Journal of Asian Earth Sciences, Vol. 16, Nos. 2-3, pp. 109-118, 1998 Pergamon 0 1998 Elsevier Science Ltd. All rights reserved Printed in Great Britain PII: SO743-9547(98)00087- 1367-9120198 $ - see front matter

Discovery of abundant arthropod trackways in the ?Lower Muth Quartzite (Spiti, India): implications for the depositional environment E. Draganits$* B. Grasemannt and S. J. Braddyt $Institut für Geologie, University of Vienna, Altanstrasse 14, A-1090 Vienna, Austria "fepartment of Palaeontology, University of Bristol, Queen's Road, Bristol BS8 lRJ, U.K.

(Received 2 July 1997; accepted in revised form 6 February 1998)

Abstract-Arthropod trace fossils are described from the ?Lower Devonian Muth Quartzite (Spiti, India), a sequence virtually devoid of fauna1 evidence. Trace fossils, which are abundant and often well preserved, mainly consist of arthropod trackways; some burrows are present, too. The ichnogenera of the trackways include numerous Palmichnium and rarer . The first can probably be assigned to and the second is probably related to myriapods. Sedimento- logical observations point to deposition of the Muth Quartzite in a foreshore/backshore environ- ment. This combination of and myriapod trackways is a spectacular indication of early terrestrialization. 0 1998 Elsevier Science Ltd. All rights reserved

Introduction erature, only the white Muth Quartzite of Hayden (1904) is regarded as being the Muth Formation, Within the Tethyan Zone (Tibetan Zone, Gansser, whereas (a) and (b) belong to the Shian 1964) sediments along the northern margin of the Quartzite Formation and (c) to the Pin dolo- Indian plate ranging from to Eocene, the mite Formation (Srikantia, l981; Bagati, 1990). white Muth Quartzite is one of the most striking mar- Bhargava and Bassi (in press) included only the pure, ker horizons, and has been traced throughout the white quartz arenite in the Muth Formation, from its whole NW Himalayas, from Kashmir to Nepal first appearance above the Pin Dolomite up to the first (Gansser, 1964). In spite of its considerable importance carbonate bands, which are regarded as lowest Lipak for correlation in regional mapping, due to its easy Formation. recognizability in the field, the age of the Muth In the Pin Valley (Fig. 1) the Muth Formation con- Quartzite is poorly constrained and its depositional en- vironment is still under debate. The recent discovery of sists of a lower unit of pure, white, mature quartzare- abundant trace fossils in the Muth Quartzite may nites, followed by alternating pure quartzarenites and prove helpful in the reconstruction of its depositional hybrid dolomitic arenites (Fuchs, 1982; Bagati, 1990). environment. The upper unit is similar to the late Devonian dolo- In the Spiti area, the Tethyan sediments were mites, calcareous quartzites and quartzarenites in wes- deformed during the Himalayan orogeny into large- tern Dolpo, Nepal (Fuchs, 1977; Flügel and Tintori, scale upright folds, with axes trending NNW-SSE and 1993). Although a littoral to aeolian deposition is wavelengths of approximately 5 km (Fuchs, 1982). The assumed for the white quartzarenites, the upper unit, quartzite represents a more competent layer within the with the rare occurrence of coral patch reefs, indicates pile of Tethyan sediments, thus showing no second a shallow marine depositional environment (Garzanti order folding as less competent formations do, and as et al., 1996). This succession seems to be invalid for a result, sedimentary structures are well preserved. the whole outcroping area of the Muth Formation, since contrasting sedimentary successions have been described, for example by Mukherjee and Dasgupta Stratigraphical setting (1972) and Kumar et al. (1977). The Muth Formation is conformably underlain by The term "Muth Series" was first used by Stoliczka the Silurian Pin Dolomite, which is correlated with the (1865), who assigned a probable Silurian age to the Takche Formation in the Ladakh area (Kumar et al., unit. Oldham (1888) correlated the Muth Series with 1977; Baud et al., 1984) and the Manchap Formation the of Kashmir, a correlation also fol- in the Kinnaur region (Bhargava and Bassi, 1986). lowed by Griesbach (1891). In the definition of Bhargava (1997) on the other hand describes a sharp Hayden (1904) the Muth System included: (a) Dark lower contact. The Pin Dolomite comprises an interti- coral , (b) Red quartzite, (c) Coral limestone dal to littoral, well sorted argillo-arenaceous succes- and (d) White Muth quartzite. However, in recent lit- sion with sporadic small reefal complexes with a gradual contact to the littoral sand deposits of the * Author for correspondence. Muth Quartzite, displaying a shallowing upward 109

