Diagenetic alteration of organic matter in DSDP Leg 57 Holes

I analyzed Leg 57 sediments organogeochemically and spectroscopically. Organic carbon and extractable organic matter prevail from the Pliocene to the Miocene. Humic acids occur widely from the Pleistocene to the lower Miocene and one portion of the Oligocene. The absence of humic acids in Oligocene and Cretaceous samples suggests that humic acids had changed to kerogen. Visible spectroscopic data reveal that humic acids in this study have a low degree of condensed aromatic-ring system, which is a feature of anaerobic conditions during deposition, and that chlorophyll derivatives that had at first combined with humic acids moved to the solvent- soluble fraction during diagenesis. The elemental compositions of humic acids show high H/C and O/C ratios, which seem appropriate to a stage before transformation to kerogen. The relation between the linewidths and g-values on the electron spin resonance data indicates that the free radicals in humic acids are quite different from those in kerogen. The low spin concentrations of kerogen and the yields of humic acids up to the lower Miocene demonstrate that organic matter in these sediments is immature. The foregoing indicate the necessity to isolate humic acids even in ancient rocks in the study of kerogen.

(Table 1) Carbohydrates, free sugars, and acid-extractable sugar at DSDP Leg 64 Holes

We analyzed 10 core samples of Pleistocene and Pliocene sediment for residual carbohydrates. All yielded positive results for total carbohydrates and acid-extractable glucose. We also detected galactose, mannose, arabinose, xylose, and traces of ribose and fucose in the Pleistocene samples. In the Pliocene samples we found only rare mannose. Only one Pleistocene sample yielded measurable cellulose and amylose.

(Table 2) Chemistry of the organic matter at DSDP Leg 62 Holes

The wide distribution of sapropelic deposits in the sedimentary cover of the oceans, their Cretaceous age, and their possible oil- and gas-generating characteristics allow us to regard these deposits as a regular global stage in the history of oceanic sedimentation. So, Cretaceous sapropelic deposits are a unique object for study. Cretaceous sapropelic deposits of DSDP Sites 463, 465, and 466, as well as similar sediments of the Atlantic and Indian Oceans, are characterized by enrichment in organic matter, which sometimes reaches 33% (Cape Verde Basin, DSDP Sites 367 and 368). The objective of this study is the elucidation of genesis, paleogeographic environment of sedimentation, and oil-generating potential of Cretaceous sapropelic deposits at these sites. Attention is given to petrographic composition and distribution of the organic matter.

Carbonate record of ODP Leg 167 sites

One of the expected scientific results of Ocean Drilling Program Leg 167 was to reconstruct the Neogene history of biogenic calcium carbonate accumulation in the northeastern Pacific along the California margin (Lyle, Koizumi, Richter, et al., 1997). This aims to constrain inorganic carbon burial rates, deep-water hydrography in the North Pacific, and linkages between deep Atlantic and Pacific circulation and carbonate accumulation or dissolution patterns. Data are presented for four sites. Two of them are located in the California bight-East Cortez Basin (Site 1012: 32°16.970?N 118°23.024?W, 1773 m) and San Nicholas Basin (Site 1013: 32°48.040??, 118°53.992?W, 1564 m). The others are the dedicated Hole 1017E at Site 1017 (34°32.099?N, 121°6.430?W, 955 m) and Site 1019 in the Eel River Basin (41¢X40.972?N, 124°55.975?W, 977 m). Reconstruction of paleo-sea-surface temperatures (SST) by determining the alkenone unsaturation index of the extractable organic matter is an independent technique and helps to verify oxygen-isotope-based estimates. Results from the uppermost 600 cm of the dedicated Hole 1017E are expected to reveal the local temperature history of the last 30 k.y.

Radiocarbon dating, sedimentation rate, granulometry and organic carbon content of ODP Leg 182 sites

This data report presents sedimentological (grain size) and geochemical (X-ray diffraction, total organic carbon, accelerator mass spectrometry radiocarbon, and percent carbonate) information obtained from the western transect (Sites 1132, 1130, and 1134) and the eastern transect (Sites 1129, 1131, and 1127) in the Great Australian Bight during Leg 182. The purpose is to quantify changing rates of sediment accumulation and changes in sediment type from the late Pleistocene and Holocene, in order to relate these changes to the well-known sea level curve that exists for this time frame. Ultimately, these data can be used to more effectively interpret lithologic variations deeper in the Pleistocene succession, which most likely represent orbitally forced sea level events.