ORIGINAL PAPER

Newly discovered mud volcanoes in the Coastal Beltof Makran, Pakistan—tectonic implications

Akhtar M. Kassi & Shuhab D. Khan &

Huseyin Bayraktar & Aimal K. Kasi

Received: 11 February 2013 /Accepted: 20 September 2013# Saudi Society for Geosciences 2013

Abstract The Makran accretionary wedge has a much largernumber of mud volcanoes then those reported earlier. Usinghigh-resolution satellite images, over 70 activemud volcanoeswere identified. These mud volcanoes occur within a well-defined zone; we call it the Makran zone of active mudvolcanoes (MZAMV), which is parallel to the regional trendof the accretionary wedge. Mud volcanoes within the zoneoccur as clusters, which form linear belts parallel to theregional thrusts associated with anticlines. TheMZAMV zonealso includes the offshore mud volcanoes occurring in theshallow shelf area, including the recurrently emerging mudislands. Several occurrences of thick deposits of old mudvolcanoes (Pleistocene or even older) are also present withinthis zone, which also display recognizable features that arecharacteristic of the fossil mud volcanoes.We propose that theMZAMV developed and evolved in response to the continuedcompression within the Makran accretionary wedge, which inturn, is a response of the subduction process. Mud diapirismhas been an ongoing phenomena since Pleistocene or evenearlier. The events of enhanced mud extrusion in mud volca-noes and/or emergence of island(s) have relevance with seis-mic phenomena and, therefore, may be closely monitored.

Keywords Accretionarywedge . Cluster . Makran .Mudvolcano

Introduction

Mud volcanoes are expressions of the ejection of mud, fluids,and gases from the rock formations in areas of high-sedimentation rates and compressional tectonics, commonlyin convergent margin settings. The extruded material formscharacteristic isometric to elongate morphological featureslargely varying both in shape (elevated plano-conical to neg-ative funnel-shaped) and size (from 100 km2 to less than10 m2) and composed of mud breccias sharply contrasting tothe surrounding host sediments.

Mud volcanoes have been reported both onshore and off-shore along the Makran accretionary wedge (Snead 1964;Tabrez et al. 1999; Wiedicke et al. 2001; Delisle et al. 2002,Delisle 2004), which is a south-convex arcuate belt of de-formed, mostly mud-rich terrigenous Tertiary succession, al-though thrust-bound blocks of Cretaceous rocks have also beenreported further northward (Hunting Survey Corporation,1961; Kassi et al. 2007). Some occurrences of the mud volca-noes at the coastal belt of Makran, such as the Chandragup,Jabel-u-Ghurab, and Khandawari (Fig. 1) are already known(Snead 1964; Wiedicke et al. 2001; Delisle et al. 2002; Delisle2004); however, we found a large number of mud volcanoesthat have not been reported and/or described before, whichoccur in the form of isolated conical volcanoes, fields/clusters, or elongated ENE–WSW to E–W-oriented ridges.The gas- and water-charged onshore and offshore mud volca-noes extrude methane and higher hydrocarbon derivates(Harms et al. 1982). Release of the pressure for their develop-ment is commonly provided by fault zones and anticlines of theQuaternary to Neogene sediments. They show variations inactivity, which in some cases are concurrent with earthquakes

A. M. KassiDepartment of Geology, University of Balochistan, Quetta, Pakistan

S. D. KhanDepartment of Earth and Atmospheric Sciences, University ofHouston, Houston, TX, USA

H. BayraktarDepartment of Geomatics Engineering, Erciyes University, Kayseri,Turkey

A. K. Kasi (*)Centre of Excellence in Mineralogy, University of Balochistan,Quetta, Pakistane-mail: aimal_kasi@yahoo.co.uk

Arab J GeosciDOI 10.1007/s12517-013-1135-7

(Snead 1964; Wiedicke et al. 2001; Delisle et al. 2002; Delisle2004).

