| Tinian and Aguijan, Commonwealth of the Northern Mariana Islands (CNMI), are volcanic, back arc islands in the western Pacific formed by Pacific Plate subduction under the Philippine Plate. The islands are composed of Eocene volcanic cores mantled by Plio-Pleistocene carbonate facies and raised Holocene beach and reef deposits. The entire sequence has been tectonically uplifted and contains high-angle normal faults, while isostatic subsidence and scarp failures overprint tectonic brittle failure features.; A cave and karst inventory on Tinian and Aguijan surveyed 114 features and is believed to adequately represent the megaporosity (cave) development. Two distinct cave classes were identified: mixing zone caves (flank margin caves and banana holes) and fissure caves. Most mixing zone caves were located in or near scarps and coastlines, often at similar elevations to nearby caves. Fissure caves were located in regions of brittle failure, forming linear features with narrow widths. (Abstract shortened by UMI.)... |
