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Tectonic and climatic evolution of the Arabian : an introduction

PETER D. CLIFT 1, DICK KROON 2, CHRISTOPH GAEDICKE 3 & JONATHAN CRAIG 4 1 Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA (e-mail: [email protected]) 2Institute of Sciences, Free University Amsterdam, de Boelelaan 1085, 1081 HV Amsterdam, The Netherlands 3Bundesanstalt fiir Geowissenschafien und Rohstoffe (BGR), Stilleweg 2, D-30655 Hannover, Germany 4Lasmo plc, 101 Bishops Gate, London EC2M 3XH, UK

The evolution of the global oceanic and atmo- The Arabian Sea is the natural laboratory to spheric circulation systems has been affected by study the interaction between orogenic growth and several forcing processes, with orbital variations regional climate change. Drilling Program being dominant on shorter geological time scales. (ODP) sampling of pelagic sediments on the Over longer periods of time (> 10 Ma) the tectonic margin has revealed a detailed history of evolution of the solid Earth has been recognized monsoonal variability (Kroon et al. 1991; Prell et as the major control on the development of the al. 1992), most notably an intensification of the global climate system. Tectonic activity acts in at 8.5 Ma, as traced by the abundance of one of two different ways to influence regional Globigerina bulloides and other eutrophic species, and global climate. The earliest solid Earth- foraminifers associated with monsoon-induced climatic interaction recognized was the effect that coastal upwelling in the modern Arabian Sea. the opening and closure of oceanic gateways had Initially this result appeared to correlate well with on the circulation patterns in the global ocean. the start of extension on the , an Major effects on regional and sometimes global event that was linked to a period of rapid plateau climate have been attributed to such changes, e.g. uplift. Consequently, Harrison et al. (1992) and closure of the Isthmus of Panama (Driscoll & Molnar et al. (1993) proposed a direct correlation Haug 1998). Since the late 1980s a second form between rapid Tibetan uplift at that time and a of climate-tectonic interaction has been recog- strong SW monsoon and increased rainfall. Mod- nized, involving the growth and erosion of oro- elling studies support a shift of increased precipi- genic belts. In this second category the Arabian tation from Indochina toward the and a Sea region must be considered the global type strengthening of the Asian monsoon during late example. Tertiary time, separate from the strengthening at Growth of the Himalaya and associated Tibetan 8.5 Ma (Flutean et al. 1999). Plateau is now believed to have substantially More recently, fieldwork in Tibet has compli- altered Cenozoic climate. Raymo et al. (1988) cated our ideas about the timing of uplift, with suggested that chemical erosion of the uplifting some workers indicating at least southern Tibet orogen resulted in the draw-down of atmospheric reaching maximum elevation at c. 19Ma CO2, which was deposited as limestone, causing (Williams et al. 2001), whereas others suggest long-term global cooling, as a result of the reduc- rapid uplift of the northern plateau during Plio- tion in this important greenhouse gas. Orogenic cene time (Zheng et al. 2000). Work on the uplift is also believed to affect regional climate monsoon also continues to change our understand- and in particular development of the monsoon. ing of the climatic evolution of South . Derry Summer heating of air above the Tibetan Plateau & France-Lanord (1997) proposed that the 8- is known to have induced a strengthening of the 7 Ma period in fact represented a weak monsoon, monsoon (Manabe & Terpstra, 1974), and so with greater regional aridity rather than the stan- tectonic uplift of the plateau has been linked to dard image of greater precipitation. Clearly much strengthening of the monsoon (Raymo & Ruddi- work remains in defining the timing of the SW man 1992; Molnar et al. 1993). monsoon and the timing of tectonism in Tibet.

From: CLIFT, ED., KROON, D., GAEDICKE,C. & CRAIG, J. (eds) 2002. The Tectonic and Climatic Evolution of the Arabian Sea Region. Geological Society, London, Special Publications, 195, 1-5. 0305-8719/02/$15.00 © The Geological Society of London 2002. Downloaded from http://sp.lyellcollection.org/ by guest on October 2, 2021

