Stratigraphic Relationships in Northeast
Syrtis Major, Mars: Approximately 250
Million Years of Geological History Spanning
the Noachian–Hesperian Boundary
Mike Bramble and Jack Mustard
Brown University
LPSC 2016 – Abstract No. 2582
Outstanding questions of the Nili Fossae region
How was the regional olivine-rich unit emplaced?
e.g. Basaltic lava flows? Impact melt?
How were the carbonate minerals formed?
e.g. Hydrothermal alteration? Contact alteration?
Stratigraphy offers important clues
Units are well-exposed in Northeast Syrtis Major
local stratigraphic relationships
highest spatial resolution
constrain outstanding questions
Bramble and Mustard – Abstract 2582 – @mbramble
Stratigraphic Relationships in Northeast Syrtis Major, Mars
Stratigraphy of Northeast Syrtis Major
~3.7 Ga
Syrtis Major Volcanics
YOUNGER →
(3.7–3.8 Ga, Hiesinger & Head, 2004)
(3.5–3.7 Ga, Ivanov et al., 2012)
[Ehlmann et al., 2008;
2009; 2010; 2011;
Ehlmann and Mustard,
2012; Mangold et al.,
2007; Mustard et al.,
2007; 2008; 2009]
Olivine-rich unit
Isidis-forming impact
(3.96 Ga, Werner, 2005)
Bramble and Mustard – Abstract 2582 – @mbramble
Stratigraphic Relationships in Northeast Syrtis Major, Mars
Context
Bramble and Mustard – Abstract 2582 – @mbramble
Stratigraphic Relationships in Northeast Syrtis Major, Mars
3 Ring Structures 1100, 1900 km (Schultz and Frey, 1990) 1500 km (Frey et al., 2000)
Mapping area in black
Bramble and Mustard – Abstract 2582 – @mbramble
Stratigraphic Relationships in Northeast Syrtis Major, Mars
Bramble and Mustard – Abstract 2582 – @mbramble
Stratigraphic Relationships in Northeast Syrtis Major, Mars
Results
Bramble and Mustard – Abstract 2582 – @mbramble
Stratigraphic Relationships in Northeast Syrtis Major, Mars
Paired
Morphology
and Mineralogy
Complexity and diversity unifiable under 5 distinct geomorphic units.
Bramble and Mustard – Abstract 2582 – @mbramble
Stratigraphic Relationships in Northeast Syrtis Major, Mars
Olivine-Rich Unit
“Fractured Unit”
Bramble and Mustard – Abstract 2582 – @mbramble
Stratigraphic Relationships in Northeast Syrtis Major, Mars
Olivine-Rich Unit Map Blue (Ody et al., 2012)
Largest olivine-rich OMEGAHesperian
& Younger Terrains Masked in White
geologic unit on Mars
Emplacement
Mechanism?
[Reyes and Christensen, 1994; Hoefen et
al., 2003; Hamilton et al., 2003; Hamilton
& Christensen, 2005; Mustard et al.,
1997; 2007; 2009; Tornabene et al., 2008;
Poulet et al., 2009; Ody et al., 2013]
NE Syrtis Major
Bramble and Mustard – Abstract 2582 – @mbramble
Stratigraphic Relationships in Northeast Syrtis Major, Mars
Bramble and Mustard – Abstract 2582 – @mbramble
Stratigraphic Relationships in Northeast Syrtis Major, Mars
a'
a
Vertically
Exaggerated
Bramble and Mustard – Abstract 2582 – @mbramble
Stratigraphic Relationships in Northeast Syrtis Major, Mars
Observations:
Sharp angles
Conforms to troughs
Evidence for pooling
Bramble and Mustard – Abstract 2582 – @mbramble
Stratigraphic Relationships in Northeast Syrtis Major, Mars
Observations:
Various orientations
Bramble and Mustard – Abstract 2582 – @mbramble
Stratigraphic Relationships in Northeast Syrtis Major, Mars
Observations olivine-rich unit emplacement
mechanism must explain:
• Draping texture on both local and regional scales
• Large linear features both conforming to troughs and
forming sharp angles at 60, 90, and 120 degrees.
• Sharp contacts below with low-Ca pyroxene/smectite
basement and above with Capping Unit.
• Coarse grain size. Modelled at > 1 mm (Mark Salvatore)
• Corroborates deep and broad ~1 µm olivine bands.
