Transcript PowerPoint Presentation - Geology of the Thaumasia region

Geology of the Thaumasia
region, Mars: plateau
development, valley origins,
and magmatic evolution
by James M. Dohm, Kenneth L. Tanaka
Geologic features
of the Thaumasia region
HIGHLANDS AND INNER PLATEAU
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Scattered massifs and
volcanoes
Mountain belts
Numerous large impact
craters
Successions of lava-flow
fields
Systems of rifts, narrow
grabens, wrinkle ridges,
and folds and thrusts
EROSION OF THE OUTER MARGIN
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Extensive valley
networks
Canyons
Troughs
Tilted, eroded rock
layers forming cuestas
Geologic Setting
Geologic Setting
Stratigraphy
Stratigraphy
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Relative ages are based on a time-stratigraphic scale from Tanka
(1986) which reflects material ages and stratigraphic relations
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This indicates 5 main stages of geologic activity (oldest to youngest)
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Stage
Stage
Stage
Stage
Stage
1:
2:
3:
4:
5:
Noachian
Late Noachian to Early Hesperian
Early Hesperian
Late Hesperian to Early Amazonian
Amazonian
Stage 1:
Noachian
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The more rugged units formed during this stage
Complex modification due to cratering, tectonic
deformation, erosional processes, and volcanic and
sedimentary burial has degraded or destroyed older
craters (making it difficult to determine onset)
Stage 2:
Late Noachian to Early Hesperian
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Some materials have been heavily modified by
folding or faulting and/or valley development during
this stage
Rock materials from stage 1 & 2 cover more than
half of the Thaumasia region
Stage 3:
Early Hesperian
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Extensive rigid plains volcanism in Sinai Planum and
Corprates East (CE)
as well as local valley formation in southern
Thaumasia Plateau
Stage 3 & 4:
Hesperian to Early Amazonian
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Extensive lava sheets were erupted from crest and
flanks of Syria Planum and Tharsis Montes (in NW)
40% rock from these stages
Stage 5:
Amazonian
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relatively small outcrops of volcanic materials and
colluvial and eolian deposits
= 3% of outcrop from region
Tectonic History
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The analysis of Thaumasia’s faults and grabens, rift systems and
wrinkle ridges indicate tectonic activity began and reached it’s peak
during Noachian (stage 1) and declined during the Hesperian and
Amazonian periods (stages 2-5)
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Additionally, intense extensional and contractional deformation appears
to have largely resulted from:
1. Tharsis- and Syria-centered volcanotectonic activity (1-5)
2. uplift and associated rifting of that plateau, including local centers
of volcanotectonic activity (mainly 1 and 2)
3. formation and tectonic relaxation of the Argyre impact basin (1 and
2)
4. Other. Tectonic deformation of region, such as compression due to
rapid planetary cooling
Volcanic History
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The Thaumasia region preserves some of the best examples of
early highland volcanoes and intermediate-age plateau lavas on
Mars
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Many of the prominent, isolated mountains that occur along or
near faults and commonly exhibit summit depression and highly
dissected flanks have been interpreted as ancient volcanoes
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complex geomorphologies may indicate interbedded lava and
pyroclastic deposits
Volcanic History
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Mapped 14 volcanoes - using stratigraphic relations as well as
morphology
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Formed throughout the Noachian and into Early Hesperian
 STAGE 1 - 11 volcanoes
 STAGE 2 - 3 volcanoes, and widespread volcanism continued to
resurface local areas throughout the map area
 STAGE 3 & 4 - Sheet lavas erupted from the crest and flanks of of
Syria Planum and Arsia Mons (outside the study) and cover several
provinces
 STAGE 5 - Continued Tharsis volcanic activity resulted in lava flows
through the Daedalia Planum province
Erosional History
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they mapped and dated > 4000 branching and single valleys
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branching or networked valleys strongly indicate water- or ice-based erosion
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single, nonbranching valleys may also form by eolian, tectonic, and/or
volcanic processes
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Valleys tend to concentrate in areas of volcano flanks and near rift systems
of the central part of the Thaumasia Highlands province and southern part
of the Coprates province
 STAGE 1 - valleys are obscure and discontinuous, probably due to later
resurfacing
 STAGE 1 & 2 - overall valley formation was most extensive
 STAGE 3 & 4 - valleys tend to be more pristine and mostly occur in the
map region
 STAGE 5 - no stage 5 valleys occur on this map
Further Studies
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The Thaumasia region is a major, complex
volcanotectonic province of Tharsis for which
comprehensive reconstruction of geologic history has
been lacking
This is an interpretive geologic history of the
Thaumasia region based on geologic mapping and
topical analysis
This detailed geologic study provides a basis to
address tectonic, magmatic, and resurfacing issues in
greater depth