by Michael J. Oard

An integral part of any comprehensive Flood model is discerning the distinction between Flood processes and post-Flood catastrophism in the rock record. The characteristics of the continental shelf, slope, and rise suggest that the location of the boundary was reasonably synchronous on a global scale. However, there is no consensus among Flood geologists on where the post-Flood boundary should be placed. The geological column concept provides a useful framework of discourse for examining different approaches to the post-Flood boundary among creationists. There are three main schools of thought: (1) the Precambrian/Paleozoic Boundary Model, (2) the K/T Boundary Model, and (3) the Late Cenozoic Boundary Model. Each one makes different assumptions and has specific issues that need addressing. Multiple criteria spanning several fields of study need to be used to examine this issue since just one can be equivocal.

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The development of a sophisticated Flood model is important to creation scientists and Christians alike. A model that is capable of integrating geology, geophysics, paleontology, and geomorphology into a coherent description of the global Flood would have great apologetic value. An integral part of such a project is understanding the nature, scope, and intensity of Flood and post-Flood processes reflected in the rock record. Distinctions that can be discerned between Flood and post-Flood phenomena will aid us in determining the location of the Flood/post-Flood boundary.

The Flood/post-Flood boundary can be defined as a horizontal line in a vertical sequence of rock and sediments below which rocks were deposited during the Flood, and above which rocks and sediments have been deposited after the Flood. Placement affects many details of a Flood model, especially the late Flood period. Our understanding of where the post-Flood boundary is located is affected by how we understand the distinction between Flood and post-Flood processes. It also reflects how we understand the extent and intensity of post-Flood catastrophism because we need to explain the rocks, fossils, and sediment above the boundary as deposited by post-Flood processes. Baraminology is affected as well, since it determines the degree of post-Flood animal and plant diversification.1,2 Unfortunately, within Flood geology, the scope and intensity of post-Flood catastrophism, the relation between Flood and post-Flood processes, and hence the location of the Flood/post-Flood boundary are all still very controversial.

Some may ask: “Is there a discernible boundary?” Did the Flood end before Day 371 in some places but continue on for some time, possibly many years, in other places? Or was the Flood complete on Day 371 everywhere on Earth? Either way, there has to be a boundary at numerous locations,3 whether it is synchronous or not. Nonetheless, unique features of the continental margins suggest the latter.

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Although few uniformitarian scientists address this issue, the continental shelf and slope are unique geomorphological features that are difficult for them to explain. The continental shelf is a seaward extension of the continent, or coastal plain, from the shoreline to the shelf break or shelf edge. The shelf edge is the seaward terminus of the continental shelf and the beginning of the continental slope. The continental shelf dips very gently seaward at less than 0.1°, with a subdued relief of less than 20 m. The seaward width of continental shelves varies considerably from several km to more than 400 km, the average being 80 km. At least one shelf is over 1,000 km wide.4 The widest shelves are found along the Arctic Ocean. The Bering Sea, Grand Banks, and Newfoundland shelves are also very wide. The continental slope is a sharp ‘drop-off’ down to abyssal depths. The sedimentary rocks that make up the continental margin are often very thick, reaching over 15 km, and show a seaward thickening wedge of slightly dipping sediment rocks (figure 1). The margin is like a continuous sheet of strata around all continents and large islands.

King described the problem of the origin of the continental margin:

“There arises, however, the question as to what marine agency was responsible for the leveling of the shelf in early Cenozoic time, a leveling that was preserved, with minor modification, until the offshore canyon cutting of Quaternary time? Briefly the shelf is too wide, and towards the outer edge too deep, to have been controlled by normal wind-generated waves of the ocean surface [emphasis added].”5

When King wrote, it was widely believed submarine canyons were of Quaternary age, but now they are believed to be much older. It would seem that natural processes, such as shore parallel currents and mass wasting, would favour a gradual descent of the slope to the ocean depths. Figure 2 contrasts the shape of the continental margin today versus what seems more likely under actualistic conditions.

