A REINTERPRETATION OF THE OLDEST HIMALAYAN FORELAND BASIN SEDIMENTS: A REVISED AGE FOR THE BALAKOT FORMATION, PAKISTAN

The Balakot Formation foreland basin sediments, located in the Hazara\|Kashmir syntaxis, Pakistan, consist of a >8km thick succession of clastic red beds and calcrete, interpreted as deposited in a tidal environment. Within this sequence are intercalated four distinct grey fossiliferous marl and silt units, 20～60m thick, dated at Late Palaeocene to Mid Eocene (Bossart & Ottiger 1989). Thus the Balakot Formation has been interpreted as the oldest continental foreland basin deposits and has been used to determine the timing of India\|Eurasia collision (Rowley 1996) which has implications for the degree of diachroneity of collision (Burbank et al. 1996; Uddin and Lundberg 1998) and rapidity of metamorphism (Treloar 1997), to interpret the palaeotectonics and palaeogeography of the mountain belt (Critelli and Garzanti 1994; Pivnik and Wells 1996), understand the relationship between mountain belt evolution and exhumation processes (Treloar et al. 1991) and construct models of foreland basin evolution and geometry (DeCelles et al. 1998; Burbank et al 1996).

The Balakot Formation foreland basin sediments, located in the Hazara\|Kashmir syntaxis, Pakistan, consist of a >8km thick succession of clastic red beds and calcrete, interpreted as deposited in a tidal environment. Within this sequence are intercalated four distinct grey fossiliferous marl and silt units, 20～60m thick, dated at Late Palaeocene to Mid Eocene (Bossart & Ottiger 1989). Thus the Balakot Formation has been interpreted as the oldest continental foreland basin deposits and has been used to determine the timing of India\|Eurasia collision (Rowley 1996) which has implications for the degree of diachroneity of collision (Burbank et al. 1996; Uddin and Lundberg 1998) and rapidity of metamorphism (Treloar 1997), to interpret the palaeotectonics and palaeogeography of the mountain belt (Critelli and Garzanti 1994; Pivnik and Wells 1996), understand the relationship between mountain belt evolution and exhumation processes (Treloar et al. 1991) and construct models of foreland basin evolution and geometry (DeCelles et al. 1998; Burbank et al 1996).