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Evidence for non-marine Jurassic to earliest Cretaceous sediments in the pre-breakup section of the Mentelle Basin, southwestern Australia

journal contribution
posted on 2023-05-20, 09:43 authored by Wainman, CC, Borissova, I, Harry, DL, Hobbs, RW, Mantle, DJ, Maritati, A, Lee, EY
The Mentelle Basin, located off the southwestern continental Australian margin, is an under-explored deep-water basin that developed during the breakup of eastern Gondwana in the Middle Jurassic through to the Early Cretaceous. There is a high degree of uncertainty in stratigraphic interpretations of the basin owing to the lack of well and seismic data in the region. As a consequence, there has been a heavy reliance on data from the neighbouring Perth Basin to infer the geological history of the Mentelle Basin. During Expedition 369 of the International Ocean Discovery Program, a single hole was drilled with a rotary core bit to 517.10 m below seafloor at Site U1515 on the continental slope in the eastern Mentelle Basin. The aim was to sample and date the inferred Permian to Jurassic pre-breakup strata. The presence of palynomorphs including Murospora florida and Retitriletes watherooensis in the fluvio-lacustrine succession below the Valanginian breakup unconformity indicates a Jurassic to earliest Cretaceous age for the upper part of the pre-rift sedimentary succession. Notable characteristics of this succession include intervals with high percentages of total organic carbon (up to 44 wt%) and high hydrogen index values (Type I source rocks) associated with an increase in Botryococcus and other freshwater algae that accumulated in shallow lakes and waterlogged floodplains. A possible example of dinoturbation was also noted in this core. The discovery of Jurassic to earliest Cretaceous pre-breakup strata at Site U1515 suggests that Jurassic rifting was not constrained to the western depocentre of the Mentelle Basin, but also extended to a number of depocentres in the eastern Mentelle Basin. This has significant implications for the understanding of the regional tectonic history and the Mentelle Basin’s petroleum potential.

  • Pre-breakup strata sampled in the eastern Mentelle Basin for the first time by IODP Expedition 369

  • Upper Jurassic–Lower Cretaceous non-marine strata below the Valanginian Unconformity

  • High TOC’s, high abundances of Botryococcus algae in a few horizons and a possible example of dinoturbation

  • Jurassic rifting not constrained to the western Mentelle Basin, but to depocentres in the east

History

Publication title

Australian Journal of Earth Sciences

Volume

67

Pagination

89-105

ISSN

0812-0099

Department/School

Institute for Marine and Antarctic Studies

Publisher

Blackwell Publishing Asia

Place of publication

54 University St, P O Box 378, Carlton, Australia, Victoria, 3053

Rights statement

© The Australian Association for Research in Education, Inc. 2020

Repository Status

  • Restricted

Socio-economic Objectives

Other environmental management not elsewhere classified