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The continental margins represent massive, widespread deposition over a huge area. It is logical to conclude that the margin sediments came from the continents. Their shape and form indicate sediment-filled, continent-wide Flood currents once rushed into the deepening ocean.6 Continental slopes likely signify the edge of this sheet flow deposition. This deposition would be analogous to the formation of a river delta; the top of the delta resembles the continental shelf and the edge of the delta the continental slope. The analogy breaks down, since most deltas can spread parallel to the shore.

However, a case where the delta could not move parallel to the shore is found in the recently formed delta of the Colorado River.7 It formed as Lake Mead filled with water and the Colorado River met with Lake Mead in the narrow Lower Granite Gorge (figure 3). There were no currents along the shore to spread the sediments since they were deposited in a narrow gorge. As such, deposition developed parallel to the flow of the river. Figure 3 shows the top of the delta is nearly flat with a slight lakeward slope until it reaches a steep drop-off. If the Colorado River delta feature is comparable to the continental shelf and slope, this example gives an illustration of how the continental shelf and slope would likely have formed when wide Flood sheet currents flowed off the rising continents.

The top of the continental slope is generally at a consistent depth of 130 m off all continents, except Antarctica where there has been isostatic depression by the massive ice sheet.8 If the Flood continued for many more years on some continents and not others, this shelf break would not have a similar depth. Instead it would be at variable depths due to variable offshore flow and vertical tectonics. It takes energy to erode and transport sediment to the margin. This would have to be supplied by continuing tectonics. The similar depth implies the tectonics and energy sustaining the Flood stopped at about the same time everywhere on Earth. If one continent continued to rise slowly for e.g. 100 years after the Flood, it would then have only weak currents with weak tectonics and form small continental margin sediments at different water depths (figure 4). In that situation shore-parallel deposition would be more likely. A chaos of small delta-like features should be found along the continental margin.

Considering the geomorphology of the continental margin, it appears the Flood and differential vertical tectonics ended everywhere by Day 371 (there could of course have been very minor tectonics at the margins). It appears the Flood did not stop in one part of the world and continue on in other parts.

Communicating the location of the post-Flood boundary is an important part of the task of assessing different conceptions of post-Flood catastrophism. Uniformitarian scientists have developed a global sequence of events called the geological column but can this geological column be used as a first approximation for the sake of discussion? The geological column is another controversial issue within creation science.9 Some creationists believe the geological column is an absolute sequence of biblical earth history, while others believe we should discard it entirely, and some, like myself, take a middle position that the geological column represents a general order with time with many exceptions.10,11,12 The geological column would then represent a Flood depositional order. Ecological zonation would be one major ordering variable.

Nonetheless, these different views are focused on the usefulness of the geological column for describing the empirical rock record, not its usefulness as an established convention of geological discourse. And since the geological column is an established framework of geological discourse, it serves as a useful way to communicate the location of the post-Flood boundary across ideological lines. If there is a globally synchronous post-Flood boundary identifiable with some level in the geological column, then it would obviously make sense to use the geological column to communicate the location of the post-Flood boundary. However, even if the post-Flood boundary is identified as e.g. Upper Miocene at one location and Middle Pleistocene at a different location, this doesn’t invalidate the use of the geological column as a convention for discourse, though it may call into question its accuracy as a reflection of the empirical rock record. The Flood geologist can say that the catastrophic nature of the Flood and the compressed absolute timescale reflected in the rock record (relative to the deep time framework) both provide enough reason in themselves to expect some geographical variation in the stratigraphic placement of the post-Flood boundary with respect to the geological column. Flood geology has no a priori commitment to the geological column. Therefore, using the geological column as a convention for discourse doesn’t necessarily imply either that there is, or that there isn’t, any real-world correspondence between the empirical rock record and the geological column. As such, if we merely use the geological column as a convention for geological discourse, we can set aside the debates about how well the geological column represents the reality of the empirical rock record and focus our attention on the placement of the boundary without the need to engage in an extended discussion on the reality of the geological column. Later, we can go back and remove the assumption of the geological column and either refine the placement of the Flood/post-Flood boundary within local or regional rock columns or use another global model, such as Walker’s biblical geological model.6

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The Flood/post-Flood boundary controversy is mainly focused at or above the Cretaceous/Tertiary boundary in the geological column; i.e. in the Cenozoic erathem (figure 5). The ‘early Cenozoic’ corresponds to the Paleogene system and the ‘late Cenozoic’ corresponds to the Neogene and Quaternary systems (figure 5). If all or most of the Cenozoic is post-Flood, then the activity deduced from geology, paleontology, tectonics, and geomorphology of the Cenozoic must occur after the Flood and diversification as seen in Cenozoic fossils occurred after the Flood. Conversely, if the boundary is in the late Cenozoic, especially in the very late Cenozoic, diversification after the Flood evinced in the rock record is slight.