2 P.D. CLIFT ETAL.

Testing climate-tectonic models? Oman margin during most of Paleogene time. Chaubey et al. analyse marine magnetic anomaly Despite the current debate, the Arabian Sea has patterns, and conclude that not only was Paleo- several features that make it the best area globally gene spreading very asymmetric, with the Arabian to examine solid Earth-climatic interactions. The Sea accreting much faster than the Somali Basin, climatic signal is strong, especially with regard to but also -Somali motion slowed rapidly after the monsoon, and the rates of sedimentation are 52 Ma. The evolution of the passive Indian margin often high, allowing detailed palaeoceanographic before collision with Asia is described by Sinew- records to be reconstructed. The has a ing et al. in a stratigraphic study of the southern large output, equivalent to that of the Mississippi Kirthar Fold Belt in . Rift shoulder uplift River, and carries an erosional record of the high and erosion of Middle Jurassic limestones dates topography north of the High Himalaya, i.e. the the separation of India from East . Subse- Karakoram and western Tibet, which are the quently, two phases of ophiolite emplacement are responsible for the monsoon. The modern recognized, in Late Cretaceous and Early Tertiary climate of arid conditions, punctuated by heavy time. Late Cretaceous (Campanian and Maastrich- seasonal rains, contributes to enhancing erosion, tian) submarine fans are interpreted to reflect the products of which can be found interbedded thermal uplift of India as a result of the Deccan with dateable fossiliferous sediments in the Indus Plume. Subsequently, Middle Eocene northerly- Fan. The western Himalaya and Karakoram have derived clastic sediments from the early Himalaya been the focus of much recent fieldwork, often constrain the age of collision in this region. The involving high-resolution radiometric dating of Kirthar Fold Belt is interpreted as an offshore basement units. This means that the thermal and equivalent of the Murray Ridge, which is under- tectonic development of these ranges can be lain by thinned continental crust. accurately correlated with the marine records. The slowing of India-Asia convergence after Indeed, the very fact that the Arabian Sea is 52 Ma described by Chaubey et al. is broadly in surrounded on three sides by land, often arid and accord with the evolving sedimentary character with good exposure, makes this an ideal area to within the Asian forearc basin revealed by Clift et attempt linked marine and land-based field experi- al. This study shows an influx of ophiolitic and ments. carbonate platform material from a deformed Much work remains to be done in understand- Indian margin into the Jurutze forearc basin no ing the tectonic and climatic evolution of the later than Ypresian time (>49 Ma). The subse- Arabian Sea area. Efforts are now under way to quent deposition of the alluvial Indus Group in expand our sampling on- and offshore so as to the Indus Suture in Ladakh has been linked by understand the temporal variations in climate, Clift to the earliest activity of a palaeo-Indus erosion and tectonism. Such efforts necessarily River, which flowed into a delta in the Katawaz require international collaboration between re- Basin of western Pakistan and Afghanistan by searchers within the region and elsewhere. Addi- Early Eocene time, and must have reached the tional marine geophysical surveys and deep Arabian Sea by Mid-Eocene time. Some of that scientific drilling are required in the Arabian Sea material has subsequently been accreted to the to construct the detailed records required to active margin of Asia. McCall shows that the quantify the nature of solid Earth-climatic cou- Makran Accretionary Complex contains large pling. None the less, much has been achieved by a volumes of Paleogene turbidites that were added series of cruises and field campaigns over the last to that margin, and may represent a palaeo-Indus 10 years, since the last major review of the region. Fan, in addition to the material still found in the It was the desire to bring together workers spread Arabian Sea. Clift et al. show that the Indus across many countries and disciplines that Group Basin was inverted no later than 14 Ma, prompted the special meeting of the Geological probably close to the time of tectonic uplift along Society, where much of the work published here the Murray Ridge (20 Ma), but that the Indus was presented. River has remained stationary in the suture since The development of the Arabian Sea before that time. India-Asia collision is reconstructed by three of Clift presents a sediment budget for the Indus the papers presented here. Royer et al. use a Fan that shows peak sedimentation rates in mid- compilation of marine geophysical data to demon- Miocene time accompanied by channel-levee strate that spreading in the Arabian Sea at 61- accumulation on the mid-fan, during a period of 46 Ma has been affected by a series of successive strong tectonic activity in the Karakoram, and ridge propagation events along the Carlsberg possibly linked to an early initiation of the SW Ridge, and that the Arabia-India plate boundary monsoon. Closer to the coast, Daley & Alam was located west of the Owen Ridge along the provide a review of the seismic stratigraphy of the Downloaded from http://sp.lyellcollection.org/ by guest on October 2, 2021

