Volume n° 1 - from PR01 to B15 32nd INTERNATIONAL GEOLOGICAL CONGRESS A GEOLOGICAL TRANSECT FROM THE INDIAN PLATE TO THE EAST HINDU KUSH, PAKISTAN Leaders: M. Gaetani, J.P. Burg, A. Zanchi, Q.M. Jan Field Trip Guide Book - PR01 Field Trip Florence - Italy August 20-28, 2004 Prestige Field Trip PR01 PR01_copertina_R_OK C 28-05-2004, 18:45:41 The scientific content of this guide is under the total responsibility of the Authors Published by: APAT – Italian Agency for the Environmental Protection and Technical Services - Via Vitaliano Brancati, 48 - 00144 Roma - Italy Series Editors: Luca Guerrieri, Irene Rischia and Leonello Serva (APAT, Roma) English Desk-copy Editors: Paul Mazza (Università di Firenze), Jessica Ann Thonn (Università di Firenze), Nathalie Marléne Adams (Università di Firenze), Miriam Friedman (Università di Firenze), Kate Eadie (Freelance indipendent professional) Field Trip Committee: Leonello Serva (APAT, Roma), Alessandro Michetti (Università dell’Insubria, Como), Giulio Pavia (Università di Torino), Raffaele Pignone (Servizio Geologico Regione Emilia-Romagna, Bologna) and Riccardo Polino (CNR, Torino) Acknowledgments: The 32nd IGC Organizing Committee is grateful to Roberto Pompili and Elisa Brustia (APAT, Roma) for their collaboration in editing. Graphic project: Full snc - Firenze Layout and press: Lito Terrazzi srl - Firenze PR01_copertina_R_OK D 24-05-2004, 15:46:48 Volume n° 1 - from PR01 to B15 32nd INTERNATIONAL GEOLOGICAL CONGRESS A GEOLOGICAL TRANSECT FROM THE INDIAN PLATE TO THE EAST HINDU KUSH, PAKISTAN AUTHORS: M. Gaetani1, J.P. Burg 2, A. Zanchi3, Q.M. Jan4 1 Dipartimento di Scienze della Terra “A. Desio”, Università di Milano - Italy 2 Geologisches Institut, ETH Zürich - Switzerland 3 Dipartimento di Scienze dell’Ambiente e del Territorio, Università di Milano-Bicocca - Italy 4 Centre of Excellence in Geology, University of Peshawar - Pakistan Florence - Italy August 20-28, 2004 Prestige Field Trip PR01 PR01_R_OK A 24-05-2004, 15:50:31 Front Cover: Panoramic view of the Chateboy Glacier and Koyo Zom (6871) from the Vidiakot area (Baroghil, upper Yarkhun Valley, Pakistan) PR01_R_OK B 24-05-2004, 15:50:33 A GEOLOGICAL TRANSECT FROM THE INDIAN PLATE TO THE E HINDU KUSH, PAKISTAN PR01 Leaders: M. Gaetani, J.P. Burg, A. Zanchi, Q.M. Jan Introduction Maps. Topographic maps: Pakistan 1: 500,000, Sheets The fi eldtrip provides a geological cross-section in Gilgit, Hunza, Tirich Mir, Peshawar. Northern Pakistan from the margin of the Indian Plate Geological maps. to the E Hindu Kush terrane, through the Kohistan Khan, K.S.A., Latif, M., Fayaz, A., Khan, N.A. and Island Arc and the Karakoram Range (Figs. 1 and 2). Khan, M.S.Z. (2000). Geological Road log along the The meeting of participants is scheduled for the Karakoram Highway: Islamabad to Khunjerab Pass. Figure 1 - Tectonic sketch map of Northern Pakistan and surrounding regions. Modifi ed from Zanchi et al., 2000 and Boulin, 1988. MFT: Main Frontal Thrust, MBT: Main Boundary Thrust, MMT: Main Mantle Thrust; SS: Shyok Suture; TMF: Tirich Mir Fault Zone, EHK East Hindu Kush, ACM Alitchur mountains, RPZ: Rushan-Pshart Zone; WAS: Wanch-Akbaital Suture, N-P: North Pamir, C-P: Central Pamir, SE-P: SE Pamir, SW-P: SW Pamir, WAZ: Waziristan, K: Kabul. 1: Quaternary, 2: Tertiary foredeeps, 3: Paleozoic belts, 4: Terranes of Gondwanan affi nity, 5: Kabul Block, 6: Wasser-Panjao Suture, 7: Waziristan ophiolitic complex, 8: Kohistan-Ladakh arc terranes, 9: Himalayas. Heavy lines represent main sutures. afternoon of 22 June in Rawalpindi-Islamabad. The Highways geological Map Series, Map N°1. itinerary will follow the Indus Valley up to near Gilgit Searle M.P. & Khan Asif M. (1996) – Geological Map (Northern Area), then it continues along the Gilgit of North Pakistan, 1: 650,000. River, crossing the Shandur Pass and entering the Le Fort P. & Gaetani M. (1998) – Introduction to North West Frontier Province (NWFT) at Mastuj. the Geological Map of Western Central Karakorum, Along the Yarkhun Valley up to the Baroghil Pass and North Pakistan Hindu Raj, Ghamubar, and Darkot PRO1 to B15 n° 1 - from Volume back to the town of Chitral (see back cover). Most Areas 1: 250,000 scale. Geologica, 1-68. of the travel is done by minibus and jeep, lodging in Le Fort, P. and Pêcher, A. (2002). An introduction to hotels. Five days however, along the upper Yarkhun the geological map of the area between Hunza and Valley are on foot, with overnight in tents. Arrival in Baltistan, Karakorum-Kohistan-Ladakh-Himalaya Rawalpindi-Islamabad scheduled for the evening of 7 region, Northern Pakistan (scale 1:150.000). July, to allow participants to fl y home the 8th of July. Geologica, 6/1, 1-199. 