Unraveling the tilting history of the submerged reefs surrounding Oahu and the Maui-Nui Complex, Hawaii

• Published in: Geochemistry, geophysics, geosystems : G3 geophysics, geosystems : G3, 2010-07, Vol.11 (7), p.np-n/a
• Main Authors: Faichney, Iain D. E., Webster, Jody M., Clague, David A., Paduan, Jennifer B., Fullagar, Paul D.
• Format: Article
• Language: English
• Subjects: Bathymetry; Camber; Coral reefs; Flexing; Hawaii; hot spot; Hot spots; lithsopheric flexure; Mathematical models; Maui-Nui Complex; Oceanography; Plate tectonics; submerged coral reefs; Subsidence; Terraces; Tilt; Uncertainty; Volcanoes
• ISSN: 1525-2027; 1525-2027
• DOI: 10.1029/2010GC003044

There is considerable uncertainty concerning the history of lithospheric flexure of Oahu and the Maui‐Nui Complex associated with the Hawaiian hot spot. Previous reconstructions based on models and sparse observational data place the zone of maximum uplift (forebulge) either under Oahu or between Oahu and Molokai. To address this issue we have compiled and analyzed all existing and new high‐resolution multibeam bathymetry, dive observations, and chronologic data from submerged terraces in the region. We have identified 89 separate submarine terraces and mapped their distribution across the volcanic flanks of Oahu and the Maui‐Nui Complex. These data are used to systematically measure the direction and amplitude of terrace tilting within the Maui‐Nui Complex and to provide new constraints on lithospheric flexure associated with volcanic loading at the hot spot. The terraces are divided into six separate geographic regions (Oahu, Molokai, Penguin Bank, Lanai, Maui, and East Maui) defined by significant discontinuities in either terrace morphology or depth. Following the sequential development of new substrate as the new volcanoes formed throughout the development of the MNC, 18 new and 51 published 87Sr/86Sr isotopic ages show that the terraces in these regions were also initiated at different times, and the tilting data show that they also responded to lithospheric flexure independently. The general pattern of terrace tilting records the plate's response to lithospheric flexure with each region continually tilting toward the zone of maximum subsidence since their formation. Our individual tilt calculations are based on the most complete and highest‐resolution bathymetric data available, and they show that plate response to volcanic loading is a gradual process. Finally, we demonstrate that the shallowest terraces we identified in the Oahu and Molokai regions tilt toward the north, away from the current zone of maximum subsidence, indicating that these regions have recently passed the zone of maximum uplift. We compare our results with two separate published numerical models and differentiate between these, resolving a long‐standing uncertainty in the position of the forebulge.