Method for distinguishing Neoproterozoic and cambrian period stratums

Abstract

The invention provides a method for distinguishing late Neoproterozoic and cambrian period stratums. The method comprises the following steps: S1, sampling a plurality of stratum rocks in a target area; S2, separating out a corresponding gypsum sample in the rock; Ss3, performing sulfur-oxygen isotope analysis on sulfate in the gypsum sample; and S4, according to a mean value range of sulfur isotopes and oxygen isotopes in the sulfate, determining geological times of the plurality of target stratum rocks. The method has advantages that rock cores and rock debris samples of gypsum and anhydritein stratums in a large number of drilling evaporative rocks with different depths or layers in an evaporative rock basin are treated and analyzed; and according to the mean value range of the sulfurisotopes and the oxygen isotopes, the cambrian period stratum and the late Neoproterozoic stratum can be distinguished, the cambrian period stratum is the key point of oil and gas exploration, the accuracy of cambrian period stratum detection can be improved by applying the method, and therefore oil and gas exploration efficiency of the evaporated rock in the basin is increased.

Description

technical field [0001] The invention relates to the field of geological exploration, in particular to a method for distinguishing Neoproterozoic and Cambrian strata. Background technique [0002] The late Neoproterozoic to early Cambrian was a critical period in the evolution of the earth's history, and the entire biosphere, atmosphere, and hydrosphere underwent tremendous changes. This period is also the peak of the deposition of evaporites and marine black shales, which provide abundant sources of natural gas and shale gas. In geological history, evaporites usually appear together with black shale, because the environment in which evaporites are formed is conducive to the formation and preservation of black shale. [0003] The isotopic composition of seawater also changed significantly from the late Neoproterozoic to the early Cambrian. Sulfate deposits in evaporite basins actually record the sulfur isotopic composition of seawater, as well as the oxygen isotopic composi...

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Problems solved by technology

[0005] Late Neoproterozoic-Cambrian sulfur isotopes are the highest values ​​in geological history (Holser and Kaplan, 1966. Isotope geochemistry of sedimentary sulfates. Chem Geol 1:93–13; Holser, 1977. Catastrophic chemical events in the history of the ocean.Nature267:403–408; (Houghton,1980.Geochemistry of the Proterozoic Hormuz Evaporites,Southern Iran.MSc thesis,University of Oregon), so the late Neoproterozoic-Cambrian The strata of the Neoproterozoic can be distinguished from other geological periods, but the late Neoproterozoic strata cannot be distinguished from the Cambrian strata by sulfur isotope (Claypool et al., 1980)

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