HOLOCENE REEF DEVELOPMENT WHERE WAVE ENERGY REDUCES ACCOMMODATON SPACE,

ABSTRACT: Analyses of 32 drill cores obtained from the windward reef of Kailua Bay, Oahu, Hawaii, indicate that high wave energy signifi-cantly reduced accommodation space for reef development in the Ho-locene and produced variable architecture because of the combined influence of sea-level history and wave exposure over a complex an-tecedent topography. A paleostream valley within the late Pleistocene insular limestone shelf provided accommodation space for more than 11 m of vertical accretion since sea level flooded the bay 8000 yr BP. Virtually no net accretion (, 1 m) took place on surrounding Pleis-tocene substrates shallower than 10 m. Holocene reef accretion oc-curred in three stages: (1) an early stage of catch-up framestone de-velopment in water depths of 11–17 m, (2) an intermediate stage char-acterized by either no accretion or by the pile-up of fore-reef-derived rubble (rudstone) and sparse bindstone, and (3) a final stage of catch-up bindstone accretion in depths. 6 m. Coral framestone accreted at rates of 2.5–6.0 mm/yr in water depths. 11 m during the early Ho-locene; it abruptly terminated at; 4500 yr BP because of wave scour as sea level stabilized. More than 4 m of rudstone derived from the upper fore reef accreted at depths of 6 to 13 m below sea level between 4000 and 1500 yr BP coincident with late Holocene relative sea-level fall. Variations in the thickness, composition, and age of these reef facies across spatial scales of 10–1000 m within Kailua Bay illustrate the importance of antecedent topography and wave-related stress in reducing accommodation space for reef development set by sea level. Although accommodation space of 6 to 17 m has existed through most of the Holocene, the Kailua reef has been unable to catch up to sea level because of persistent high wave stress