INTRODUCTION 3 offshore Indus Basin (Pakistan Shelf), highlighting Quaternary period and the SW monsoon was the existence of two distinct phases of canyon active during interglacial periods. development on the upper part of the Indus Fan: Upper Holocene sediments cored from the Paki- one in Early Miocene time and the other in Plio- stan margin within the minimum zone are Pleistocene time. Both phases are interpreted as used by Von Rad et al. to show a varying related to relating to pulses of tectonic activity in the seasonal river flood events. A climate with reduced collision zone between the Indo-Pakistan and precipitation and river runoff, possibly 'winter Eurasian plates. monsoon' dominated, is recognized at 5600-4700 a The regional stratigraphy of the northern Ara- bp on the basis of the thin varves, whereas other bian Sea is defined by Gaedieke et al., who periods characterized by thicker varves document employ seismic data to construct a four-part wetter periods, with summer-monsoon domina- stratigraphy to the Indus Fan and . tion. These workers relate the cyclicity found in They show that opening of the in the varved sequence to lunar cycles, which result mid- to late Miocene time caused a reorganization in variations in the amplitudes of tides, which in of the plates and subsequent tilting of the oceanic turn may have controlled sediment redeposition. crust of the Arabian Plate toward the Makran Also, Luckge et ai. describe Holocene varved subduction zone, thus generating the regional 'M- sediments and their causes, and calibrate the unconformity'. Uplift of the Murray Ridge during variations in thickness of the varves to meteoro- late Miocene to early Pliocene time has caused a logical records such as rainfall. separation in sedimentation between the Gulf of In a separate contribution, Von Radet al. Oman and the Arabian Sea, with the modem discuss the discovery of a discrete ash layer Indus Fan prevented from flowing westward by the derived from the Indonesian volcano Toba (70 + Murray Ridge. Burgath et ai. provide sedimentary 4 ka) and recovered from sediments deposited in evidence that the Murray Ridge was uplifted close the oxygen minimum zone offshore the Indus to sea level in late Miocene to early Pliocene time delta. In addition, two rhyolitic ash layers are and subsequently subsided to modern depths. dated at AD 1885-1900 and 1815-1830. The glass These workers also present geochemical data shards were probably derived from eruptions of derived from samples for the volcanic and pluto- Indonesian volcanoes, although it is not possible nic basement to the Murray Ridge demonstrating to correlate these two ashes with well-known an origin within a Mesozoic Neotethyan active historical eruptions. A complete, high-resolution margin setting. stratigraphic record of the past 75 ka, with 21 interstadials or Dansgaard-Oeschger cycles and equivalents of Heinrich events H1-H6 is recog- Pleistocene-Holocene sedimentation nized. Rapid climate oscillations with periods Glacial sea-level lowstand periods are identified around 1.5 ka can be tuned to the 6180 record of by Williams & Walkden as times when the a core and to the GISP-2 ice core was subaerially exposed, allowing from Greenland. Changes in the intensity of the changes in sea level to be quantified. Sediments Indian summer monsoon are tightly coupled with deposited during the last interglacial contain evi- suborbital climate oscillations in the Northern dence for two highstands during this period, Hemisphere. peaking at around 1.5 and 6 m above present sea The late glacial-Holocene evolution of the level. Following the second highstand, sea level monsoon is reconstructed by Jung et al. using fell to more than 23 m below present level. cores from the Arabian Sea offshore . Palaeocurrent directions indicate that during the Using a multiproxy approach they determine that last interglacial (125 ka) the prevailing blew bulk sediment chemistry, most notably Ba/A1, from the NE. Evidence for a pluvial episode provides the best record of productivity associated during this period is provided by palaeokarstic with monsoon strength. Foraminifer-based records pits, believed to represent the former positions of conflict with the sediment chemistry on centennial trees or large plants. and millennial time scales, indicating that more Glennie et al. provide an overview of the than upwelling controls their productivity. Disso- development of the distribution of sand dunes over lution on the sea floor has affected foraminiferal the southern half of Arabia during the Quaternary abundances during the transition period. During period. They discuss the expansion and contrac- glacial times upwelling and productivity were tion of deserts and their relationship to changes in stronger during the winter NE monsoon, as climate. Two wind systems influenced desert opposed to the modem situation, where production formation: the northern 'Shamal' and the strong is strongest during the summer SW monsoon. of the SW monsoon. The Shamal was Particle flux, sediment trap data, in the NE particularly active during the cold parts of the Arabian Sea are described by Sehulz et aL Those Downloaded from http://sp.lyellcollection.org/ by guest on October 2, 2021

