402-pp25 - UNIVERSITY OF SOUTH ALABAMA GY 402: Sedimentary...

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Unformatted text preview: UNIVERSITY OF SOUTH ALABAMA GY 402: Sedimentary Petrology Lecture 25: Sea Level Change and Sedimentation, A trip to New Zealand Last Time Reefs Types of reefs Reef facies/characteristics Reef growth Coral Reefs Reefs are biochemical sedimentary rocks consisting of corals and other calcite and aragonite-secreting organisms Coral Reefs Reefs are a type of sedimentary environment and as such, are characterized by distinct facies Basic Reef Facies James, N.P., 1984. Reefs. In R.G. Walker, (ed) Facies Models (2nd ed). Geoscience Canada Reprint Series 1., 317p 1., Coral Reefs But as "biologically-produce facies", expect to see bioinfluences on facies character (e.g., coral morphology zonation) James, N.P., 1984. Reefs. In R.G. Walker, (ed) Facies Models (2nd ed). Geoscience Canada Reprint Series 1., 317p 1., Coral Reefs Past studies suggest that reefs go through 4 stages of growth linked to sea level change: James, N.P., 1984. Reefs. In R.G. Walker, (ed) Facies Models (2nd ed). Geoscience Canada Reprint Series 1., 317p 1., Temperate vs Tropical Carbonate Shelves http://www.pal.uni-erlangen.de/uploads/pics/cwcabb3.jpg http://www.pal.uni- Today's Agenda Sea level Change Tectonic setting/stratigraphy of New Zealand Sedimentology of Hawkes Bay Sea level influence on shelf deposition Sea level influence on temperate carbonate diagenesis Location/ Setting Study Area "Tangoio Block" Block" Location/ Setting Study Area "Tangoio Block" Block" http://joangg154.files.wordpress.com/2007/10/maori-warrior.jpg Location/ Setting Study Area "Tangoio Block" Block" http://hawaiiantrading.com/herb-kane/image-pg/war-canoes-new-zealand.jpg Location/ Setting Study Area "Tangoio Block" Block" Location/ Setting Location/Setting Overriding Plate Accretionary Borderland Trench/Subducting Plate (Lewis, 1980) Study area (Stephens, 1985) Stratigraphy Stratigraphy 5 The stratigraphy is characterized by 5 cyclothems. Cyclothems: a package of sedimentary rocks deposited over a sea level cycle (low high- low) 4 3 2 1 150 m 5 4 3 150 m Sedimentology Three types of sedimentary rock occur in the study site 1) Mudstone (`papa') 2) Siliciclastic sandstone +/- conglomerate 3) bioclastic limestone (variable silic. sand content) Sedimentology Three types of sedimentary rock occur in the study site 1) Mudstone (`papa') 2) Siliciclastic sandstone +/- conglomerate 3) bioclastic limestone (variable silic. sand content) In addition, there are 5 distinct lithofacies assemblages Non-marine (3 component facies) Estuarine (3 component facies) Siliciclastic shoreline (6 component facies) Carbonate shelf (4 component facies) Offshore (4 component facies) Mudstone (papa) 5m Mudstone (papa) Siliciclastic Sandstone 50 m Siliciclastic Sandstone 5 cm 5 cm Temperate Shelf Limestone 50 m 50 cm Temperate Shelf Limestone 2m 10 cm Limestone Petrography 2 mm 8 mm "carbonate sandstone" both thin sections in PPL coquina Sea level & Deposition Lithofacies assemblages (and component facies) stack up to provide a record of PlioPleistocene sea level change Sea level & Deposition Sea level & Deposition HST Lower Stratigraphy HST RST Upper Stratigraphy Sea level & Diagenesis 0.5 mm PPL Paleohydrology & Diagenesis Paragenesis Upcoming Stuff Homework 1) Skeletal/Temperate thin section lab due Today 2) ML introduction/methodology Tomorrow Lab this Week Skeletal/Temperate Limestones Next Lecture: Carbonate diagenesis part 1 (not PowerPoint) ...
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