Figure 1  Palo Duro Canyon, Texas.   Palo Duro Canyon is one place where Young Earth Creationists (YEC) have claimed that the unconformities recognized by geologists cannot really represent long periods of time. (Thomas 2019; Clarey 2018) 

The observation is true in the sense that in many areas, layers can be parallel to subparallel and there are apparently long periods of time between them in some cases.  YEC have written about this observation many times.  One example is from Ariel Roth in 2009 is “ “Flat gaps” in sedimentary rock layers challenge long geologic ages” . (Roth 2009)

Unconformities with parallel layers that locally do not show obvious erosion do not surprise most geologists. Erosion along unconformities is not expected to be dramatic everywhere along it.  In fact, dramatic unconformities where the dip of the beds above and below them are markedly different, known as angular unconformities, are typically local features enhanced by faulting or the folding that took place. Away from this enhancement, the same surface may not show obvious signs of erosion. Sometimes it is a matter of the scale that we are looking at. I have traced unconformities on seismic lines for hundreds of miles, usually apparently conformable, but in local areas, often at the ancient shelf edge, we will find demonstratable erosion at the seismic scale.

Perhaps one characteristic that surprises YEC and other non-geologists is that parallel beds can be millions of years different in age. The unconformity surface can be compared to a Bible.  The time between when the Old Testaments was written and New Testament times was about 400 years.  In some Bibles, there is a section of extra pages, while in others, virtually nothing separates them.  The missing time interval from the Bible is just missing.  We have to use data from other sources to learn what happened.  With geologic outcrops, what we can prove at a particular site is what happened when the beds below were formed and what happened afterward. If the processes right above the unconformity were erosional, we may get a clear erosional surface.  It may be relatively depositional.  It also may include a lot of time of just non-deposition.  At one particular site, we can’t prove how much material has been eroded, if any.

Roth, 2009 believed that he could use an average rate of erosion to determine how much material should have been removed.  This would be like trying to calculate the rate of calendar time represented in the Bible by counting the pages. Average rates of deposition and erosion similarly are often meaningless and can be misleading. The point is that much could have happened between the layers and we simply have nothing to tell us locally what that was. We can’t calculate how much should have been eroded any more than we can somehow calculate that there were 400 years between the Old and New Testaments by counting the pages between them in our Bible.

What appears in an outcrop to be parallel and without erosion may not be the case at all.  Often, we need to look at data over a bigger region and even use visualization tools to make the subtle features more recognizable. The observation that in some locations the beds are parallel (or roughly so) is not surprising because these occur in settings that were stable in terms of tectonic activity. Erosional surfaces in tectonically stable areas can be carried over large distances without showing recognizable erosion at a seismic scale.  If we are able to follow them far enough, there will always be evidence of erosional truncation.  When examining seismic to identify unconformities and important surfaces, we always look at it vertically exaggerated.  Beds which look parallel and without incision often show a change in dip and erosion when the seismic is stretched vertically. 

Roth, 2009 believed that he could use an average rate of erosion to determine how much material should have been removed.  This would be like trying to calculate the rate of calendar time represented in the Bible by counting the pages. Average rates of deposition and erosion similarly are often meaningless and can be misleading. The point is that much could have happened between the layers and we simply have nothing to tell us locally what that was. We can’t calculate how much should have been eroded any more than we can somehow calculate that there were 400 years between the Old and New Testaments by counting the pages between them in our Bible.

What appears in an outcrop to be parallel and without erosion may not be the case at all.  Often, we need to look at data over a bigger region and even use visualization tools to make the subtle features more recognizable. The observation that in some locations the beds are parallel (or roughly so) is not surprising because these occur in settings that were stable in terms of tectonic activity. Erosional surfaces in tectonically stable areas can be carried over large distances without showing recognizable erosion at a seismic scale.  If we are able to follow them far enough, there will always be evidence of erosional truncation.  When examining seismic to identify unconformities and important surfaces, we always look at it vertically exaggerated.  Beds which look parallel and without incision often show a change in dip and erosion when the seismic is stretched vertically. 

It might surprise people to realize that major changes in erosion and deposition are often not obvious to the eye.  Dr. Jim Coleman, a famous geologist from LSU taught a seminar for Mobil Oil on the Mississippi Delta that I attended.  He loved to give the example that if the water were missing, you could walk down from the Mississippi River delta in New Orleans across the continental shelf, down the slope, across the Mississippi fan to the abyssal floor without the eye ever perceiving a bit of relief.  Important stratigraphic changes are often subtle when viewed without vertical exaggeration. It is not as though beds deposited millions of years apart are actually totally parallel, but the eye simply does not pick up on the subtle differences. Large scale erosion when beds are almost parallel is often virtually unrecognizable until the tool of squeezing the seismic or the photograph is used.

In looking at the Palo Duro Canyon, I used the unconformity between the Triassic and Miocene sediments as a case in point. (Mitchell 2021) (Figure 2) Dr. Timothy Clarey of ICR reported “The lack of any visible erosion is strong evidence that there were not millions of years between the deposition of the Triassic beds and the overlying Ogallala.” (Clarey 2018)  It is true that in many areas, the Triassic and Miocene aged sediments are almost parallel.  When the setting is a broad relatively stable continental basin, we should expect that there will be a lot of parallel sediments. The fact is that when this unconformity surface is  carried towards the Gulf of Mexico, a thickness of over 7 miles of rock is present there that is younger than the Triassic and older than the Ogallala (Mitchell 2018; 2021). Some material has been eroded away in the Palo Duro Canyon area, but very little deposition probably ever took place in the Llano Estacado area over most of the early Cenozoic era. We do find outcrops with thin late Mesozoic, i.e. Cretaceous marine sediments, but even these sediments are thin. The major deposition took place in the Gulf of Mexico basin during the period that is missing in Palo Duro Canyon.