It has been proposed that fault activity may be the keyplayer governing the rate of mud extrusion (Kopf 2008;Bonini 2007, 2008). Even the location of mud volcanoes issometimes used to infer the presence of active fault systems(Lynch and Hudnut 2008). Relationship between earth-quakes and enhanced eruption of mud volcanoes has alsobeen analyzed at the Pede–Apennine margin of theNorthern Apennines and in Sicily (Jakubov et al. 1971;Deville et al. 2003; Bonini 2009). Mud volcanoes some-times erupt within days after nearby large earthquakes(Mellors et al. 2007; Manga 2007; Manga et al. 2009;Madonia et al. 2011), but a correlation between these eventsis not always straightforward. Liquefaction typically occursafter earthquakes in shallow soils and is often manifestedby sand volcanoes (Galli 2000). Liquefaction caused byshaking (dynamic strain) has been proposed to be a poten-tial mechanism for triggering the eruption of mud volca-noes expelling mud from depths exceeding a few kilome-ters (Manga and Brodsky 2006).

The active subduction and compression within the Makranaccretionary wedge has been causing frequent seismic activityand mud volcanism. Three severe earthquakes occurred dur-ing the last 66 years, which also caused tsunamis as well asemergence of mud islands in the coastal belt (Sondhi 1947;Tabrez et al. 1999; Delisle et al. 2002; Delisle 2004).

The objective of this paper is to discuss several newlydiscovered occurrences of the onshore mud volcanoes andold mud volcano deposits in the coastal belt of Makran, usingremote sensing techniques and field observations. Also, we

aim to highlight their tectonic control and relevance withearthquake occurrences.

Geological setting

The Makran convergent margin comprises a wide accretion-ary wedge (Fig. 1), built up by the sediments scraped off theArabian Plate during Late Cretaceous to Early Paleocene(Leggett and Platt 1984; Platt et al. 1985, 1988), which isextremely thick with a gently (2–3 °) sloping subduction zone(Harms et al. 1982, 1984; Kopf et al. 2001). Accretion andunderplating of the sediments caused uplift of the coastal beltand seaward migration of the coastline (White 1983; Plattet al. 1988). Based on morphology, the Makran accretionaryprism has been divided into three domains (Kukowski et al.2001; Schluter et al. 2002; Ellouz-Zimmermann et al. 2007):the accretionary wedge, the trench, and the Murray Ridgesystem.

The onshore accretionary wedge, comprising thousands ofmeters of sedimentary rocks of Cretaceous to Recent age, isarranged in east–west-aligned subparallel ridges and valleys(Table 1; Fig. 2). The succession consists mainly of the LateEocene–Early Miocene turbidite succession. Further inlandthrust-bound inliers of the Upper Cretaceous–Eocene lime-stone, conglomerate, mafic rocks, purple and varicoloredshale, chert and pelagic limestone are also present (HuntingSurvey Corporation, 1961; Cheema et al. 1977; Kassi et al.2007, 2011) within the Late Eocene to Early Oligocene turbi-dites. The younger sedimentary succession is exposed in thecoastal belt of the accretionary wedge, which is composed ofmudstone, cyclically interbedded sandstone and mudstone

Fig. 1 Landsat-5 TM (bands 3-2-1 displayed as Red-Green-Blue) image of the coastal belt of Makran area showing positions of active mud volcanoeswithin the Makran Zone of Active Mud Volcanoes, and deposits of the old mud volcanoes

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and limestone succession (Table 1; Fig. 2; Hunting SurveyCorporation, 1961; Kassi et al. 2007; Kassi et al. 2011).

Due to active subduction and compressive tectonism, theMakran accretionary belt has frequent seismic activity mudvolcanism. Severe earthquakes have occurred, which causedtsunami; enhanced extrusion of mud volcanoes and recurringemergences of mud volcano islands in the Arabian Sea nearthe coastal belt of Makran (Sondhi 1947; Delisle et al. 2002;Delisle 2004; Bilham et al. 2007). The accretionary beltcontains numerous onshore and offshore mud volcanoes,which provide a wonderful opportunity to further study thephenomenon of mud diapirism.

Materials and methods

The paper is based on the use of remote sensing techniquesand field observations. Landsat-5 TM (bands 3-2-1 displayedas Red-Green-Blue) satellite images of the coastal belt ofMakran, specifically of the territory of the coastal belt ofPakistan, have been used for navigation purposes in order toidentify mud volcano occurrences. Field photographs of themud volcanoes and their deposits in some parts of the Makran

accretionary wedge have been used to further elaborate theirmorphological characteristics.

