CHARACTERIZATION OF LATERALLY CONTIGUOUS PHYLLOSILICATE DEPOSITS IN WEST MARGARITIFER TERRA, MARS 3rd Planetary Data Workshop and Planetary Geologic Mappers Meeting June 12-15, 2017

K. D. Seelos, R. E. Maxwell, F. P. Seelos, D. L. Buczkowski, C. E. Viviano-Beck Regional Pedogenesis?

Mawrth Fig. 16, McKeown et al. 2009 MargaritiferRegional stratigraphiesBasin: : Fe/MgAl phyllosilicates phyllosilicates over with darkFe/Mg capping phyllosilicates material with dark capping material

Mawrth Fig. 9, Noe Dobrea et al, 2010

Margaritifer Basin Valles Marineris / Noachis From Fig. 14, Salvatore et al. 2016 Fig. 16, Le Deit et al. 2012 West Margaritifer . ShallowA complex Fe/Mg phyllosilicategeologic history: deposits: Remnants of ancient impacts  Widespread (Ladon)  Variety of  Noachian valley elevationsnetworks and  Exposedchannels at the  surface,Hesperian in fractureoutflow walls, bychannels impacts and chaos terrain  Spectrallyformation consistent 3 Types of Exposures

. Crater Walls & Ejecta . Chaos/Fracture Walls . Intercrater (Surface)

. Outcrops above identified in CRISM data (Certain and Less Certain) . Note: Outcrops are not found within chaos terrains, mountainous terrain (e.g., Ladon Montes) Intercrater & Crater Exposures

9 Datasets:  CRISM – Mapping (180 m/pix, multispectral map tiles) – Targeted (20 m/pix, hyperspectral MTRDRs)  THEMIS (100 m/pix, controlled mosaics) – Daytime IR – Qual. thermal inertia next  MOLA (460 m/pix) slide  HRSC (50-175 m/pix)  CTX (6 m/pix)  HiRISE – Red and color (≥ 25 cm/pix) PFM browse – DTMs and orthos Thin, low albedo overburden obscures CRISM and moderates thermal inertia signatures.

ESP_018662_1750_COLOR 200 m Intercrater Exposure

CTX light-toned morphology + THEMIS elevated thermal inertia allows units to be extended beyond/between CRISM observations.

PFM browse Crater & Escarpment Exposures

next Phyllosilicate slide layer likely exposed along all of these scarps…

PFM browse 200 m ESP_021853_1780_COLOR 9 ESP_021853_1780_COLOR 200 m Inferred MOLA topography, 100 m contours THEMIS qualitative TI over CTX Units . “Extended” and “Buried” units necessitate spatially coherent THEMIS TI and CRISM data anchors CRISM D2300 over CTX Phyllosilicate Units over CTX  Extended unit connects surficial exposures  Buried map unit connects impact- excavated exposures Continuum Removed CRISM Spectral Nontronite

Library Spectra

Characteristics Saponite 2.304 µm Reflectance Mg . Examined 138 CRISM Map- Projected Targeted Reduced Fe Data Records (MTRDRs)

. Light-toned layer is dominated by Mg-smectite (e.g., saponite)

. Little to no variability across region . Absorptions at 1.41, 1.92, Mg smectite . No discernable vertical 2.304, variation Fe smectite sometimes  No indication of Al- for Ratio (offset CRISM clarity) phyllosilicates CRISM Reference Spectra 2.39 µm (Viviano-Beck et al., 2014) Formation Mechanism(s) A multiple-process EXPECTED OBSERVATIONS: emplacement Fluviolacustrine: Burial/ Diagenesis: Pedogenesis: Hydrothermal: Minerals fall from suspension or Interaction of water table with Alteration due to rain Alteration of precursor scenario? precipitate directly in low energy buried precursor material results water percolation and material caused by aqueous settings. in zone of alteration. leaching of precursor heating of subsurface 1. Initial air fall deposition CHARACTERISTIC material. water. Alteration zone corresponds to Conforms to surface Topography/ Horizontal deposition in basins or 2. Reworked by water table depth – follows topography at time of Variable low areas adjacent to channels aeolian/aqueous elevation - topography X formation X processes, settles into Limited to extent of basin or Spatial distribution Extensive Extensive Localized to heat source local topographic lows flooded areasX* X Variable; thicker in basin center Layer thickness Little variation Little variation Variable 3a. Capped/preserved by or local lows ? ?+ ?+ X Depends on heat source subsequent volcanic May or may not be preserved in Fine to massive; planes are and precursor material; deposits precursor material; compaction Not preserved Bedding horizontal, subparallel may or may not be may produce layering X - 3b. Aqueously altered, either preserved through surficial or Deltas, distributary systems, Mineralized veins, concretions Dendritic channel Associated inlet/outlet channels, fluvial Volcanoes or volcanic groundwater interaction (may not be observed using systems may or may not channels, erosional scours or deposits, impact craters morphologies ?+ remote sensing)?+ be preserved?- 4. Exposed/eroded by channel bars, mudcracks X fluvial activity and chaos Unconformable; drapes pre- Gradational lower Stratigraphic Alteration zone could intersect Cross-cuts preexisting formation existing topography; may embay contact, sharp upper pre-existing stratigraphyX terrains X relationships high-standing areas contact Depends on precursor material Sequence of more- Higher-temp. smectites, Smectites, evaporates, sulfates, Mineralogy and water chemistry: hydrated altered (kaolinites) to kaolinites, hydrated carbonates silica, smectites, zeolites, illite, less-alteredX* (smectites) silica, jarositeX, prehnite, kaolinites, chlorite, prehnite with depth chlorite, serpentine Mineralogy With distance from basin center Diverse and variable with or within local lows (possible Regionally consistent Regionally consistent distance from heat variation “bath tub ring” effect)X source X *not a deal breaker Summary .. Ongoing/Last(?)WestConstrained Margaritifer to be stepshosts Noachian an - extensiveaged Measure layer layer of thickness Fe/Mg to smectite assessEmbays-bearing regional Early Noachian material trends  CompareSurfacialhighstanding, tochaos/fracture similarterrain nearby walls,  phyllosilicateimpactPartially-exhumed exposed units and  Large,probably– Valles contiguous reworkedMarineris walls/plainsoutcrops by at varietyNoachian– Northwest of elevations“overland” Noachis Terrachannels  FewCrosscut 10s of by meters reactivated thick, internalHesperian layering, outflow capped channels by dark,and chaos basaltic terrain material fractures  Regionally consistent spectral characteristics