Fueten, Frank

Gwinner, Klaus

Hauber, Ernst

HRSC, Co-Investigator Team

MacKinnon, Paula

Neukum, Gerhard

Scholten, Frank

Stesky, Robert

Zegers, Tanja

Institute of Transport Research:Publications

LAYERING ATTITUDES IN SOUTHWESTERN CANDOR CHASMA FROM HRSC IMAGE DATA AND 1 2 2 3 3 3STEREO-DERIVED DTM  R. Stesky , F. Fueten , P. MacKinnon , E. Hauber ,  K. Gwinner , F. Scholten , T.E. 4 5 1 Zegers , G. Neukum  and the HRSC Co-Investigator Team, Pangaea Scientific, Brockville, Ontario, Canada  2(rstesky@pangaeasci.com),  Department of Earth Sciences, Brock University, St. Catharines, Ontario, Canada,3 4 Institute of Planetary Research, German Aerospace Center (DLR), Berlin, Germany,  Faculty of Geosciences, Utrecht 5University, Netherlands,  Remote Sensing of the Earth and Planets, Freie Universität, Berlin, GermanyIntroduction: Layered deposits occur widely mound, the dips show marked changes in direction and within the chasmata of Valles Marineris, but  their origin angle within relatively short distances, yet nearby layers and mechanism of formation are uncertain [1, 2]. They give very similar attitudes. The topographic surface may form distinct mounds or may be more widely shows little apparent variation to account for the dip distributed, and often show signs of post-depositional changes.modifica tion , large ly by wind eros ion.  Recent The resistant cap rock on the mound shows the same geochemical soundings by the OMEGA instrument on unconformable relation with the underlying strata as Mars Express [3] indicate the presence of sulfates in observed previously and gives a consistent westward some of the deposits. dip of about 8°.Less is known about their internal geometry and New to this work is the measurement of fine layers in structural setting, properties that may give clues to their the deep part of the chasma in the northeastern part of formation process. Recent high resolution imagery and the image area. The layers are subhorizontal, similar to stereo-derived digital terrain models (DTMs) from the the attitudes found for deep layers in nearby Ceti Mensa High Resolution Stereo Camera (HRSC) experiment on [10] and in Hebes [8] and Ophir [9] chasmata.the Mars Express orbiter can provide this information, Discussion: As we concluded earlier [6], the pattern by allowing the attitudes of observed layering to be of dip angles and directions is most likely the result of calculated at various locations throughout the image. the stra ta draping over  an irregular basement  Geological Setting: This study focused on the topography. The basement likely consists of fault blocks deposits in southwestern Candor Chasma where they that formed during the initial opening of the chasma and are associated with a linear ridge that lies parallel to the then were rotated and downdropped with continued chasma wall. Mapping by Lucchitta [4] defined a opening and collapse of the chasma. The fact that the number of units of Hesperian or Amazonian age, based linear ridge in this area is parallel to the chasma wall on their morphology and surface appearance, including suggests that this interpretation is reasonable. In a mottled, layered and resistant. Prominent in the area is a number of places, outcrops of more resistant units, mound of strongly layered material, unconformably visually similar to wallrock, appear surrounded by capped by a resistant dark unit situated on the west side younger layered strata, suggesting that they are of the mound. The surface of many of the units show basement blocks that were never buried or have winnowing erosional structures and fields of dark subsequently been exhumed by erosion. The regions dunes, attesting to strong and persistent wind erosion. showing marked dip variations unaccounted for by Data and Methodology: The multispectral image topography, may contain buried basement blocks that lie and DTM were calculated from HRSC data collected just below the present surface, close enough to have during orbit 2116. The image has a spatial resolution of affected the deposition attitudes of the overlying strata.12.5 m and the DTM, 50 m, significantly higher than Our draping model, if correct, suggests that was used in our previous work in this area [5, 6]. Fig. 1 deposition must have occurred under low energy shows an oblique 3-dimensional view of part of the conditions. High energy situations such as fluvial or region, including the mound and distant chasma wall. subglacial deposition are unlikely. Subaerial or deep Pangaea Scientific's software ORION was used to water conditions are more likely, suggesting either sample the image and calculate the layering attitudes. pyroclastic ash fall or the presence of a deep ocean (in The method was described in detail by Fueten et al. [7]. this case, at least 6 km deep). We tend to favor the Briefly, points are chosen along the observed layering former, as proposed by Hynek et al. [11].contact deemed to be planar, while Orion computes the References: [1] Nedell S.S. et al. (1987) Icarus 70, best-fit plane to the 3-dimensional points using 409-441, [2] Lucchitta, B.K. (2000) LPSC XXXI #1139, multilinear regression. The repeatability of orientation [3] Gendren A. et al. (2005) Science, 307, 1587-1591 [4] measurements of nearby layers suggests that the results Lucchitta, B.K. (1999) U.S. Geol. Survey Map I-2568 are reasonably reliable and accurate. [5] Fueten F. et al. (2005) LPSC XXXVI #1498 [6] Measurements and Results: The layer dips are Fueten F. et al. (2006) Geophys. Res. Let. (in review) [7] generally low (less than 30°, typically) and tend to be in Fueten F. et al. (2005) Icarus, 175, 68-77 [8] Hauber E. the direction of the local topographic slope (Fig. 2), as et al. (2006) this conference, [9] Zegers T. et al. (2006) we found earlier [6] and as is also observed in other this conference, [10] Gaddis, L.R. et al. (2006) this ILDs [8, 9, 10]. conference, [11] Hynek B.M. et al. (2003) J. Geophys. In some areas, such as immediately to the east of the Res. 108(E9), 5111-5127.Lunar and Planetary Science XXXVII (2006) 2013.pdfFigure 1. (Left) Oblique false-colored 3-dimensional view of the southwestern Candor Chasma, seen from the north-northeast. The layered mound in the center is unconformably capped by a west-dipping resistant unit. The chasma walls are in the distance. The scale bar is approx. 5 km.Figure 2. (Below) The image area of orbit 2116. The layering attitude measurements are shown as standard strike/dip symbols, with the dip angle shown. A colored topographic map underlies the image. Note how the layer dips tend to be in the down-slope direction. The chasma wall is at the southwest corner of the image; wall strata show shallow dips into the chasma.Elevation (m)-220043006°S 6°S7°S7°S75.5°W 75°W75°WLunar and Planetary Science XXXVII (2006) 2013.pdf

Layering Attitudes in Southwestern Candor Chasma from HRSC Image Data and Stereo-derived DTM

https://elib.dlr.de/44815/1/Stesky.LPSC37.2013.pdf

Layering Attitudes in Southwestern Candor Chasma from HRSC Image Data and Stereo-derived DTM

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