Paper Abstracts

Flood/post-Flood boundary

A.A. Snelling

Discipline: Geology

Abstract: Erosion at the end of and after the Flood exposed the tops of primary ore deposits to subsequent weathering and the formation of supergene minerals. The 40Ar/39Ar and (U-Th)/He radioisotope methods applied to these supergene minerals provide the dates for when these minerals formed. But given the documented problems with the radioisotope methods, they can only provide at best relative dates. When the Flood waters retreated, the ground surface was dry, but extra time was needed to allow the water table to drop, soil to form and plants to grow before Noah stepped off the Ark, which marked the end of the Flood event. The weathering front then progressed downwards during the early post-Flood decades for supergene minerals to start forming. Residual post-Flood catastrophism may have involved mountains still rising and ore deposits still forming, such as the porphyry copper deposits associated with granite intrusions as the Andes continued to rise. Erosion exposed those later-formed ore deposits to subsequent weathering to produce supergene minerals well into the early post-Flood era. Thus, the relative ages of the supergene iron oxides, and potassium-bearing sulfates and manganese oxides produced span the whole Cenozoic. It is proposed that relative dates for the first formation of supergene minerals can possibly be used as a criterion for determining the placement of the Flood/post-Flood boundary at the K-Pg boundary with a relative age of 66 Ma. The few slightly earlier relative ages likely resulted from weathering that commenced before the Flood event ended, though deep weathering would have required decades. The spread of relative ages through the Cenozoic thus represents the progressive formation of supergene minerals as primary ore deposits emplaced during, and maybe after, the Flood were subsequently exposed to weathering by residual catastrophism. Continuing investigation of this criterion for placement of the Flood/post-Flood boundary seems warranted.