Mass Transport Deposit and Turbidite Interaction in the Mio-Pliocene - PowerPoint PPT Presentation

Mass Transport Deposit and Turbidite Interaction in the Mio-Pliocene Fish Creek-Vallecito Basin, Salton Trough, California Jeremy Slaugenwhite RioMAR Annual Meeting The University of Texas at Austin November 21, 2014

Agenda  Problem Statement  Tectonic Setting and Stratigraphy – Salton Trough and the Fish Creek – Vallecito Basin – Miocene – Pliocene Stratigraphy  Mass Transport Deposits – Fish Creek – Vallecito Basin cross section  MTD / Turbidite Interactions  Findings and Next Steps

Problem Statement Mass transport deposits (MTD) are a significant component of modern and ancient deep-water depositional systems Geophysical data lack the resolution needed to identify meso-scale interactions between MTDs and the underlying and overlying sediment Few studies use outcrop as deep-water analogs; most use only geophysical data

Problem Statement Fish Creek – Vallecito Basin: An exposed section of rift basin sedimentary deposits containing earliest GoC infill Debris flows and turbidites provides an opportunity to examine the variability related to debris flow emplacement

Fish Creek – Vallecito Basin Location Anza-Borrego Desert State Park, Southern California

Tectonic Setting and Stratigraphy Gulf of California and the Salton Trough ~12-14 Ma  Middle Miocene extension ~6.3 Ma  Northern GoC subsidence and marine inundation ~5.3 Ma  Arrival of Colorado River  Separates Salton Trough in NW from the rest of the From Dorsey et al. 2007 Fish Creek – Vallecito Basin GoC

Tectonic Setting and Stratigraphy Fish Creek – Vallecito Basin  Rift basin in SW Salton Trough  Formed in the upper plate of the West Salton detachment fault From Dorsey et al. 2013

Tectonic Setting and Stratigraphy Fish Creek – Vallecito Basin  5.5-km-thick Mio-Pliocene sedimentary rocks  Strike-slip faulting (San Andreas, Elsinore, others) beginning ~1 Ma caused uplift and tilting Basement exposures: Vallecito Mtns. (west) Fish Creek Mtns. (east) From Dorsey et al. 2012

Tectonic Setting and Stratigraphy Fish Creek – Vallecito Stratigraphy  Stratigraphic section records – Opening of the basin – Flooding by the Gulf of California – Arrival of the Colorado River  Multiple times during the earliest filling of the basin unstable alluvial slopes and basin walls collapsed to form fast, far travelling debris flows  Mass transport deposits have been interpreted as both subaerial and subaqueous flows  Occur when marine water first appears in the basin (~6.3 to ~5.3 Ma) Abbott et al., 2002; Hsu, 1975

Tectonic Setting and Stratigraphy Nonmarine (fluvial, lacustrine, alluvial) Colorado River delta progradation Turbidites First appearance of Colorado River- Upper debris flow derived sediment Gypsum and turbidites Lower debris flow Alluvial fans Volcanics and bedload stream sandstones From Dorsey et al. 2011

Mass Transport Deposits Both MTDs described as sturzstroms  “A stream of very rapidly moving debris derived from the disintegration of a fallen rock mass of very large size” (Hsu, 1975)  Long run-out distances  Emplacement speeds often > 100 km/hr Volume is commonly in excess of 10 6 m 3   Characteristically result in a jigsaw-puzzle fabric and compositional domain segregation  Composition: – Granodiorite (lower MTD), granodiorite + metamorphic (upper MTD) Abbott et al., 2002; Hsu, 1975

Mass Transport Deposits Compositional zoning from laminar flow  Matrix composition (including finest fraction) reflects composition of adjacent clasts

Mass Transport Deposits Jigsaw-puzzle fabric

Cross Section Wind Caves turbidites (Pw) N Upper MTD from E/SE (Fish Creek Mtns.) Gypsum + Lycium turbidites (MPl) Lower MTD from W/NW (Vallecito Mtns.) Elephant Trees alluvial fans (Me) Red Rock sandstone (Mr) + Alverson volcanics (Ma) >20 Ma

