Re-evaluation of Mentelle Basin, a polyphase rifted margin basin, offshore southwest Australia: new insights from integrated regional seismic datasets
Maloney, D and Sargent, C and Direen, NG and Hobbs, RW and Grocke, DR, Re-evaluation of Mentelle Basin, a polyphase rifted margin basin, offshore southwest Australia: new insights from integrated regional seismic datasets, Solid Earth, 2, (2) pp. 107-123. ISSN 1869-9510 (2011) [Refereed Article]
Vintage 2-D (two-dimensional) seismic reflection
surveys from the sparsely explored Mentelle Basin (western
Australian margin) have been reprocessed and integrated
with a recent high-quality 2-D seismic survey and stratigraphic
borehole data. Interpretation of these data sets allows
the internal geometry of the Mentelle Basin fill and
depositional history to be reanalysed and new insights into
its formation revealed. Basin stratigraphy can be subdivided
into several seismically defined megasequences separated by
major unconformities related to both breakup between India-
Madagascar and Australia-Antarctica in the Valanginian-
Late Hauterivian and tectonically-driven switches in deposition
through the Albian.
Resting on the Valanginian-Late Hauterivian breakup unconformity
are several kilometre-scale mounded structures
that formed during Late Jurassic to Early Cretaceous extension.
These have previously been interpreted as volcanic edifices
although direct evidence of volcanic feeder systems is
lacking. An alternative interpretation is that these features
may be carbonate build-ups. The latter interpretation carries
significant climatic ramifications since carbonate build-ups
would have formed at high palaeolatitude, 60 S.
Soon after breakup, initial subsidence resulted in a shallow
marine environment and deposition of Barremian-Aptian
silty-sandy mudstones. As subsidence continued, thick successions
of Albian ferruginous black clays were deposited.
Internally, seismic megasequences composed of successions
of black clays show previously unresolved unconformities,
onlapping and downlapping packages, which reflect a com-
plex depositional, rifting and subsidence history at odds with
their previous interpretation as open marine sediments.
Southwestwards migration of the Kerguelen hotspot led to
thermal contraction and subsidence to the present day water
depth (3000 m). This was accompanied by Turonian-
Santonian deposition of massive chalk beds, which are unconformably
overlain by pelagic Palaeocene-Holocene sediments.
This substantial unconformity is related to the diachronous
breakup and onset of slow spreading between
Australia and Antarctica, which may have led to the reactivation
and inversion of basement faults and was followed
by rapid seafloor spreading from the Middle Eocene to the