110 E. Draganits et al.

Fig. 1. Geological map of the study area. Arrow indicates the outcrop with trackways. throughout the whole basin (Bhargava and Bassi, limit and a Mid Devonian upper age limit for the 1986). Muth Quartzite. Talent et al. (1988, p. 22) suggest a In contrast to the transitional lower boundary, the sedimentation of the Muth Quartzite somewhere in the upper contact of the Muth Formation, with the over- interval Ashgill-Ludlow. lying Lipak Formation, is conformable but fairly sharp (Baud et al., 1984). Gaetani et al. (1986) report Lower age limit an intercalation of white quartzarenites (Muth Quartzite) with dark grey arenites (Lipak Formation) Hayden (1904) found the Pentamerus in some parts of the contact near Tanze (Zanskar), but oblongus in the Pin Dolomite in beds just below the also a sudden contact between white microconglome- Muth Quartzite and suggested a Late Silurian to rates with black silty can be found. An con- Devonian age. Mukherjee and Dasgupta (1972) men- formable, gradual upper contact has been confirmed tioned the existence of tabulate corals in grey siliceous by own field studies at the type locality near Muth limestones below the Muth Formation, near the type (Pin Valley). The dark limestones, with minor incur- locality, and proposed a Mid Silurian age. Fuchs sions of and mudstone in the lower part, of (1982) described the frequent occurrence of the Lipak Formation represent a shallow subtidal car- Psilophyton princeps from beds just below the Muth bonate shelf environment (Bagati, 1990). Formation, west of Losar (Spiti, Pin Valley). The Early to Mid Silurian age of the reefal buildups within the Pin Dolomite are well established from numerous Age of the Muth Formation corals, bryozoans and (Bhargava and Bassi 1986). Copper and Brunton (1991) favoured an Due to its very limited fossil content, the age of the Early Silurian Age. Muth Quartzite is highly controversial (see Talent et al. (1988) for the special problems of this subject). Upper age limit Commonly the Muth Formation has been dated in- directly by its stratigraphic position. In its type locality Mukherjee and Dasgupta (1972) describe brachio- the Muth Quartzite gradually passes from underlying pods of Mid- to Late Devonian age in greyish fossili- fossiliferous Silurian dolomites into limestones of the ferous limestone-beds of the Lipak Formation, just overlying Lipak Formation containing Mid- to Late 7 m above the top of the Muth Formation. Fuchs Devonian fossils (Chaterji, 1967). Mukherjee and (1982) found badly preserved Late Devonian brachio- Dasgupta (1972) estimated a Mid Silurian lower age pods in the basal beds of the Lipak Formation WNW Discovery of abundant arthropod trackways in the ?Lower Devonian Muth Quartzite 111

Muth. Baud et al. (1984) mentioned a rich fauna of brachiopods and bryozoans north of Sarchu (Zanskar) about 20 m above the bottom of the Lipak Formation, representing an Early Carboniferous age. Bassi (1988) discovered Orthis aff. rustica in the middle part of the Muth Quartzite, 1 km W of Khimokul La, Kinnaur. Conodont dating in carbonates of the upper Muth Formation indicated Late Fammenian age (Garzanti et al., 1996). Recent dating of the Lipak Formation in the Pin valley, near Guling, using conodont fauna, in- dicate a Devonian age for the whole formation, a sample from 27 m above the Muth Formation at the type locality gave a reliable Mid Devonian age (pers. comm. Krystyn, 1997). Although there may exist considerable variations of facies and stratigraphic range in its broad extent (Fuchs, 1977), the consensus is that the Muth Formation in the Spiti area was deposited at some time in the Late Silurian to Mid Devonian, the authors believe in a Early Devonian age.