Results

The Makran zone of active mud volcanoes

Mud volcanoes occur at several localities in the coastal belt ofMakran near the towns/villages of Gawadar, Ormara, KundMalir, Bela, and Awaran. Using Google satellite images, weidentified and plotted over 70 active mud volcanoes on theLandsat-5 TM images of the coastal belt (Fig. 1; Table 2),which indicates distribution within a well-defined zone—wecall it the Makran zone of active mud volcanoes (MZAMV).Most of the mud volcanoes are currently active and theirdeposits show various (2–5) clear phases of flows. Depositsof the nearby mud volcanoes of the clusters coalesce to formthick mud volcano deposits. Also, mud volcanoes are distrib-uted in 14 clusters/subclusters. TheMZAMVis aligned parallelto the main trend of the south-convex arcuate accretionary beltand aligned along the major thrusts and anticlinal axes, specif-ically eastwards near the Ornach–Nal Fault System, where theE–W-oriented Makran accretionary wedge bends toward

Table 1 Stratigraphic successionof the Makran Belt [modifiedafter Hunting Survey Corporation(1961; Cheema et al., 1977;Kassi et al. 2007)]

Age Group Formation Lithology

Pleistocene to Holocene Makran group Haro formation Shelly and reefoid limestone,sandstone, and conglomerate

Unconformity

Upper Pliocene Ormara Formation Soft and poorly consolidatedmudstone with minorsandstone

Unconformity

Lower Pliocene Chatti Formation Calcareous shale and marl

Upper Miocene Hinglaj Formation Cyclic succession of sandstoneand shale

Lower Miocene Parkini Mudstone Mudstone with occasionalthin sandstone

Oligocene–Miocene Turbat Group Panjgur Formation Sandstone interbeddedwith shale

Upper Eocene-Lower Oligocene Hoshab Shale Shale with occasional thinbedded sandstone

Thrust

Eocene Wakai Limestone Highly fossiliferous to reefoidlimestone

Thrust

Paleocene Ispikan Formation Conglomerate, sandstone, andminor shale

Thrust

Cretaceous–Paleocene Wakai mélange Agglomerate, purple shale, marl,chert, pelagic limestone, marbleand mafic and ultramafic rocks

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northeast (Fig. 1; Table 2). Here, quantity of mud extrusions ishigher and distances of mud volcano clusters from each otherare smaller as compared to those further westward. Denseoccurrences of the mud volcanoes towards the east is in linewith the eastward increasing rate of plate convergence, frequentoccurrences of thrust-related anticlines, and faults having left-lateral strike-slip components near the Ornach–Nal fault system

(Figs. 2 and 3). Recognition of the MZAMV is in line with thenotion of Schluter et al. (2002), that development and distribu-tion of the mud diapirs and volcanoes are largely controlled bythrusts associated with asymmetrical anticlines (Figs. 2 and 3).

The size and characters of the larger mud volcanoes, i.e.,those recognizable on high-resolution satellite images, werestudied. Coordinates, estimated covered areas, and diameters

Fig. 2 Geological map of part of the coastal belt of Makran (modified after Hunting Survey Corporation, 1961), showing major structural features andtheir relationship with mud volcanoes and their deposits

Table 2 Characters of variousclusters/subclusters of the activemud volcanoes based on satelliteimages

S. No. Name of the cluster No. of mudvolcanoes

Range of coveredareas (ha)

Range of craterdiameters (m)

