The 1:1,000,000-Scale Geology of Western Libya Montes and Northwestern Tyrrhena Terra Alexandra Huff and James Skinner, Jr. Astrogeology Science Center U. S. Geological Survey Planetary Geologic Mappers Meeting 2017 Quadrangle Location • 6 MTM quads covering the highland lowland transition from Tyrrhena Terra to Isidis Planitia • Improved understanding of this area will provide insight into the evolution of ancient Martian highlands Previous Mapping • USGS maps • 1:20M Global Map (Tanaka et al., 2014) • 1:15M Eastern Region of Mars (Greeley and Guest, 1987) • 1:5M Syrtis Major Quadrangle (Meyer and Grolier, 1977) • 1:5M Iapygia Quadrangle (Schaber, 1977) • Topic-based Maps • Crumpler and Tanaka, 2003 (blue) • Jaumann et al., 2010 (red) • Bishop et al., 2013 (purple) Regional geology questions: How many massif units are there? How many channelization periods were there? What is the history of the intermediate cratered plains? PGM2017 Abstract #7112 Our Map Purpose: We are filling this scale-based gap in understanding by assembling a 1:1M scale geologic map to bridge existing global and local schemata. • Methodology • 1:250,000 mapping scale • THEMIS Daytime IR base map • Supplemented with MOLA, CTX, and THEMIS Nighttime IR data sets Unit Mapping: Grouping • 4 Unit Groups • Impact crater units (blue) • Older massif group (brown) • Intermediate-aged terra group (tan) • Younger plains group (green) Unit Mapping: Impact Crater Units Crater Unit 1/ Crater Units Smooth Crater Infill Crater Unit 2 Crater Unit 3 Differentiated c2 c3 c1 cs Unit Mapping: Massif Units Massif 1 Massif 2 m1 m2 Unit Mapping: Terra Units Terra 1 Terra 2 Terra 3 t1 t3 t2 Unit Mapping: Plains Units Plains 1 Plains 2 Plains 3 p2 p3 p1 Unit Mapping: Plains Units Rough Plains Etched Plains pe pr Unit Relationships: Massif and Terra Oenotria Plana Oenotria Scopuli Unit Relationships: Massif and Terra m2 t1 t1 m2 Unit Relationships: Syrtis Major embaying Libya Montes Libya Montes Syrtis Major Planum Unit Relationships: Syrtis Major embaying Libya Montes Unit Relationships: Syrtis Major embaying Libya Montes p3 p3 Unit Relationships: Etched Plains pe pe p2 pe p2 Unit Relationships: Etched Plains Unit Relationships: Etched Plains Geologic Sequence Up-thrown massifs that are then eroded and subsequently embayed. • Highlands formation • Isidis impact • Erosion and dissection of terra units • Dissection of Libya Montes • Embayment of plains 3 Final Steps Goal: Submit for review by end of July • Clarify problem areas • Integrate contact and linear feature unit boundaries • Compile model crater-dating • Finalize unit correlations • Complete map text • Clean and compile GIS geodatabase Questions?.