4 P.D. CLIFT ETAL. workers document that the particle flux, including composition and depth habitats of extant plank- biota, in the NE Arabian Sea is determined by tonic foraminifers by using plankton tows. The sediment resusPension and winter productivity temporal distribution of assemblages of planktonic rather than by summer upwelling. This is in foraminifers is associated with the hydrography of contrast to numerous sediment trap observations the area, which is in turn controlled by the in the western Arabian Sea. The new evidence is monsoon system. Highest abundances of eutrophic used to reconstruct the seasonal intensity of both species occur during the upwelling phase triggered for the past 25 ka. Schultz et al. use by the SW monsoon. Vertical abundance profiles planktonic foraminiferal abundances for monsoon in the water column are recorded to document intensity in a core with a high temporal resolution. depth habitats of individual species. This is The NE monsoon peaked during the stadial phases important for interpretations of stable isotope and the SW monsoon during the Holocene period. studies using the shells of the planktonic foramini- Combined sediment trap and box core records of fers in sediments. nitrogen isotopes (rlSN) in organic matter are studied by Brummer et al. Complex patterns of Neotectonics annual nitrogen fluxes and 6]15N are described, and their fate in the sediments. Upwelling processes The Arabian Sea region is still involved in the have a strong effect on the 615N of settling active deformation associated with India-Asia nitrogen. Freshly upwelled waters show minima in convergence and opening of the and Gulf dlSN, and maxima are found in stratified waters. of Aden. In a review of this activity, Vita Finzi Also, diagenesis is dicussed as a potential source describes the Holocene record on the coasts of the for altering the primary signal. Arabian Sea and interprets it in the context of the Staubwasser & Dulsld reconstruct the early- interaction between the Indian, Arabian and Eur- mid-Holocene evolution of the oxygen minimum asian plates. Marine terraces from the Makran zone in the Arabian Sea by using a trace metal margin show infrequent but vigorous coseismic proxy. Century-scale fluctuations are recorded in uplift, similar to that seen in other accretionary the laminated sediments off Pakistan. Complex subduction settings. Vita Finzi notes a landward ventilation patterns of the subsurface waters in- rotation of the imbricate faults along which short- clude lateral advection from Central Indian Water ening is distributed. The lack of significant Holo- and ventilation by winter surface convection in the cene deformation on the SE coast of the Arabian northern Arabian Sea. peninsula is consistent with its position parallel to Stow et ai. describe shallow cores from the a transform, although large-scale buckling may be upper slope, mid-slope and the abyssal plain occurring at the Straits of Hormuz. Localized offshore the Makran. They employ an oxygen uplift on the SW of India represents compressional isotope stratigraphy to provide an age determina- buckling related to India-Asia collision. tion for statistical analyses. The upper 5-14 m of Sattarzadeh et al. examine the nature of fold- sediment is dominated by fine-grained, thin turbi- ing in the Zagros Mountains as a result of the dites, averaging 5-10 turbidite events per metre enhanced Pliocene deformation caused by faster of section, or one turbidite event per 200-300 a. Arabia-Asia convergence driven by opening of the The range of turbidite bed thicknesses is typical Red Sea. The deformation in the Zagros is for beds triggered by seismicity on active margins. controlled by plate velocity and the regional The lateral distribution of both turbidites and stratigraphy, which is composed of four mechani- hemipelagites is influenced by sediment focusing cally contrasting litho-structural units overlying a along pathways between slope basins. At a larger rigid basement. The sedimentary cover and the scale, climate, sea level and tectonic effects have underlying metamorphic basement decouple along all controlled the margin sedimentation. an important detachment horizon, the Hormuz Salt Two papers discuss the ecology of plankton Formation. The uneven thickness and distribution groups in the Arabian Sea and their potential as of the Hormuz Salt plays a key role in