Publication Date:
2014-04-14
Description:
Geophysical data acquired using R/V Polarstern
constrain the structure and age of the rifted oceanic margin of
West Antarctica. West of the Antipodes Fault, the 145 km wide
continent-ocean transition zone (COTZ) of the Marie Byrd Land
sector resembles a typical Atlantic-type margin. New gravity and
seismic reflection data indicates initial continental crust of
thickness 24 km, that was stretched 90 km. Farther east, the
Bellingshausen sector is broad and complex with abundant evidence
for volcanism, the COTZ is c. 670 km wide, and the nature of
crust within the COTZ is uncertain. Margin extension is estimated
to be 106-304 km in this sector. Seafloor magnetic anomalies
adjacent to Marie Byrd Land near the Pahemo Fracture Zone indicate
full-spreading rate during c33-c31 (80-68 Myr) of 60 mm/yr,
increasing to 74 mm/yr at c27 (62 Myr), and then dropping to
22 mm/yr by c22 (50 Myr). Spreading rates were lower to the
west. Extrapolation towards the continental margin indicates
initial oceanic crust formation at around c34y
(84 Myr). Subsequent motion of the Bellingshausen plate relative
to Antarctica (84-62 Myr) took place east of the Antipodes Fault
at rates 〈40 mm/yr, typically 5-20 mm/yr. The high extension
rate of 30-60 mm/yr during initial margin formation is
consistent with steep and symmetrical margin morphology, but
subsequent motion of the Bellingshausen plate was slow and
complex, and modified rift morphology through migrating
deformation and volcanic centres to create a broad and complex
COTZ.
Repository Name:
EPIC Alfred Wegener Institut
Type:
Article
,
isiRev
Format:
application/pdf
