Creationist flood models that assign a significant portion of the fossiliferous sedimentary rock record to the Genesis flood must include these sandstones and somehow interpret them as flood sediments.
Could the currents of the flood erode granite or other source rocks rapidly enough, to provide the source of all the sand that was deposited in the flood? Would the sand grains and pebbles formed in this way have the characteristics corresponding to those of sandstones? Would sediments formed by currents of a great flood resemble the sandstones we find? Could violent currents of a great flood produce sandstones that are very pure, up to 99% quartz, with the patterns of cross strata seen in typical sandstones? These are all important questions that need to be answered.
In geology, there is an axiom that all rocks exposed at the earth's surface, igneous, metamorphic, and sedimentary, slowly break down due to processes such as weathering, erosion, and abrasion due to ice, to form sand, silt, and clay; when these are deposited in the sea, they form sedimentary rocks such as sandstones, shales, and siltstones.
Geologists believe in the geological cycle:
Uplift of igneous rocks => erosion => transport => deposition => burial => metamorphism => erosion => deposition etc.This concept, first expressed about two centuries ago by James Hutton, called the "father of uniformitarianism," is a fundamental one in geology. Sands of sandstones are defined as detrital; this is assuming what needs to be proved.
The assumption of a detrital, sedimentary origin of all the sand and pebbles in the earth, has its origin in the uniformitarian premises of James Hutton and his disciples, John Playfair, and Charles Lyell. They proposed the dogma of uniformitarianism, that rules out a great catastrophic flood, before much was learned about chemistry, thermodynamics, and such things as the effects of changing stress fields on sediments.
Trying to base a flood model on the same premises that Hutton and Lyell built their theory of uniformitarianism upon seems to me to be unsound, and leads to contradictions.
Creationists who support flood models that involve former catastrophic conditions need to be looking for signs of former processes that could have operated in such former conditions, that are not found acting today. This is simply common sense.
An example is the possibility of increased silica solubility and mobility in former conditions, when sediments were being compacted. Silica solubility is very low in present conditions. Yet it is very common to find sandstones cemented by quartz. Perhaps these rocks were lithified under conditions of higher pressure due to burial, and elevated temperatures; if so, abundant silica might have been precipitated in a short time span, as silica solubility increases with increase pressure and temperature.
Creationist flood models that assume both that the quartz sand grains of sandstones were rounded by abrasion during transport, and that the pure quartz sandstones were deposited by catastrophic currents of the flood, seem to be contradictory. Furthermore, they are untestable; experiments indicate quartz sand grains do not become rounded very much during transport in water, and the violent currents of a flood would be unlikely to produce "pure" sediments, as the turbulence associated with violent currents seems to preclude the deposition of pure sediment.
However, during the compaction process, after the flood waters had deposited their load of sediment, when thick piles of sediment became lithified, and the land was raised again from the depths or as the overburden was removed due to erosion caused by rapid currents of the retreating flood waters, there may have been segregation of minerals within the sediment piles into discrete layers, by concretionary mechanisms.
In conventional geology, several cycles of erosion, transport, deposition, erosion, etc are invoked to explain the quartzites and sandstones that are composed of well rounded sand grains or rounded pebbles, so it seems unreasonable to propose compressing the time scale of conventional geologic theories (that span hundreds of millions of years) into only a few thousand years, as the geologic theories of some Creationists have proposed; completely new and different mechanisms and theories about the origin of sand and pebbles are needed, such as my disintegration theory of the drift, and the proposed crystallization of sills and dikes of hydrous amorphous silica in successive layers, forming patterns of cross strata.
A proper interpretation of quartz sandstones would seem to be crucial for the development of a viable flood model by creationists.
The composition of shales seems to support this. In the Paleozoic shales, the illite/smectite abundance ratio is higher than in Tertiary shales; this occurs world wide. Geologists think that much of the original smectite present in the older shales has converted to illite by addition of aluminum and potassium, during diagenesis and compaction. In the flood model, the compaction of sediments in thick sediment piles was accompanied by a drop in fluid pressure that accompanied jointing, and the development of a directed stress field as the overburden was eroded, lowering the vertical stress, and as the land was uplifed.
The smectite => illite reaction released silica along with the ions of sodium, iron, and magnesium, and water. The variation in the composition of shales in the rock record indicates a large amount of silica was probably released to solution during the compaction of sediments.
Perhaps, as it was forced upwards, the silica accumulated in sills at various levels, in hydrous amorphous form. Eventually, as overburden was removed by the action of currents of the retreating flood waters, and as the sediment piles became lithified, the silica in these sills crystallized, releasing the water, which escaped upwards to the surface via joints. The crystallization proceeded in successive layers, forming sand grains arranged in patterns of cross strata. These non-sedimentary patterns of laminations in ancient sandstones are invariably supposed to be sedimentary ones by geologists.
Two sandstone dikes are shown in the photo at right, one in the center of the picture, and a smaller one to the left. They occur in dolerite rock, (a form of basalt) on the south coast of Tasmania's Tasman Peninsula. The white pocket knife just visible beside the dike in the center of the photo is about 3 inches long. Note that the joints pass through both the dolerite and the sandstone. Joints would probably form during cooling of the igneous host rock. How could sand have been injected into these dikes, before the rock had cooled? It seems much more likely that the sandstone in these dikes formed in place, perhaps by a crystallization process. Veins of amorphous silica formed in the dolerite, which crystallized to form quartz sandstone. The dike in the center is wider at the top than at the bottom; the sandstone dikes are known to pinch and swell, which is easily explained by in situ crystallization.
Click on the image at left for another picture showing a sandstone dike with a band of rounded pebbles of quartzite in it [jpeg, about 40 kbytes]. This is one of several sandstone dikes exposed at Clear Lake, Ontario, along highway 68, about 1 mile south of Espanola, north of Lake Huron. The dike cuts through the horizontally bedded carbonate siltstone of the Espanola formation. Light and dark sections are due to uneven drying after recent rain; the wet rock (darker in the photo) highlights the quartz pebbles.
In the in situ theory, these sandstone dikes may have formed by the crystallization of amorphous silica deposited in the vicinity of a fracture or joint, in former conditions of rapidly changing pressure. The interstitial fluids migrated towards the dike, which represented a permeable zone, where fluids escaped during compaction of the rock. This could explain the arrangement of pebbles in a central band, and the variation of grain size in the dikes; coarse in the center, finer near the walls. The quartzite pebbles likely formed in place by concretionary growth processes and recrystallization. It seems unlikely that the arrangement of pebbles seen here would be produced by conglomerate being injected into fissures in the siltstone, as claimed in geology text-books.