determin- 'proxies' in the sediments. Wendler et al. discuss ing the geometry of the deformation belt. The abundances of calcareous dinoflagellate cyst spe- median surface of the fold belt has an asymmetric cies in surface sediment samples, and these are topography, its elevation ascending northeastward compared with environmental parameters in the in a series of steps, consistent with neotectonic upper water column. Certain assemblages can be field evidence for serial folding and imbrication of clearly correlated with temperature and nutrient the footwall. levels, particularly in the SW Arabian Sea. In the Delisle & Berner present a numerical model of NE Arabian Sea diagenetic processes must be the geothermal field of the Makran accretionary taken into account in interpreting sediment assem- prism, which suggests that conductive heat trans- blages. Peeters & Brummer record the faunal port is dominant and that there is little contribu- Downloaded from http://sp.lyellcollection.org/ by guest on October 2, 2021

INTRODUCTION 5 tion from fluid flow or frictional heat. They FLUTEAU, F., RAMSTEIN, G. & BESSE, J. 1999. Simulat- demonstrate that gas hydrate layers in the accre- ing the evolution of the Asian and African mon- tionary prism act as a very effective seal to the soons during the past 30 Myr using an atmospheric upward flow of fluids in water depths greater than general circulation model. Journal of Geophysical 104, 11995-12018. 800 m, but that they break down when uplifted Research, KROON, D., STEENS, T. & TROELSTRA, S.R. ET AL. 1991. out of the gas hydrate stability field into shallower Onset of monsoonal related upwelling in the and warmer water. western Arabian Sea as revealed by planktonic foraminifers. In: PRELL, W.L. t~ NIITSUMA, N. The papers in the volume arise from a special meeting of (eds) Proceedings of the Ocean Drilling Program, the Tectonic Studies, Marine Studies and Petroleum Scientific Results, 117. Ocean Drilling Program, Groups of the Geological Society of London, held at the College Station, TX, 257-263. Geological Society, Burlington House, Piccadilly, on 4-5 HARRISON, T.M., COPELAND, P., KIDD, W.S.F. & YIN, April 2001. The meeting was convened by Peter Clift, A. 1992. Raising Tibet. Science, 255, 1663-1670. Christoph Gaedicke, Jonathan Craig and Dirk Kroon. MANABE, S. & TERPSTRA, T.B. 1974. The effects of Lasmo UK plc and the Geological Society are thanked for mountains on the general circulation of the atmo- their partial financial support of the meeting, proceeds sphere as identified by numerical experiments. from which helped cover the costs of colour figures and Journal of Atmospheric Scences, 31, 3-42. fold-outs in this publication. Chryseis Fox is thanked for MOLNAR, P., ENGLAND, P. & MARTINOD, J. 1993. creating and maintaining the related web pages. Mantle dynamics, the uplift of the Tibetan Plateau, The editors wish to acknowledge reviews by the and the Indian monsoon. Reviews in Geophysics, following geoscientists: A. Beach, D. Benn, C. Betzler, J. 31, 357-396. P. Burg, S. Carey, S. Clemens, R. Coleman, P D. , PRELL, W.L., MURRAY, D.W., CLEMENS, S.C. • ANDER- T. Daley, K. Darling, P. Degnan, P. DeMenocal, R. SON, D.M. 1992. Evolution and variability of the Edwards, P. Friend, R. Ganeshram, E. Garzanti, E. GriDS, summer monsoon: evidence from the R. Graham, R. Harland, P. Hildebrand, M. Higginson, E western Arabian Sea drilling program. In: DUNCAN, Jansen, G. Jones, C. Kendall, M. Khan, E. Kirby, N. R.A., REA, D.K., IODD, R.B., YON RAD, U. & Kukowski, E Marret, K. Mclntyre, J. McManus, P. Miles, WEISSEL, J.K. (eds) Synthesis of Results from Scien- T. Minshull, G. Mountain, N. Nowaczyk, E Peeters, J. tific Drilling in the Indian Ocean. Geophysical Mono- Pike, M. Prins, G. J. Reichart, J. J. G. Reijmer, L. R. graph, American Geophysical Union, 70, 447-469. Sautter, B. Schreckenberger, D. Schelling, R. Schneider, RAYMO, M.E., RUDDIMAN, W.F. t~ FROELICH, P. 1988. M. P. Searle, P. Sharland, A. D. Singh, E Sirocko, J. Influence of late Cenozoic mountain building on Smewing, S. Swift, A. H. E Robertson, E. Uchupi, J. ocean geochemical cycles. Geology, 16, 649-653. Warburton, R. Whittington, C. Vita Finzi, U. yon Rad. RAYMO, M.E. & RUDDIMAN, W.F. 1992. Tectonic forcing of the late Cenozoic climate. Nature, 359, 117-122. References WILLIAMS, H., TURNER, S., KELLEY, S. & HARRIS, N. DERRY, L.A. & FRANCE-LANORD, C. 1997. Himalayan 2001. Age and composition of dikes in southern weathering and erosion fluxes; climate and tectonic Tibet: new constraints on the timing of east-west controls. In: RUDDIMAN, W.F. (ed.) Tectonic Uplift extension and its relations to post-collisional vol- and Climate Change. Plenum, New York, 289-312. canism. Geology, 29, 339-342. DRISCOLL, N.W. & HAUG, G.H. 1998. A short circuit in ZHENG, H., POWELL, C.M., AN, Z., ZHOU, J. & DONG, thermohaline circulation; a cause for Northern G. 2000. Pliocene uplift of the northern Tibetan Hemisphere glaciation? Science, 282, 436-438. Plateau. Geology, 28, 715-718.