SLIDE 1
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
SLIDE 2 Agenda
- Problem Statement
- Tectonic Setting and Stratigraphy
– Salton Trough and the Fish Creek – Vallecito Basin – Miocene – Pliocene Stratigraphy
– Fish Creek – Vallecito Basin cross section
- MTD / Turbidite Interactions
- Findings and Next Steps
SLIDE 3
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
SLIDE 4 Problem Statement
Fish Creek – Vallecito Basin: An exposed section of rift basin sedimentary deposits containing earliest GoC infill Debris flows and turbidites provides an
- pportunity to examine the variability related
to debris flow emplacement
SLIDE 5
Fish Creek – Vallecito Basin Location
Anza-Borrego Desert State Park, Southern California
SLIDE 6 Tectonic Setting and Stratigraphy
Gulf of California and the Salton Trough ~12-14 Ma
~6.3 Ma
and marine inundation ~5.3 Ma
- Arrival of Colorado River
- Separates Salton Trough in
NW from the rest of the GoC
From Dorsey et al. 2007 Fish Creek – Vallecito Basin
SLIDE 7 Tectonic Setting and Stratigraphy
Fish Creek – Vallecito Basin
Trough
- Formed in the upper plate
- f the West Salton
detachment fault
From Dorsey et al. 2013
SLIDE 8 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
From Dorsey et al. 2012
Basement exposures: Vallecito Mtns. (west) Fish Creek Mtns. (east)
SLIDE 9 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
SLIDE 10 Tectonic Setting and Stratigraphy
From Dorsey et al. 2011
Volcanics and bedload stream sandstones Alluvial fans Gypsum and turbidites Upper debris flow
First appearance of Colorado River- derived sediment
Turbidites Colorado River delta progradation Nonmarine (fluvial, lacustrine, alluvial) Lower debris flow
SLIDE 11 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 106 m3
- Characteristically result in a jigsaw-puzzle fabric and compositional
domain segregation
– Granodiorite (lower MTD), granodiorite + metamorphic (upper MTD)
Abbott et al., 2002; Hsu, 1975
SLIDE 12 Mass Transport Deposits
Compositional zoning from laminar flow
- Matrix composition (including finest
fraction) reflects composition of adjacent clasts
SLIDE 13
Mass Transport Deposits
Jigsaw-puzzle fabric
SLIDE 14
Cross Section
N Wind Caves turbidites (Pw) 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
SLIDE 15 MTD / Turbidite Interaction
Lower debris flow
- Subaerial
- Sharp basal contact with
underlying alluvial fan
– Alluvial fan top deformed, or a previous landslide
Alluvial fan Lower MTD
SLIDE 16 MTD / Turbidite Interaction
Lower debris flow
- Irregular top surface
- 5m + protruding boulders common
SLIDE 17 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
SLIDE 18 MTD / Turbidite Interaction
Upper debris flow Upper MTD
~ 4 m
- Upper MTD penetrates 10s of
meters into underlying turbidites
- Leading edge inserted between
two turbidite beds
SLIDE 19 MTD / Turbidite Interaction
Upper debris flow Upper MTD Lower MTD Alluvial fan
- Upper MTD penetrates 10s of
meters into underlying turbidites
~ 1000 ft.
Split Mountain
SLIDE 20 MTD / Turbidite Interaction
Upper debris flow
- 10+ m zone of deformed and
folded turbidites under upper MTD Upper MTD
SLIDE 21 MTD / Turbidite Interaction
Upper debris flow Upper MTD
- Upper MTD penetrates 10s of
meters into underlying turbidites
SLIDE 22 MTD / Turbidite Interaction
Upper debris flow
2 m
- Turbidite incorporated into base of
upper MTD
SLIDE 23 MTD / Turbidite Interaction
Upper debris flow
- 20+ m of large-scale deformation
and folding of underlying turbidites Upper MTD
~ 2 m
SLIDE 24 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
SLIDE 25 MTD / Turbidite Interaction
Upper debris flow
- Irregular top surface
- 5m + protruding boulders common
SLIDE 26 MTD / Turbidite Interaction
Upper debris flow Upper MTD
- Irregular top surface
- Turbidite channelization
1 m ~ 10 m
SLIDE 27 MTD / Turbidite Interaction
Upper debris flow Upper MTD
- Overlying turbidites thicken and
thin over irregular top surface of upper MTD
1 m
SLIDE 28 MTD / Turbidite Interaction
Lower debris flow
2 m
- 10+ m of channelized turbidites
- verlying lower MTD / lower
landslide
SLIDE 29 MTD / Turbidite Interaction
Upper debris flow
- ~1 – 2 m edge of upper MTD
- Minor deformation of underlying
turbidites
- Channelization of upper turbidites
Upper MTD
1 m
SLIDE 30 MTD / Turbidite Interaction
Upper debris flow
- ~1 – 2 m edge of upper MTD
- Minor deformation of underlying
turbidites
- Channelization of upper turbidites
1 m
Upper MTD
SLIDE 31 MTD / Turbidite Interaction
Upper debris flow
- ~1 – 2 m edge of upper MTD
- Minor deformation of underlying
turbidites
- Channelization of upper turbidites
1 m
SLIDE 32 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
From Moscardelli et al. (2006)
Can Fish Creek – Vallecito Basin be used as an outcrop analog?
SLIDE 33 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
- utcrop and geophysical data, and provide outcrop analogs to deep-water subsurface
systems?
SLIDE 34
Thank you.
Jeremy Slaugenwhite RioMAR Annual Meeting The University of Texas at Austin November 21, 2014
