Although the rock strata do not represent a series of epochs of Earth history, as is widely believed, they still follow a general pattern. For example, relatively immobile and bottom-dwelling sea creatures tend to be found in the lower strata that contain complex organisms, and the mobile land vertebrates tend to be found in the top layers. Consider the following factors:
Vertebrate fossils are exceedingly rare compared with invertebrate (without a backbone) sea creatures. The vast proportion of the fossil record is invertebrate sea creatures, and plant material in the form of coal and oil. Vertebrate fossils are relatively rare and human fossils are even rarer.
If there were, say, 10 million people at the time of the Flood.1 and all their bodies were preserved and uniformly distributed throughout the 700 million cubic kilometres of fossil-bearing sedimentary rock layers, only one would be found in every 70 cubic kilometres of rock. Thus you would be unlikely to find even one human fossil.
A global Flood beginning with the breaking up of the fountains of the great deep would tend to bury bottom-dwelling sea creatures first – many of these are immobile, or relatively so. They are also abundant and generally robust, for example, shellfish (however, the preservation of impressions of soft creatures such as jellyfish also occurs, and this testifies to the rapidity of burial). As the waters rose to envelop the land, land creatures would be buried last. Also water plants would tend to be buried before land-based swamp plants, which, in turn would be buried before upland plants.
On the other hand, land animals, such as mammals and birds, being mobile (especially birds), could escape to higher ground and be the last to succumb. People would cling to rafts, logs etc. until the very end and then tend to bloat and float and be scavenged by fish, with the bones breaking down rather quickly, rather than being preserved. This would make human fossils from the Flood exceedingly rare.
Further, the more mobile, intelligent animals would tend to survive the flood longest and be buried last, so their remains would be vulnerable to erosion by the receding floodwaters at the end of the Flood and in the aftermath of the Flood. Hence their remains would tend to be destroyed. The intelligence factor could partly account for the apparent separation of dinosaurs and mammals such as cattle, for example.2
Another factor is the sorting action of water. A coal seam at Yallourn in Victoria, Australia, has a 0.5 m thick layer of 50% pollen. The only way such a layer of pollen could be obtained is through the sorting action of water in a massive watery catastrophe that gathered the plant material from a large area and deposited it in a basin in the Yallourn area.
‘Cope’s Rule’ describes the tendency of fossils (e.g. shellfish) to get bigger as you trace them upward through the geographical strata. But why should evolution make things generally bigger? Indeed, living forms of fossils tend to be smaller that their fossil ancestors. A better explanation may be the sorting action of water. (Although bigger rocks tend to be sorted to the bottom, larger shellfish, for example, are overall less dense that smaller ones and could be deposited after smaller ones in a sorting situation)
Conclusion - These are some of the factors that could account for the patterns seen in the fossil record, including the general absence of human fossils in Flood deposits. Most of the fossil record does not represent a history of life on Earth, but the order of burial during the Flood. We would expect a pattern with a global Flood, but not an entirely consistent pattern, and this is what we find in the geological strata.
Batten D., Ham K., Sarfati J.,Wieland C., The Answers Book Ch 15 pp. 183-185
1. Woodmorappe, J., 1983. A Diluviological treatise on the stratigraphic separation of fossils. Creation Research Society Quarterly 20(4):133-185
2. Most creationists would regard large mammal fossil deposits, such as in the John Day County of Oregon, USA, as post-Flood.