Prepared for the National Aeronautics and Space Administration Geologic Map of MTM –30247, –35247, and –40247 Quadrangles, Reull Vallis Region of Mars By Scott C. Mest and David A. Crown Pamphlet to accompany Scientific Investigations Map 3245 65° 65° MC-01 MC-05 MC-07 30° MC-06 30° MC-12 MC-15 MC-13 MC-14 0° 45° 90° 135° 180° 0° 0° MC-21 MC-22 MC-20 MC-23 SIM 3245 -30° MC-28 -30° MC-27 MC-29 MC-30 -65° -65° 2014 U.S. Department of the Interior U.S. Geological Survey Contents Introduction.....................................................................................................................................................1 Physiographic Setting ...................................................................................................................................1 Data .............................................................................................................................................................2 Contact Types .................................................................................................................................................2 Fluvial Features ..............................................................................................................................................2 Waikato Vallis ........................................................................................................................................3 Eridania Planitia ....................................................................................................................................4 Reull Vallis ..............................................................................................................................................4 Channels .................................................................................................................................................5 Gullies ....................................................................................................................................................5 Structural Features ........................................................................................................................................5 Crater Counting Methodology .....................................................................................................................6 Stratigraphy ....................................................................................................................................................6 Highland Materials ...............................................................................................................................6 Plains Materials ....................................................................................................................................6 Vallis Materials ......................................................................................................................................9 Surficial Deposits .........................................................................................................................................11 Crater Materials ..................................................................................................................................12 Geologic History ...........................................................................................................................................14 Acknowledgments .......................................................................................................................................15 References Cited..........................................................................................................................................15 Tables 1. Crater size-frequency data and time-stratigraphic determinations for Reull Vallis region of Mars .............................................................................................................................19 2. Contact relations of geologic units in Reull Vallis region of Mars .....................................20 i Introduction 1986; Tanaka and others, 1988, 1992; Schubert and others, 1992). Within the circum-Hellas region, erosion of highland Mars Transverse Mercator (MTM) –30247, –35247, and materials began during the Late Noachian Epoch and continued –40247 quadrangles cover a portion of southern Hesperia throughout the Hesperian Period, resulting in deposition of Planum and the highlands of eastern Promethei Terra, east extensive plains materials in and around the Hellas basin. of the Hellas basin (fig. 1). The map area (lat 27.5–42.5° S., Regionally, the units of the Hellas basin and its surrounding long 110–115° E.) consists of cratered ancient highland rim are grouped into the Hellas assemblage and range from the materials of moderate relief, isolated knobs and massifs of ancient basin-rim unit, consisting of rugged highland plateaus rugged mountainous materials, extensive tracts of plains, and and massifs dissected by channels and valley networks, to surficial deposits. Waikato and Reull Valles extend through younger plains units, some of which contain channels, ridges, plains and highland terrains. Regional slopes are generally to scarps, and mesas (for example, Greeley and Guest, 1987; the southwest toward the Hellas basin (fig. 1), but local slopes Crown and others, 1992; Tanaka and Leonard, 1995; Mest and (for example, highlands to plains) dominate the landscape. Crown, 2001; Tanaka and others, 2002). The Martian highlands cover more than 60 percent of Highland volcanism began north and northwest of the the planet’s surface and are primarily found in the southern map area in the Late Noachian/Early Hesperian Epochs with hemisphere (Tanaka and others, 1992). Most of the highlands the formation of Tyrrhenus and Hadriacus Paterae (Crown and consist of rugged, densely cratered terrains believed to others, 1992; Tanaka and Leonard, 1995; Crown and Greeley, represent the final phase of heavy bombardment in the inner 1993, 2007; Gregg and others, 1998), initially by explosive solar system ~4.0 billion years ago (Murray and others, 1971; eruptions (Greeley and Spudis, 1981; Greeley and Crown, 1990; Schubert and others, 1992; Tanaka and others, 1992). Parts of Crown and Greeley, 1993), and ending with effusive activity the Martian highlands show evidence of extensive degradation during the middle to Late Hesperian/Early Amazonian (Crown and modification. The map area exhibits landforms created and others, 1992; Mest and Crown, 2001). The ridged plains of by numerous geologic processes, including tectonism, fluvial Hesperia Planum (Tanaka, 1986; Greeley and Guest, 1987), the activity, and mass wasting. The occurrence of features that may basal referent for the Hesperian System, is one of many areally have been formed or modified by water, such as the eastern extensive plains-forming units found on the surface of Mars Hellas valles and valley networks, has significant implications (Scott and Tanaka, 1986; Greeley and Guest, 1987) believed to for past Martian conditions. Determining the geology of have been emplaced as flood lavas (Potter, 1976; King, 1978; the highlands east of the Hellas basin provides a better Greeley and Spudis, 1981; Scott and Tanaka, 1986; Greeley understanding of the role and timing of volatile-driven activity and Guest, 1987). However, despite the abundance of high- in the evolution of the highlands. resolution images from recent missions (MOC, THEMIS, CTX, Geologic mapping at 1:1,000,000 scale from analysis of and HiRISE), definitive evidence for the presence of volcanic images—including Mars Observer (MO) Thermal Emission features (edifices, flow fronts, rilles) has not been observed, Imaging System (THEMIS) daytime infrared (IR) and visible and thus a volcanic origin of these plains is uncertain (Mest and (VIS), Mars Reconnaissance Orbiter (MRO) High Resolution Crown, 2001; Crown and others, 2005, 2007; Gregg and Crown, Imaging Science Experiment (HiRISE) and Context Camera 2005, 2007). (CTX), Mars Global Surveyor (MGS) Mars Orbiter Camera The abundance of channels and valley networks in the (MOC), and Viking Orbiter (VO) images—and MGS Mars eastern Hellas region, along with the presence of several canyon Orbiter Laser Altimeter (MOLA) topographic data complements systems, suggest water played a major role in modifying this previous local and regional geologic mapping and geomorphic part of the Martian landscape. Well-developed valley networks studies of Reull Vallis (Mest and Crown, 2001, 2002, 2003) appear to be the oldest fluvial features in the area; they are and the other eastern Hellas valles (Crown and others, 1992; found in rugged ancient highland terrains and are most likely Price, 1998), drainage networks (Mest and Crown, 2001, 2004; Noachian to Hesperian in age (Crown and Mest, 1997; Mest Ivanov and others, 2005; Mest and others, 2010), and highland and Crown, 2001, 2002, 2003). The presence of widespread debris aprons (Pierce and Crown, 2003). Crater size-frequency plains units northeast of the Hellas basin provides evidence that distributions have been compiled to constrain the relative ages extensive degradation and resurfacing occurred in the highlands. of geologic units and determine the timing and extents of the Subsequent erosion of these plains units is believed to have observed geologic processes. occurred in the Late Hesperian/Early Amazonian Epochs (Greeley and Guest, 1987). Activity along the highland valles (Waikato, Reull, Dao, Niger, and Harmakhis)