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Re: Age Abstractions

Delurking for a moment under the mass of DML posts of recent which seem to come in huge waves.....

I often find dinosaurian remains in Holocene sediments which have obviously been placed there by erosion of Cretaceous material uphill. The Hell Creek sediment was removed by wind and water leaving the heavier bone pieces and parts behind in modern soil horizons. These have included complete isolated bones of dinosaurian origin as well as many other species thriving during the Cretaceous. This reworking process has not been mentioned in the abstract. I have a classic location of this for any doubters. Go figure, dinosaur material in obviously modern sediment. If I sieved hard enough, I would find man made material from the nearby abandoned 1900 ish dug out homestead mixed with dinosaur bones which would perk up those man living with dinosaurs people. If this horizon lithified with geologic time, the mixing of fauna might lead to the abstract below leading to the dogma that man and dinosaur existed together.

My belated and abused point is: Dinosaurian bones are often found above the Cretaceous boundary that have been reworked into younger sediments from below by a variety of processes. Was this possibility discussed in this paper? Are there any "complete" fossils of articulated bones in the formation? An articulated remain is not likely to survive any reworking by natural processes (sometimes they don't survive removal by paleontologists!).

Frank (Rooster) Bliss
MS Biostratigraphy
Weston, Wyoming

On Jun 20, 2007, at 7:02 AM, Jeff Hecht wrote:

It's curious that the coauthors of previous papers that Roberto cited have vanished. Perhaps there's a message there?

At 5:12 PM -0700 6/19/07, Jerry D. Harris wrote:
OK, so it's just an abstract (so far, not counting all that's been published on the topic previously), but:

Fassett, J.E. 2007. The documentation of in-place dinosaur fossils in the Paleocene Ojo Alamo Sandstone and Animas Formation in the San Juan Basin of New Mexico and Colorado mandates a paradigm shift: dinosaurs can no longer be thought of as absolute index fossils for end-Cretaceous strata in the Western Interior of North America. New Mexico Geology 29(2):56.

ABSTRACT: Extensive geochronologic studies of the rocks adjacent to the Cretaceous-Tertiary (K-T) interface in the San Juan Basin have now provided compelling data attesting to the Paleocene age of the dinosaur-bearing Ojo Alamo Sandstone in New Mexico and the Animas Formation in Colorado. These data consist of radiometric age determinations for Cretaceous strata underlying the K-T interface and palynologic, paleomagnetic, and geochemical evidence attesting to the Paleocene age of the strata above the K-T interface. The identification of the paleomagnetic normal interval - C29n - in the dinosaur-bearing lower part of the Ojo Alamo Sandstone in the southern San Juan Basin at multiple localities allows for the precise dating of the last occurrence of Paleocene dinosaurs at the top of chron C29n at 64.432 Ma.
The conventional wisdom (entrenched dogma) among most geologists, and especially among vertebrate paleontologists has been, for more than 100 years, that all dinosaurs became extinct at the end of the Cretaceous. Thus, dinosaur bone found in place in a formation provided indisputable evidence that the formation was Cretaceous in age. Now, with the discovery of Paleocene dinosaurs, the paradigm of Cretaceous-only dinosaurs must shift. Let us hope that this paradigm-shift will be a smooth and placid lateral-slip along planar fault blocks rather than a grumbling, rumbling, herky-jerky sliding of jagged-edged, opposing sides past each other. Science must always be conservative and accept such paradigm shifts only on the basis of the most solid evidence, however, when the data do finally speak, the shift must be accepted by all of us who follow the data in the noble pursuit of finding out how the world was made.

I'd've thought he'd put out a press release...?!?

-- Jeff Hecht, science & technology writer jeff@jeffhecht.com http://www.jeffhecht.com 525 Auburn St., Auburndale, MA 02466 USA v. 617-965-3834; fax 617-332-4760