Showing papers by "Wolfgang H Berger published in 1982"

Increase of carbon dioxide in the atmosphere during deglaciation: the coral reef hypothesis

Abstract: Analyses of ice cores from Greenland and Antarctica [1, 2] have shown that the CO2 content of the atmosphere increased rather suddenly from a glacial low near 180 ppm to a postglacial high near 350 ppm early during deglaciation some 13 000 years ago. Here I present a hypothesis accounting for this observation. First, a look at the data to be explained. The various series of measurements on CO2 content exhibit considerable scatter (Fig. 1A). However, the most recent results have confirmed that a deglacial CO2 pulse exists [3]. The Dome 10 data (D10 in Fig. 1) of Delmas et al. [2] show the least scatter, and agree well with the new Camp Century profile of Neftel et al. [3]. I take the D 10 data as being representative, therefore (filled circles in Fig. 1A and B). A sharp step appears in this profile. What mechanisms can produce such a CO2 step? The CO2 reservoirs which are able to yield substantial quantities of CO2 to the atmosphere on short notice are (l) the biosphere (mainly forests), (2) the ocean, (3) sediments (carbonate and organic carbon). The biosphere was growing during deglacial warming of the globe [4]. Thus, it was not a source but a sink for COg. The ocean was a potential source of COa for two reasons : (1) warming the sea reduces its ability to hold C02 in solution, and (2) a drop in fertility, as indicated in decreasing deep-sea sedimentation rates and changing plankton composition [5], also reduces the COz content of the deep sea [6]. Warming apparently was unimportant, because from isotopic evidence and the composition of benthic faunas we know that the temperature of deep waters stayed about the same from glacial to postglacial

Climate in Earth history

Abstract: Complex atmosphere-ocean-land interactions govern the climate system and its variations. During the course of Earth history, nature has performed a large number of experiments involving climatic change; the geologic record contains much information regarding these experiments. This information should result in an increased understanding of the climate system, including climatic stability and factors that perturb climate. In addition, the paleoclimatic record has been demonstrated to be useful in interpreting the origin of important resources-petroleum, natural gas, coal, phosphate deposits, and many others.

Acoustic and Related Properties of Calcareous Deep-Sea Sediments

Abstract: Three expeditions to the Ontong-Java Plateau and the eastern equatorial Pacific obtained unusually good samples of calcareous sediment from box and piston cores; water depths ranged from 1600 m to 4900 m. Two sedimentary environments are represented. Dissolution, dilution, and winnowing cause reductions (with increasing water depth) of CaCO3, percent sand, mean grain size, sediment rigidity, and sound velocity. The best indices to predict sound velocity are percent sand, mean grain size, and the velocity ratio; this ratio varies from about 1.05 on top of the Plateau to about 1.00 at 4400 m. Hollow tests of Foraminifera act as solid particles in transmitting sound. Density and porosity are good predictors of velocity in the east Pacific but not in the Plateau area because of large amounts of hollow Foraminifera. There is no significant increase in sound velocity as CaCO3 increases from 35 to about 75 percent; above that percent, increases in velocity are mainly due to increases in sand-size particles. Eastern Pacific sediment has higher porosities and lower densities (than the Plateau samples) because of less CaCO3 and more biogenous silica. Biogenous silica content causes good correlation between density and CaCO3 content in the eastern Pacific but not in the Plateau sediment; density or impedance cannot be used to determine CaCO3 content in sediment lacking significant amounts of biogenous silica. As water depth increases from 1600 m to 4900 m, percent sand and mean grain size decrease markedly but total porosity increases only 1 to 3 percent. This is due to dissolution and breakdown of hollow tests of Foraminifera and transfer of intraparticle porosity (within the tests) to interparticle porosity between the grains. New estimates of intraparticle porosity range from 13 percent in clayey sand to zero in silty clay. New relations between the frame bulk modulus and porosity allow computations of elastic properties which indicate very small differences in bulk moduli or densities over wide ranges of grain sizes and water depths, but large changes in dynamic rigidities cause both shear and compressional wave velocities to decrease with increasing water depth.

Benthic Foraminifera: Depth Distribution and Redeposition

Abstract: This study demonstrates that benthic foraminifera can be quantitatively related to depth by an indexing method. An Apparent Depth Zone (ADZ) is computed for each major species in the taxonomic lists at-hand and the combination of those values is then used to produce a Depth EsTimate (DEST) for each sample. For W Africa, species’ ADZs compare favorably in value and in sequence with published depth ranges of the same species. In four of the five study areas examined the ADZbased sample depth predictions are systematically related to the actual sample depth. Anomalous samples are identifiable as outliers on depthDEST plots. The method, therefore, is a promising data-editing technique that could be applied to eliminate reworked samples prior to further Statistical analyses.