[N] 2006 Chasmosaurus mariscalensis from Northern Mexico
Benammi, M. (2006) New data from the continental Late Cretaceous faunas from Northern Mexico. JVP 26(3) Abstracts pp.41 [Chasmosaurus mariscalensis]
During recent years field work had been carried out in the continental and transitional marine Late Cretaceous deposits in the northern areas of the states of Coahuila and
Chihuahua. As a result several fossiliferous sites bearing dinosaur, other vertebrates and plant remains had been located. Sediment for screen-washing was collected and microvertebrates were recovered.
The geological framework in this area is practically unknown. To determine the stratigraphic position of each fossiliferous site, five sections were established. A marine section represents the lowest part and it is characterized by alternating calcareous shale, shale, silty shale and phosphate nodule facies with interbedded sandstones. The sandstone layers yield poorly preserved gastropods and bivalves, and well preserved shark teeth. The continental section is characterized by a sequence of variegated mudstones and sandstones with conglomeratic lags of paleo-caliche nodules, it suggests a fluvial environment in a deltaic coastal plain and inland floodplain. There is no evidence of faulting or folding.
Samples were collected from the five sections for magnetostratigraphic analysis. All of them showed normal polarity which correlates to the Chron C33n.1n and corresponds
to the upper Campanian age. It is interesting to mention that ceratopid remains identified as Chasmosaurus mariscalensis are stratigraphically in higher position than titanosaurid remains. This is contrary to the order present in the Big Bend National Park, Texas. The record of the titanosaurid supports the hypothesis that the group was present during the Campanian in North America. The ceratopid record is congruent with the age suggested by the magnetostratigraphy results. This new geological information and that provided by the fossils will help to establish a more detail correlationship with the Late Cretaceous outcrops of the Big Bend National Park.