Sea Level and Reefs in Hawaii Reefs 300
- Slides: 28
Sea Level and Reefs in Hawaii
Reefs
300 N and 300 S, shallow sunlight seas
Reef Types • Barrier Reefs • Fringing Reefs • Atolls • Patch Reefs
Reef Evolution
Methods • • Drilling Ecosystem surveys Dating (C 14 & U-series) Carbonate petrography
Holocene reef and dune Leahi reef and dune Waimanalo reef and dune Waianae reef None recognized ? Kaena Stand ? Carbonate System of Oahu
Rotary cores Ecosystem surveys
Ecosystem surveys
Wireline Drilling the Island Shelf
Large, bottom shearing swell events govern the geologic record
High energy ~2 -10 m Pocillopora meandrina stout branching Shallow, high energy ~0 -10 m Montipora sp. Moderate energy ~2 -8 m Porites lobata massive Shallow, high energy ~0 -5 m Porolithon sp. Low energy ~5 -20 m Porites compressa branching High energy ~0 -2 m Porites lobata encrusting
High bed shear LONO HARBOR HALE O LONO SITE: -High wave exposure -Sparse coral cover -Shore parallel ridge and runnel morphology HIKAUHI SITE -Medium wave exposure -Abundant coral cover -Shore normal spur and groove morphology
Modern Ecosystem Investigations: Results Study Sites Modified from Storlazzi et al. (in press)
Modern Ecosystem Investigations: Results Modified from Storlazzi et al. (in press)
Typical facies Encrusting coral-algal bindstone Mixed skeletal rubble High energy Massive Unconsolidated Branching coral floatstone coral framestone Moderate energy Low energy
Typical facies Rudstone Bindstone Grainstone Framestone Wackestone
Bindstone (algal pavement) Angular silt to pebble clasts (coral and algal) encrusted and bound by coralline algae, encrusting foraminifers and bryozoans; Extensive micritization of skeletal grains; Microcrystalline Mg-Calcite fills inter- and intraparticle pores
Framestone (reef framework) Intraskeletal pores lined by aragonitic accicular cement; Pores filled by peloidal Mgcalcite grading out to siltsized skeletal debris; Thick crusts of coralline algae, encrusting foraminifers (Homotrema, Planorbulina? ), bryozoans and serpulids