(Appendix) Bulk inorganic chemistry at DSDP Leg 77 Holes

Clay mineralogic and inorganic geochemical investigations of Cretaceous and Cenozoic sediments of the western Gulf of Mexico lead to the following main conclusions. (1) Transition of lowermost Cretaceous continental to marine sedimentation is marked by a clay evaporitic stage, north of the Campeche Escarpment. (2) Existence of combined mineralogic and geochemical stratigraphy allows us to propose correlations between Sites 535 and 540, especially for the Albian. (3) Predominance of detrital clay assemblages is indicative of hot and variably humid continental climate until the early late Cenozoic. (4) Tectonic destabilization of the margins of Gulf of Mexico occurred at different periods, especially until the middle Cretaceous, with a mixed erosion of rocks and soils and temporary oxidized conditions of deposition. (5) Successive developments of confined perimarine basins occurred from the earliest Cretaceous until the Miocene, chiefly in the Florida area. The sources of inorganic materials were chiefly situated on the east of the studied area until the late Tertiary and after that in the Mississippi River basin. (6) Occasionally, volcanic activity influenced the clay mineralogy and mainly the geochemistry, and possibly contributed to the rather strong magnesian character of the deposition until the late Paleogene. (7) The argillaceous diagenesis is weak; variability of the carbonate diagenesis is marked by the relation Sr = f(CaO) and chiefly depends on the depth of burial, the clay content, the porosity, and the geologic age.

Grain-size distributions and bulk chemistry of sediment core MD00-2361

The terrigenous fraction of sediments from a deep-sea sediment core recovered from the northwestern Western Australian continental slope offshore North West Cape, SE Indian Ocean, reveals a history of Western Australian climate throughout the last 550 ka. End-member modelling of a data set of grain-size distributions (n = 438) of the terrigenous sediment fraction allows to interpret the record in terms of aeolian and fluvial sediment deposition, both related to palaeo-environmental conditions in the North West Cape area. The data set can be best described by two aeolian end members and one fluvial one. Changes in the ratio of the two aeolian end members over the fluvial one are interpreted as aridity variations in northwestern Western Australia. These grain-size data are compared with bulk geochemical data obtained by XRF scans of the core. Log-ratios of the elements Zr/Fe and Ti/Ca, which indicate a terrigenous origin, corroborate the grain-size data. We postulate that the mid- to late Quaternary near North West Cape climate was relatively arid during the glacial and relatively humid during the interglacial stages, owing to meridional shifts in the atmospheric circulation system. Opposite to published palaeo-environmental records from the same latitude (20°S) offshore Chile and offshore Namibia, the Australian aridity record does not show the typical southern hemisphere climate variability of humid glacials and dry interglacials, which we interpret to be the result of the relatively large land mass of the Australian continent, which emphasises a strong monsoonal climatic system.

X-ray fluorescence data (calcium and iron), bulk organic d13C, and dinoflagellate cysts of ODP Hole 189-1172D

The 'Paleocene/Eocene Thermal Maximum' or PETM (~55 Ma) was associated with dramatic warming of the oceans and atmosphere, pronounced changes in ocean circulation and chemistry, and upheaval of the global carbon cycle. Many relatively complete PETM sequences have by now been reported from around the world, but most are from ancient low- to midlatitude sites. ODP Leg 189 in the Tasman Sea recovered sediments from this critical phase in Earth history at Sites 1171 and 1172, potentially representing the southernmost PETM successions ever encountered (at ~70° to 65° S paleolatitude). Downhole and core logging data, in combination with dinoflagellate cyst biostratigraphy, magneto-stratigraphy, and stable isotope geochemistry indicate that the sequences at both sites were deposited in a high accumulation-rate, organic rich, marginal marine setting. Furthermore, Site 1172 indeed contains a fairly complete P-E transition, whereas at Site 1171, only the lowermost Eocene is recovered. However, at Site 1172, the typical PETM-indicative acme of the dinocyst Apectodinium was not recorded. We conclude that unfortunately, the critical latest Paleocene and PETM intervals are missing at Site 1172. We relate the missing section to a sea level driven hiatus and/or condensed section and recovery problems. Nevertheless, our integrated records provide a first-ever portrait of the trend toward, and aftermath of, the PETM in a marginal marine, southern high-latitude setting.

(Table 1) Sound velocity, wet-bulk density, and acoustic impedance of some indurated sediment from DSDP Leg 64 Holes

The Pliocene-Quaternary sediments that we drilled at eight sites in the Gulf of California consist of silty clays to clayey silts, diatomaceous oozes, and mixtures of both types. In this chapter I have summarized various measurements of their physical properties, relating this information to burial depth and effective overburden pressure. Rapid deposition and frequent intercalations of mud turbidites may cause underconsolidation in some cases; overconsolidation probably can be excluded. General lithification begins at depths between 200 and 300 meters sub-bottom, at porosities between 55 and 60% (for silty clays) and as high as 70% (for diatomaceous ooze). Diatom-rich sediments have low strength and very high porosities (70-90%) and can maintain this state to a depth of nearly 400 meters (where the overburden pressure = 1.4 MPa). The field compressibility curves of all sites are compared to data published earlier. Where sediments are affected by basaltic sills, these curves clearly show the effects of additional loading and thermal stress (diagenesis near the contacts). Strength measurements on well-preserved hydraulic piston cores yielded results similar to those obtained on selected samples from standard drilling. Volumetric shrinkage dropped to low values at 100 to 400 meters burial depth (0.3 to 2.0 MPa overburden pressure). Porosity after shrinkage depends on the composition of sediments.