Integrated litho-ichnofacies and ichnofabric analysis of the lowermost part of the Kunzum La Formation along the Khemangar khad and the Parahio Valley sections, Spiti Region (Zanskar-Spiti-Kinnaur Basin), Northwest Himalaya, India)

Abstract

The Cambrian sequence, designated as the Kunzam La Formation, is exposed along the cLassical Parahio Valley section and also on left bank of the Khemangar khad in the Parahio Valley (Spiti), the Latter constitutes the lowermost exposed part of the Kunzum La Formation. The lower part of the Parahio Valley section and outcrop near the left bank of the Khemangar khad were studied for integrated litho-ichnofacies and ichnofabric analysis. The study establishes a genetic reLationship of the strata of these two localities. Five lithofacies are recognised in both the examined sections. The lithofacies indicate a wave-dominated shallow marine environment of deposition for these Cambrian rocks. The overall calcuLated ichnofabric indices in 74 m exposed strata at the Khemangar khad locality range from ii1=80.% (represented by 25.8 m), ii2= 17% (represented by 5.4 m) and ii4=2.5 % (represented by 0.8 m). The 42 m rocks examined in the main Parahio Valley section indicate ichnofabric indices ranging from ii1=37% (represented by 17.8 m), ii2=21% (represented by 8.0 m), ii3=40% (represented by 15.2 m) and ii4=2.0% (represented by 1.0 m). The presence of archetypal Cruziana ichnofacies, parallel and wavy Laminations, hummocky cross stratification (HCS) and trough cross stratification (TCS) supports a wave-dominated shallow water environment from upper shoreface to middlelower shoreface setup for the deposition of the lowermost part of the Kunzum La Formation in the Parahio Valley.