Giant submarine landslide grooves in the Neoproterozoic/Lower Cambrian Phe Formation, northwest Himalaya: Mechanisms of formation and palaeogeographic implications E. Draganits a, ⁎, J. Schlaf b , B. Grasemann c , T. Argles d a Institute for Engineering Geology, Vienna University of Technology, Karlsplatz 13/203, A-1040 Vienna, Austria b Conoco Phillips Petroleum UK Ltd, Exploration and Production, Rubislaw House, Anderson Drive, Aberdeen AB15 6FZ, UK c Department of Geodynamics and Sedimentology, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria d Department of Earth Sciences, The Open University, Milton Keynes MK7 6AA, UK ABSTRACT ARTICLE INFO Article history: Received 28 February 2007 Received in revised form 16 February 2008 Accepted 21 February 2008 Keywords: India Submarine landslides Groove casts Depositional environment Palaeogeographic reconstruction Giant groove casts have been found in the upper Proterozoic to Lower Cambrian Phe Formation (Haimanta Group), a siliciclastic sandstone/shale succession in the Tethyan Zone of the Higher Himalaya tectonic unit. The grooves are among the largest linear erosion structures related to submarine mass-movements observed in the geologic record. They are up to 4 m wide, about 0.2 m deep and can be traced for more than 35 m without changing their character. The grooves are straight, subparallel to cross-cutting striations with shallow semi-circular cross-sections and well-defined superimposed minor ridges and grooves. Groove casts exist on the soles of several sandstone beds within a 73 m thick logged section, commonly associated with flute casts. Their characteristics were compared with several other types of ancient and modern submarine linear erosion structures. A sand-rich, non-channelized basin floor depositional environment is inferred from the lithofacies, the combination of sedimentary structures, the lack of coarse-grained pebbly facies, the lateral continuity of beds, and the lack of channel structures. The grooves probably formed by laminar debris flows/concentrated density flows dragging blocks of already lithified sediment across the basin floor. When the bedding is structurally rotated back to horizontal, the groove casts show consistent North–South oriented palaeocurrent trends, with South-directed palaeocurrent directions indicated by flute casts. These palaeocurrent orientations contrast with previous palaeogeographic reconstructions of this area, which propose sediment delivery from the South. We therefore suggest a new “double provenance” model for the spatial relationship of late Proterozoic to Early Cambrian strata of the Himalaya, in which Lesser and Tethyan Himalayan age-equivalent sediment was deposited in a connected basin, where the former received detritus from the South, and the latter from a hitherto unknown source in the North. One possible candidate for this northern source is the South China Block and an associated Neoproterozoic volcanic arc. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Direct observation of modern sedimentary processes associated with deep water gravity flows is hindered by the great water depths and by the flows' sporadic and unpredictable occurrences. Hence deep water depositional environments have mainly been investigated by exploring their ancient deposits in outcrop. Consequently, sedimen- tary structures from deep water gravity flows (Kuenen, 1957; Dżułyński and Walton, 1965; Allen, 1982), as well as their three- dimensional geometry and vertical stacking patterns (Bouma, 1962; Walker, 1978; Pickering et al., 1986; Mutti, 1992; Reading and Richards, 1994; Stow et al., 1996), have long been well known from outcrop studies. Additionally, the combination of field observations and laboratory experiments (e.g., Dżułyński and Walton, 1965; Mohrig and Marr, 2003; Felix and Peakall, 2006) provide important insights into the physical parameters of deep water gravity flows, resulting in their classification based on fluid rheology, sediment/water ratio, clay content and clast-support mechanisms (e.g., Lowe, 1979; Shanmugam, 2000; Gani, 2004; Amy et al., 2006). There is a multitude of sole marks observed in the ancient, but only a few achieve the outstanding size of the Indian groove casts described herein. Those most comparable in size and shape are interpreted as having formed from (a) submarine slides/slumps (Kuenen and Sanders, 1956, plate 2); (b) turbidites (Kuenen and Sanders, 1956, plate 3B; Kuenen, 1957 , figs. 11, 12; McBride, 1962, figs. 12, 13; Enos, 1969, figs. 6, 8, 11; Hiscott and Middleton 1979, fig. 7; Ricci Lucchi, 1995, plates 98, 99) and (c) iceberg keel marks (Pettijohn and Potter, Sedimentary Geology 205 (2008) 126–141 ⁎ Corresponding author. E-mail address: Erich.Draganits@tuwien.ac.at (E. Draganits). 0037-0738/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.sedgeo.2008.02.004 Contents lists available at ScienceDirect Sedimentary Geology journal homepage: www.elsevier.com/locate/sedgeo