Carbon dating biogenic sediments

The shells of these organisms are made of either calcium carbonate (Ca CO ).Although ubiquitous, particularly elevated concentrations of such organisms are most commonly found in biologically productive waters such as the Equatorial Pacific, or the Southern Ocean ringing the continent of Antarctica.More typical deep-sea rates are on the order of several centimeters per 1,000 years.The production of marine sediment is more complex than it may seem.The resuspension of the sediment into the bottom water causes it to be more dense than the overlying water, and thus these turbidity currents flow downslope to the more distant ocean basin.

Also, during such time periods the wind speed tends to be higher, and thus terrigenous grains that are slightly larger than usual are preferentially transported.The different combinations of each process' effectiveness result in a commensurate variety of sedimentation rates.Sediment can accumulate as slowly as 0.1 millimeter (0.04 inch) per 1,000 years (in the middle of the ocean where only wind-blown material is deposited) to as fast as 1 meter (3.25 feet) per year along continental margins .Terrigenous sediment is produced by an interplay of chemical and physical weathering processes, which collectively serve to create small grains of material ranging in size from thousandths of millimeters to 1 or 2 millimeters(0.04 or 0.08 inch).(The larger grains of coarse sand, gravel, and boulders are too large to be transported to the deep sea and therefore are not discussed here.) Physical weathering is caused by mechanical fracturing of rocks, such as that due to the freezing of water in cracks, and results in finer grained, compositionally similar examples of the original rock.

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