CADIC   02618
CENTRO AUSTRAL DE INVESTIGACIONES CIENTIFICAS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
COUPLED PALEOGEOGRAPHIC PATTERNS IN LATE CRETACEOUS, SHALLOW-MARINE BODY AND TRACE FOSSILS FROM ANTARCTICA
Autor/es:
OLIVERO E.B.; LOPEZ CABRERA, M.I
Lugar:
Mendoza
Reunión:
Congreso; 4th International Palaeontological Congress; 2014
Institución organizadora:
IPA - CONICET MENDOZA
Resumen:
Late Cretaceous mollusks from the Marambio Group, James Ross Basin, NE Antarctic Peninsula,
record a long cooling trend of seawater temperatures from the Coniacian/Santonian (~18C°) to
the Maastrichtian (~8C°). Accompanying this trend are remarkable shifts in the biogeographic
distribution of pelagic (ammonites) and benthic (bivalves) faunas. A strong biogeographical contrast
is apparent between nearly cosmopolitan or Indo Pacific Santonian faunas and Southern Gondwanarestricted
mid Campanian-Maastrichtian ones. The pelagic elements of the latter are characterized
by radiation and dominance of the stenothermal kossmaticeratid ammonites and early extinction of
the scaphitid, nostoceratid, and baculitid ammonites; and the benthic fauna by the early extinction
of inoceramid and most trigoniid bivalves. Here we document and discuss accompanying changes
in fossil behavior, expressed by complex spreite burrows that are mostly restricted to southern highlatitudes.
The 3 km-thick Marambio Group records a variety of deltaic, estuarine, storm-influenced,
and shelfal fine-grained deposits bearing ichnological suites characteristic of the proximal and
distal Cruziana ichnofacies. Typical Upper Cretaceous ichnogenera that are well-known elsewhere
in the world include: 1) for the proximal and archetypal Cruziana ichnofacies, Asterosoma, Chondrites,
Nereites, Ophiomorpha, Phycodes, Phycosiphon, Planolites, Rhizocorallium, Rosselia, Schaubcylindrichnus,
Scolicia, Taenidium, Teichichnus and Thalassinoides; and 2) for the distal Cruziana ichnofacies, the
addition of large specimens of Stelloglyphus, Zoophycos, and restricted horizons with graphoglyptids.
Among these a distinctive group of complex spreite burrows appears at different times with
increasing diversity and dominance, including Paradictyodora antarctica (Santonian); P. antarctica
and Tasselia ordamensis (late early Campanian); P. antarctica, T. ordamensis, and Euflabella singularis
(mid Campanian); P. antarctica, T. ordamensis, E. singularis and Euflabella multiplex (late Campanian);
and P. antarctica, T. ordamensis, E. singularis; E. multiplex, Euflabella radiata, Patagonichnus stratiformis
and Patagonichnus thalassiformis (Maastrichtian). These complex spreite burrows are shallow-tier
fodinichnia, but some of their producers were also trophic generalists, living on detritus from
the burrowed sediment, fresh detritus from the surface, and bacterial gardening. Except for T.
ordamensis, which is poorly known outside Antarctica and Tierra del Fuego, the rest of these spreite
burrows appears to be restricted to southern high paleolatitudes. By the Late Cretaceous, the James
Ross Basin was already positioned at its present latitude of about S64° and we hypothesize that
high paleolatitudes, resulting in strong seasonal variations in primary production, and cooling,
both favored the appearance of specialized strategies and behaviors offering a causal explanation
for the observed concurrent paleogeographical restrictions in the pelagic and benthic faunas and
trace fossils.