MTD / Turbidite Interaction Lower debris flow  Subaerial  Sharp basal contact with underlying alluvial fan – Alluvial fan top deformed, or a previous landslide Lower MTD Alluvial fan

MTD / Turbidite Interaction Lower debris flow  Irregular top surface  5m + protruding boulders common

MTD / Turbidite Interaction Upper debris flow Erosive base  10 – 20+ m cutting into underlying turbidites common  Numerous examples of MTD lobes / tongues penetrating turbidites – Impacts lateral continuity of turbidites and causes deformation  Turbidite “rip-up” incorporation into base of MTD at all scales  Instances where erosion and incorporation of turbidites are minimal – Does not appear to correlate with MTD thickness Irregular / undulatory top  Pressure ridges formed during the flow  Control thickening and thinning of overlying turbidites  May have acted as channel conduits

MTD / Turbidite Interaction Upper debris flow  Upper MTD penetrates 10s of meters into underlying turbidites  Leading edge inserted between two turbidite beds Upper MTD ~ 4 m

MTD / Turbidite Interaction Upper debris flow  Upper MTD penetrates 10s of meters into underlying turbidites Split Mountain Upper MTD ~ 1000 ft. Lower MTD Alluvial fan

MTD / Turbidite Interaction Upper debris flow Upper MTD  10+ m zone of deformed and folded turbidites under upper MTD

MTD / Turbidite Interaction Upper debris flow  Upper MTD penetrates 10s of meters into underlying turbidites Upper MTD

MTD / Turbidite Interaction Upper debris flow  Turbidite incorporated into base of upper MTD 2 m

MTD / Turbidite Interaction Upper debris flow  20+ m of large-scale deformation and folding of underlying turbidites Upper MTD ~ 2 m

MTD / Turbidite Interaction Upper debris flow  Thick cap of fining-up sand is common  Clearly distinct from the Wind Caves member turbidites above the MTD Upper MTD

MTD / Turbidite Interaction Upper debris flow  Irregular top surface  5m + protruding boulders common

MTD / Turbidite Interaction Upper debris flow  Irregular top surface  Turbidite channelization ~ 10 m Upper MTD 1 m

MTD / Turbidite Interaction Upper debris flow  Overlying turbidites thicken and thin over irregular top surface of upper MTD Upper MTD 1 m

MTD / Turbidite Interaction Lower debris flow  10+ m of channelized turbidites overlying lower MTD / lower landslide 2 m

MTD / Turbidite Interaction Upper debris flow Upper MTD 1 m  ~1 – 2 m edge of upper MTD  Minor deformation of underlying turbidites  Channelization of upper turbidites

MTD / Turbidite Interaction Upper debris flow 1 m Upper MTD  ~1 – 2 m edge of upper MTD  Minor deformation of underlying turbidites  Channelization of upper turbidites

MTD / Turbidite Interaction Upper debris flow 1 m  ~1 – 2 m edge of upper MTD  Minor deformation of underlying turbidites  Channelization of upper turbidites

MTD / Turbidite Interaction Seismic Moscardelli, Wood, and Mann (2006): Mass-transport complexes and associated processed in the offshore area of Trinidad and Venezuela  2 km x 30m basal scours  Large-magnitude lateral erosional edges  Side-wall failures  MTC can act as lateral and top seals Can Fish Creek – Vallecito Basin be used as an outcrop analog? From Moscardelli et al. (2006)

Findings and Next Steps  Debris flows and turbidites in the Fish Creek – Vallecito Basin – Outcrop examples of how MTDs can erode sediment below and influence deposition above – At a scale that may not be resolvable in seismic, yet may be significant  Not analogous to other deep-water systems in important ways – Deposited in a tectonically active rift basin – Debris flows were composed of igneous and metamorphic basement rock Would we expect to see the same types of MTD / turbidite interaction in deep-water systems where debris flows are comprised of sediment from shelf / slope failures?  How might they differ?  Can FCV be compared to other described debris flow – turbidite interactions, both from outcrop and geophysical data, and provide outcrop analogs to deep-water subsurface systems?

Thank you. Jeremy Slaugenwhite RioMAR Annual Meeting The University of Texas at Austin November 21, 2014