Print this pageQuaternary Stratigraphy of the Lower Hunter River Valley, NSW, Australia
WALKER, ANDREW, RON BOYD, and PETER ROY
The Hunter Valley contains one of the most extensive deposits of Quaternary sediments on the south east Australian coast. The basis of our new stratigraphic interpretation here is a cross-section of 10 boreholes extending upstream from the coastline 40 km to the upper limit of estuarine sedimentation at Maitland. These boreholes were continuously cored up to 87 mbsl from the surface to bedrock and over 450 m of continuous core has been recovered. Analysis of these cores has consisted of splitting, photographing, detailed sedimentological description, sampling for microfauna, palynology, and dating using TL, amino acid racemisation, uranium series and radiocarbon techniques.
The stratigraphy of the Quaternary Hunter Valley indicates a compound fill over at least three sea level cycles and a range of depositional environments including marine, estuarine and fluvial. Based on correlations with nearby marine seismic data, the lowermost 35 percent of the Hunter Valley fill is interpreted to be Tertiary (possibly Miocene-Pliocene) in age, and mostly terrestrial in nature. The remaining sediments fit a valley-fill model of regressive and transgressive sedimentation under oscillating sea levels. During sea level fall and at lowstand, fluvial processes excavated most of the preceding valley-fill and deposited a basal fluvial channel] gravel and sand facies. During at least two episodes of transgressive deposition, bay head delta and estuarine central basin muds accumulated, followed by a regressive phase of bay head delta infilling the central basin at sea-level highstand. At each interglacial highstand event the seaward end of the valley accumulated coastal strand plain and barrier sands, including extensive flood tidal deltas The youngest cycle of valley-fill is Holocene in age and the one or more older cycles are at least late Pleistocene in age.