High-Resolution Carbonate and Quaternary Organic-Carbon Stratigraphies for the Late Neogene and Quaternary from the Western Caribbean and Eastern Equatorial Pacific

Abstract

Concentrations of calcium carbonate and organic carbon were determined in closely spaced samples from two nearly continuous sections of the late Neogene and Quaternary, one from Site 502 in the western Caribbean and the other from Site 503 in the eastern equatorial Pacific. Each section records the past 7.5 m.y. with a sampling interval of approximately every 5 k.y. Both sections show cyclic carbonate concentrations with three classes of dominant periodicities. The longest-period carbonate cycles have periods of 500 to 600 k.y. and appear to be broad-scale oceanic responses. These cycles appear throughout the entire Pacific record but only occur in the 4.0 to 7.5 m.y. interval in the Caribbean record. This difference is probably related to the more active tectonic setting of Site 502 and the oceanic character of Site 503. Intermediate-scale carbonate cycles, S-cycles, occur throughout both records, but the only interval that can be correlated between the two is the 0 to 1.4 m.y. interval. These cycles can also be correlated with records of changes in other Pleistocene sections. The range of periodicities of the S-cycles suggests they are responses to global climatic changes that are in phase with the eccentricity of the Earth's orbit. The smaller-scale carbonate cycles, C-cycles, also occur throughout both records but are difficult to correlate because of the different settings of the two sites. C-cycles are apparently out-of-phase between the two sites from 7.5 to 4.0 Ma, but then, inexplicably, they become much more similar in trend from 4.0 Ma to present. C-cycles have periodicities that fall in the range typical of these of the obliquity of the Earth's orbit, again suggesting a control by global climatic changes. Organic-carbon concentrations show no correlation with carbonate in the western Caribbean section but they show a strong negative correlation with carbonate in t]ie eastern equatorial Pacific record. The relationship in the Pacific section is opposite to that found by others, and the relationships at both sites are opposite to what one would intuitively expect.

Coarse fraction fluctuations in pelagic carbonate sediments from the tropical Indian Ocean: A 1500‐kyr record of carbonate dissolution

“…Farrell and Prell [1991], who observed such a long-term increase of carbonate preservation in pelagic sediments from the Pacific, proposed that it results from a gradual lowering of sea level which fractionates carbonate from the world's shelves to the basins [e.g., Berger, 1970;Berger and Winterer, 1974]. A late Pleistocene ~500-kyr dissolution oscillation has been previously observed by Vincent [1981] and Gardner [1982] in carbonates from the deep Pacific and was recently found in aragonite-bearing periplatform deposits from the Bahamas [Droxler et al, 1988] and the Maldives [Droxler et al, 1990]. The last 700 kyr of this long-term oscillation correspond to the well-known "mid-Brunhes dissolution cycle" [Adelseck, 1977], with its characteristic dissolution maximum (grain size minimum) centered at about 400 ka and bounded by preservation maxima (grain size maxima) at about 100 ka and 700 ka.…”

Late Quaternary terraces and their cover beds, north-western Wairarapa, New Zealand, and provisional correlations with oxygen isotope stages

“…Ages of oxygen isotope stage boundaries given by Froggatt et al (1986). Oxygen isotope stages 1 to 10 after Emiliani (1966), Hays et al (1976) and Gardner (1982).…”

A 420,000‐year record of cyclicity in oceanic and atmospheric processes from the eastern equatorial Pacific

“…The weight percent of CaCO3 and of organic carbon in these sediments has been given by Gardner [1982] and we utilize his data here (Table 3) and may vary at a higher frequency than the "longer wavelength" •5•80 or CaCO3 records.…”