1 South Chandragup 4 11.90–138.0 22.5–145

2 North Chandragup 5 01.70–1921.0 9.0–118

3 West Chandragup 2 43.70–64.5 108.0–112

4 Jabel-u-Ghurab 4 0.60–02.6 1.5–11

5 North Khandewari 3 0.09–308.2 13.5–110

6 South Khandewari 3 41.00–163.4 Up to 138

7 Kund Malir 16 0.04–118.6 1.0–4.5

8 South Awaran Hills 8 0.03–265.7 1.0–10.5

9 North Awaran Hills 9 0.13–336.2 1.0–7.5

10 Sipai Sing 3 0.19–10.21 5.0–85

11 East Ormara 6 0.63–20.92 1.0–67

12 Central Ormara 1 10.5 1.0–30

13 West Ormara 4 0.06–00.47 1.0–6

14 Gwadar 2 0.11–00.46 1.0–7

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of craters of the recognized mud volcanoes were measuredand their visible characters briefly described (Fig. 1; Table 2).The mud volcanoes pierce the Early Miocene to Pleistocenemudstone-dominant successions. Most of the clusters/subclusters have major vents having large covered areas ofmud flows and a number of smaller satellite vents in thesurroundings. In addition to the previously describedChandragup, Jebel-u-Ghurab and Khandewari clusters(Snead 1964; Tabrez et al. 1999; Wiedicke et al. 2001;Delisle et al. 2002; Delisle 2004), we also discovered a num-ber of mud volcanoes within these clusters. We further dis-covered and named the Awaran Hills, Sipai Sing, KundMalir,Ormara, and Gwadar clusters after the nearby towns/villagesof the coastal belt (Fig. 1; Table 2). They are described asunder:

Chandragup cluster

In the Chandragup cluster, mud volcanoes are spread 2–8 kmnorth of the coast east and southeast of the Hingol River and isconsidered as the largest active mud volcanoes of the region(Table 2; Figs. 1, 4a and b). It comprises 11 mud volcanoes,along with some dried-up vents, distributed in three subclus-ters named as South, North, and West Chandragup. The WestChandragup subcluster is 18 km northwest of the alreadyknown Chandragup (i.e., our South Chandragup subcluster)(Snead 1964; Wiedicke et al. 2001; Delisle et al. 2002; Delisle2004). A number of small mound-like features are also pres-ent, which were satellite vents that are presently not active.Covered areas of the mud volcano deposits range between 1.7and 1,921 ha (Table 2). Diameters of the craters range from 9to 145 m. Diameter of the craters have no relationship with thesize and covered area of the mud deposits. Most of the mudvolcanoes (8 out of 11) of the North and South Chandragupclusters are presently active, i.e., extruding fluidized mud andhydrocarbon gases; however, they show fluctuations in extru-sion activity. Mud deposits, by virtue of their episodic activity

of mud extrusion, indicate 2–5 apparent phases of mud flowsthat are clearly visible on high-resolution satellite images.

The Chandragup-I has a crater of 20-m diameter filled withviscous fluidized mud. The mud bubbles up and sometimesburst violently in order to emanate hydrocarbon gases(Fig. 4b). Crater of the South Chandragup-II is a circularwater-filled lake, which is 2.5 m below the circular edge ofits crater, showing very minor activity of gas bubbling andweak extrusion of muddy water in its central part (Fig. 4b).Circular walls of the crater are partly eroded and collapsed. Itseems that mud extrusion has decreased currently, whichcaused the water level to drop within the crater and erode itsolder deposits. The Chandragup-III is 30-m high from thesurrounding ground level and appears to have dried-up cur-rently. Our data (Fig. 1; Table 2) indicates that, instead of just3–4 mud volcanoes, that were reported earlier (Stiffe 1874;Snead 1964; Reimann 1989; Delisle et al. 2002), 11 moremudvolcanoes exist in the Chandragup area, which make up threesubclusters of the South, North, and West Chandragup.

Jebel-u-Ghurab cluster

The Jebel-u-Ghurab cluster of mud volcanoes (Fig. 1) lieswithin the flat-lying Dhak Desert formed by playa-like sedi-ments, 1 km west of the Dhak Anticline (Reimann 1989).Because of their small sizes, only four mud volcanoes arerecognizable on the satellite image (Fig. 1; Table 2), althoughseveral small mound-like feature have been reported(Reimann 1989; Delisle et al. 2002). Mud volcanoes of theJebel-u-Ghurab range in covered area from 0.6 to 2.6 ha.Diameters of the observed craters range from 1.5 to 11 m.Delisle et al. (2002) suggested that presence of these mudvolcanoes within the core of the anticline might be because oftheir relevance with this tectonic feature for concentration ofgas near the crest of anticline. Also, fractures along the axis ofthe anticline may have provided passages for extrusion ofmud-water and gas. Delisle et al. (2002) further explained that

Fig. 3 Sections across the area showing major structural features and their relationship with mud volcanoes and their deposits

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several small-size active mud volcanoes and mounds arepresent, which have elevations from 1 to 8 m and range incircumference from <5 to 50 m; some are dried-up others arewater-filled. One of the mud volcanoes represent a hummockyhill with a flat top surface having several small mini-craterswith bubbling of gas discharge and minor outflows of mud.The larger mud volcano shows two subcircular water andmud-filled craters having lateral slumps (over-steepenedmudflows) and fans of mudflows onto the adjacent playa-like plain.

