- Title
- Quaternary sequence stratigraphy of the Lower Hunter River Valley
- Creator
- Walker, Andrew Reid Robert
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 1999
- Description
- Masters Research - Master of Philosophy (MPhil)
- Description
- The Lower Hunter River Valley contains one of the most extensive Cainozoic sediment deposits on the south east Australian coast. Ten boreholes were continuously cored to a maximum of 89 mbsl; the deepest drilled on the coast. Over 450 m of continuous core was recovered. These holes extended 40km upstream from the coastline to the upper limit of estuarine sedimentation at Maitland. Analysis of the cores entailed splitting, photographing, detailed sedimentological description and subsampling. Amino acid racemisation, TL dating, uranium series and radiocarbon dating techniques were also employed. A further 280 locally drilled holes have supplemented the correlation and interpretation of valley sedimentation. Evidence from cores supports four episodes of transgressive deposition, each following a regressive erosional phase and sea-level lowstand. Tertiary sediments are fluvially dominated. Clay deposits at the base of the Williamtown hole, below 59 m, were presumed to be Pleistocene but are also dated Pliocene age. This concurs with the landward extrapolation of seismic data from the inner shelf that showed a Quaternary/Tertiary boundary at 59 metres below the surface at Williamtown. The Pleistocene provided two depositional episodes during highstands at Oxygen Isotope Stage 5e and 5a; the Inner Barrier was formed during Stage 5e, 120 000 to 140 000 yrBP. A second barrier, seaward, was formed at Stage 5a, approximately 83 000 yrBP, and is overlain by the Outer Barrier and Fullerton Cove today. Each subsequent highstand event led to infilling by estuarine lithofacies and the progradation of barriers. During the early Holocene lowstand, fluvial regressive incision occurred through estuarine and barrier deposits. As deposition and accumulation of the transgressive estuarine basin facies subsequently occurred, bay-head deltaic facies stepped backward into the valley. Distal deltaic facies overlie proximal deltaic facies at Duckenfield which mark the early Holocene transgression there at approximately 9000 yrBP. The majority of Hunter valley-fill has been deposited during transgressions, with rising sea-level, and at highstand. The incised valley-fill model at Dalrymple et al. [1994] provided a sequence stratigraphic framework to organise the depositional history in the valley. From the model organisation and correlated stratigraphy it can be seen that there are three broad packages infilling the valley. Deposition of estuarine sediments was greater than the model suggested due to the Holocene transgression and the accommodation space available. However, the valley-fill model appears to generally fit the observed sedimentary facies associations and is a useful framework for understanding the compound nature of the Hunter River valley-fill. A detailed knowledge of the internal geometry and facies within modern-incised-valleys is important to hydrocarbon exploration and exploitation in ancient equivalents. As a large proportion of the world's population live in coastal valley, a detailed knowledge of incised-valleys is also important for the assessment of other resources, urban planning, flood mitigation and the prediction of possible sea-level rise from global warming. The incised valley-fill model is a predictive tool that may be useful to describe other valley-fill sequences along the east Australian coast. This was a joint project between the University of Newcastle and the Department of Mineral Resources, NSW.
- Subject
- Lower Hunter River Valley; Cainozoic sediment deposits; quaternary sequence stratigraphy; core analysis; transgressive deposition
- Identifier
- http://hdl.handle.net/1959.13/1321433
- Identifier
- uon:24359
- Rights
- Copyright 1999 Andrew Reid Robert Walker
- Language
- eng
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