Facies Although the appearance of the Muth Formation is quite uniform throughout its whole outcrop, the thick- ness varies from about 200 m to 444 m (Baud et al., 1984; Bagati, 1990). The formation consists of thick bedded, striking white to light grey, fine to medium grained, submature to supermature, quartz-cemented quartzarenites (Gaetani et al., 1986). Beds of grey car- Fig. 2. Muth Quartzite outcrop SE of Mikkim, looking to the South. bonaceous quartzites, sandy dolomites and dolomites B. Grasemann is standing on sub-horizontal, large-scale tabular fore- intercalated with quartzites occur in the uppermost sets, a sedimentary surface is visible in the background, running part (Fuchs, 1982; Bagati, 1990). from the left to the right side dipping to the West with an angle of Several depositional environments have been pro- about 40°. Foresets and sedimentary surfaces are tilted due to fold- posed for the Muth Quartzite: Mukherjee and ing around a NNW-SSE trending fold axis. Dasgupta (1972) discussed a shallow marine re-sedi- mentation of eolian desert sands. A beach environment was assumed by Banerjee (1974), Ranga Rao et al. layers remains constant during orthogonal flexure. The (1984), Bhargava and Bassi (1986) and Gaetani and quartzite predominantly shows large scale, tabular- Garzanti (1991). Kumar et al. (1977) and Bagati planar cross-stratification, with subordinate tangential, (1990) considered a shallow marine sand bar/shoal concave-up crossbeds, but wedge-shaped-planar sets complex, while an aeolian origin is mentioned by and horizontal stratification also occur (Fig. 2). Dasgupta (1971) and Garzanti et al. (1996). Reactivation surfaces are present. Single foresets are Fuchs (1977) emphasised a pronounced facies vari- about 20 cm thick, display a millimetre to centimetre ation during the Devonian, with a distinct shallowing scale lamination of finer and coarser sand. Some fore- towards the W. The flyschoid Tilicho Pass Formation set-laminae are reverse graded in the upper part, simi- of central Nepal grades laterally into the dolomites lar to the aeolian pin-stripe lamination described by and calcareous quartzites of western Dolpo, which are Fryberger and Schenk (1988). The angle between fore- probably equivalent to the beach sands of the Muth sets and bedding surfaces ranges between 13-30° with Quartzite in Spiti (Fuchs, 1977). Flügel and Tintori a mean angle of 24°. (1993) suggested that the correlation of the dolomites After restoring the bedding surfaces to the horizon- in central Dolpo with the Muth Formation of Spiti tal around the fold axis, the dip of the foresets indi- was too poorly constrained and preferred to designate cates a bimodal ENE- and WSW-ward paleocurrent these beds as "fossiliferous Late Devonian direction with a strongly dominating ENE-ward direc- Limestone". tion, corresponding well with the paleocurrent direc- In the Pin Valley east of Mikkim, the white Muth tions of the Muth Formation in the Malla Johar area, Quartzite crops out in a 2 km long area in an inclined, to the ENE (Kumar et al., 1977), and in the Zanskar horizontal, SW-vergent anticline, with a NNW-SSE area, to the E (Gaetani et al., 1986). Asymmetrical rip- trending fold axis and a total thickness of about 300 m ples on bedding surfaces show a greater variation of (Fig. 1). Deformation is related to orthogonal flexure directions, but mainly also point to a NE-directed (Twiss and Moores, 1992) accommodated by a micro- paleocurrent. fracture cleavage, extension gashes and pressure sol- Ripples are common, most of them are symmetrical, ution. Concerning sedimentological sections it is but slightly asymmetrical ripples are also present. They important to note that the orthogonal thickness of the have average amplitudes of 0.6 cm and 4-6 cm wave- 112 E. Draganits et al. lengths; the ripple index L/H ranges from 4 to 14. part, containing most of the arthropod traces, and a Ripples are typically sub-parallel crested, slightly sinu- shallow marine, tidal influenced upper part (Trewin ous and often bifurcated, resembling many attributes and McNamara, 1995 and references cited therein). of wave ripples. Interference ripples with rounded The sedimentary environment of the Taylor Group of crests, also recorded in the Muth Quartzite in Lahul the Beacon Supergroup of southern Victoria, by Vannay (1993) can be found. A strong argument Antarctica was under debate for a long time, in the for at least temporarily emergent conditions is the more recent literature a non-marine in a fluvial to allu- occurrence of scour-remnant ridges (Allen, 1965). They vial plain environment is favoured (Woolfe, 1990, and occur on upper bedding surfaces, showing a stream- references cited therein). lined shape with the steeper side facing windwards and are up to 4 cm long, about 0.2 cm high and up to 0.7 cm wide. This feature, which is wholly erosional in Locality details origin, is chiefly related to aeolian deflation and rep- resents a common surface structure on beaches (Allen, In the Pin Valley, at