Fossil Trove Colorado

26 Oct 2019

This one is quite good and has even been picked up by Clark Whelton (on his email list). At https://phys.org/news/2019-10-fossil-trove-life-fast-recovery.html ... and concerns a fascinating fossil bed being investigated in Colorado which is said to date from not long after the K/T boundary event (which with a bit of twitching might even be said to have been laid down at the same time). However, giving the authors the benefit of the doubt, and accepting that geology is laid down in a gradualist manner, the finds are said to show that life on land bounced back extraordinarily quickly - much more quickly so than in the marine environment. Colorado is of course upwind of Chicxulub but we may ignore that fact for the moment - even though mainstream accept the K/T event was catastrophic in nature and should therefore have laid down sedimentary layers rapidly.

The story does have a nice human angle. The fossils come from steep bluffs near Colorado Springs (see www.corralbluffs.org/ ) where the hunt for fossils was unproductive at first as they were looking for pieces of bone. When they happened to switch focus and started cracking open concretions they discovered fossilised skulls and bones of animals - in apparent abundance. Why they were fossilised into concretions, and by what process, or what kind of rock encased the fossils is not illuminated in the press release (or abstract) - but see https://science.sciencemag.org/content/early/2019/10/23/science.aay2268. It seems the region had been thickly forested when the asteroid struck, home to dinosaurs such as T. Rex. Mammals were very small in comparison - mainly of the rodent variety. Not long after K/T the environment was blanketed with ferns and rodents were still the norm. However, just 100,000 years after K/T this had all changed and mammals had got a bit bigger. By 300,000 years ago this had all changed and walnut trees had evolved and branched out and mammals had become plant eaters and were as big as a beaver. By 700,000 years ago legume plants appear (forerunners of peas and beans) and mammals are said to be bigger still. One is left thinking this might represent some massaging of the strata. It is a perfect uniformitarian interpretation. Catastrophism would demand it all happened in one event and the fact the bluffs also embrace the K/T boundary one can only think the whole bluffs were laid down at that time - somewhat like what occurred at the Mount St Helens eruption.

The researchers claim the bluffs were laid down over hundreds of thousands of years and during this process of gradual laying down of the strata mammals changed from mice size to beaver size - and plants evolved also. However, from a catastrophist perspective the bluffs may have been laid down much more quickly and dividing the fossils into size (like eggs are graded by farmers) might be a misnomer. In order to dispute such a uniformitarian interpretation one must be able to point to mammals as big as beavers prior to K/T. They do not seem to exist. Also, as we shall see, walnut trees (or their ancestors) and legumes (and their ancestors). In other words, were modern plants and trees evolving even during the Cretaceous and managed to survive the impact event (seeds). It is a moot question.

We learn at the last link that at Corral Bluffs the stratigraphy is tied to the Geomagnetic Polarity Time Scale (GPTS 2012). I have no idea how reliable this is or at what point in time it is able to define almost exactly a transition of 100,000 year intervals as required in this study. It is unlike C14 or tree rings for example and must therefore be a more blanket like dating system, providing a rough estimate. Can it be used to specifically divide the bluffs into a series of strata, segments of time that can be used to catalogue the progress of life after the asteroid strike. In the marine environment it is thought life took much longer to return to normality - or be replenished with life forms. Using paleomagnetic and CA-ID-TIM1-U-Pb dating for volcanic ash is an added point which implies considerable evidence of volcanoes in the bluffs - the sort of thing one might expect following a large impact event. Likewise, the authors assume the Deccan Traps occurred long after the impact as a result of interpreting the sedimentary layers as uniformitarian in nature. In a catastrophist interpretation the Deccan Traps will have occurred shortly after the asteroid strike - as a consequence (seismic activity on the opposite side of the world as the earth rang like a bell). We are told the study area contains an exceptionally dense vertebrate and megaflora record with fossils occurring at more than 150 stratigraphic levels in what is a 250m thick formation. The extensive and nearly continuous sequence of the outcrop spans the last 100,000 years of the Cretaceous and the first one million years of the Paleocene. The composite lithostratigraphic log is dominated by intercalated mudstones and sandstones reflecting a variety of fluvial facies. Pollen zones are defined by diversification and the K/T boundary is demarcated by the decrease in abundance of Cretaceous pollen taxia, without recovery, and a subsequent spike in ferns. The latter of course thrived in the dinosaur age and commonly occur in Jurassic cliff formations on the Dorset coast of southern England. The inference is that trees were replaced by ferns but is this an artifact of the cataloguing methodology. For example, in a fluvial situation (strata laid down by a tidal wave) the heaviest objects (trees) would sink to the lowest levels, and lighter material (such as ferns, pollen, seeds etc) at a higher level. An abundance of ferns and palms occurred after the K/T boundary we are told, as revealed mainly by their pollen.

Hence, the bluffs seem to be mostly composed of mudstones and sandstones (with volcanic ash) with a fluvial origin - in Colorado. A long way from the sea. How could a tidal wave penetrate that far inland (assuming the ocean was still roughly consistent with the modern Caribbean). The alternative, from a catastrophist angle, is to suppose a series of catastrophes occurred - after the K/T boundary event. We then have the problem they involved a series of fluvial intrusions. Seems somewhat unlikely. The uniformitarian explanation would seem preferable to that. However, the concretions tell us something peculiar had occurred - and it was probably rapid. In spite of scepticism by a catastrophist one has to admire the level of work and explanation that went into this study, a truly stupendous effort. I take my hat off to them. It is also done fully in accord with geological thinking - and can't be criticised on that front. It must have been a painstaking process but one that must receive accolades from fellow professionals (involved in the same uniformitarian processes). From another angle it brings into perspective the ongoing debate over the K/T boundary and those who might think the sediments were laid down quickly and those who insist on sticking to the uniformitarian timetable (something rumbling along in the background). Yes, some geologist think some layers can be laid down rapidly, in spite of mainstream dogma to he  contrary. In fact, it makes sense as we are talking about a truly big slam into the earth. To suppose that sediments were not laid down quickly in the aftermath is to be dogmatic. The fun will start if geologists try and recognise which ones were rapid and which ones took place over a long period of time.

In the biological model of punctuated equilibrium, evolution in bursts separated by long periods with little change, there should be evidence of rapid mutation in the aftermath of the asteroid strike. Does the evidence presented in this study suggest that is so? The fact that mammals are catalogued as growing bigger (but not by too much) would suggest that rapid diversification on the part of the survivors had not occurred (in the bluffs) - or is that a misrepresentation of the facts. We might bear in mind that small mammals appear during the Jurassic era which means they could have evolved into bigger animals by the end of the Cretaceous - and probably did.