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Three main schools of thought or models have developed in regard to the location of the Flood/post-Flood boundary (table 1).13 They represent a considerable divergence of opinion and as a result, contradictory concepts of the Flood have developed.

The first school of thought believes that the Flood/post-Flood boundary is generally in the late Paleozoic.14,15,16,17,18,19,20,21,22 One suggested model is the recolonization model, which states that the rocks and fossils in the geological column above the boundary represent a ‘recolonization’ of organisms from Flood refugia. According to this model, animals came off Noah’s Ark and spread from the “mountains of Ararat” beginning in the Paleozoic. However, some advocates place the boundary event even lower—in the late Precambrian. One such model is the Collapse Tectonics Model,23 which was recently reviewed in this journal.24

Advocates of the Precambrian/Paleozoic Boundary Model believe that certain features in the rocks seem to require much more time than a one-year Flood allows, such as dinosaur tracks, eggs, and scavenged bonebeds. They attempt to find more time for these features to form after the Flood. Because of the scale of the sedimentary rocks, they must posit at least regional- to continental-scale post-Flood catastrophes,23 such as continental split at the time of Peleg25 to explain such a large amount of post-Flood sedimentary rocks and fossils. Moreover, they do not seem to be careful in suggesting certain features of the rocks and fossils could not be produced during the Flood. We have a few hundred such challenges in the earth sciences anyway. Some we have found good answers for,26 while many others await research.

Few creation scientists accept the Precambrian/Paleozoic location of the Flood/post-Flood boundary. Because the model is not well developed, I will not compare this model in this series of papers. Many find that the model causes many more problems than it solves.27

The second school of thought believes the Flood/post-Flood boundary is near the Cretaceous/Tertiary (K/T) boundary in the geological column.28,29,30,31,32,33 Some within this school believe the boundary could be in the early Cenozoic,34,35 at least in places. I will simplify and group all these positions into the K/T Boundary Model for the sake of discussion, realizing that some favour the early Cenozoic.

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In this school of thought, most, if not all, the Cenozoic strata would have been laid down after the Flood. Similar to advocates of the Precambrian/Paleozoic Boundary Model, they conclude that certain rocks and fossils, as well as deduced processes, take more time than a one-year Flood. For instance, they point out that the Cenozoic cooling curve, especially from ocean bottom sediments, is evidence of slow cooling after the Flood.36 They also believe that kangaroos found in karst deposits in Australia, dated as old as Miocene, show that the boundary is near the K/T.37 The kangaroos would have to spread out from the “mountains of Ararat” and reach Australia in the early to mid Cenozoic. Fossil occurrences also seem to indicate that much of the Cenozoic is post-Flood.38,39,40

However, this school of thought needs to explain geomorphological features on the Earth’s surface that appear to have been formed by fast-moving water.41,42 For instance, planation and erosion surfaces have planed folded and faulted rock, sometimes leaving behind erosional remnants (figure 6). Some of these planation surfaces are huge, such as the one that has flattened much of Africa with variable faulting and folding afterwards.43 Hard, well-rounded quartzite cobbles and boulders have been transported by water for many hundreds of kilometres east and west from their source in the Rocky Mountains of central and northern Idaho and extreme western Montana.41,42 The long transport is about 1,200 km into central Saskatchewan and south-west Manitoba, Canada, from Idaho. Another example is the thick Cenozoic strata found in many basins of the world, such as the 26–28 km of mostly Cenozoic strata from the 450 km diameter South Caspian Basin!44 There is also the problem of thick, widespread coal seams.45

Recently, Whitmore has offered an explanation for how the Cenozoic can be post-Flood.46 This defence extends his previous articles on the subject from the 2008 International Conference on Creationism.47,48 He has presented a case that post-Flood mass wasting of generally unlithified sediments occurred during mountain uplift, heavy precipitation, a lack of vegetation, giant earthquakes, meteorite impacts, and massive volcanic activity. Whitmore concludes he can explain the geology, paleontology, tectonics, and geomorphology by placing the Cenozoic after the Flood. Mass wasting or mass movement refers to all the processes by which soil and rock are eroded and transported downslope by gravity.49 It includes slow displacements, such as creep, and rapid movements such as rock falls, rockslides, and debris flows.

