CARNIAN-NORIAN BIOCHRONOLOGY, CORRELATION AND
BIOTIC EVENTS OF THE NONMARINE TRIASSIC OF NORTH
AMERICA
HUBER, Phillip, Department of Education, University of
Bridgeport, Bridgeport, CT 06601
LUCAS, Spencer G., New Mexico Museum of Natural History
and Science, 801 Mountain Rd., NW, Albuquerque,
NM 87104
HUNT, Adrian P., Mesalands Dinosaur Museum, Mesa
Technical College, Tucumcari, NM 88401
Strata of the Newark Supergroup and Chinle Group contain the most
diverse, nonmarine biotas known from the Laurasian Triassic. Four
land vertebrate faunachrons (lvf's) of Carnian-Norian age are
recognized in each region that are temporally parallel and provide a
substage-level, biostratigraphic framework through which trends of
biotic change can be examined. Moderately diverse assemblages of
Sanfordian (early Tuvalian) age are found in the Deep River,
Richmond, Taylorsville and Fundy basins. Age diagnostic taxa include
Metoposaurus bakeri, a variety of thecodonts (cf. Scaphonyx,
Longosuchus, Doswellia) and dicynodont Placerias, all common to
coeval, basal Chinle Group assemblages of Otis Chalkian age. The
Conewagian lvf (late Tuvalian) guidefossil is the phytosaur Rutiodon
carolinensis. Other taxa include metoposaurids (Buettneria perfecta),
procolophonids, numerous archosaurs (Euscolosuchus olseni,
Desmatosuchus sp.), moderately diverse dinosaurian and
lepidosaurimorph (Tanytrachelos, Icarosaurus) components and
numerous cynodonts (Microconodon, Dromotherium,
Boreogomphodon). Formations that contain Conewagian assemblages
include the type Pekin and Cumnock (Chatham Gp.), Turkey Branch
(Richmond basin), New Oxford (Gettysburg basin), and upper
Stockton and Lockatong (Newark basin) Fms. Conewagian
assemblages are correlative with the Chinle Group Adamanian lvf, as
indicated by the shared distributions of Buettneria, Rutiodon, and
Desmatosuchus.
The early to middle Norian Neshanician lvf is defined by the
stratigraphic range in the Newark basin (Warford through Perkasie
Mbrs.) of the aetosaur Aetosaurus arcuatus. Other Neshanician
assemblages (upper Chatham Gp., New Haven Arkose) include indet.
labyrinthodonts, one or more rauisuchians, indet. phytosaurs, and a
coelurosaur and are broadly correlative with the Chinle Group
Reveultian lvf. Late Norian-Rhaetian Cliftonian lvf assemblages
contain the procolophonid Hypsognathus (upper Passaic, upper New
Haven and possibly Wolfville Fms.) and are correlative with much
more diverse, Apachean lvf assemblages from the uppermost Chinle
Group.
Independent calibration of vertebrate-based correlations is
provided by developing magnetostratigraphies tied to the Newark
cyclostratigraphic timescale. These correlations indicate that most
Newark strata dated as "middle Carnian" by palynomorphs actually are
of late Carnian (Tuvalian) age, and that the hypothesized Newark
"middle Carnian" extinction event is an artifact of poor, independent age
control. The most significant biotic turnover occurs during the late
Carnian and there is no evidence for terrestrial mass-extinctions at the
Carnian-Norian boundary.
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