An Overview of the Geologic Record

By: 

Richard Burky

"You can prove anything from the Bible" may seem to be true to someone who is vaguely acquainted with the Bible. Such a person may have heard quotes taken out of context that seem to give contradictory facts and advice. When a person understands the clear meaning and purpose of the Bible, however, such a statement becomes ridiculous.

Similar statements may be made about the geologic record. A person vaguely familiar with it may feel it presents information that may be interpreted however one chooses. This is not the case. There may be things difficult to understand in the geologic record, just as there are in the Bible. However, as with the Bible, when one has a sound basic understanding, the overall meaning is simple, clear and consistent. It is not subject to multiple or contrasting meanings.

Does a complete geologic record occur anywhere?

A previous article showed that the internal evidence of many strata discussed the evidence that showed they were neither deposited rapidly nor under worldwide flood conditions. In this article our primary goal is to give a tangible overview of what the geologic record is like.

Creationists who believe the earth is very young often raise the issue that a complete geologic record doesn't exist anywhere on earth. They imply that the existence of long periods of geologic time is a fabrication made by piecing together concurrent geologic events from many different geographic areas. This conclusion can be misleading to people not familiar with the geologic record.

Technically, a complete geologic record doesn't occur anywhere. For such a record to develop would require the area to have been receiving sedimentary deposits continually ever since the origin of the earth. Nowhere is such a situation known to exist. If it did exist, we could not effectively look at the strata because they would still be buried, and modern strata would continue to be deposited on top of them.

The earth's surface has been far too dynamic to allow that to occur anywhere. No area has been in such a static condition throughout the earth's long history. Areas that have had sediment deposited on them at one time are later uplifted and eroded. In some places this has occurred many times. There is ample evidence to prove such a sequence of events.

We have to take the geologic record as it is, not as we wish it might be. As with the Bible, we may wish certain things were plainer and more specific, but we have to work with what exists, not what we wish were available. In spite of any drawbacks, however, a good understanding of the history of the earth and fossil life forms can be obtained from the geologic record.

The purpose of this article is to give a simple and clear overview of the geologic record. The best way to do this is to examine a unique area in the western United States where an extensive record of the earth's geologic history can be observed. It's not 100 percent complete, but it is probably without equal in the rest of the world for our purpose.

All four major geologic time divisions (Precambrian, Paleozoic, Mesozoic and Cenozoic) are represented here in clear superposition order. Each division is represented by great thicknesses of strata. The area is like a giant layer cake. The relative age of each of the stratified layers — their age in relation to one another — is absolutely certain. Most of the layers contain fossils that allow us to identify the type of animal life living when the layer was deposited.

The Colorado Plateau

The area we will examine is known to geographers and geologists as the Colorado Plateau. The area has been fairly stable for long periods of time. It has been near or below sea level for long periods. Because it was low, it was able to receive sediments from higher areas around it. This allowed an extensive geologic record to be deposited and preserved. More recently (geologically speaking) the area has been lifted. Because of its current high elevation, it is eroding rapidly. The erosion strips away overlying material and allows us to see what lies below.

The magnitude of the record found in this area is phenomenal. It contains miles of strata that were deposited before there were abundant living organisms on earth. More miles of strata record the time when primitive living organisms were first abundant. Later times of the dinosaurs are represented by more than two miles of strata. The times of the mammals, after the demise of the dinosaurs, are also represented by more than two miles of strata.

A cross section of the Colorado Plateau strata

If we were to cut the strata of the Colorado Plateau as if we were cutting a giant layer cake, we would obtain a cross section. Some of the strata are so extensive that they can be traced over the whole area and even into regions beyond the Colorado Plateau. Others cover only portions of the area. Those that cover the whole area give a solid time marker for comparisons when the other strata were deposited. By using these, we can tell the sequence of the strata shown in the diagram.

The strata are systematically laid out and show clearly the sequence of deposition. The important thing is to fix in mind the simplicity of determining the sequence of events. Lower strata are always older, having been deposited before the overlying ones. Exactly how old they are and how much time passed between their periods of deposition must be determined by other means.