Khandewari cluster

The Khandewari cluster of mud volcanoes comprises six mudvolcanoes located at the NNE–SSW-oriented Haro Range,30–35 km northeast of the South Chandragup subcluster(Fig. 1; Table 2). Mud volcanoes within the cluster are orient-ed parallel to the strike of the range, however, they comprisethe South and North Khandewari subclusters (Figs. 1 and 4c).One of the mud volcanoes in the North Khandewari subclusteris represented by a very large, circular cone-shaped mud

Fig. 4 Satellite images and field photographs showing mud volcanoes ofthe Chandragup, Khandewari and KundMalir clusters; a Satellite view ofthe South Chandragup subcluster; note contrasting colors of variousfluxes of mud flows of the same vent; blue colored mud shows the mostrecent flow, b field photographs of a mud volcano of the South

Chandragup subcluster, showing mud and gas extrusion and formationof huge mud bubbles, c close-up view of the mud volcanoes of the SouthKhandewari subcluster; contrasting colors of various fluxes of mud flowsare very clear, d close-up view of the main mud volcano of the KundMalir cluster with several satellite crates in the surrounding area

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volcano deposit, which resulted from the outpouring of mudfrom one or more central vents. Presently, the cone seems tohave been built from a series of dried-up and erodedmud flows.Covered areas of mud volcano deposits of the Khandewaricluster vary between 0.09 and 308.2 ha (Table 2). Diametersof the craters of the Khandewari cluster range from 9 to138 m;however, they have no relationshipwith the size or covered areaof mud deposits. All six mud volcanoes of the cluster are activeand extrude fluidized mud, however, they show recurrentlyactive periods followed by periods of quiescence. Mud volca-noes, by virtue of their episodic activity, clearly show 2–5phases of mud flows on the high-resolution satellite image.

Kund Malir cluster

TheKundMalir cluster is named after the village of KundMalir,situated near the Makran Coastal Highway (Fig. 1), but notmentioned or described before. The cluster is situated 4.5 kmnortheast of the KundMalir village (Figs. 1 and 5c; Table 2). Thecluster comprises 16 mud volcanoes, spread over a 5-km NE–SW-oriented strip along the southwestern side of the MalanRange and arranged subparallel to the orientation of the range.Covered area of the Kund Malir mud volcano deposits a rangebetween 0.04 and 118.6 ha. Mud flows of most of the mudvolcanoes coalesce with each other to form thick mud volcanodeposits. Diameter, the largest crater within the Kund Malircluster is 25 m. Generally the old mud volcano deposits coverlarger areas as compared to their fresh mud extrusions (Figs. 1and 4d; Table 2). All mud volcanoes of the cluster are active.

Awaran Hills and Sipai Sing clusters

The Awaran Hills and Sipai Sing clusters of mud volcanoeshave not been mentioned or described before. Over 20 mudvolcanoes are present in the Awaran Hills west and southwestof the town of Bela (Fig. 1; Table 2). Mud volcanoes arespread over a 58-km longN–S-oriented strip generally parallelto the strike of the Awaran Hills and grouped into the Southand North Awaran Hills and Sipai Sing subclusters. Theircovered areas range from 0.03 to 336.2 ha. Most of the mudvolcanoes in the Awaran Hills clusters are active and theircrater diameters range between <1 to over 85 m. The SipaiSing subcluster comprises three mud volcanoes present withina vast area (18 km2) of old mud volcano deposits near theSipai Sing area, 45 km east of the Awaran (Fig. 1; Table 2).Two mud volcanoes of the Sipai Sing subcluster have thelargest crater diameters among the Awaran Hills and SipaiSing clusters, having crater diameters of 85 and 13.5 m,respectively. Mud volcanoes of these clusters are mostly ac-tive showing 2–5 clear phases of mud flows.Mud flows of theadjacent mud volcanoes coalesce to form thick deposits.

