The similarity of fluidized ejecta blankets of double-layer ejecta (DLE) craters and long run-out landslides: morphometry and modeling

• Applicant: Professor Dr. Thomas Kenkmann
• Subject Area: Palaeontology ; Geodesy, Photogrammetry, Remote Sensing, Geoinformatics, Cartography
• Term: from 2011 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 195366123

• Final Report Year: 2016

Final Report Abstract

Key results of the first part: 1) Based on a rigorous GIS-based compilation of new borehole data, analyses of all geological and topographic data from maps, and outcrops we could demonstrate for the first time that the Ries ejecta blanket contains a massive and continuous concentrically trending rampart structure at 1.45–2.12 crater radii from the crater center. Ejecta distribution and thickness, as well as the ejecta fabric indicate the presence of fluids during the emplacement process. A consequence of this is that the emplacement mode of ejecta derived from lunar impact craters cannot be applied to terrestrial impact craters. 2) The ejecta blanket of the Ries crater shows striking similarities to Martian craters, in particular, those with double-layered ejecta morphologies. The position of the massive rampart is almost identical to that of Martian craters. 3) The ejecta layers of the investigated double-layer ejecta (DLE) craters on Mars are compositionally distinct as indicated by the analysis of CRISM data. 4) The inner ejecta layer of DLE craters superimposes the outer ejecta layer which rules out previous models e.g. by Boyce and Mouginis-Mark (2006). Based on our high-resolution remote sensing studies we derived a phenomenological model for the formation DLE craters. The inner ejecta layer moves as a translational slide whereas the outer, more fluid-rich ejecta blanket flows as a debris flow or debris avalanche. Key results of the second part: 1) The striations of all study objects are scaled versions of a common shape. The scaleinvariance was revealed by the frequency- size distribution of the spectrum of the topography tracks obtained from FFT analysis. The power spectral densities show a power law dependency on wavelength with an exponent of ~2-2.4, which is generally reserved for Brownian motion. 2) Longitudinal topography tracks along ridges reveal an undulating surface similar to that observed in perpendicular profiles. The dimensions of the minima and maxima have the same characteristics, including the scale-invariance with a power law exponent of ~2. This implies the formation of a scale invariant wavelike pattern in two directions and indicates that the formation process is more complex than apprehended. 3) The ratios of ridge height and the absolute flow thickness have constant ratios between ~0.02-0.22 on landslide deposits, with stronger variations for impact crater ejecta blankets in areas of rapid thickening and thinning of the deposit. This constant ratio can be implemented as a tool to estimate flow thickness of deposits where the geometry of the substrate is unknown. This can help improve the volume estimation of landslide and impact crater ejecta deposits.

Publications

• (2013). Rampart collapse of DLE craters on Mars and implications for deposition chronology. European Planetary Science Congress 2013, Vol. 8, EPSC2013-941
  Wulf G., Kenkmann T.
  
• (2013). The Ries impact, a double-layer rampart crater on Earth. Geology 41, 531–534
  Sturm S., Wulf G., Jung D., Kenkmann T.
  
• (2014). A high-resolution study of double-layered ejecta craters: morphology, inherent structure, and phenomenological modeling. Meteoritics and Planetary Science 50, 174-203
  Wulf G., Kenkmann T.
  
• (2014). A new phenomenological ejecta excavation and emplacement model for DLE craters. 45th Lunar and Planetary Science Conference, #1792
  Wulf G., Kenkmann T.
  
• (2014). The distribution of megablocks in the Ries crater, Germany: Remote sensing, field investigations and statistical analyses. Meteoritics and Planetary Science 50, 141-173
  Sturm S., Wilmes M., Poesges G., Hiesinger H., Kenkmann T.
  
• (2015).Ries Bunte Breccia revisited: indications for the presence of water in Itzing and Otting drill cores and implications for the emplacement process. Meteoritics and Planetary Science 51, 1203-1222
  Pietrek A., Kenkmann T.
  
• (2016). Morphometric Analysis and Comparison of Martian Landslides and Layered Deposits of Impact Crater Ejecta Blankets. 47th Lunar and Planetary Science Conference (2016), Abstract# 2250
  Pietrek A., Weis J., Hergarten S., G. Wulf, Kenkmann T.
  
• (2016). Understanding the Dynamics of Long Runout Mass Movements of Impact Crater Ejecta Blankets and Landslides on Mars through Morphometric Analysis. 79th Annual Meeting of the Meteoritical Society (2016), Abstract# 6294
  Pietrek A., Kenkmann T., Hergarten S.