(Table 1) Sr isotopes and chemical composition of DSDP Hole 61-462A basalts

Sixteen elemental abundances and 87Sr/86Sr ratio of the Nauru Basin basalt (Cores 75 to 90: sub-bottom depths 950 m to 1050 m) from Hole 462A have been determined by inductively coupled plasma-optical emission spectroscopy and mass spectrometry. The result indicates that the basalt is a new type of oceanic tholeiite, elementally similar to normal mid-oceanic ridge basalts and isotopically similar to oceanic island-type basalts.

Geochemistry at DSDP Leg 62 Holes

A total of 191 samples was collected for inorganic geochemical analyses from DSDP Holes 463, 464, 465, 465A, and 466. These samples were collected with two main goals. First, at least one sample was collected from each core, whenever possible, to document the general geochemical variability within lithologic units. Unfortunately, several lithologic units were inadequately sampled because of poor recovery, mostly due to the presence of chert. The least-sampled units are Units III in Hole 464 and Units IB and II in Hole 466. The second goal was to look for geochemical differences between contrasting lithologies within main lithologic units, particularly between cyclic interbeds of red and green limestone in Lithologic Unit II, Hole 463, and between olive, laminated limestone and gray, massive limestone in Lithologic Unit II, Hole 465A.

Geochemistry and isotopes at DSDP Leg 80 Holes

Thirty-eight samples from DSDP Sites 549 to 551 were analyzed for major and minor components and trace element abundances. Multivariate statistical analysis of geochemical data groups the samples into two major classes: an organic-carbon- rich group (> 1% TOC) containing high levels of marine organic matter and certain trace elements (Cu, Zn, V, Ni, Co, Ba, and Cr) and an organic-carbon-lean group depleted in these components. The greatest organic and trace metal enrichments occur in the uppermost Albian to Turanian sections of Sites 549 to 551. Carbon-isotopic values of bulk carbonate for the middle Cenomanian section of Site 550 (2.35 to 2.70 per mil) and the upper Cenomanian-Turonian sections of Sites 549 (3.35 to 4.47 per mil) and 551 (3.13 to 3.72 per mil) are similar to coeval values reported elsewhere in the region. The relatively heavy d13C values from Sites 549 and 551 indicate that this interval was deposited during the global "oceanic anoxic event" that occurred at the Cenomanian/Turonian boundary. Variation in the d18O of bulk carbonate for Section 550B-18-1 of middle Cenomanian age suggests that paleosalinity and/or paleotemperature variations may have occurred concurrently with periodic anoxia at this site. Climatically controlled increases in surface-water runoff may have caused surface waters to periodically freshen, resulting in stable salinity stratification