--> ABSTRACT: Aggregate Resources in Reef Environments: Three Examples from the South Pacific, by Bruce M. Richmond; #90097 (1990).

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ABSTRACT: Aggregate Resources in Reef Environments: Three Examples from the South Pacific

Bruce M. Richmond

Rapid growth in many South Pacific island countries has led to an increased demand for aggregate material used in the construction industry. Traditional aggregate sources include the beaches that encircle many of the islands. Continued mining of beaches has been partly responsible for severe coastal erosion. This paper summarizes the results of three CCOP/SOPAC investigations for aggregates from diverse island type/reef setting localities. The case studies include: (1) Upolu, in Western Samoa, is a high volcanic island surrounded by fringing reefs and shallow barrier reefs. Construction materials, consisting predominantly of mixed terrigenous and carbonate sand and gravel, are concentrated in drowned river valleys fronted by active reefs. The deposits were trapped in rive valleys during the Holocene rise and stabilization of sea level by barrier reef growth that prevented their off-shelf transport. The sediments become more carbonate-rich toward the surface due to an increase in the landward transport of reef material and rivermouth migration. (2) Tongatapu, in the Kingdom of Tonga, is a high limestone island surrounded by fringing reefs with a nearby broad reef platform and barrier reef complex. Extensive back-reef carbonate deposits occur throughout the reef platform. Widespread megaripple fields suggest that the distribution of the deposits are controlled by wave and tidal induced currents. (3) Funafuti, Tuvalu, is an atoll with characteristics similar to numerous other atolls in the central Pacific. It contains a deep (^sim60 m) central lagoon, a rim dotted by narrow islets, and a few deep passages. Aggregate, needed to fill on-land borrow pits created during World War II, can be found over large areas of the lagoon bed. The sediment is composed primarily of Halimeda remains and is the result of in situ lagoon production.

AAPG Search and Discovery Article #90097©1990 Fifth Circum-Pacific Energy and Mineral Resources Conference, Honolulu, Hawaii, July 29-August 3, 1990