an altitude of about 3640 m, 1965). It is important to note that these scour-remnant SE of Mikkim, at the river junction of the Pin River ridges indicate a paleowind direction to the west, and the Parahio River, where the Pin River cuts into which is exactly the opposite direction indicated by the the western termination of the Muth Quartzite, river dip of the foresets. An additional sedimentological fea- erosion and weathering have exposed the steeply dip- ture are desiccation cracks, which have also been ping quartzite, producing fresh bedding and foreset observed by Bagati (1990) in the Muth Quartzite near surfaces, on both of which abundant superbly pre- Takcha and Khar. served trackways have been found (Fig. 1). Trackways The general mineralogy of the Muth Quartzite in also occur in other parts of the Muth Quartzite out- the Pin Valley near Mikkim is strongly dominated by crop, but are scarce and often badly preserved. moderately to well sorted quartz grains, with a very The rock surfaces show a white color when they are low polycrystalline to total quartz ratio (Gaetani et al., relatively fresh, but become progressively darker, from 1986). There are hardly any other minerals present in pale yellow to orange to dark brown, when they have thin section; of the heavy minerals only zircon and been exposed to weathering for a long time. They com- well rounded blueish tourmaline occur (Vannay, 1993), monly display dissolved surfaces with small, irregular which are considered as ultrastable during sedimentary solution hollows (resembling raindrop impressions), processes. There is virtually no clay matrix present. due to chemical weathering under probable weak alka- Due to post-depositional alterations of the quartzar- line rainwater conditions (Dongarrá and Francofonte, enite, including pressure solution and silica over- 1995). Additionally, rock surfaces are coated with dark growth, grain size analyses are difficult to carry out. brown to black, shiny rock varnish, often veiling the The size of quartz grains varies from 0.12-0.75 mm, trackways and primary sedimentary structures. Rock with two maxima of about 0.13-0.16 mm and 0.35- surfaces more exposed to the wind show substantial 0.60 mm. This bimodal distribution of grain sizes has abrasion. been described from the Muth Quartzite in several areas; Spiti (Dasgupta, 1971; Mukherjee and Dasgupta, 1972), Zanskar (Gaetani et al., 1986) and Description of trackways Lahul (Vannay, 1993). Several authors explain this bimodal distribution of grainsizes by grain sorting Several clearly distinct arthropod trackway types during aeolian transportation in the Muth Quartzite. have been recorded. The trails vary in their external However, bimodal grainsize distributions are also width from 4-50 cm and comprise circular, elongate, found in several other depositional environments crescent-shaped and scratch-like imprints, forming (Taira and Scholle, 1979). straight to curved trackways with track lengths of up The nearshore/foreshore/backshore environment to 3 m or more. A variety of limb and telson im- shows a huge variety of depositional structures due to pressions have also been preserved. the action and interaction of several marine processes Besides the more striking arthropod trackways also driven by wind, waves and currents. Many of these some burrows have been recorded (Fuchs 1982; sedimentary structures are quite similar and often Bhargava and Bassi 1988). They consist of gently grade laterally into one another, resulting in a complex curved endichnial burrows, usually continuous for pattern of depositional environments, complicating about 10 cm, occuring mainly horizontally on bedding their interpretation, especially in the fossil record surfaces, gradually fading-out across the surface. These (Davis 1992). burrows generally preserved as open tunnels, circular The present authors suggest a deposition of the in cross-section and are 0.9-1 cm in width (Fig. 3(a)). Muth Quartzite in the Pin Valley in a foreshore/back- A second distinct group of burrows are only about shore environment. Comparable sedimentary environ- 0.4 cm in width. These burrows are more strongly ments with striking similar ichnoassemblages of curved and show several junctions. They are also end- roughly the same age are described from Antarctica ichnial burrows on bedding surfaces, but as a differ- and Australia (Gevers et al., 1971; Trewin and ence they are filled in their whole length (Fig. 3(b)). McNamara, 1995). The ?Upper Silurian Tumblagooda The interpretation and ichnotaxonomy of the trace- Sandstone of Kalbarri, Western Australia consists fossils remains preliminary; more observations, which mainly of sand-size sediments interpreted as a fluvial will be carried out during the fieldwork in the Summer braided outwash plain in its lower part, a mixed fluvial of 1997, are required for a complete systematic sandsheet and aeolian dune development in the middle ichnology. Discovery of abundant arthropod trackways in the ?Lower Devonian Muth Quartzite

