Sedimentology of the Modern and Holocene Burdekin River Delta of North Queensland, Australia—Controlled by River Output, not by Waves and Tides
Christopher R. Fielding, Jonathon Trueman, Jan Alexander, 2005. "Sedimentology of the Modern and Holocene Burdekin River Delta of North Queensland, Australia—Controlled by River Output, not by Waves and Tides", River Deltas–Concepts, Models, and Examples, Liviu Giosan, Janok P. Bhattacharya
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The Burdekin River Delta of northeastern Australia has been described previously as a type example of a wave-dominated delta, or as a “mixed-energy” delta. A reexamination of the geomorphology, sedimentology, and Quaternary stratigraphy herein leads, however, to the conclusion that the Holocene delta has been constructed primarily by flood-related processes. The surface of the upper delta plain is composed dominantly of sand and gravelly sand deposited in channel, paleochannel, and floodplain environments. The lower delta plain, by contrast, comprises a lithologically more diverse array of sands, muds, and chemical and organic sediments deposited in a variety of coastal environments. The lower-delta-plain channel and paleochannel sands are similar in texture to their upper-delta-plain counterparts, whereas deposits of smaller tidal creeks are finer-grained, in many cases muddy sands. Beaches, beach ridges, and spits are composed of well sorted, medium-grained sand, and eolian dune facies are somewhat finer-grained but equally well-sorted sands. Three varieties of coastal flats are recognized (mangrove, salt, and other types), the sediments of which are dominated by mud, typically rich in organic debris, and in some cases microbial mats, with minor sand laminae. Mouth bars are well developed at the present river mouth and throughout the lower delta plain. These bodies are composed of medium to very coarse-grained sand, texturally similar to channel sands, though slightly finer-grained. The narrow delta front comprises a sandy-mouth-bar zone passing distally into a mud-dominated clinoform set extending to -10 m (and only 10 km wide in total). Sharp-based coarse sand bodies of interpreted
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River Deltas–Concepts, Models, and Examples
Deltas are amongst the most environmentally and economically important coastal sedimentary environments. Studies of deltas lag behind research in both fluvial and deep-water depositional systems, as well as more geomorphologically oriented land studies. This knowledge lag reflects both a reorientation of the petroleum industry in the last two decades toward deep-water systems, as well as the difficulty of working across the shoreline with the traditional tools used for oceanographic or land-based work. However, deltaic studies are experiencing a renewed focus, because of their global importance in environmental and other societal concerns. This volume stems from a special session: Deltas: Old and New, held at the Annual Geological Society of America conference in October 2002, that was convened to highlight these new directions in deltaic research.