(Table 1) Organic geochemistry at DSDP Leg 71 Holes

Forty-three core samples from Sites 511 through 514 of DSDP Leg 71 were analyzed geochemically. The black shales at the bottom of Hole 511, in the basin province of the Falkland Plateau, contain an average of 1590 ppm extractable organic matter (EOM) and 120 ppm hydrocarbons. Whereas molecular type-carbon number distributions of mono- and polynuclear aromatic hydrocarbons and their sulphur and oxygen analogues in the black shale "aromatic hydrocarbon" fractions are very similar to those of many crude oils, other data - gas chromatography (GC) fingerprint, pyrolysis GC, visual kerogen analysis, H/C ratio - suggest the black shale section is thermally immature. Together, these observations imply that many of the hydrocarbons were deposited with the original sediments or are diagenetic products of other biological compounds. Pyrograms of the humic acid and kerogen fractions from the black shale interval are typical of geopolymers derived from marine algal material. It appears that these humic acids and kerogens are derived from the same lipid stock.

Early Cretaceous large, few-chambered Globigerinelloides from the Tethys

New findings of well-preserved Early Cretaceous planktonic foraminiferal assemblages from the Cismon core (NE Italy), Calabianca (NW Sicily), Lesches en Diois (SE France) and DSDP Site 545 (off Morocco) sections allow a better understanding of the morphological features of several taxa. This paper deals with the revision of the small, planispiral individuals that several authors include in the genus Blowiella Krechmar and Gorbachik. Comparison of morphological characteristics between Blowiella and the genus Globigerinelloides Cushman and ten Dam has resulted in retention of the latter as senior synonym of Blowiella. In fact, the morphological differences (i.e. the number of chambers in the outer whorl, the width of the umbilical area, and size and spacing of pores) used to distinguish Blowiella from Globigerinelloides cannot, in our opinion, be used in discriminating genera, but can only be applied at species level. The small, few-chambered species of the genus Globigerinelloides retained here are Globigerinelloides blowi(Bolli), Globigerinelloides duboisi (Chevalier), Globigerinelloides maridalensis (Bolli), and Globigerinelloides paragottisi sp. nov. (=Globigerinelloides gottisi auctorum). Stratigraphically, in the sections studied Globigerinelloides blowi and Globigerinelloides paragottisi sp. nov. are first recorded from the mid-Upper Barremian in the Cismon core and Calabianca section, while rare individuals belonging to Globigerinelloides maridalensis and Globigerinelloide duboisi occur intermittently from the Barremian/Aptian boundary and from the Lower Aptian, respectively. All of these taxa become more frequent and abundant just above the Selli Level (OAE1a, Lower Aptian), within the Leupoldina cabri Zone (Upper Aptian). Based on the DSDP Site 545 succession, all four globigerinelloidid taxa range up to the Ticinella bejaouaensis Zone (uppermost Aptian), with Globigerinelloides maridalensis disappearing at the base of the zone, followed in close succession by the disappearance of G. blowi, G. paragottisi and finally G. duboisi.

(Table 1) Calcium carbonate at DSDP Hole 81-552A

DSDP Hole 552A, cored with the HPC on Hatton Drift, represents an almost complete and undisturbed sediment section spanning the late Neogene and Quaternary. Lithologic, faunal, isotopic, and paleomagnetic analyses indicate that the section represents the most complete deep sea record of climatic evolution hitherto recovered at high latitudes in the northern hemisphere. A glacial record of remarkable resolution for the late Pliocene and Pleistocene is provided by oxygen and carbon isotope ratios in benthic foraminifers. In the upper part of the section, the whole of the standard oxygen isotope record of the past million years is well preserved. The onset of ice-rafting and glacial-interglacial alternations occurs at about 2.4 m.y. ago.

Benthic foraminiferal number of specimens in Cretaceous samples of various DSDP and ODP Sites (Table 2)

Benthic foraminifera from 24 DSDP/ODP sites were investigated to assess their global horizontal and vertical distribution in the deep-sea environment at the end of the Cretaceous period. The samples analyzed are from the late Maastrichtian and within the planktic foraminiferal Abathomphus mayaroensis Zone from a wide range of oceans and paleolatitudes, including the low-latitude Sites 10 and 384 (Atlantic Ocean), 47, 171, 305, and 465 (Pacific Ocean), the mid-latitude Sites 20, 111, 356, 363, 516, 525, 527, 548, and 605 (Atlantic Ocean), 216, 217, and 758 (Indian Ocean), and the high-latitude Sites 208 (Pacific Ocean), 689,698,700,738 and 750 (Southern Ocean). Correspondence analysis, based on the 75 most common taxa, shows a clear biogeographic trend along the first correspondence axis by arranging the sites in paleolatitudinal order. The assemblages from the Tethyan Realm (i.e., low latitudes) are marked by abundant heavily calcified buliminids (such as Bulimina incisa, B. trinitatensis, B. velascoensis, and Reussella szajnochae) and Aragonia spp., whereas high-latitude faunas are characterized by abundant Alabamina creta, Gyroidinoides quadratus, and Pullenia coryelli. The results indicate that the faunas at low and high latitudes, respectively, were influenced by quite different environmental conditions. This is based on the much higher abundance of infaunal morphotypes at low and mid latitudes compared to high latitudes, suggesting that the biogeographic trend found in the data set coincides with the trophic regime at the various sites. The results also provide support for the hypothesis that postulates two simultaneous sources and mechanisms for deep-water formation during the Late Cretaceous, including warm, saline deep water produced by evaporation at low (equatorial) latitudes in contrast to the formation of cold deep waters at high (southern) latitudes.

(Table 1) Carbon and carbonate at DSDP Leg 71 Holes

Leg 71 sediments were analyzed for total carbon and acid-insoluble (organic) carbon, using the Leco WR-12 analyzer, according to the standard technique outlined below. The 3 cm**3 sediment samples were first dried and ground into a homogeneous powder. The ground sediment was redried at 105 to 110°C, and two samples, a 0.1 g and a 0.5 g sample, were weighed into Leco clay crucibles. The 0.5 g sample was acidified with 10% hydrochloric acid and washed with distilled water. The sample was then dried and analyzed for acid-insoluble carbon. The 0.1 g sample was analyzed for total carbon without further treatment. If the sample contained less that 10% CaCO3, an additional 0.5 g sample was analyzed for greater accuracy. The calcium carbonate percentages were calculated as follows: (% total C - % organic C) x 8.33 = % CaCO3. Although other carbonates may be present, all acid-soluble carbon was calculated as calcium carbonate.