Q. 85: From where did the vast quantities of Flood sediments and cementing agents originate?
CPT Q. #85 – 101 Q&A on Catastrophic Plate Tectonics
Question: 85. The sources of the enormous amounts of material found in the earth’s vast sediment deposits (averaging more than a mile in thickness on the continents) as well as of the cementing agents (quartz, calcite, etc.) for these sediments are important issues that concern many Flood geologists. In your opinion, what are the sources for these sediments and cementing agents? Was the majority of sedimentary material from catastrophic processes during the Creation Week, or was most of it generated by processes during Noah’s Flood?
Response: This question involves two issues, namely, the source of the sediments deposited during the Flood and the source of the cementing agents which cemented these sediments to produce what in most cases is hard rock today. Let me preface my answer by emphasizing that I am not a specialist in sedimentary geology. However, from the background I do have, it is my present conclusion that a moderate volume of sedimentary rock existed in the pre-Flood world. I base that on vestiges of Precambrian sedimentary rocks which still exist and can readily be observed such as those exposed in the inner gorge of the Grand Canyon and the Belt Supergroup rocks in Montana and surrounding areas. These sediments indicate to me that the earth which God created using supernatural processes during Creation Week did indeed contain a moderate amount of sedimentary rock including sandstone, mudstone, and carbonates, in some cases many kilometers in total thickness.
One diagnostic that has come into prominence during the last ten years is U-Pb dating of detrital zircons in sedimentary rocks, especially sandstones. This has proved especially useful in identifying the original crystalline source rocks for the sediments. Although this approach is relatively new and it thus far has been applied to a relatively small number of sedimentary formations, the conclusion I take away from the publications I have reviewed is that a large fraction of the clastic sediments deposited during the Flood represent material eroded and mechanically reduced to sand- and silt-sized particles during the Flood itself. So as a very crude estimate on my part, I would conjecture that something less than 15-20% of the silicic sediment in the rock record today was formed during Creation Week and the remainder was formed during the Flood. This, of course, implies extreme amounts of erosion of the earth’s crystalline basement rocks and extreme mechanical abrasion of the rock fragments into very small particle sizes during the Flood. Roughly two-thirds of the silicic sediment volume is estimated to be mudstone, which means silt-sized and smaller particle sizes.
What about the source of carbonate sediment, which corresponds to roughly a quarter of the total sediment inventory (with silicic sediments comprising most of the rest)? My response to this is definitely in the realm of speculation, but to me the most likely source of new calcium and magnesium carbonate is from the chemical degradation of basalt, which typically consists of about 10 weight percent CaO and 5-12 weight percent MgO, combined with outgassed carbon dioxide from the mantle. Some of the needed chemical degradation of basalt would logically accompany the erosion and mechanical abrasion of basaltic rock in the overall erosive action of the Flood waters at the earth’s surface. Another place where some significant chemical degradation of basalt conceivably might also occur is in the rift zones where basalt near its melting temperature is in contact with supercritical water. We certainly could use a good physical chemist to explore this possibility as to how much calcium and magnesium might be extracted from the rock matrix. I would not be surprised if most of the carbonate we observe to be in the sediment record can be accounted for from these sources.
Finally, what about the source of the cementation agents? Sediments, especially mudstones, when they first form, can contain as much as 60-80% water. To me this pore water is the most logical and likely source for the cementation agents. The solubility of silica increases markedly at higher temperatures and pressures. The fact that ocean water temperatures were significantly higher during and after the Flood than at present suggests that levels of dissolved silica in sediment pore waters were also higher. Therefore, warm, mineral-laden pore waters, high in dissolved silica, to me represents a plausible way to account for the rapid cementation of the Flood sediment, regardless of where it had been deposited.