British Honduras Cays and the Low Wooded Island Problem

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THE TERM 'low wooded island', applied to all types of reef islands by early navigators,1 was redefined byJ. A. Steers in I9292 to refer to islands with distinctive characteristics situated in the steamer channel between the Queensland coast and the inner reefs of the Great Barrier system. Located on small patch reefs, they consist (Fig. I) of a simple sand cay on the leeward side, a complex of shingle ridges on the windward side, and, between them, a shallow 'pseudolagoon'3 or sand flat,4 partly covered by mangrove and almost drying at low water. Steers recognized the homology of a number of islands in similar situations, and described a generalized low wooded island;5 M. A. Spender mapped two of them, Low Isles and Three Isles, at a scale of I : 5ooo, and these were described in detail by the Great Barrier Reef Expedition ecologists;6 and the type was accepted in text-books7 as a distinctive variety of reef-island on the basis of its occurrence in a limited sector of the Australian Barrier Reef. Steers later mapped fifteen more low wooded islands,8 and proposed Bewick and Enn Islands as type-examples.9 Spender,10 concerned with the island foundations, termed the same features 'island reefs'. R. W. Fairbridge and C. Teichertll compromised with 'low wooded island-reef', but the original term is well established and is used here. The Queensland type-examples are found between 16° 23' S. (Low Isles) and I2° S. (Chapman Island), mostly within ten miles of the mainland coast, from fifteen to twentyfive miles from the outer reefs of the Great Barrier system. The linear outer reefs generally lack cays altogether, but immediately lagoonward is a series of large, undefined and mostly unmapped 'inner reefs' with simple sand cays. Between these inner reefs and the coast, in ten to twenty fathoms of water, are the knolls or patches on which the low wooded islands have formed. The reef flat or upper surface of the Low Isles patch lies from three to twentyseven inches below mean sea-level; the extreme tidal range reaches nearly eleven feet.12 At Low Isles the south-east Trades blow from March to December, and similar conditions obtain throughout the low wooded island area. At Low Isles and others of the Queensland low wooded islands, the windward shingle rampart system is complex, with an inner cemented rampart and a newer, outer, uncemented rampart. Much controversy has arisen over the origin and significance of these multi-rampart systems: Spender13 believed that rampart accumulation is a cyclic process, initiated on high standing reef flats, whereas Steers,14 having studied emerged platforms on the mainland coast, regarded the formation of successive ramparts as resulting from spasmodic eustatic emergence of the reef flats. Fairbridge and Teichert15 later not only found evidence of an even older rampart within the inner rampart at Low Isles, but described a new outer rampart, formed