On the global flood
So a creationist on facebook has challenged me for an explanation of the "Austin chalk line". I take it for some reason that the existence of the Austin Chalk is evidence for a global flood. I must admit that were I ever to return to young earth creationism, I would not use the Austin chalk as evidence for the great flood, let alone a young earth. In fact, I would be very careful not to mention chalk deposits like this one (or the white cliffs of dover) in the hope that the old earther I was debating would forget to bring it up. Why is this such a poor example for flood geology?
There are several arguments relevant to chalk deposits that are often used to counter the flood model. The first has to do with the incredible density of microscopic organisms required to make up the deposits if they were deposited in a single year. A second problem has to do with the time it takes for chalk deposits to form. These are microorganisms that rain down on the seafloor. In surface water, the dead tests of these organisms can be carried by currents and remain suspended for some time though eventually they will fall to the seafloor and accumulate. Even if the massive blooms required for the chalk deposits were formed in a flood, the tests would not settle down in such pure layers during the flood. Most, if not all, would remain suspended in the water column. The third problem with chalk layers is where they reside in the rock record. For the most part the large deposits of chalk are Cretaceous in age and that forces flood geologists to pin down at least part of the flood during this interval in the rock record. So let's look at the creationist explanation.
Creationist like Steve Austin (aka evolutionist Stuart Nevins) claims that chalk deposits are not problematic for the flood. While I encourage you to read the entire article, I want to highlight several 'explanations' given by Austin:
(1) Creationist geologists may have different views as to where the pre-Flood/Flood boundary is in the geological record, but the majority would regard these Upper Cretaceous chalks as having been deposited very late in the Flood.
Interesting claim by Austin, more on this in a moment.
(2)Quite clearly, under cataclysmic Flood conditions, including torrential rain, sea turbulence, decaying fish and other organic matter, and the violent volcanic eruptions associated with the ‘fountains of the deep’, explosive blooms on a large and repetitive scale in the oceans are realistically conceivable, so that the production of the necessary quantities of calcareous ooze to produce the chalk beds in the geological record in a short space of time at the close of the Flood is also realistically conceivable.
Now there are many things to take issue with in Austin's article, but these two are problematic in their own right. Let's start with point #2. Austin concedes the conditions under which these organisms form. Torrential rain, sea turbulence and violent eruptions are the stated conditions. Now let's review the biology of these microorganisms. Coccoliths and forams that make up these deposits are planktonic. Indeed the most abundant form of coccolith occupies the photic zone (upper 100 m of surface waters), but reread Austin and note that he places them in water depths 5x the 'norm' and this in turbulent, cloudy waters of the flood. In short, he changes the entire ecosystem and claims that these conditions would 'foster' blooms of these organisms! Secondly, Austin tries to deal with the population density problems outlined by Glen Morton who astutely points out the ridiculous population densities required by flood proponents. Austin's sleight of hand many be difficult for the creationist to grasp, but the simple answer is that Austin deals with the population problem by essentially assuming that these are the only things in the ocean. Morton discusses the physics and life cycle issues in far more detail than Austin and I encourage you to read Morton's discussion as well as the discussion of land fossils in that essay.
Now turning to point #1 placing these blooms in the latter part of the flood. Ok, let's assume that Austin is correct and that the Chalk beds represent the latter part of the flood. That means that the earlier part of the flood waters would be represented by strata of Jurassic, Triassic and Paleozoic age. But let's forget about the Paleozoic strata and look just to the strata that immediately pre-dates the Austin chalk (namely Jurassic and Triassic). We will use these terms without any absolute time connotation and assume that what normal geologists call Jurrassic and Triassic are all less than 6000 years old and that they were deposited in the year of the great flood.
More to come.