(a)

(b)

Fig. 3. (a) Gently curved endichnial burrows, generally preserved as open tunnels, circular in cross-section and 0.9-1 cm in width. (b) Burrows which are only about 0.4 cm in width and moderately curved showing several junctions. They are endichnial burrows on bedding surfaces and are filled in their whole length.

Palmichnium antarcticum (Gevers et al., 1971) In most trackways, there are two pairs of tracks on either side of the mid-line. However two excel- Trackways of this type are preserved on both bed- lently preserved trackways show three tracks in a ding surfaces and foresets, in approximately equal series (Fig. 4(a) and (b)). The outer and middle abundance. Trackways display a wide size range; the tracks are variable in their appearance, depending on internal width (Trewin, 1994) varies from 3.9-24.5 cm their level of preservation. In well preserved track- and the external width from 7.4-49.8 cm. Commonly, ways the outer and middle track are associated with trackways are straight to gently curved, and when thin, elongate imprints oblique to the mid-line at an occurring on foresets they show a surprisingly uniform angle of about 40°, with distinct ridges, often more uphill walking direction. Some of the trackways dis- than 0.5 cm high, pushed up behind each imprint. play a continuous medial impression, this rarely occurs Some scratch marks and some abraded tracks, that along the mid-line, but more commonly lateral to the penetrate to a deeper level, suggest a bifid terrnin- median axis of the trackway. The medial impressions ation of the outer limb. Where preserved, the inner vary in thickness varies from 0.2-1.5 cm, with an tracks form shallower circular imprints, which are imprint depth of 0.1-0.4 cm, and are semi-circular in not in line with the middle and outer track, but off- cross-section. Some medial impressions show weak set to lie between the stride of the middle and outer variations in impression depth, indicating the variation tracks (Fig. 4(a) and (b)). in the force that the telson was applied to the sub- Usually there is a great regularity in the spacing and strate, possibly corresponding with the stride. arrangement of the tracks, but more irregular track E. Draganits et al.

(a)

Fig. 4. (a) and (b) One of the best preserved Palmichnium antarcticum trackways. The outer and middle track show thin, elongated impressions oblique to the median with an angle of about 40°, with distinct ridges pushed up behind each imprint. The inner track forms shallower circular imprints, which are not in line with the middle and outer track, but off- set to lie essentially between the stride of the middle and outer tracks. Walking direction is uphill to the right. The telson drag mark is left lateral from the track axis, probably wiping out the inner track on this side.

