(Table 1) n-alkane distribution, and stable carbon and deuterium isotope ratios of DSDP Hole 10-94

Hydrology, source region, and timing of precipitation are important controls on the climate of the Great Plains of North America and the composition of terrestrial ecosystems. Moisture delivered to the Great Plains varies seasonally and predominately derives from the Gulf of Mexico/Atlantic Ocean with minor contributions from the Pacific Ocean and Arctic region. For this work, we evaluate long-term relationships for the past ~ 35 million years between North American hydrology, climate, and floral change, using isotopic records and average carbon chain lengths of higher plant n-alkanes from Gulf of Mexico sediments (DSDP Site 94). We find that carbon isotope values (d13C) of n-alkanes, corrected for variations in the d13C value of atmospheric CO2, provide minor evidence for contributions of C4 plants prior to the Middle Miocene. A sharp spike in C4 input is identified during the Middle Miocene Climatic Optimum, and the influence of C4 plants steadily increased during the Late Miocene into the Pleistocene - consistent with other North American records. Chain-length distributions of n-alkanes, indicative of the composition of higher plant communities, remained remarkably constant from 33 to 4 Ma. However, a trend toward longer chain lengths occurred during the past 4 million years, concurrent with an increase in d13C values, indicating increased C4 plant influence and potentially aridity. The hydrogen isotope values (dD) of n-alkanes are relatively invariant between 33 and 9 Ma, and then become substantially more negative (75 per mil) from 9 to 2 Ma. Changes in the plant community and temperature of precipitation can solely account for the observed variations in dD from 33 to 5 Ma, but cannot account for Plio-Pleistocene dD variations and imply substantial changes in the source region of precipitation and seasonality of moisture delivery. We posit that hydrological changes were linked to tectonic and oceanographic processes including the shoaling and closure of the Panamanian Seaway, amplification of North Atlantic Deep Water Production and an associated increase of meridional winds. The southerly movement of the Intertropical Convergence Zone near 4 Ma allowed for the development of a near-modern pressure/storm track system, driving increased aridity and changes in seasonality within the North American interior.

Median grain size and distribution of sand in ODP Hole 108-660A (Fig. 5)

50 m of Middle Eocene pure radiolarian ooze were drilled at ODP Site 660 in the equatorial East Atlantic, 80 km northeast of the Kane Gap. The oozes comprise a 10 m high and 2 km broad mound of seismic reverberations, covered by manganese-rich sediment, and contain trace amounts of sponge spicules and diatoms, negligible organic carbon (0.15%), clay, and variable amounts of pyrite. The yellow to pale brown silty sediments are relatively coarse-grained (30-45% coarser than 6 µm), little bioturbated, and commonly massive or laminated on a cm-scale. The unlithified radiolarian ooze may indicate an interval of high oceanic productivity, probably linked to a palaeoposition of Site 660 close to the equatorial upwelling belt during Middle Eocene time. The absence of organic matter, however, and both the laminated bedding and the mound-like structure of the deposit on the lower slope of a continental rise indicate deposition by relatively intense contour currents of oxygen-rich deep water, which passed through the Kane Gap, winnowed the fine clay fraction, and prevented the preservation of organic carbon. The ooze may be either a contourite-lag deposit, or a contourite accumulation of displaced radiolarians, originating south of the Kane Gap and being deposited in its northern lee, thus documenting the passage of a strong cross-equatorial bottom-water current formed near Antarctica. These Eocene contourites may be an analogue for ancient radiolarites in the Tethyan Ocean.

(Figure 2) Range and distribution chart of dinoflagellate cysts recovered from Campanian to Maestrichtian sediments at DSDP Hole 95-612

Fifty-nine samples from the basal 110 m of DSDP Hole 612 (United States Atlantic Margin) were analyzed for palynomorph content. In total, 84 species and subspecies of dinoflagellate cysts were recorded which, on comparison with published data and shipboard analyses, indicate a Campanian to Maestrichtian age for this part of the succession. The Campanian/Maestrichtian contact is taken to occur in the upper part of Core 612-69.

Distribution and abundance of calcareous-nannoplankton species in the Cretaceous sediments of DSDP Leg 62 Holes

Cretaceous sediments were recovered at all four sites (Sites 463-466) of the central North Pacific drilled during Leg 62 of the Deep Sea Drilling Project. One of the objectives was to get more information about the development of ocean plankton communities and early evolution of planktonic groups of the Mesozoic. In this article, the Cretaceous calcareous nannofossils from two areas of the central North Pacific (Mid-Pacific Mountains and Hess Rise) are listed and discussed. (The Cenozoic calcareous nannofossils are discussed by R. Schmidt 1981). Coring was continuous at all sites. Mesozoic calcareous nannoplankton assemblages range on the Mid-pacific Mountains from Barremian to Early Maastrichtian, and on Hess Rise from Albian to Late Maastrichtian. (No calcareous nannofossils older than Barremian or Albian respectively were found).

Distribution of quaternary siliceous sponge spicules in sediments of ODP Leg 180 sites

Siliceous sponge spicules were found in Quaternary sediments recovered during drilling of Leg 180. The assemblage consists mainly of monaxon forms. Relative abundances of the various types are tabulated.