I was now willing to believe that the different suites of fossilized organisms to be found in a given place had indeed lived at distinct times in the geologic past. But determining that one of two scenarios (“same place, different times”) is much more probable, or even that one of them (“same time, different places”) is highly improbable, still does not prove what actually happened. This can only be determined from field observations.
In other words, I wanted to see proof in the ground for myself. It would not suffice to observe that different suites of fossils characterize sedimentary rocks in geographically separate areas; after all, we see different assemblages of plants and animals living in different areas today. Rather, I needed to see differing suites of fossils stacked one on top of another in the same area, preferably somewhere without complex faulting and folding induced by mountain building.
In addition to seeing several distinct suites of organisms preserved in one place, the icing on this geologic cake for me would consist of finding fossils preserved in different layers right where they had once lived and died. Paleontologists refer to these kinds of fossils as being preserved in a “life position.” Coral reefs, clams in their feeding burrows, plants rooted in paleo-soils, clutches of eggs preserved in their nests, and very delicate fossils too fragile to have moved any distance from where they lived are good examples of organisms preserved in a life position.
To find these kinds of fossils at several different levels within the geologic column would establish definitively that fossilized organisms are found in distinct groups because they lived at different times. There would simply have been insufficient time during the one-year-long flood for organisms to be preserved in life positions at many different levels in one area.
Even if they survived being carried into the depositional basin, they would then have to have re-established themselves and lived for a while before becoming entombed by the next sediment-laden wave. This process would have to have repeated itself over and over again. But the accumulations of sedimentary rock in the earth are a mile deep in many places, and in some places even deeper. For 5280 feet of sediment to pile up in one year, an average depth of over 14 feet of sediment has to be added to the pile every day. (The thickness of Carboniferous strata at Joggins, Nova Scotia would require over twice that daily rate of sedimentary accumulation.) A rate of even 14 feet of sediment per day is astronomically too fast for any organism therein to be found in a true life position.
So if I could find differing suites of fossils, many of them in life position, stacked several layers high, this would prove that these organisms had lived in this same place at different times. I was aware of numerous published accounts of fossil deposits that would confirm the “same place, different times” hypothesis, including the work by George Cuvier and Alexandre Brongniart on the Paris Basin, published in 1811. But I wanted to see one of these deposits first hand.
My opportunity came quite unexpectedly when, in the spring of 1989, I accepted a one-year contract position at the Tyrrell Museum of Palaeontology (now known as the Royal Tyrrell Museum) in Drumheller, Alberta, Canada. There I became a member of the museum’s team commissioned by the Gakken and Hitachi corporations of Japan to assemble a large dinosaur exhibit.
The museum is nestled in the badlands along the Red Deer River where sediments laid down during the Late Cretaceous epoch are exposed—a dinosaur paleontologist’s dream come true. The fossilized remains of dinosaurs continue to come to light as the relatively soft strata weather.
But while the abundance of dinosaur fossils in this area commands popular attention, there are actually many more non-dinosaurian fossils to be found there. In southern Alberta, I found a place where I could view a number of different suites of fossilized organisms buried in one vertical sequence, many of which were preserved in life positions.
Approximately one mile below Drumheller, as elsewhere throughout much of southern Alberta, the fossil-bearing strata record a marine reef community from the Devonian Period. These Devonian reefs were formed by stromatoporoids (extinct sponges with massive calcareous skeletons), corals, and other marine organisms.
Although rocks from the Devonian do not surface anywhere near Drumheller, the presence of reefs is confirmed by the hundreds of exploration cores that have been drilled by resource companies searching for crude oil and natural gas. (Hundreds of producing wells encircle Drumheller.) The fossils present in these test cores indicate that at one time there were reef communities living in a shallow marine sea that covered much of southern Alberta.
Just three hours’ drive to the west of Drumheller, Devonian reefs are exposed in the Rocky Mountains. Seismic profiles and innumerable core samples taken in the search for fossil fuels have confirmed that the reef rocks one mile below Drumheller were once part of an unbroken sequence of sedimentary rocks extending to those currently exposed in the mountains.
For me, the most important feature of the fossilized reefs below Drumheller was that they were preserved in life position. That is, the organisms making up this community were preserved right where they had once lived. Reefs are massive carbonate structures that are not moved about very easily. No reef is preserved upside down, sideways, or end-on within the strata. Relative to the rocks around them, the reefs give no indication that they were picked up, moved, and redeposited in their current location.
Therefore, the sponges and corals must have lived, died, and become fossilized in one place. There are, to be sure, the fossilized remains of other marine organisms such as cephalopods and fishes that were capable of movement, and which are thus not preserved in a life position as are sessile or very slow-moving organisms. Nevertheless, these are Devonian marine organisms typically associated with the species of sponges and corals making up the reefs. Furthermore, the fossilized remains of terrestrial plants or animals are nowhere to be found in these marine fossil beds. They only preserve extinct, marine species.
The description of the various fossil-bearing formations in this area continues in the next post.