During our 2003 Permian-Triassic boundary study in the
Central Transantarctics, we decided to move out to some exposures
near the Shackleton Glacier to search for fossil vertebrates
and evidence for an impact breccia. Initially, helicopter
aerial reconnaissance was used to determine the best potential
sites and we settled upon Collinson Ridge across the way from
Shenk Peak, and Halfmoon Bluff in the Cumulus Hills at the
junction of the Shackleton and McGregor Glaciers.
Only the lower portion of the Fremouw Formation (Early Triassic)
have produced vertebrates at this locality so finding Late
Permian vertebrates would be a coup for our science team (including
myself, Greg Retallack, Roger Smith and Shaun Norman). The
reason we chose to go to Collinson Ridge was that this location
was amongst the most productive sites in previous expeditions
(e.g. Hammer and Collinson, 1995-96). The upper part of the
Falla Formation that had produced Early Jurassic dinosaur
material near the Beardmore Glacier was not found at any site
near the Shackleton Glacier in these previous investigations.
Hammer and Collinson (1996) did find vertebrates of both carnivorous
and herbivorous therapsids. Small skulls and skeletons of
diapsids (possibly eosuchians) as well as anapsids (including
at least one type of procolophonid) have also been recognized
(all early Triassic). In particular, the abundant amount of
small anapsid, diapsid, and temnospondyl material includes
specimens found by Hammer and Collinson that represented a
new genera not previously identified in any known Antarctic
location.
Our study will include a faunal analysis of each stratigraphic
horizon in search of the Permian-Triassic boundary to determine
if certain depositional settings preferentially preserve certain
taxa, and/or if the distribution of some taxa is related to
climate. We will also focus on the abrupt lithostratigraphic
changes that commonly mark the Permian-Trassic boundary (e.g.
South Africa, Sydney basin etc.) in an attempt to locate the
claystone breccia that was identified in the Graphite Peak
and Mt. Crean Antarctic locations (see notes and photo gallery
on Mt. Crean and Graphite Peak).
|
