Olistostromes

Olistostromes
William D. O’Brien O Brien
GEY 251
http://www.vdf.ethz.ch/service/Erde/Data/Gesteinskreislauf/Transport/Transport_Schwer_debrisflow.htm

�� Olistostromes
�� Definition
�� Classification
�� Examples
�� Causes
Discussion
�� Olistostromes vs. Mèlanges langes
�� Definition of mèlanges langes
�� Classification of mèlanges langes
�� Conclusion

Olistostromes
�� Sub-aqueous
Sub aqueous “slide slide layers”, layers , Debris-flow Debris flow deposit
�� Lens like layer with no true bedding (chaotic,
mélange) ange)
�� Heterogeneous material (blocks and mud)
�� Caused by slumping or gravity sliding of
unconsolidated sediments (allochthonous
( allochthonous)
�� Deposited within normal bedding sequences on
the continental slope
�� Term coined by Flores (1955)
Neuendorf, Neuendorf,
K.K.E., et. al., 2005

Olistostromes
�� Two types… types with or with out blocks defined by
Elter and Raggi (1965)
�� Exotic Blocks are “a a mass of rock occurring in
a lithologic association foreign to that in which
the mass formed.” formed. eg. eg.
Slump Blocks. (Neuendorf Neuendorf, , 2005)
�� Allolistostromes – Containing exotic blocks
(Neuendorf Neuendorf, , 2005)
�� Endolistostromes – Without exotic blocks (Neuendorf
2005)
�� These blocks are called Olistoliths
Neuendorf, ,

Examples of Olistostromes
� Duncan Canal-Zarembo Island Area
� Dunnage mèlange Formation in North-
Centraal Newfoundland
� Eastern Coast of New Zealand
� Great Valley Group in the California
Coastal Range
� Any present day passive or active margin

Duncan Canal-Zarembo Island Area, Southeastern Alaska
Olistoliths
http://geopubs.wr.usgs.gov/open-file/of99
http://geopubs.wr.usgs.gov/open file/of99-168/of99 168/of99-168 168-pamphlet.html
pamphlet.html

Slide layers and slumps
�� Slide layers are layers of sediment that
were deposited due to sediment slides,
slumps or debris-flows.
debris flows.
�� Sediment slides are described as “slope slope
failures in which the sediment was
deformed and fluidized during its
transport downslope, downslope,
resulting in highly
deformed layering and ultimately a slurry,
or debris flow” flow (Jacobi, 1984)

Sub-marine Sub marine Debris-flows
Debris flows
�� Water saturated sediment that has a
consistency similar to quicksand
�� Resulting deposit is a jumbled mass of
sediment
�� Caused by slope failure, rapid deposition,
tectonic activity, dewatering of sediment,
methane release from underlying
material (?)
�� Similar to terrestrial mudflows and
avalanches
Neuendorf, Neuendorf,
2005, Prothero, Prothero,
1990

Prothero and Schwab, 2004
Slope failures
Slope failure -
�� debris-flow, debris flow, slumping,
sliding :(olistostromes
:( olistostromes)
�� turbidity current:
(turbidites turbidites)

Mélanges langes
“A A body of rock mappable at a scale of
1:24,000 or smaller, characterized by a
lack of internal continuity of contacts or
strata and by the inclusion of fragments
and blocks of all sizes, both exotic and
native, embedded in a fragmental matrix
of finer-grained finer grained material” material (Raymond,
1984)

Classification of Mélanges
M langes
Classification of Melanges as proposed by
Raymond (1984)

Olistostromes vs. Tectonic
Potter and Pettijohn, 1977
Mèlanges langes

Conclusion
�� Olistostromes – mèlanges langes of sedimentary
origin with or without blocks of
allochthonous material
�� Caused by slumping and debris-flow debris flow
�� Mèlanges langes – chaotic sequence of material
�� Classification of mèlanges langes
�� Olistostromes vs. tectonic derived
mèlanges langes

Refrences
Elter, Elter,
P., and Raggi, Raggi,
G., 1965, Contributo alla conoscenza dell’Appennino
dell Appennino ligure: ligure:
Considerazioni sul problema degli olistostromi:
olistostromi:
Bollettino della Societa Geologica
Italiana, Italiana,
v. 84, p. 303-322. 303 322.
Flores, G., 1955, Discussion: Proceedings of the 4 th World Petroleum Conference,
Sec. I/A/2, p. 121-122. 121 122.
Jacobi, R.D., 1984, Modern submarine sediment slides, in Raymond, L. A., ed.,
Mèlanges langes: : Their nature, origin, and significance: Geological Society of America
Special Paper 198, p. 81-102. 81 102.
Neuendorf, Neuendorf,
K.K.E., et al., 2005, Glossary of Geology 5 th ed., American Geological
Institute, Alexandria, Virginia.
Prothero, Prothero,
D.R., 1990, Interpreting the Stratigraphic Record, W. H. Freeman &
Company, New York.

Prothero, Prothero,
D.R., Schwab, F., 2004, Sedimentary geology: an introduction to to
sedimentary
rocks and stratigraphy, stratigraphy,
2 nd ed., W. H. Freeman & Company, New York.
Potter, P.E., Pettijohn, Pettijohn,
F.J., 1977, Paleocurrents and Basin Analysis, 2 nd ed. Springer- Springer
Verlag, Verlag,
Berlin ,Heidelberg, New York.
Raymond, L.A., 1984, Classification of mélanges, m langes, in Raymond, L. A., ed., Mélanges: M langes:
Their nature, origin, and significance: Geological Society of America America
Special Paper
198, p. 7-20 7 20