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Paleocene Dinosaurs:
FASSETT

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Multilingual  Abstracts

Abstract

Introduction

Physical Stratigraphy of K-T Boundary Strata  

Geochronology

Paleomagnetism (Part1)

Paleomagnetism (Part 2) 

NW to SE Thinning of Cretaceous Strata in SW San Juan Basin

Paleobotany

Vertebrate Paleontogy

Geochemistry of Vertebrate Bones Samples

Age of Ojo Alamo Sandstone Based on Alamosaurus Sanjuanensis

Conclusions

Acknowledgements

References

Appendix

Test

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NEW GEOCHRONOLOGIC AND STRATIGRAPHIC EVIDENCE CONFIRMS THE PALEOCENE AGE OF THE DINOSAUR-BEARING OJO ALAMO SANDSTONE AND ANIMAS FORMATION IN THE SAN JUAN BASIN, NEW MEXICO AND COLORADO

James E. Fassett

ABSTRACT

Dinosaur fossils are present in the Paleocene Ojo Alamo Sandstone and Animas Formation in the San Juan Basin, New Mexico, and Colorado. Evidence for the Paleocene age of the Ojo Alamo Sandstone includes palynologic and paleomagnetic data. Palynologic data indicate that the entire Ojo Alamo Sandstone, including the lower dinosaur-bearing part, is Paleocene in age. All of the palynomorph-productive rock samples collected from the Ojo Alamo Sandstone at multiple localities lacked Cretaceous index palynomorphs (except for rare, reworked specimens) and produced Paleocene index palynomorphs. Paleocene palynomorphs have been identified stratigraphically below dinosaur fossils at two separate localities in the Ojo Alamo Sandstone in the central and southern parts of the basin. The Animas Formation in the Colorado part of the basin also contains dinosaur fossils, and its Paleocene age has been established based on fossil leaves and palynology.

Magnetostratigraphy provides independent evidence for the Paleocene age of the Ojo Alamo Sandstone and its dinosaur-bearing beds. Normal-polarity magnetochron C29n (early Paleocene) has been identified in the Ojo Alamo Sandstone at six localities in the southern part of the San Juan Basin.

An assemblage of 34 skeletal elements from a single hadrosaur, found in the Ojo Alamo Sandstone in the southern San Juan Basin, provided conclusive evidence that this assemblage could not have been reworked from underlying Cretaceous strata. In addition, geochemical studies of 15 vertebrate bones from the Paleocene Ojo Alamo Sandstone and 15 bone samples from the underlying Kirtland Formation of Late Cretaceous (Campanian) age show that each sample suite contained distinctly different abundances of uranium and rare-earth elements, indicating that the bones were mineralized in place soon after burial, and that none of the Paleocene dinosaur bones analyzed had been reworked.

James E. Fassett. U. S. Geological Survey, Emeritus, 552 Los Nidos Drive, Santa Fe, New Mexico 87501

KEY WORDS: Paleocene dinosaurs; K-T interface, geochronology, palynology, paleomagnetism, vertebrate paleontology

PE Article Number: 12.1.3A
Copyright: U.S. Geological Survey, Public Domain April 2009
Submission: 13 December 2007. Acceptance: 28 January 2009

 

Next Section

Paleocene Dinosaurs
Plain-Language & Multilingual  Abstracts | Abstract | Introduction | Physical Stratigraphy of K-T Boundary Strata
Geochronology Paleomagnetism | NW to SE Thinning of Cretaceous Strata in SW San Juan Basin
Paleobotany | Vertebrate Paleontogy | Geochemistry of Vertebrate Bones Samples
Age of Ojo Alamo Sandstone Based on Alamosaurus Sanjuanensis | Conclusions
Acknowledgements | References | Appendix
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