3 - PR01 PR01_R_OK 3 24-05-2004, 15:50:58 Leaders: M. Gaetani, J.P. Burg, A. Zanchi, Q.M. Jan PR01 Figure 2 - Satellite overview of the area crossed by the fi eld trip. Zanchi A., Gaetani M., Angiolini L., (in press) Much of the Phanerozoic shelf sequence (shales, – Geological Map of the NW Karakoram and E sandstones and limestones) is of Gondwana type, Hindu Kush, 1:100,000 scale. A pre-print copy will be starting in the Middle-Paleozoic. Early-Permian provided to the participants. magmatic ages of metabasaltic dikes and granite- gneiss intrusive into older Indian gneiss are evidence Regional geologic setting of pervasive magmatism during rifting (Anczkiewicz 1998, DiPietro & Isachsen 2001), which is associated The Indian Plate margin with the break-up of Gondwana. Rifting produced a The northernmost parts of the Indian continent crop suite of alkaline intrusions, including carbonatites out between the Main Boundary Thrust (MBT), to the (Kazmi & Jan 1997). Sedimentary records indicate south, and the Indus Suture to the North. Northern that the onset of extension tectonics is Early metamorphic units and a southern, fold-and-thrust Carboniferous (Pogue et al. 1992, Pogue et al. 1999). sedimentary belt constitute the so-called Lower- (or Marine shelf sedimentation was re-established in the Lesser-) Himalaya of Pakistan (Chaudhry et al. 1997). Late Triassic. The Mesozoic sedimentary history Altogether, it is a low-grade assemblage of a 20 km is that of carbonates deposited during thermal thick, imbricate thrust pile of Mesozoic sequences subsidence of a continental margin, on the southern originally deposited on the Indian continental crust side of Neo-Tethys. represented by mid-Proterozoic and Paleozoic All these rocks were deformed and metamorphosed gneisses and sediments. between 75 and 40 Ma (Treloar et al. 1989, Volume n° 1 - from PRO1 to B15 n° 1 - from Volume Cambrian stromatolitic dolomites record the Chamberlain et al. 1991). Subduction of at least parts epicontinental marine transgression on 1.5 - 2.2 Ga old of the Indian craton to depths equivalent to 27-32 remobilised gneisses. Around 500 Ma old granitoids, kbars at ca. 50 Ma is indicated from the occurrence, which have been deformed into orthogneiss (Le Fort in the Kaghan Valley, of coesite-bearing eclogites et al., 1980, Anczkiewicz 1998, DiPietro & Isachsen likely derived from basaltic Permian dykes (Tonarini 2001), record the widespread magmatic event of that et al. 1993, O’Brien et al. 2001, Kaneko et al. 2003). time, which is documented on all Gondwana-derived Thermochronologic studies suggest that before 13 continental blocks. Ma most of the Lower Himalaya rocks were located PR01 - PR01_R_OK 4 24-05-2004, 15:59:53 A GEOLOGICAL TRANSECT FROM THE INDIAN PLATE TO THE EAST HINDU KUSH, PAKISTAN PR01 either beneath a paleo-foreland basin or beneath Main graywackes and volcanoclastic rocks form a probable Central Thrust (MCT)-related nappes. back-arc basin of Cretaceous age. They grade Molasse conglomerates siltstones and shales (termed upward into fi ne grained shales and tuffs and contain Siwalik or Sub-Himalaya sediments) lap onto the limestones with an Albian-Aptian fauna (Pudsey et Indian Shield. In detail the discontinuous series al. 1985). comprises most of the Cenozoic but there was a Volcanites (Chalt Volcanites) are calc-alkaline general lack of sedimentation during the Late Eocene andesites to rhyolites succeeding to andesitic lavas, and almost the entire Oligocene. This unconformity tuffs and agglomerates of Early Cretaceous age. of 15-20 Myr may refl ect an important change in Exceptionally well-preserved pillow lavas are orogenic processes. One interpretation involves the primitive island-arc-type, tholeiitic lavas that possibly passage of a fl exural forebulge migrating southward represent part of an ophiolite assemblage obducted through India. Late Oligocene to Early Miocene during the Kohistan-Asian collision. The size of this fl uvial formations record the emergence of the oceanic back arc basin (with respect to the Kohistan) Himalaya Mountains. is conjectural. - To the Southwest and within the Kohistan Complex, The Kohistan Island Arc Complex: metasedimentary sequence of deep marine origin Outline (Dir, Utror and Kalam Groups) yielded Eocene fossils The Kohistan terrane in NE Pakistan (Fig. 3) is in upper-level limestones. Depositional models regarded as a fossil island arc obducted between the point to rapid subsidence in Paleocene times in an collided Indian and Asian plates (Bard et al. 1980, extensional, restricted basin. Associated volcanic Tahirkheli et al., 1979). Owing to the admirable and volcanoclastic series are calc-alkaline basalts, quality of exposures, the Kohistan offers an unrivalled basaltic andesites and andesites, emphasising an arc opportunity to investigate the structure of an island environment (Sullivan et al. 1993). arc and related subduction processes (Bard 1983, Searle et al., 1999, Treloar et al., 1996). In particular, PLUTONIC CRUST numerous time markers in the form of intrusive bodies Kohistan batholith: is a name that gathers intrusive make the Kohistan an exceptional place to study the calc-alkaline granitoids. The fi rst plutonic stage is signifi cance of magmatic structures in the deep crust dated at ca 105 Ma.