The third school of thought believes the Flood/post-Flood boundary is near the end of the Cenozoic.50,51,52,53,54,55,56,57,58,59,60 Critics of this position have claimed advocates believe the boundary is at the Pliocene/Pleistocene.33 This is not so. Late Cenozoic is a broad range because we are assuming the geological column, which is not precise enough to pinpoint the boundary worldwide. There are too many problems with the precise dating of the geological column to use it for more than a general order.10,11,12

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In practice, this school of thought believes that most of the lithified sedimentary rocks are from the Flood, and the boundary is near or at the surface of these rocks. Therefore, it assigns practically all Cenozoic catastrophes to the Flood. This school of thought questions whether inferences made from Cenozoic activity could have taken place after the Flood. For instance, how can thousands of metres of erosion over wide areas occur? How can thousands of metres of deposition occur in basins and other areas of the world? How can thick, widespread Miocene coal seams be explained? How can thick, widespread ‘evaporites’ from the late Miocene of the Mediterranean area be explained after the Flood? Post-Flood catastrophism in this model would include greater volcanism, earthquakes, shifts in the land at faults, probably due to the earth settling down after the Flood, but on a considerably smaller scale than other schools of thought. And of course the Ice Age is one of these ‘catastrophes’ postulated by this school.

On the other hand, the late Cenozoic Flood Model must explain a few hundred earth science challenges that appear to take more time than a one-year Flood would allow, such as ‘fossil reefs’, worm burrow zones, basalt lava flows, and buried soil zones.61 The Flood/post-Flood boundary can be very difficult to pinpoint in some regions, for instance the Ashfall Fossil Beds State Historical Park in north-east Nebraska, USA,62 the super-eruptions of Yellowstone National Park,63 and the sediments and sedimentary rocks along the Arctic coast of North America.64

There is a great deal of subjectivity in such an evaluation of post-Flood catastrophism:

“The list of criteria is not exhaustive, and there may be debate on the relevance of each criterion. The criteria are currently qualitative, but it is hoped that further research will enable quantification.” 55

Whitmore and Garner concur:

“Obviously, this is a subjective evaluation on our part and may be open to criticism. Other young-age creationists may disagree with us concerning the relative importance of our criteria and may be able to suggest other criteria we have not included.”65

This is precisely why defining the post-Flood boundary must be an interdisciplinary endeavour. Because of the importance of developing a sophisticated Flood model, and the controversy over the nature and extent of post-Flood catastrophism, it is essential to study as much evidence as possible before determining the Flood/post-Flood boundary. Just a few fields of study, such as sedimentology, paleontology, or geomorphology, are not enough. They should be included but along with other fields of earth science. One field taken alone may be misleading.

The only way forward on this contentious issue is to lay all the ‘cards’ on the table. For this I am grateful that Whitmore has presented mechanisms that can account for the Cenozoic being post-Flood. For my part, I too will encourage disagreement. In this way, we can all analyze the pros and cons of our different assessments of the nature of post-Flood catastrophism, and hopefully come to a consensus.

In forthcoming papers, I plan to identify over 30 features generally evident into the Late Cenozoic rocks that reflect Flood processes rather than post-Flood catastrophism. I will not address just one field or subfield of study but many within the earth sciences. I will also reflect on current assessments of these features by those who apportion most of the Cenozoic to post-Flood catastrophism to determine the relative difficulty current post-Flood explanations of these features face.

It is possible that with more research the K/T Boundary Model may be able to explain one or several of these evidences better than the Late Cenozoic Boundary Model. However, the K/T Boundary Model would have to better explain most of these 30-plus evidences to be the superior model.

I thank all the reviewers and editors, including my wife Beverly, for improving the content and the flow of this article.