Ormara clusters

Although mud volcanoes have been mentioned to be presentin the Ormara area (Delisle et al. 2002), they have not beendescribed before. The Ormara mud volcanoes are present in aflat area 9–10 km north–northeast of the coastal town ofOrmara, south of the Gurad Hills (Figs. 1 and 5a). They aredistributed in three subclusters, spread over a 9-km long and2.5-km wide area, having east–west orientation generallyparallel to the regional trend (Fig. 1; Table 2). Eleven mudvolcanoes have been recorded in the cluster, which range in acovered area between 0.63 and 20.92 ha. Covered areas of thelarge mud volcanoes also include several (in some cases up to25) small mounds/satellite craters. Crater diameters rangebetween <1 and 67 m. Almost all mud volcanoes listed inthe Ormara cluster are active.

Gwadar cluster

Mud volcanoes have been reported near the coastal city ofGwadar (Delisle et al. 2002); however, they have not beendescribed before. A cluster of mud volcanoes is present 9 kmnorth–northeast of the Gwadar town near the western edge ofan east–west trending hill, 3 km south of the Gwadar Airport(Figs. 1, 5a and b; Table 2). On the high-resolution satelliteimage, two mud volcanoes may be seen along with some mudmounds in the nearby surroundings (Fig. 5a). The main mudvolcano has a covered area of 0.47 ha and a small crater lakeof 7-m diameter. A nearby mound covers an even smallercovered area of 0.11 ha and does not seem to be active. Somevery small mud volcanoes have also been reported by the localcommunity; however, they are not large enough to be ob-served on satellite image.

Discussion

In addition to the four mud volcanoes reported by the previousworkers (Snead 1964; Wiedicke et al. 2001; Delisle et al.2002; Delisle 2004), we have identified and described theSouth Chandragup subcluster and the South Khandewarisubcluster. Our data (Fig. 1; Table 2) indicates that 11 mudvolcanoes are present in the Chandragup area, making threeprominent subclusters. Furthermore, we have reported sixmud volcanoes within the Kundewari cluster.

The Kund Malir cluster, comprising 16 mud volcanoes, andAwaran Hills and Sipai Sing cluster/subclusters, comprising 20mud volcanoes, are hereby reported and described for the firsttime. (Table 2; Fig. 4d). Also, we have reported 13 mudvolcanoes in the Ormara area, comprising 3 prominent subclus-ters, and a cluster of 4 mud volcanoes in the Gwadar area(Figs. 1 and 5; Table 2). The plot shows that mud volcanoesand their deposits are distributed over a much wider area of the

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Makran accretionary wedge (Fig. 1; Table 2) than those report-ed earlier (Stiffe 1874; Snead 1964; Reimann 1989; Delisleet al. 2002) and that mud volcanoes are more common withinthe eastern part of the accretionary wedge.

Old mud volcano deposits

In addition to the onshore and offshore occurrences of mudvolcanoes, several occurrences of old mud volcano depositsare present in the coastal belt of Makran (Fig. 1), which maybe as old as Pleistocene (or even older). Old mud volcanodeposits comprises greenish gray to bluish green mudstonefound in the Haro Range, Awaran Hills, Malan Range,Kappar, and Barambah (north of Gwadar) and several otherlocalities. Occurrences of the old mud volcano deposits(Fig. 1) indicate that they are part of the MZAMVand parallelto the regional trend of the accretionary wedge. However, theold mud volcano deposits are also spread further north of theMZAMV.

On a road-side exposure 46 km northeast of the coastaltown of Gwadar, 4 km north of the Kappar village, thePliocene mudstone has been dissected by streams and inter-esting features of the old mud volcanoes are exposed over awide area. They include vertically oriented cylindricalchimney-like features of variable diameters (up to 3 m indiameter) and a network of smaller branched cylindrical fea-tures of different orientations (Figs. 5d, e). These featuresindicate that mud extrusion has been a widespread phenome-non during Pliocene. The Hunting Survey Corporation (1961)termed one unit in a north–south section along the HingolRiver as "extrusive mud formation" (Figs.2 and 3) and sug-gested that during the past, huge amounts of gas- and water-charged mud were extruded to the surface, in analogy tocircular mud volcanoes, and emplaced along fault structures(several tens of kilometers long) unconformably into the EarlyPliocene mudstone succession (Hunting Survey Corporation,1961; Bannert et al. 1992). Figures 2 and 3 indicate that theactive mud volcanoes and the old mud volcano deposits, the"extrusivemud formation" of the Hunting Survey Corporation(1961), are clearly related with the asymmetrical anticlines ofthe coastal belt of Makran. The thrusts had been providingpassages for the extrusion of water mixed with mud and gasand the mud being derived from older mud-rich succession ofParkini Formation.