Bramble and Mustard – Abstract 2582 – @mbramble
Stratigraphic Relationships in Northeast Syrtis Major, Mars
Olivine-Rich Unit Emplacement Hypotheses
Hypotheses to be reconciled with
observations:
• Intrusive complex or basaltic
volcanic flows pre-dating the
Isidis impact
• Picritic lava flows emplaced
subsequent to the Isidis basin
• Impact melt produced from the
formation of the Isidis basin
• Other Hypotheses? Komatiites?
Mobile Erosion Product?
Bramble and Mustard – Abstract 2582 – @mbramble
Stratigraphic Relationships in Northeast Syrtis Major, Mars
Olivine-Rich Unit Emplacement Hypotheses
Hypotheses reconciled with
observations: in NE Syrtis Major
• Extrusive complex? or basaltic
volcanic flows pre-dating the
Isidis impact varying stress field?
• Picritic lava flows emplaced
subsequent to the Isidis basin
• Impact melt produced from the
formation of the Isidis basin
• Other Hypotheses? Komatiites?
Mobile Erosion Product?
Bramble and Mustard – Abstract 2582 – @mbramble
Stratigraphic Relationships in Northeast Syrtis Major, Mars
Carbonate Formation
Bramble and Mustard – Abstract 2582 – @mbramble
Stratigraphic Relationships in Northeast Syrtis Major, Mars
Carbonate-bearing Units
Bramble & Mustard, 2016
Formation Mechanism?
Testable Hypotheses
[Ehlmann et al., 2008; Ehlmann et al., 2009;
Brown et al., 2010; Ehlmann and Mustard,
2012; Viviano et al., 2013; Mustard et al., 2014]
Viviano et al., 2013
Bramble and Mustard – Abstract 2582 – @mbramble
Stratigraphic Relationships in Northeast Syrtis Major, Mars
Targeting contact between olivine-rich unit and basement
Olivine-rich Unit
CRISM Spectra
Basement
No 2.5 µm
No carbonate
Bramble and Mustard – Abstract 2582 – @mbramble
Stratigraphic Relationships in Northeast Syrtis Major, Mars
Observations formation mechanism must explain:
• Olivine-rich unit overlying a
Fe/Mg smectite basement
• Carbonate only observed
within the olivine-rich unit
• Not as a distinct stratum
Capping
Unit
Olivine-rich unit
AND carbonate
Phyllosilicatebearing basement:
Fe/Mg smectite
Bramble and Mustard – Abstract 2582 – @mbramble
Stratigraphic Relationships in Northeast Syrtis Major, Mars
Carbonate Formation in Northeast Syrtis
Major
Hypotheses to be reconciled with observations:
• In situ hydrothermal alteration or percolation of
groundwater through the olivine-rich host rock.
• Contact hydrothermal alteration on the contact between
a hot olivine-rich unit and phyllosilicate-rich basement.
• Surface weathering in a manner akin to carbonates on
Antarctic meteorites
• Tuesday Night – Poster #324 Abstract #2553 – Come Chat!
• Precipitation from shallow lakes
Bramble and Mustard – Abstract 2582 – @mbramble
Stratigraphic Relationships in Northeast Syrtis Major, Mars
Carbonate Formation in Northeast Syrtis
Major
Hypotheses reconciled with observations:
• In situ hydrothermal alteration or percolation of
groundwater through the olivine-rich host rock.
• Contact hydrothermal alteration on the contact between
a hot olivine-rich unit and phyllosilicate-rich basement.
• Surface weathering in a manner akin to carbonates on
Antarctic meteorites
• Tuesday Night – Poster #324 Abstract #2553 – Come Chat!
• Precipitation from shallow lakes
Bramble and Mustard – Abstract 2582 – @mbramble
Stratigraphic Relationships in Northeast Syrtis Major, Mars
Conclusions – Northeast Syrtis Major
—Stratigraphy spans the Noachian-Hesperian boundary (~250 Myr).
Great small-scale morphological heterogeneity, but unifiable under five
distinct geomorphic units.
In Northeast Syrtis Major:
—Olivine-rich unit was emplaced as an impact melt sheet or via
extrusive volcanism shortly after the impact.
—Observations support the in situ formation of carbonate via
hydrothermal alteration, or as a surface-weathering product.
NE Syrtis from the rim of
Jezero, CTX mosaic DEM, 3x VE
Bramble and Mustard – Abstract 2582 – @mbramble
Stratigraphic Relationships in Northeast Syrtis Major, Mars