Strata 2 1 Forward Modeling to learn about
Strata 2. 1 Forward Modeling to learn about the controls of Tectonics, sedimentation and eustasy on stratigraphic geometry Strata 2. 1 is Open Source software was written by Flemings, Grotzinger, Morris and Nelson, 1996
Baltimore Canyon Trough • Movie produced by students Spinelli an Hotsinski • http: //hydro. geosc. psu. edu/Sed_html/movie 1. html Sea-level drops produces major regional unconformity
Mixed Carbonate-clastic systems Middle to Late Ordovician, Central Pennsylvania • The following movie was created by Roberta Hotsinski and Andrew Hoover: http: //hydro. geosc. psu. edu/Sed_html/movie 2. html
Low heat-flux rift basin • http: //hydro. geosc. psu. edu/Sed_html/movie 4. html Sediment traps heat faster than it can escape (thermal blanket effect)
High sediment-flux rift basin • http: //hydro. geosc. psu. edu/Sed_html/movie 5. html A thick thermal blanket traps heat in deeper parts of the basin
Near-forebulge stratigraphy • Prediction
Near-forebulge stratigraphy • Prediction
Near-forebulge stratigraphy • Prediction Erosion
Near-forebulge stratigraphy • Prediction
Near-forebulge stratigraphy • Strata 2. 1
Near-forebulge stratigraphy • Strata 2. 1 Erosion
Input parameters in Strata • • • Sediment types Compaction and composition Tectonic styles Sea-level changes Heat flow Output data in Strata (versus time) Depth-sections Time-sections Wheeler plots Seismic responses
Input parameters in Strata • • • Sediment types Compaction and composition Tectonic styles Sea-level changes Heat flow Output data in Strata (versus time) Depth-sections Time-sections Wheeler plots Seismic responses
Sediment Types Clastic sediments Continental diffusion rate Sediment flux pelagic Marine diffusion rate Sedimentation rates
q-volume sediment flux (m^2/s) k- diffusion constant Continental diffusion rate h-elevation x-horizontal distance Values can vary across the model and input in tabular form (x q 1; x 2 q 2; x 3 q 3 etc. ) Sedimentation rates
Sediment Types Carbonate sediments • Sedimentation rate types : simple exponential decay (“epeiric”) • Sedimentation rate types : constant and simple exponential decay below a certain depth (“oceanic”) Sedimentation rates
Input parameters in Strata • • • Sediment types Compaction and composition Tectonic styles Sea-level changes Heat flow Output data in Strata (versus time) Depth-sections Time-sections Wheeler plots Seismic responses
Compaction and Composition Porosity versus depth- exponential compaction relation Sand-shale ratios based on water-depth or diffusion constants
Input parameters in Strata • • • Sediment types Compaction behavior Tectonic styles Sea-level changes Heat flow Output data in Strata (versus time) Depth-sections Time-sections Wheeler plots Seismic responses
Tectonic styles of subsidence • Subsidence increases linearly left to right (‘foreland’) • Subsidence is constant (flat geometry/’cratonic’) • Subsidence increases linearly right to left (‘passive’) • Simple elastic flexure or local isostasy (Te=0)
Input parameters in Strata • • • Sediment types Compaction behavior Tectonic styles Sea-level changes Heat flow Output data in Strata (versus time) Depth-sections Time-sections Wheeler plots Seismic responses
Sea-level changes • As a file (all parameters can be entered as such) • As a sinusoid
Input parameters in Strata • • • Sediment types Compaction behavior Tectonic styles Sea-level changes Heat flow Output data in Strata (versus time) Depth-sections Time-sections Wheeler plots Seismic responses
Heat Flow • m. W/m^2 (e. g. , 60 for continents) • Thermal conductivity is calculated as a funciton of the sand, shale and fluid content which may be derived from the sedimentation diffusion constants and water depths • Thermal maturation indices can then be calculated • Heat flow is one-dimensional (“hot-to-cold --`downup”)
Input parameters in Strata • • • Sediment types Compaction behavior Tectonic styles Sea-level changes Heat flow Output data in Strata (versus time) Depth-sections Time-sections Wheeler plots Seismic responses
Input parameters in Strata • • • Sediment types Compaction behavior Tectonic styles Sea-level changes Heat flow Output data in Strata (versus time) Depth-sections Time-sections Wheeler plots Seismic responses
Wheeler Plot Erosion time sea-level drop distance
Input parameters in Strata • • • Sediment types Compaction behavior Tectonic styles Sea-level changes Heat flow Output data in Strata (versus time) Depth-sections Time-sections Wheeler plots Seismic responses
Seismic Responses • Seismic velocity is calculated using the ration of sand, shale and water • Density for sand, shale and fluid is user-input • Seismic sections are displayed
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