Stratigraphic reconstruction of the Strzelecki Group outcrops in west Gippsland: new data on the present-day thickness and amount of erosion

ABSTRACT

The Lower Cretaceous Strzelecki Group forms the basement to the eastern part of the Gippsland Basin, but is exposed in the west and forms spectacular outcrops, especially along the coastal area between San Remo and Inverloch. The coastal area is highly faulted and lacks stratigraphic markers so matching sections in different fault blocks based only on lithology has not been possible. A combination of mapping, detailed logging, vitrinite reflectance measurements and palynology were used to determine the present-day thickness of the coastal sections and the amount of erosion that occurred during the Late Cretaceous. A total thickness of about 1500 m is inferred between Harmers Haven and Inverloch but because of the amount of faulting and probable repeated sections, the true thickness of Strzelecki Group exposed in the coastal outcrops is only about 300 m. Based on palynology and vitrinite reflectance results, the reconstructed Strzelecki Group stratigraphy has been subdivided into three distinct ‘bio-blocks’, with an eroded section estimated to range from 1.5 km (0.3–2.6 km at ±95% confidence limits) to 2.7 km (2.2–3.1 km at ±95% confidence limits).

KEYWORDS:

• Gippsland Basin
• Wonthaggi
• Lower Cretaceous
• Strzelecki Group
• vitrinite reflectance
• palynology
• stratigraphic reconstruction

Acknowledgements

The authors wish to thank the School of Earth, Atmosphere and Environment, Monash University and Geological Survey of Victoria for their financial support. We are also grateful to Dr Paddy Ranasinghe for VR measurements and acknowledge the support of Kevin and Kathy Hill, and our school research students, especially, Jim Driscoll, Syed Amir Mahmud, Daniel Thompson and Crystal Lee. Some of the figures used in this publication have also been used by Aghaei et al. (2014).

Disclosure statement

No potential conflict of interest was reported by the authors.