ALBERT

Description: DSDP Leg 26, is the fifth cruise of D/V Glomar Challenger in the Indian Ocean, and the first cruise of Phase III of the Deep Sea Drilling Project. The Indian Ocean is the smallest of the three major ocean basins but appears to be geologically the most complex. The sites drilled on Leg 26 were selected to try to elucidate a number of specific problems of both local and broad regional significance, as well as to add to the general knowledge of the area. In particular: a) To locate the oldest sediment in the Indian Ocean and thus possibly the date of the initial breakup of Gondwanaland (Sites 250, 256, 257); b) To determine the effects of the initiation of the Circumpolar Current on southern Indian Ocean sedimentation (Sites 250, 252, 256, 257, 258); c) To determine the history of spreading of the Southwest Branch of the Indian Ocean Ridge and the history of the crust and oceanic sedimentation in that general region (Sites 250, 251, 252).

Description: Site 76 was selected in order to core a thick sequence of sediments north of the Tuamotu ridge that had been crossed by Glomar Challenger justprior to the termination of Leg 8 in Tahiti. Two holes at this site continuously cored 27 meters of lower Pliocene to Recent phillipsitic clay and calcareous nannofossil ooze interbedded with calcareous turbidites. The drill bit was stopped by a silicified calcareous turbidite of Early Pliocene age.

Description: Site 79 is located on the crest of the equatorial Pacific sediment belt (Ewing and others, 1968) and is the westernmost of a series of sites (79, 81, 82 and 83) that follow the crest of this belt eastward to and across the crest of the oceanic ridge, locally known as the East Pacific Rise. The purpose of these sites is two-fold: 1) to study variations in biostratigraphy and sediment type from west to east across the Pacific and 2) to paleontologically date basement and determine the rate of spreading of the Pacific plate since the time of deposition of the oldest sediments at Site 77.

Description: Late Cretaceous and younger sediments dredged from the upper continental slope and canyon walls in the Great Australian Bight Basin between 126° and 136°E broadly confirm the stratigraphy which had been established previously from scattered exploration wells. Late Cretaceous to Early Eocene marine and marginal marine terrigenous sediments are overlain by Middle Eocene and younger pelagic carbonate (fine limestone and calcareous ooze). The samples provide the first evidence of truly marine Maastrichtian sedimentation, with abundant calcareous nannoplankton, on the southern margin of the continent. Other samples of interest include Precambrian sheared granodiorite on the upper slope south of Eyre Terrace, Paleocene phosphatic sediment in 'Eucla' Canyon at 128° 30'E, and terrigenous Early Miocene mudstone at 133° 20' and 134° 50'E. The mudstone is of note as an exception to the uniform pelagic carbonate wackestone and ooze which characterise Middle Eocene and younger sedimentation at all other sites. Fragments of alkali basalt lava of unknown age were recovered in 'Eucla' Canyon. Cores are mostly pelagic calcareous ooze, but those from submarine canyons include terrigenous turbidites.

Description: During Ocean Drilling Program (ODP) Leg 105, three sites (Sites 645 through 647) were drilled in Baffin Bay and the Labrador Sea to examine the tectonic evolution and the climatic and oceanic histories of this region. Biostratigraphic and magnetostratigraphic results vary at each site, while stratigraphic resolution depends on the limited abundance of marker species and the completeness of the paleomagnetic record. Because of the paucity of planktonic microfossils and the poor paleomagnetic record signatures, stratigraphic determinations at Site 645 often rely on defining minimum temporal constraints on specific samples or stratigraphic intervals. The completed stratigraphy indicates that the sedimentary sequence recovered at Site 645 is early Miocene to Holocene in age. The magnetostratigraphy and biostratigraphies are better defined at Sites 646 and 647 in the Labrador Sea. Site 646 generally contains a well-developed magnetostratigraphy and calcareous microfossil biostratigraphy. This biostratigraphy is based on calcareous nannofossils and planktonic foraminifers typical of the North Atlantic Ocean. Siliceous microfossils are also present at Site 646, but they are restricted to upper Pliocene through Holocene sediments. The stratigraphic sequence recovered at Site 646 is late Miocene to Holocene in age. Based primarily on the calcareous nannofossil stratigraphy, the sequence recovered at Site 647 consists of lower Eocene to lower Oligocene, lower Miocene, upper Miocene, and upper Pliocene through Holocene sediments. Three hiatuses are present in this sequence: the older hiatus separates lower Oligocene sediments from lower Miocene sediments, another hiatus separates lower Miocene sediments from upper Miocene sediments, and the youngest one separates upper Miocene from upper Pliocene sediments. A magnetostratigraphy is defined for the interval from the Gauss/Matuyama boundary through the Brunhes (Clement et al., this volume). Both planktonic foraminifers and siliceous microfossils have restricted occurrences. Planktonic foraminifers occur in Pliocene and younger sediments, and siliceous microfossils are present in lower Miocene and lower Oligocene sediments. The near-continuous Eocene through lower Oligocene sequence recovered at Site 647 allows the calcareous nannofossils and diatom stratigraphies at this site to act as a Paleogene stratigraphic framework. This framework can be compared with the stratigraphy previously completed for DSDP Site 112.

Description: Forty-three core-catcher samples from the upper Miocene to uppermost Pleistocene of ODP Site 677 were examined for planktonic foraminifers. Range charts were compiled for Holes 677A and 677B, and zonal markers and datum planes are correlated with the most recently published time scale. The absence of key species such as Globorotalia truncatulinoides, Globorotalia tosaensis, Globorotalia miocenica, and Globorotalia margaritae prohibits the use of any of the standard tropical zonal schemes. The zonal scheme used here was devised for this area on DSDP Leg 9.