In the oceans today, calcareous material is dissolved below the carbonate compensation depth (CCD) — usually at a depth of about 4000 m, depending on carbon dioxide concentration. Neither benthic nor planktonic calcareous foraminifers are generally found below that depth on the abyssal plains or in deep sea trenches, because their calcareous shells would be dissolved. Agglutinated forms are dominant (Figure 2).
Agglutinated species are common in the Lower Paleozoic, and the benthic calcareous foraminifers found generally have thicker walls than forms higher in the geologic column. They could have lived near the pre-flood CCD where most calcareous forms, especially thinner-shelled planktonic species, would have been completely dissolved. Lower Paleozoic foraminifers are consistent, therefore, with the distribution expected by a catastrophic flood.
The fusulinids in the Upper Paleozoic, however, are an anomaly. Some species of fusulinids grew to volumes of more than 100 m3 (Ross 1979). Foraminifers which grew that large today have symbiotic photosynthetic algae living in their tests, and so must live within tens of meters of the ocean surface where sunlight is available. Large foraminifers from other groups live in shallow water tropical environments today; therefore, the fusulinids are interpreted also to have lived in a similar environment (Ross 1979), yet we do not find them at the top of the geologic column. Possibly they grew at the surface of pre-flood bodies of water of low altitude (Figure 1).
Planktonic foraminifers are not found in Paleozoic or Lower Mesozoic deposits. Even though living planktonic foraminifers float and would not be expected to be found in the early flood deposits, tests of those which had died before the flood should have been on the sea floor and should have been buried with those living there. Either they were not present in those ecologic zones, or they were not preserved as fossils. Because they have thinner, more porous tests than benthic forms, they could easily have been dissolved preferentially on the sea floor before the onset of catastrophic flooding, if their shells sank below the CCD.
Benthic hyaline calcareous foraminifers become abundant in the Mesozoic. Triassic and Jurassic foraminifers are generally not as well preserved as later forms. In Cretaceous strata, both benthic and planktonic forms are diverse and abundant, making it correlative with the upper bathyal zone of the ocean today.
Foraminifers older than the Cretaceous are generally widely distributed. A Triassic species may be found in both Australia and Idaho, but nowhere in between (Tosk and Andersson 1988). Cretaceous and younger foraminifers have distribution patterns correlative with modern assemblages (Sliter 1972). Under the prevailing paradigm, this would mean that the pre-Cretaceous seas were more cosmopolitan because modern hydrographic patterns and ecologic distributions had not yet developed. Continental fragmentation and sea-floor spreading during the Cretaceous are used to account for the development of modern oceanic patterns at that time.
In a flood model, however, this pattern is what would be expected. During the more violent stages of the flood events, foraminifers from a small area would be scattered widely over the earth. As the violence of the flood died down, foraminifers would not be transported as far and might even begin developing their own ecologic distribution patterns. Major deposition during and after the Cretaceous could have become localized in basins and at continental margins. Life for foraminifers may have returned to normal in less affected areas.
Post-Flood Foraminifers
Some foraminifers must have lived through the flood. Those that could survive such a catastrophe would be forms tolerant of turbidity and strong wave action, and possibly the juveniles of more delicate forms.
All major groups of foraminifers in the fossil record are represented by living forms except the complex fusulinid group which dominated the Paleozoic. As discussed above, they are interpreted to have lived in a tropical-type environment with low sediment output, and they may have had little tolerance for storm conditions. The agglutinated forms found in Paleozoic strata are found in many extreme environments today. They may have been better able to withstand the flood events.
No particular biogeographic distribution would be expected of foraminifers, unlike the animals which were saved in the ark and would have dispersed afterwards. Foraminifers would have continued living wherever they happened to be after the flood events subsided. With the availability of the many open niches and much organic material stirred up by the flood, foraminifers could have multiplied rapidly. Roth (1985) discussed the volume of biogenic sediments, especially foraminiferal oozes, on the ocean floor and showed that it is plausible that the foraminiferal deposits found on today's ocean floors could have been formed in the time since the flood.