Using the Characteristic Elementsfrom Meteoritic Must in Strata to Calculate Sedimentation Rate

WU Zhi ping; ZHOU Yao qi

In the study of sedimentology,one of the most fundamental quantities that geoscientists seek to measure is the sedimentation rate,and it is crucial to a complete understanding of depositional process. The meteoritic dust is a kind of extraterestrial material with high abundance of iridium and cobalt.Most people think that the deposition quantity of meteoritic dust per year is almost constant on earth surface,and the average abundance of some characteristic elements such as Ir and Co in meteoritic dust are fixed,so there is a correlation between sedimentation rate and Ir (or Co) concentration.The abundance of Ir (or Co) in the sedimentary sample with low sedimentation rate is higher than in the sample with high sedimentation rate.According to this,the abundance of the element Ir or Co in sediment can be used to measure the deposition rate as a dating tool.Based on the previous work,the theory and method of using characteristic element from meteoritic dust ot calculate sediment rate have been suggested,and the formulae can be pariticularly expressed as follows: V s= V (Co)/｛ ρ ×[ A (Co)- w (Co)× A ”(Co)] ｝ where V s is the sedimentation rate of the sample which we want to calculate, V (Co) is the deposition rate of Co from meteoritic dust (6.48×10 -7 g/cm 2a), ρ is the density of the sample, A (Co) is the total abundance of Co in the sample, A ”(Co) is the abundance of Co in the source rock and w (Co) is contribution coefficient of Co from the terrigenious sources. Using this method,the sedimentation rates of the Eogene-Neogene section in Linqu County of Shandong Province has been measured as a case in this paper. Comparing with common methods,the method of using characteristic element from meteoritic dust to calculate sedimentation rate is more practical and accurate.

Department of Resources Science,University of Petroleum,Dongying Shandong 257062

Received Date: 1999-05-11

Rev Recd Date: 2000-01-22

Publish Date: 2000-09-10

Key words:

Abstract: In the study of sedimentology,one of the most fundamental quantities that geoscientists seek to measure is the sedimentation rate,and it is crucial to a complete understanding of depositional process. The meteoritic dust is a kind of extraterestrial material with high abundance of iridium and cobalt.Most people think that the deposition quantity of meteoritic dust per year is almost constant on earth surface,and the average abundance of some characteristic elements such as Ir and Co in meteoritic dust are fixed,so there is a correlation between sedimentation rate and Ir (or Co) concentration.The abundance of Ir (or Co) in the sedimentary sample with low sedimentation rate is higher than in the sample with high sedimentation rate.According to this,the abundance of the element Ir or Co in sediment can be used to measure the deposition rate as a dating tool.Based on the previous work,the theory and method of using characteristic element from meteoritic dust ot calculate sediment rate have been suggested,and the formulae can be pariticularly expressed as follows: V s= V (Co)/｛ ρ ×[ A (Co)- w (Co)× A ”(Co)] ｝ where V s is the sedimentation rate of the sample which we want to calculate, V (Co) is the deposition rate of Co from meteoritic dust (6.48×10 -7 g/cm 2a), ρ is the density of the sample, A (Co) is the total abundance of Co in the sample, A ”(Co) is the abundance of Co in the source rock and w (Co) is contribution coefficient of Co from the terrigenious sources. Using this method,the sedimentation rates of the Eogene-Neogene section in Linqu County of Shandong Province has been measured as a case in this paper. Comparing with common methods,the method of using characteristic element from meteoritic dust to calculate sedimentation rate is more practical and accurate.

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Using the Characteristic Elementsfrom Meteoritic Must in Strata to Calculate Sedimentation Rate

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