Originally published in Creation 19, no 3 (June 1997): 18-19.
The Green River Formation of Wyoming, USA, is familiar to geologists not only for its well-preserved fossils but also because it has come to the forefront of debate on the age of the earth.
The reason is that the deposit is said to consist of several million thin layers of shale, each of which is said to represent a single season‘s deposition in an ancient lake (the coarser layers in the summer, and the finer layers in the winter). Each summer/winter pair of layers — called varves — would thus represent a single year. Most geologists claim that this formation alone must have taken several million years to be laid down. Old-earth geologist (and professing evangelical) Dr Davis Young put it like this:
‘There are more than a million vertically superimposed varve pairs in some parts of the Green River Formation. These varve deposits are almost certainly fossil lake-bottom sediments. If so, each pair of sediment layers represents an annual deposit . . . . The total number of varve pairs indicates that the lakes existed for a few million years.‘ 4
Obviously, this is a serious challenge to those who believe in a young age for the earth as indicated by Scripture (less than 10,000 years).
However, the critics (who in any case err by relying on the incomplete data of fallible scientists, rather than the infallible God who knows all data) leave out some vital information that sheds light on the origin of ‘varves’. As long ago as 1961, creationists were pointing out features of the Green River Formation that were difficult to reconcile with the conventional varve interpretation.5 For instance, well-preserved fossils are abundant and widespread throughout the sediments. According to two conventional geologists:
‘. . . fossil catfish are distributed in the Green River basin over an area of 16,000 km6 . . . The catfish range in length from 11 to 24 cm, with a mean of 18 cm. Preservation is excellent. In some specimens, even the skin and other soft parts, including the adipose fin, are well preserved.’7
Another evolutionist stated:
‘During the early to mid-1970s enormous concentrations of Presbyornis [an extinct shorebird] have been discovered in the Green River Formation.’8
This should tell us that the Green River Formation is no ordinary lake deposit! Modern-day lakes do not provide the conditions needed for the preservation of abundant fossil fish and birds.
Experiments by scientists from the Chicago Natural History Museum have shown that fish carcasses lowered on to the muddy bottom of a marsh decay quite rapidly, even in oxygen-poor conditions. In these experiments, fish were placed in wire cages to protect them from scavengers, yet after only six-and-a-half days all the flesh had decayed and even the bones had become disconnected.9
The Presbyornis fossils are even more problematic. Birds have hollow bones that tend not to preserve well in the fossil record. How were these bird bones protected from scavenging and decay for thousands of years until a sufficient number of the fine annual layers had built up to bury them? ‘Enormous concentrations’ of bird bones are a clear indication that something is seriously wrong with the idea of slow accumulation. Instead, such fossils support the notion of rapid burial.
Creationist suspicions about the validity of the varve interpretation were confirmed in a study by two geologists published in 1988.10 Near Kemmerer in Wyoming the Green River Formation contains two volcanic ash (tuff) layers, each about two to three centimetres thick.
A volcanic ash layer is an example of what geologists call an ‘event horizon’, because it is laid down essentially instantaneously by a single event, in this case a volcanic eruption. The two ash layers are separated by between 8.3 and 22.6 centimetres of shale layers.
If the standard interpretation is correct, then the number of shale layers between the ash layers should be the same throughout the Green River basin, since the number of years between the two eruptions would be the same.
However, the geologists found that the number of shale layers between the ash beds varied from 1160 to 1568, with the number of layers increasing by up to 35% from the basin centre to the basin margin! The investigators concluded that this was inconsistent with the idea of seasonal ‘varve’ deposition in a stagnant lake.
So how were the great thicknesses of finely laminated shale in the Green River Formation laid down? Creationist geologists need to investigate the issue more closely, but there seems to be great potential for developing a catastrophic model for the origin of these sediments. There is a large body of experimental and observational data that shows that varve-like sediments can build up very rapidly under catastrophic conditions.11,12,13,14,15 For instance, in 1960 Hurricane Donna struck the coast of southern Florida and deposited a blanket of thinly-laminated lime-mud six inches thick.16 Another example comes from a Swiss lake, in which up to five pairs of layers were found to build up in a single year, deposited by rapid underflows of turbid water.17
Given the right conditions, thinly-laminated muddy sediments can and do form by rapid sedimentation. Contrary to claims by old-earth proponents, long periods of time are not demanded.