Material Fluxes on the Surface of the Earth (1994) / Chapter Skim
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Pleistocene--Holocene Fluxes Are Not the Earth's Norm
Pleistocene--Holocene Fluxes Are Not the Earth's Norm
Pages 15-27
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From page 15... ...
Quantitative estimates of the masses of material eroded, transported, and deposited during the Pleistocene-Holocene have been difficult to obtain because of the lack of consistent information on the thicknesses and areal extent of the deposits on land and in shallow seas. Geologic maps commonly show extensive areas of Quaternary cover on older sediments, but information on the thickness of the tills, alluvium, and colluvium that make up these deposits is scattered throughout the literature and is often incomplete.
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From page 16... ...
Many of the estimates of Pleistocene sediment masses involve calculation or extrapolation of accumulation rates, so that knowledge of its duration is critically important. The age of the base of the Pleistocene was thought for many years to be about 2 Ma; this was revised to 1.8 Ma by Hays and Berggren (1971)
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From page 17... ...
The best data on Quaternary sediment masses are from the deep sea. This is in spite of the fact that the base of the Pleistocene usually lies below the depth of penetration of piston cores and is too shallow to be recovered completely intact and undisturbed even by the hydraulic piston corer developed in the later phase of the Deep Sea Drilling Project (DSDP)
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From page 18... ...
Long-term flux rates are integrated fluxes over a longer, inhomogeneous period of geologic time, such as the Holocene, the Wisconsinan, or the Pleistocene. LONG- AND SHORT-TERM APPARENT ACCUMULATION RATES OF QUATERNARY AND HOLOCENE SEDIMENT Most of the information on apparent accumulation rates is from the marine realm, and most of it is for long-term rates.
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From page 19... ...
presented maps of sedimentation rates for Holocene and late Pleistocene sediments in the equatorial Atlantic. Average Holocene apparent accumulation rates for different regions can be calculated from the data presented on the maps, as shown in Table 1.5.
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From page 20... ...
0.0156 176.0 74.2 333.0 0.50 0.66 0.84 0.0089 0.0054 0.0098 TABLE 1.5 Holocene Apparent Accumulation Rates for Sediment in the Equatorial Atlantic Ocean (after Damuth, 1977) Continental Basins Basins Rises <5 km >5 km Average sedimentation rate (crn/kyr)
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From page 21... ...
In the Mediterranean, as in the major ocean basins, the Holocene accumulation rate is about one-quarter the Quaternary average. Investigations by the DSDP permit comparison of Pleistocene, glacial, Holocene, and late Holocene apparent accumulation rates in the Black Sea basin.
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From page 22... ...
suggested that the present carbonate flux onto shelves and banks is at least equal to the supply from rivers and might exceed the river supply by a factor of three. In the estimates presented in Table 1.8, I have assumed an average Holocene sedimentation rate of 100 cm/kyr for detrital sediment, a solidity of 33 percent, and a carbonate TABLE 1.8 Quaternary and Holocene Sediment Fluxes on Continental Shelves Accumulation Rates (g/cm2/kyr)
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From page 23... ...
These areas were multiplied by the estimated average thickness of 20 m, an assumed solidity of 80 percent, and a solid grain density of 2.65 g/cm3. Because the same thickness and solidity were assumed everywhere, the Quaternary average apparent accumulation rate works out to be 2.65 g/cm2/kyr everywhere.
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From page 24... ...
If continental glaciers are effective erosional agents, most of the sedimentary material on the Laurentian and Fennoscandian shields would have been eroded by the first significant ice cap, in the early Pleistocene. Increased Tectonic Activity The idea that the large mass of young sediment is the result of increased tectonic activity dominated geological thinking throughout the first half of this century (Stifle, 1936~.
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From page 25... ...
(1977~. Late Quaternary sedimentation in the western equatorial Atlantic, Geological Society of America Bulletin 88, 695-710.
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From page 26... ...
Kohl (1986~. Accumulation rates of Mississippian sediments cored during Deep Sea Drilling Project Leg 96, in Initial Reports of the Deep Sea Drilling Project 96, A
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From page 27... ...
Hay (1988~. Estimating ancient sediment masses and flux rates, Geological Society of America Abstracts with Programs 20, A78.
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