurred in this period of growth of the Antarctic ice cap and cooling of deep ocean waters (14.9-14.2 Ma). A drastic change in benthic foraminifer faunas coincided with a hiatus from 8.4 to 5.9 Ma. Shortly after this hiatus, in the latest Miocene, the CaCO3 content of the sediments dropped from 75% to 0%. From that time ( 5.8 Ma) through the early Pliocene, Site 751 has been situated beneath a high biogenic siliceous productivity zone. Carbonate contents of upper Pliocene and Pleistocene sediments vary between 20% and 70%. The benthic foraminifer faunas in the uppermost Pliocene and lower Pleistocene reflect strong bottom current conditions, in contrast to those in the upper Pleistocene, which indicate calm sedimentation and high food supply. High d13C values of planktonic foraminifers compared with low values of benthic foraminifers suggest high primary productivity in the late Pleistocene. The changes in productivity were probably a result of latitudinal migration and meandering of the Polar Frontal Zone.