Slide 1Deltas and Desert lakesMississippi DeltaNile DeltaSequencesDelta cross-sectionSlide 7Natural Gamma Ray: increases and the amount of K-U-Th –bearing minerals decreasesResistivity: Decreases with the presence of free ions and ion-rich interstitial fluidsGamma Ray-Resistivity Bell plotsSlide 11Slide 12Slide 13Atchafalaya Basin-Crevasse SplayTurbiditesTurbidites- ODP 195 Mariana West Phillipine SeaTurbiditeSubmarine Fan EnvironmentChapter 8: Stratigraphic PatternsThis presentation contains illustrations from Allen and Allen (2005)Deltas and Desert lakesMississippi Deltahttp://earth.rice.edu/mtpe/bio/biosphere/hot/humanimpacts/delta.htmlNile Deltahttp://www.artsci.wustl.edu/~anthro/courses/306/Nile%20Delta.jpgSequences•Prograding delta slope: upward thickening and coarsening decrease gamma•Meandering stream: upward fining-increase gamma•Turbidite: upward fining- increase in gamma•Desert Lake: fine- low gammaDelta cross-sectionhttp://strata.geol.sc.edu/exerices/seismic/10MelangeOfDownSlopeFans&Slumps.jpghttp://fosi.iagi.or.id/mahakam/mah-facies-des.htmMahakam Delta, IndonesiaNatural Gamma Ray: increases and the amount of K-U-Th –bearing minerals decreases http://www.ldeo.columbia.edu/BRG/ODP/ODP/LEG_SUMM/174A/fig7.htmlResistivity: Decreases with the presence of free ions and ion-rich interstitial fluidshttp://www.dot.ca.gov/hq/esc/geotech/gg/resistivity_log.htm“A resistive, feldspar sand between 27.5 and 30 meters.C High gamma counts are due to the presence of small amounts of radioactive K in the feldspar grains of the sand.C This signature is common in these arkosic sands, and they are often referred to as ‘hot sands’ “Gamma Ray-Resistivity Bell plotsMore claysandier“clay”“sand”Gamma Ray-Resistivity Bell plotsMore claysandier“clay”“sand”Gamma Ray-Resistivity Bell plotsGamma Ray-Resistivity Bell plotshttp://www-odp.tamu.edu/publications/197_IR/chap_01/images/01_f16.jpg (Hawaiian-Emperor Seamount Trend)Atchafalaya Basin-Crevasse SplayTurbiditesresistivitygammaTurbidites- ODP 195 Mariana West Phillipine Seahttp://www-odp.tamu.edu/publications/195_IR/chap_01/images/01_f22.gifTurbiditehttp://cg.ensmp.fr/Chenaux/home_turmy.htmlMovie:http://learningobjects.wesleyan.edu/turbiditycurrents/Submarine Fan