Geoheritage significance of the Holocene Yanrey Delta, Pilbara Coast, Western Australia

Semeniuk V1,2,4 & Brocx M3,5

1V & C Semeniuk Research Group, Warwick, Australia, 2School of Arts & Sciences, Notre Dame University, Fremantle, Australia, 3Environmental and Conservation Sciences, Murdoch University, Perth, Australia

From a geoheritage perspective, the Holocene Yanrey Delta of the southern Pilbara Coast, Western Australia is a unique arid-zone delta of international significance.  It provides a deltaic model unlike any established deltaic forms documented elsewhere globally. The delta in the discharge zone of the Yanrey River is located on the eastern shore of a semi-protected large embayment (Exmouth Gulf) in an arid climate. With limited rainfall in the hinterland, the Yanrey River floods episodically and, over the Holocene, has built a triangular deltaic plain.  In its east to west orientation (normal to the coast) the river traverses a linear red-sand dune field of northerly-oriented dune.  As such, instead of building a classic wave-, tide-, or fluvially-dominated delta form, the Yanrey Delta has geomorphically and sedimentologically interacted with the dune field developing a complex of arid-zone dunes interspersed with deltaic deposits, the latter composed of sand and mud. In its migration and switching of channels from north to south over the Holocene, the delta in combination with regional winds has transformed the originally coarsely-spaced northerly-oriented linear dunes to more finely-spaced northerly-oriented linear dunes.  While there is a sand-and-mud component to the deltaic deposits on the delta plain, the inter-dune swales also are being filled with floodplain red mud to form scattered (isolated) mud lenses.  As such the deltaic sequences is a mixture of deltaic sediments sensu stricto, deltaic sediments admixed with reworked red sand dune sediments, and patches of reworked red sand dune sediments.  At its seaward edge, the Yanrey Delta is tidal, and the deltaic sediments are tidal flat in character but, in addition, they also interfinger with and overlie pre-existing earlier tidal flat deposits.  The Yanrey Delta adds an extra delta form to the existing suite of delta types.


Biography

Margaret Brocx is a multi-disciplinary Earth scientist and natural-history scientist with experience ranging from general and geomicrobiology, to coastal zone processes and products, to wetlands and estuaries, to large-scale geology, to geoheritage and geoconservation. She is both the WA State Convener and National Convener for Heritage for the Geological Society of Australia. In Australia, her research interests include pursuing National inventory-based geoconservation, via Science and Education. Margaret has a long and productive history in geoconservation, environmental management and community liaison and, in this context, she has successfully secured a number of important geosites and regions for geoconservation and for National listing. Internationally, Margaret is the Oceania Representative for the IUCN WCPA Geoheritage Specialist Group, the Oceania Representative for the International Association for the Promotion of Geoethics, and is on the Editorial Board of the International Journal Geoheritage. In terms of publications, Margaret has published over 30 geoheritage papers in peer-reviewed international and national journals. Academically, Margaret obtained her Honours and PhD, in the Discipline of geoheritage, from Murdoch University, where she holds the position of Adjunct Associate Professor. Margaret is a founding member in 1999 of the Wetlands Research Association. Inc., and 2019 Geoheritage Australasia

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