[dinosaur] Alberta St. Mary River Formation dinosaur bonebed taphonomy + Horseshoe Canyon Formation dating

Ben Creisler
[email protected]

New papers:

James Alexander Campbell, Michael P.J. Ryan & Jason Anderson (2019)
A taphonomic analysis of a multi-taxic bonebed from the St. Mary River
Formation (uppermost Campanian to lowermost Maastrichtian) of Alberta,
dominated by cf. Edmontosaurus regalis (Ornithischia: Hadrosauridae), with
significant remains of Pachyrhinosaurus canadensis (Ornithischia:
Ceratopsidae).
Canadian Journal of Earth Sciences (advance online publication)
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1139_cjes-2D2019-2D0089&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=E1QrN9ak0d-wSfF0qCTNkyfBK6OxX9OjcAR2lk3ufNc&s=n0yVUq99rFCBCNtPJe2eHlVA-avyZuOdMa9B6n9t2Tw&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__www.nrcresearchpress.com_doi_abs_10.1139_cjes-2D2019-2D0089-23.XaCkz1VKjX4&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=E1QrN9ak0d-wSfF0qCTNkyfBK6OxX9OjcAR2lk3ufNc&s=M20MD_j8rg8ulZpuJ8MWACOJFryaK4-ett_hraon98c&e= 

Scabby Butte is an isolated exposure of Upper Cretaceous (uppermost
Campanian to lowermost Maastrichtian) strata of the St. Mary River
Formation. These rocks have produced a diverse assemblage of both
terrestrial and aquatic vertebrates, although hadrosaurid and ceratopsid
dinosaurs represent the largest component by volume. Almost all of these
dinosaur remains were collected from a single bonebed (Site 2) at Scabby
Butte and have been referred to the hadrosaurid Edmontosaurus regalis and
the ceratopsid Pachyrhinosaurus canadensis. This study presents a
quantitative taphonomic reanalysis of the originally published data,
providing new information previously overlooked and important information
about the age class structure of the dinosaur fauna preserved at the site.
Site 2 is a lag deposit with a minimum number of individuals = 11 (two
ceratopsid, nine hadrosaurid), with three quarters of the material being
adult-sized based on size class analysis. Most elements have undergone
moderate to severe breakage and abrasion, and are completely
disarticulated, suggesting that they were transported from where they died;
post-mortem scavenging is also a possibility, as evidenced by the presence
of toothmarks and trample marks on several elements. Burial took place soon
after scavenging, as there is little evidence of subaerial weathering.

===

David A. Eberth & Sandra L. Kamo (2019)
High-precision U-Pb CA-ID-TIMS dating and chronostratigraphy of the
dinosaur-rich Horseshoe Canyon Formation (Upper Cretaceous,
Campanian–Maastrichtian), Red Deer River valley, Alberta, Canada.
Canadian Journal of Earth Sciences (advance online publication)
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1139_cjes-2D2019-2D0019&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=E1QrN9ak0d-wSfF0qCTNkyfBK6OxX9OjcAR2lk3ufNc&s=UZ3tcH2XVN3XHmEt5wo_f5pLCEQx4ShVuJEzovv889E&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__www.nrcresearchpress.com_doi_abs_10.1139_cjes-2D2019-2D0019-23.XaClZ1VKjX4&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=E1QrN9ak0d-wSfF0qCTNkyfBK6OxX9OjcAR2lk3ufNc&s=CeGX_RvqBi6Cjbwi9Hr4T9_B7sEeALBZ_KNd4gi2xPo&e= 


The non-marine Horseshoe Canyon Formation (HCFm, southern Alberta) yields
taxonomically diverse, late Campanian to middle Maastrichtian dinosaur
assemblages that play a central role in documenting dinosaur evolution,
paleoecology, and paleobiogeography leading up to the end-Cretaceous
extinction. Here, we present high-precision U-Pb CA-ID-TIMS ages and the
first calibrated chronostratigraphy for the HCFm using zircon grains from
(1) four HCFm bentonites distributed through 129 m of section, (2) one
bentonite from the underlying Bearpaw Formation, and (3) a bentonite from
the overlying Battle Formation that we dated previously. In its type area,
the HCFm ranges in age from 73.1–68.0 Ma. Significant paleoenvironmental
and climatic changes are recorded in the formation, including (1) a
transition from a warm-and-wet deltaic setting to a cooler, seasonally
wet-dry coastal plain at 71.5 Ma, (2) maximum transgression of the
Drumheller Marine Tongue at 70.896 ± 0.048 Ma, and (3) transition to a
warm-wet alluvial plain at 69.6 Ma. The HCFm’s three mega-herbivore
dinosaur assemblage zones track these changes and are calibrated as
follows: Edmontosaurus regalis-Pachyrhinosaurus canadensis zone, 73.1–71.5
Ma; Hypacrosaurus altispinus-Saurolophus osborni zone, 71.5–69.6 Ma; and
Eotriceratops xerinsularis zone, 69.6–68.2 Ma. The Albertosaurus bonebed—a
monodominant assemblage of tyrannosaurids in the Tolman Member—is assessed
an age of 70.1 Ma. The unusual triceratopsin, Eotriceratops xerinsularis,
from the Carbon Member, is assessed an age of 68.8 Ma. This
chronostratigraphy is useful for refining correlations with
dinosaur-bearing upper Campanian-middle Maastrichtian units in Alberta, and
elsewhere in North America.

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