The old mud volcano deposits are common within thePliocene mudstone succession further inland in the Makrancoastal belt (Figs. 1, 5d, e). We have identified and mappedseveral occurrences of old mud volcano deposits within thecoastal belt of Makran (Figs. 1 and 2), which suggests thatmud volcanism had been a widespread phenomena during thepast, and that some mud volcano deposits may be Pliocene oreven older. Earlier publications have not differentiated be-tween mud volcanoes sensu stricto and mud intrusions termed

“extrusive mud formation” (Hunting Survey Corporation,1961). Our plots of the old mud volcano deposits on satelliteimages (Fig. 1), as well as the “extrusive mud formation” ofthe Hunting Survey Corporation (1961) indicate that they areclosely related with the MZAMV.

Offshore mud volcanoes

A number of offshore mud volcanoes have been reported onthe shallow shelf and deeper parts of the Makran accretionarywedge (Sondhi 1947; Tabrez et al. 1999; Delisle et al. 2002;Delisle 2004; Wiedicke et al. 2001). Some of these mudvolcanoes, occurring on the shallow shelf area, have beenemerging recurrently as mud islands. Sondhi (1947) docu-mented the emergence of three mud islands in the ArabianSea off the coast of Makran, which he linked with the bigearthquake (magnitude 8.2) of November 1945. A typicalexample is the Malan Island (Figs. 1 and 5c), which emergedthree times on the same locality since 1945. Its first emergenceduring November 1945 was in association with the big earth-quake of November 1945, whereas its second emergence (on15th March 1999) was seemingly without any associationwith an earthquake. The island, in its initial stage of emer-gence, was round-shaped and covered an area of up to 5.2 ha,however, being mainly composed of soft sediments, waves/tides eroded the island in less than a year. The third emergenceof the Malan Island occurred during November 2010.

The recurring emergence of mud islands indicates episodesof enhanced mud extrusion, which may be relevant withhigher rates of compression and/or major (or minor) seismicevents. The enhanced mud extrusion events of onshore mudvolcanoes within the Makran coastal belt have been shown tobe associated with the earthquakes (Sondhi 1947; HuntingSurvey Corporation, 1961). Aerial photographs taken on 25January 1946 of Chandragup-I and the Khandawari mudvolcano show evidence of vigorous mud flow from bothcraters. Snead (1964) mentioned enhanced activity ofChandragup-I and -II in response to a small earthquake on26 September 1956. He further reported that the clear watercrater of the Chandragup-II was replaced by mud, the level ofthe fill rose by 2 ft, and mud extrusion was found to have"splattered approximately 20 ft upon the side of the crater" and

�Fig. 5 Satellite images and field photographs showing mud volcanoes ofthe Ormara and Gwadar clusters and features present in the old mudvolcano deposits; a satellite view of theOrmara cluster, b satellite view ofthe Gwadar cluster, c field photograph of the main mud volcano of theGwadar cluster, d photograph of the recurrently emerging Malan Islandin the Arabian Sea near the coastal belt of Makran, e flat-lying mudstonesuccession containing profusion of comparatively resistant cylindricalchimney-shaped features sticking out of the soft mudstone, and f close-up view of the cylindrical chimney-shaped features cutting across themudstone/siltstone horizons, hammer for scale

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that the presently dormant, 30-m high, mud volcano ofChandragup-III had erupted in the summer of 1959 and pro-duced mudflows on its flank, which had dried-up during hisvisit in fall.

