ABSTRACT A Cretaceous (Aptian) to Cenozoic composite oxygen isotope curve is presented and correlated to eustatic records and to global tectonic events. The curve was built using deep water benthonic foraminifera from DSDP/ODP sites. In addition, well-dated outcrop and subsurface whole rock samples were used. This composite record provides insight about the evolution of deep-water temperatures and/or ice volume changes from the Aptian to the present. Two important observations can be made from the isotope record. First, three low-frequency isotope cycles are recognized, encompassing most of the Upper Cretaceous (named Uki), most of the Paleogene (named Pi) and most of the Neogene (named Ni) period. These low-frequency cycles correspond well with the sequence stratigraphic supercycle sets Upper Zuni A, Tejas B and Tejas A, respectively. Second, oxygen isotope values for deep-water benthonic foraminifera during the Aptian to lower Albian and Campanian to Maastrichtian are similar to those observed during middle Eocene. Due to the evidence for middle Eocene Antarctic glaciation, similarity between Cretaceous and Eocene isotope values could indicate the presence of polar ice as early as the Aptian.

Abstract Detailed sequence stratigraphic analysis allowed the interpretation of seventeen depositional sequences in the Oligocene through middle Miocene succession of the Pannonian Basin (Hungary), the largest basin of the central Paratethyan area (central/eastern Europe). Depositional sequences were identified based on the analysis of published geological descriptions of outcrops and study of 3,000 km of 2D reflection seismic profiles and 45 hydrocarbon exploration wells. Eight depositional sequence boundaries coincided with regional stage boundaries; and additional nine depositional sequence boundaries were identified within the regional stages. The sequences were stratigraphically positioned on the basis of calcareous nannofossil data from 26 wells. Within the constraints of the biostratigraphic resolution in this interval, the stratigraphic position of the sequences correlates well with the previous records of depositional sequences (Haq et al., 1988). Three sequences, one in the Rupelian Stage and two in the Burdigalian Stage, were not identified by Haq et al. (1988). The examined regional stages correlate within the Paratethyan region, from Switzerland to the Caspian Sea and show a direct correlation with the standard stages. Stage boundaries typically correlate with episodic closures of connections between the European epicontinental seas from Oligocene through middle Miocene time. These closures are interpreted to result from short-term glacio-eustatic falls that overprint longer-term local tectonics. Depositional sequences are believed to result from glacioeustasy superimposed on a tectonic signal. The results, obtained in this study, and compared with oxygen isotope records (Abreu and Haddad, this volume), show a close agreement between the number and the stratigraphic position of oxygen isotope events and sequences. This supports that the major driving mechanism of depositional sequence boundary formation is glacioeustasy rather than a local or regional tectonic mechanism, and the identified sequences in this study may thus be global in nature.

Abstract One of the most difficult challenges of sequence stratigraphy is the establishment of synchrony between events observed in widely separated depositional basins. Problems arise primarily because the chronostratigraphic control in most passive margins is not adequate to constrain the ages of sequence boundaries to better than plus or minus a few million years. This resolution is often insufficient for the correlation of third-order sequences. Furthermore, unless a common mechanism affecting eustasy is assumed, such as variations in the volume of ice on the planet, there is no a priori reason to expect that sequences of similar age in widely separated basins are indeed synchronous. The stable oxygen isotope composition (δ 18 O) of marine carbonates is an independent proxy for ice volume (sea level) which has been under utilized in sequence stratigraphic analyses. This is somewhat surprising given the number of studies that have established a good relationship between foraminifera δ 18 O and ice volume in Pliocene to Pleistocene units. This paper builds on the work of Miller et al. (1987, 1991) and Abreu and Savini (1994) in identifying major Oligocene to middle Miocene isotope events and correlating them to sequence stratigraphic events. Identification of isotope events is based on δ 18 O data from DSDP sites 522, 529, 563, and 608, and ODP Site 747, drilled in abyssal water depths in the Atlantic and Indian oceans. These isotope records were used by Miller et al. (1991) to define Oligocene and Miocene oxygen isotope zones. In addition to the DSDP/ODP sites, we present oxygen and carbon isotope data from Petrobrás Well A drilled in bathyal water depths in the campos Basin on the Brazilian passive continental margin. Detailed biostratigraphy indicates that this well contains a fairly complete Oligocene to middle Miocene record. Ages of common isotope events in DSDP and ODP sites and Well A correspond remarkably well with the ages of Oligocene to middle Miocene sequence boundaries identified by Hardenbol et al. (this volume) and Vakarcs et al. (this volume) and correlated to the new time scale of Berggren et al. (1995). Because of the good correlation between the isotope and sequence stratigraphic records, we reconfirm that ice-volume change is the common mechanism driving both oxygen isotope and sea-level fluctuations from Oligocene to present time. We propose four previously unidentified early Oligocene to middle Miocene heavy oxygen isotope events that correlate with sequence boundaries identified in the Pannonian Basin (Vakarcs et al., this volume) and presented in the new cycle chart of Hardenbol et al. (this volume). Additionally, we suggest new chronostratigraphic positions for most of the heavy oxygen isotope zonal boundaries observed previously by Miller et al. (1991). We also present the chronostratigraphic positions for minimum ice-volume events (maximum flooding surfaces) determined from the isotopic record.