Coral and Coral Reefs Preclude a Young Earth and a Global Flood

​Today's subject is that of the one of the most basal organisms on our planet, and it is capable on it's own of disrupting the possibility of a global flood as well as a 6000 year old Earth. It also validates Evolutionary Theory and the currently listed mass extinctions.
It may be a simple cnidarian, but we'll explore just how damaging this animal is to a literalist interpretation of the Bible.
Part 1: The Crash Course on Corals
Corals are marine invertebrates of the phylum Cnidaria. They are sessile, meaning they lack a means of locomotion, and individual corals (polyps) form coral groups known as colonies, whose polyps are thus genetically identical. They reproduce primarily sexually though, and coral colonies will release gametes into open water simultaneously according to the lunar cycle.
As such, coral reefs are made of many coral colonies which many vary on species, but all of which grow upwards and outwards asexually. In the case of stony coral (as opposed to the other type, soft coral) their immense skeleton is made of calcium carbonate in the form of calcite or aragonite (both polymorphs of limestone).
Coral reefs are interesting though, due to their nature of growth. As coral reefs proliferate, coral groups die and are replaced by new polyps. This leads to a continuous growth of new coral colonies on the dead skeletons of their colonial fore-bearers.
In fact, the largest reefs on our planet are living coral groups on thousands of years of dead coral groups including the Great Barrier Reef.
The coral type we are going to investigate here is that of large stony corals (scleractinian) which build shallow-water coral reefs, including fringing reefs, barrier reefs and atolls; the majority of which occur in tropical and subtropical seas. This is because these particular corals are not only incredibly common, but they are of interest thanks to their abysmally slow growth rate adding an average of 0.2-1.0 inches per year to the overall height of the reef.
According to this same source corals have ideal growing conditions that apply generally across the board: " Coral reefs grow best in warm water (70–85° F or 21–29° C). Corals prefer clear and shallow water, where lots of sunlight filters through to their symbiotic algae. It is possible to find corals at depths of up to 300 feet (91 meters), but reef-building corals grow poorly below 60–90 feet (18–27 meters). Corals need salt water to survive, so they grow poorly near river openings or coastal areas with excessive runoff."
All of the following will be important to remember and refer to for the following analysis.
Part 2: A History of Corals
Geologically, we first see corals appear in Cambrian rock, although their record really begins to bloom in the Ordovician. Here we see the rise of the incredibly prolific Rugose Corals.
They are represented heavily in the Thorton Reef in Illinois at the Silurian Racine Formation, where ancient reef cavities are filled with thick oil, and layering is interspersed. The Devonian Tract in Alberta is similar.
These corals no longer exist today, as they were wiped out in the Permian, leaving an enormous void in the fossil record. But shortly after in the Triassic the scleractinian corals arrive on the scene, and become the dominant corals we see today.
This is important: Prior to the extinction of the Rugose corals, we never see a scleractinian specimen in the fossil record. It isn't until the rugose niche opens up that the scleractinians can diversify into their spots. This is not to say that scleractians did not exist before the Triassic, but rather, they were represented by much fewer species due to competition with the rugose corals. In fact, current molecular data suggests that scleractinians were out and about deep in the Paleozoic, but their radiation was choked by the sheer success of the rugose species.
The shoe would be on the other foot though, as the anoxic conditions that obliterated the rugose corals could not squelch the scleractinians, who had been quietly subsisting in the background. They would explode in diversity in the Mid-Triassic once a symbiotic relationship with algae was developed.
Part 3: Corals Confound Creationists
So hopefully you're already seeing the problems, but let's point them out and dive in a bit more.
Rugose Coral Reefs bust up a Global Flood AND a Young Earth
Flood Geology generally has the first layer of the flood deposits as that which overlays the basement granite of our planet, or layers corresponding to the Pre-Cambrian. In the context of the Grand Canyon, this would be the Grand Canyon Supergroup as the first.
Now, as we mentioned above, Thorton Reef is a Silurian Reef, and the Silurian begins some 443 MYA. This is certainly smack-dab in the middle of the Flood Layers.
Thorton Reef is a remarkably intact reef, with incredibly preserved brittle coral heads, crinoid fossils and other fragile organisms. But it is located in a layer that would have been deposited in the very heat of what is considered by Creationists as the most powerful natural disaster of all time.
But somehow we are expected to accept an enormous global flood that instantly buried some organisms, and tore other apart (depending on the state of the fossil examined), raged for months without burying an enormous reef, and then, midway through, covered it instantly without it's earthshaking power obliterating all the fragile bits.
The Rugose corals too are slow growers and make up an enormous tract of land in the Devonian formation in Alberta: "...the Upper Devonian Swan Hills Formation of the Beaverhill Lake Group. Kaybob reef is a flat north-south elongate lens, 250 ft thick, 11 mi long, and 3 mi wide, built on the Slave Point Formation, a widespread platform carbonate."
It is far too large to have formed in less than 3000 years from Creation to the Flood, even using the most liberal Creation date by YEC's of 10,000 years.
Add to this the trouble of the flood wiping out all corals, due to their requirements clear shallow water and low turbidity (rugose corals are shown to require these as well, given the shaping of the Thornton Reef) and all current reefs then having a maximum age of 4319 years (presuming the flood was in 2300 BCE)
And Modern Corals do the Same.
Take the Enewetok atoll. This atoll was cored many decades ago, and indicated that it is an enormous coral reef growing on volcanic rock. As the volcanic rock sunk (as some do) the coral was forced to grow upwards in order to maintain proper conditions. This is similar to how trees grow towards sunlight. And it created a massive slab of coral around 1380 meters thick, nearly a mile. The deepest parts were so old, that the aragonite skeletons of the coral were geochemically converted to dolomite.
Let's give Creationists the best possible scenario and assume all these corals are growing at the fastest known coral growth rate of 8 inches per year. To be clear, we know that these corals abide by the far more common growth rate of 0.1-1.0 inches per year, but we're being generous.
A depth of 4540.8 feet X 12 inches / 8 inches per year yields an age of 6811.2 years. nearly 3000 years too old to have begun growing before the flood, and using the most generous possible growth rate, applied to corals who definitively do not grow that quickly.
The more realistic math using these species actual growth rates gives the atoll a minimum age of 138,000 years old, and that is still eliminating any erosional events in the core sample.
Coral Reefs line Enewetok or the Great Barrier Reef are ignored though, or spun to fit the narrative as in this link, where Old Earth Ministries busts YEC authors Snelling and Reed for misrepresentation, or, dishonesty.
Sometimes in an effort to explain this, Creationists invoke that the ancient coral colonies such as Thorton did not grow in one place, but are a result of many colonies that grew in separate places and were transported to a new location by the current, and subsequently buried.
Of course this brings us right back around to the problem of the fragile corals and other organisms, as well as the orientation of the reef itself. If it were carried by strong currents and placed elsewhere it should be heavy-side-down. But the heavy part of the reef, the enormous upward growth, is facing upward as it would if it had never been moved.
And so, Creationists are left with either invoking coral growth faster than ever before seen (which is not empirical) or suggesting physics defying currents, which have also never been seen.
Conclusion/TL;DR
Corals are incredible animals whose appearance, diversification and persistence in the fossil record aligns not with sudden Creation but with Evolutionary Theory given the succession of Rugose corals by Scleractinians. Additionally, their growth rates even at their most generous preclude the traditional YEC timeline both in modern reefs and ancient reefs. This leaves Creationists dealing with the coral issue by ignoring it or invoking never-before-seen physics and biologic concepts.