Transcript Slide 1
HISTORY OF THE SNAKE RIVER PLAIN HOTSPOT PALYNOLOGY •Environmental Sequence •Global Climate Change •Tectonism •Sierran Rain Shadow •Local Uplift/Subsidence VOLCANOLOGY •SRP History •Plume – Crust Interactions •Hotspot Dynamics HISTORY OF THE SNAKE RIVER PLAIN HOTSPOT PALYNOLOGY •Environmental Sequence •Global Climate Change •Tectonism •Sierran Rain Shadow •Local Uplift/Subsidence Dated Tephra Dated Flows Uplift/Subsidence VOLCANOLOGY •SRP History •Plume – Crust Interactions •Hotspot Dynamics HISTORY OF THE SNAKE RIVER PLAIN HOTSPOT PALYNOLOGY Dated Tephra Dated Flows Uplift/Subsidence •Environmental Sequence •Global Climate Change •Tectonism •Sierran Rain Shadow •Local Uplift/Subsidence VOLCANOLOGY •SRP History •Plume – Crust Interactions •Hotspot Dynamics Paleoelevation Interbed Ages Correlation Strong influence of elevation on vegetation & palynology Climatic changes (glacial/interglacial) subtle Marked late-Neogene evolution of vegetation Climate = global + tectonic 4200 ft Trends: late Miocene – early Pleistocene (means of dating and correlating flows) 0.7 m.a. 5 m.a. 10 m.a. Composite of Bruneau and MHAB-1 cores 4000 ft Tentative Chronology (based on correlation) Pliocene Pleisto Terteling Spr 5-6 m.a. Mio Dated Lava Volcanic Tephra Chronology for palynology, Before Lake Idaho ~8 Ma ~11 Ma Interbedded Sediments: east of Lake Idaho younger than Lake Idaho 4 Ma 6.25 Ma Interbedded Sediments: cores & wells INEL (thanks to Linda Davis) Deerflat, Simplot, etc. 1.12 & 3.16 km 8.2 Ma Tentative Sequence Preliminary Palynological Results • Tentative vegetation-climate sequence – Potential value of long cores – Apparent ages consistent with HOTSPOT • Paleoelevation: large changes – INEL-1 ~km • Interbedded sediments provide: – Wider coverage (not just Lake Idaho) – Tephra & flow dates for Palynology sequence Horseshoe Bend Additional INEL, Hagerman Fossil Beds and Simplot Well samples Age: Nothing in “Lk Idaho” older than mid-Miocene? Elevation: big changes & high elev. flora very different Sand Spr. 0.095 Ma Snake River Plain Cross-section Homedale - Boise Surface elevation of Lake Idaho sensu lato Bruneau Fm. Miocene Riparian Vegetation