The island was composed of irregular mass of light greenishgray to very light gray mud breccias with very poorly sortedangular boulder- to cobble-size fragments of sandstone. Itcontained various circular vents, which episodically extrudedthick mud slurry, violently in the initial stages, along withhighly inflammable methane gas. We propose that the recur-rently emerging Malan Island represents response of cyclicphases of enhanced mud extrusion, which in turn, are relatedwith the compression and seismic events. The enhanced extru-sion events are followed by periods of relative quiescencecharacterized by moderate activity and subsequent disappear-ance in response to erosion by waves/tides (Deville andGuerlais 2009). The plot of the occurrences of mud volcanoeson satellite image and geological map (Figs. 1 and 2) indicatesthat the offshore mud volcanoes, including the Malan Island,are part of the MZAMV. The Malan Island (previously calledHingol Island) is the lateral continuation of the Chandragup andKhandawari clusters, which also line-up along the axis of theDhak Anticline with a thrust (Figs. 1, 2, and 3). The active mudvolcanoes lay along the major fault zones (Vredenburg 1909;Sondhi 1947). The previously reported four mud volcanoes ofthe Chandragup-I, -II, -III, and -IV and Jebel-u-Ghurab clusterare associated with the axis of the Dhak Anticline, however, theremaining two subclusters of the North and West Chandragupline-up with another thrust north of the Dhak Anticline (Fig. 1;Table 2). Plot of the mud volcanoes on the Landsat-5 TMimages indicates that mud volcanoes occur within a prominentzone, which we call the Makran zone of active mud volcanoes(Fig. 1). Our plot demonstrates that almost all clusters andsubclusters of mud volcanoes line-up along the tectonic linea-ments and define the ascend paths of the fluidized mud.

Apart from the offshore mud volcanoes that occur in theshallowmarine part of theMakran coastal belt, Wiedicke et al.(2001) have mapped conical mounds of 1±1.5-km diameterand up to 65-m height at the foot of the active Makrancontinental margin, which developed seaward of the accre-tionary front in a relatively planar zone, where the build-up oftectonic pressure initiates deformation. Wiedicke et al. (2001)suggest that mud volcanism evolved at twomain sites seawardof accretionary front of the Makran continental margin, wherelarge conical mounds have been developed and currentlyappear to be inactive. These large mounds are accompaniedby several small mounds; judging from the shallow seismicrecords, some of these may be very young. A nearby buriedmound, approximately 460 ka old, suggests that the process ofmud extrusion may not be ephemeral at this structural positionof the accretionary margin; a careful survey should discovermore features of this kind, active and fossil ones (Wiedickeet al. 2001).

Conclusions

(1) The number of active mud volcanoes in the Makranaccretionary wedge is much higher than those reportedearlier. Using high-resolution satellite images, over 70active mud volcanoes were recognized, plotted on mo-saic of four Landsat TM images and described. Mudvolcanoes occur in 14 clusters and subclusters.

(2) The active mud volcanoes occur in a well-defined zone;we call it the MZAMV, which is parallel to the regionaltrend of the accretionary belt. The zone, as well as itscomponent clusters and subclusters, generally line-upalong thrusts related with the axes of the anticlines.

(3) The MZAMValso includes the offshore mud volcanoesof the shallow shelf area, specifically the “Malan Island,”that has periodically emerged and vanished three timessince 1945 on the same locality. The phenomena hasbeen going on during the geological past and anticipatedto continue in the future. The Malan Island (previouslycalled Hingol Island) is the lateral continuation of theChandragup and Khandawari clusters, which also line-up along the axis of the Dhak Anticline associated with athrust. Several occurrences of very thick mud depositsare present within the MZAMVand further north, havingtrends parallel to the Makran accretionary wedge anddisplay features that are characteristic of the old mudvolcanoes, suggesting that mud volcanism has been anongoing phenomena since Pliocene or even earlier.

(4) The enhanced mud extrusion activity, i.e., violent extru-sion of mud volcanoes and/or emergence of islands haverelevance with seismic phenomena and, therefore, maybe taken seriously.

(5) The clusters/subclusters of mud volcanoes line-up alongthe thrusts and anticlinal axes, which defining the ascendpaths of the fluidized mud.

Acknowledgments AMK is thankful to the J. William Fulbright For-eign Scholarship Board, Bureau of Educational and Cultural Affairs,United States Department of State, and Council for International Ex-change of Scholars for his selection for the Post-Doctoral Fellowshipand cooperation throughout his stay during 2010–2011. Vice Chancellor,University of Balochistan is acknowledged for approval of sabbaticalleave for AMK.

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