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The Holocene Record of Climatic, Eustatic and Tectonic Events Along the Coastal Zone of Western Australia—A Review
Journal of Coastal Research
Special Issue No. 17. HOLOCENE CYCLES: CLIMATE, SEA LEVELS, AND SEDIMENTATION (1995), pp. 247-259
Published by: Coastal Education & Research Foundation, Inc.
Stable URL: http://www.jstor.org/stable/25735651
Page Count: 13
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Western Australia contains a vast reservoir of geomorphic and stratigraphic information along a quite diverse coast, that varies in geomorphology, tectonics, climate, and oceanography. Models derived from there reflect a wide range of possible settings. Since it fronts the Indian and Southern Oceans, changes in oceanic climate may be transmitted to the coast via wave spectra, storminess, frequency of cyclones, and rainfall. As such the Western Australian coast provides an excellent natural laboratory for the study of Holocene climate and the relationship of eustatic and tectonic effects. The areas that best record Holocene climate, eustasy and tectonism, are those with large sedimentary records such as coastal plains, tidal flats and beach/dune plains, involving geomorphic, stratigraphic, palynological, faunal, and isotopic features. In this context, the arid Pilbara Coast may contain a wealth of information, since there is much geomorphic/stratigraphic variability and thick accumulations of sediments. Similarly, the Rockingham-Becher cuspate foreland, the largest and best preserved in Western Australia, potentially stores information on Holocene climate that could be related to cycles of rainfall, storminess, erosion, and beachridge/dune accretion. To date, the archival material in coastal Western Australia, in terms of its Holocene climate record, remains largely unexplored. Fifteen coastal sites have been studied in Western Australia, some of which have provided information on Holocene climate, eustasy and tectonism. All recent studies involving sealevel history concluded that there was no evidence for mid-late Holocene eustatic oscillations but that tectonism was a major factor in sealevel history. Studies on climate history show aridity during the mid Holocene for southwestern Australia but with no consensus on its exact timing and the periods of juxtaposed relative humidity. Calcrete, used to reconstruct Holocene climate, shows two features: the migration of climate boundaries northwards in the late Holocene, and a migration rate of c. 10 km/century. The direction of migration of increasing wetness agrees with the sense of climate change elsewhere in Western Australia. Beachridges within the Rockingham-Becher cuspate foreland provide insight into climatic cycles. Three types of patterns are evident (1) regularly spaced low ridges, (2) higher-than-normal ridges, regularly interspersed with the low ridges, and (3) a complex erosion/accretion pattern at the tips of the foreland. When combined with radiocarbon dates, two cycles emerge from the geomorphic patterns, a 50-year and a c. 250-year cycle. The limited information from coastal Western Australia suggests four cycles of climate that have, or could have influenced the geomorphic and stratigraphic record. Those four cycles are as follows: (1) that related to the Polar Axis Precession to explain the shifting of climatic regions over the past 7000 years; (2) a c. 250-year cycle that builds higher-than-normal beachridges; (3) a c. 50-year cycle that builds low beachridges, which could be related to the "Double Hale" 45-year cycle; and (4) a 19–20-year periodicity (= 18.6-year lunar nodal periodicity) that may be reflected in cycles of beach erosion.
Journal of Coastal Research © 1995 Coastal Education & Research Foundation, Inc.