A REMARKABLE VERTEBRATE ASSEMBLAGE FROM THE LANCE FORMATION, NIOBRARA
SPENCER, Lee, Earth History Research Center, 4736 Carberry Ck. Rd, Jacksonville,
OR 97530, firstname.lastname@example.org,
TURNER, Lawrence E., Mathematics and Physical Sciences, Southwestern Adventist Univ, 100 Hillcrest, Keene, TX 76059,
CHADWICK, Arthur V., Geology, Southwestern Adventist Univ, 100 Hillcrest,
Keene, TX 76059.
During the process of an on-going taphonomic study of the Lance
vertebrates, a small quarry was opened up on a sandstone ridge abutting a calcareous cemented cobbly
sandstone bone bed one meter in thickness. The deposit concerned here occurs in a poorly
cemented well-sorted immature white sandstone and appears as a lag deposit
on the trailing edge of the larger mass of the bone bed itself.
Transport of the entire
unit appears to have been to the south, based upon imbrication of the flat pebble clasts contained in the unit.
The bone bed contains a transported assemblage of disarticulated bones in
all size categories, ranging from small bone chips and ossified tendons to whole femora.
The lag deposit contains a variety of bones, but they tend to be smaller than those
of the main bone bed, and the entire thickness of the lag deposit is less than 20 cm.
The profile of the residual tails and disappears in the white sandstone over a distance of two
meters upstream of the bone bed.
The materials described below were recovered from 20 cm depth in an area of two square meters in this lag.
The lag deposit contained a variety of bones of Edmontosaurus, fragments of
turtle and fish bones, fish scales, and numerous teeth.
While many of the teeth were
Edmontosaurus, and a dentary of a juvenile Edmontosaurus was recovered,
teeth of several other species of dinosaur were recovered, including Triceratops horridus,
Tyrannosaurus rex, Nannotyrannus sp.dub., and Troodon formosus.
Associated with the dinosaur teeth were teeth from crocodilians, fish, multituberculates and
other forms still under study.
The accumulation of teeth from a variety of species in such a small area is consistent with a
residual deposited upstream of a high energy debris accumulation.
poster session presented at GSA 2001 meeting, Boston, MA, Nov 2001.