Some strata at the bottom of the Grand Canyon are tilted. These strata (nearly two miles thick) were not deposited in their current inclined position. Strata are normally deposited horizontally. In this example, significant earth movements took place after deposition to uplift and tilt the strata. After that, tremendous amounts of material were eroded away before the next layers were deposited.

The strata lying on the flank of the Uinta Mountains reveal when the Uinta Mountains were raised. It is possible to tell which strata were deposited before the uplift of the mountains and which strata were deposited after their primary period of uplift.

We know the mountains were uplifted after, or near the end of, the time the dinosaurs lived. How do we know? The strata containing dinosaur remains are strongly bent by the upward movement of the mountains, while overlying strata are deformed very little.

An additional fact supporting this conclusion is that some of the overlying strata were formed by material eroded from the older strata and from material that forms the heart of the mountains themselves. This would not have been exposed until erosion had removed a considerable amount of strata from the top of the uplifted mountains.

The geologic time periods of the strata

The key concept to understand is that the geologic time periods are not arbitrary ideas. If they were incorrect concepts, a scientist could easily make a name for himself by studying this area and revealing any problems and inconsistencies. But such gross inconsistencies don't exist.

The fossils found here fit the worldwide pattern and framework. Where to place the exact boundary between each of the time periods can be a matter for continued discussion among geologists, but the broad, general pattern is clear and consistent.

The fossils found in these strata will be the subject of a future article. They are a vital part of the geologic record and of our understanding of it.

The geologic column

Erosion or lack of deposition in part of an area may prevent a full complement of strata from occurring at any one location. However, strata whose superposition and/or relative ages can be clearly proven may be correlated and stacked one on top of the other to create a geologic column. This is done for clarity, efficiency and convenience. It is much easier to illustrate and discuss the strata in this manner.

However, if one is not aware of how or why it is done in this way, wrong conclusions can be easily drawn. For instance, if one had seen only a drawing of the geologic column, he might feel he should be able to walk to a cliff in the Colorado Plateau and see all these strata in one grand pile as shown in the illustration. On the other hand, he might think the geologist was trying to mislead him by saying strata existed that really don't. Neither of these is true. It is just a convenient manner of presenting the data. It allows much data to be summarized in a very little space.

Strata are usually named for geographic locations or features near their most complete outcrop. Sometimes they are named for some obvious characteristic, e.g., the stratum labeled "Redwall" is named for its exposure in the Grand Canyon, where it forms a sheer red cliff or wall. It is actually composed of gray limestone, but the overlying red shales have given its surface a red color — hence the name "Redwall."

Summary

There is no 100 percent complete geologic record. It is not the nature of geologic forces to allow such an area to exist. However, the area of the Colorado Plateau in the western United States has a very clear and extensive record preserved. It is probably one of the most complete available. There, miles of strata exist for each of the four major geologic time periods. The strata are in observable superposition, one lying physically on top of the other.

Evidence for extended periods of depositional time occur throughout the stratigraphic sequence. Though there are gaps in the record, the record reveals a tremendous amount about past geologic activity. The strata contain fossil organisms that correspond to the standard sequence of life forms found in the geologic record throughout the world.

We can waste much time looking for the "loose brick" in the factual understanding of modern geologists and paleontologists. The loose-brick approach is typical of many modern creationists, but it is a fruitless search. When the facts are carefully studied, it is not the geologist, but rather this type of creationist who is in error.

There really is a long history to the earth and a sequence of life forms that have lived on it. This is clearly evident from the geologic record. This, however, does not exclude a Creator, nor does it prove that the changes and progression observed in the fossil organisms are the result of evolution. Jesus said, "My Father has been working until now, and I have been working" (John 5:17).

This brief overview should help dispel many of the misconceptions some may have had about the nature of the geologic record. In our next article we will begin exploring the nature of the changes that have occurred in the life forms that are found as fossils in the strata of the Colorado Plateau.

Richard Burky

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