series have also been found. Sometimes there is a (Trewin, 1994). The angle of the "V" ranges from 98- change of stride, symmetry or the angle of the series to 180° apparently depending on the stride and/or foreset the mid-line (Trewin, 1994) along the trackways. The slope-angle. symmetry of these trackways is not always opposite The ichnotaxonomy of these trackways is uncertain but in places staggered or occasionally alternate at this preliminary stage of analysis. Well preserved Discovery of abundant arthropod trackways in the ?Lower Devonian Muth Quartzite 115 trackways are similar to Paleohelcura ( = Beaconichnus) when the animal walked uphill on foresets, but this is antarcticum (Gevers et al., 1971), which was recently more difficult to determine for trackways on bedding transferred to Palmichnium by Braddy and Milner (In surfaces. review). These type of trackways in the Muth Quartzite were Diplichnites gouldi (Gevers et al., 1971) produced by large, heteropodous, hexapodous or octo- podous animals. The size of the trackways, the rela- The trackways consist of straight to gently curved tively large size, the structure and heteropodous rows and single trackways can be traced over more appearance of the tracks favour eurypterids as prob- than 73 cm on a bedding surface. Imprints define two able candidates. The wide size range displayed by the rows with a relatively constant width of 2.3 cm. Where trackways possibly indicates a wide range of ontogen- the trackway is curved, the outer track row is flanked etic stages or different genera of the animals resposi- by slightly raised outer ridges. Due to missing pos- ble. terior ridges the direction of movement cannot be The broad, deep medial impressions were most likely determined unequivocally. Individual tracks commonly produced by the animals dragging their telson. The show undisturbed, distinct imprints, tending to be cir- genital appendages of these animals are unlikely to cular to ellipsoidal to semi-circular in shape and range have produced the median drag marks (cf. Hanken in dimensions from c. 0.7-0.8 cm. Tracks tend to be inclined at 65-70 to the trace axis, the angle possibly and Stormer, 1975), as appendage imprints tend to ° occur as isolated marks (e.g. Braddy, 1995). closing anteriorly (Johnson et al., 1994). Single tracks are spaced c. 0.9 cm apart along the length of the Most of the trackways are surface tracks, often trackway and the symmetry of tracks changes slightly demonstrated by the undisturbed sand laminae directly along the trail from opposite to weak staggered above them. Although rare undertracks (Goldring and (Fig. 5). Seilacher, 1971) do occur, it seems that the coarse Trackways of this type are rare compared with the grain size of the Muth Quartzite did not facilitate the Palmichnium traces. The size and appearance of the development of undertracks, which tend to occur pre- trackways imply that these probably originated from ferably within laminations of clay and silt sized sedi- myriapods (see the discussion of possible trailmakers ments (Goldring and Seilacher, 197 1). in Johnson et al., 1994). A widely believed general rule for eurypterid track- ways is that opposing pairs of tracks "V" in the direc- tion of movement, as in the xiphosuran trackway Kouphichnium (but not the scorpion trackway Discussion Paleohelcura). As eurypterids were so morphologically diverse, it is likely that they also had diverse walking According to Buatois and Mangano (1993) just techniques (Selden, 1984). Therefore additional criteria about 20 non-marine, Devonian invertebrate ichnogen- are required to assess the direction of movement. The era are known so far, of which only a small number walking direction is considered to have been in the have been assigned to arthropods. Most of these have direction of series divergence, as evidenced by small been described from marginal marine and lacustrine sand ridges pushed up behind each track, especially settings allthough subaerial environments have been

Fig. 5. Diplichnites gouldi. Imprints define two rows with a relatively constant width of 2.3 cm. Due to missing posterior ridges the direction of movement cannot be determined unequivocally. Where the trackway is curved, the outer track row is flanked by slightly raised outer ridges. This picture shows a combination of Palmichnium and Diplichnites track- ways on the same slab. 116 E. Draganits et al. noted. The depositional setting of the Muth Quartzite Brand (1979, 1996) carried out extensive field studies is still under debate; this discovery of abundant trace to investigate the appearance of trackways produced fossils in the Muth Quartzite may prove helpful in the by modern amphibians and reptiles on different sub- reconstruction of its ancient depositional environment. strates, slope angles and moisture contents. The differ- Another outcrop in the Muth Quartzite with arthro- ent substrate conditions were found to cause a big pod trackways evident was mentioned by Bhargava variation in the appearance of trackway within one and Bassi (1988), who described arthropod trackways species. Comparison of the trackways considered here possibly produced by chelicerates 4.5 km WSW of with the work of Brand (1979, 1996), reveals an Leo, Spiti, lying 15 m below the contact to the over- obvious similarity between some uphill trackways lying Lipak Formation. found on foresets in the Muth Quartzite and these pro- The high maturity in its mineral composition and duced on sloping dry sand in the laboratory studies. sorting and the lack of any fine grained matrix point There are only a few arthropods known from the to a high energy sedimentary environment for the Devonian which are big enough to have been the Muth Quartzite. This raises the question, why have trackway producers. Eurypterids or scorpions are can- these trackways been preserved in such large numbers? didates as possible trailmakers (cf. Briggs and Rolfe, The majority of trackways reported in the literature 1983 for a discussion of possible arthropods). Besides occur in clay-silt sized sediments, which are often the size, there are several other arguments favouring finely laminated, whilst reports of trackways from eurypterids. Eurypterids are thought to have had an sandstone are rare. For this reason, it has often been amphibious habit (Briggs and Rolfe, 1983; Selden, argued that sand, and especially dry sand, does not 1984; Walter, 1984), which is consistent with the have the degree of cohesion necessary for the preser- appearance of some trackways, apparently formed vation of trackways (McKeever, 1991). A substantial under at least temporarily dry conditions. Eurypterids moistening of sand or infiltrating clay minerals were are strongly heteropodous, which corresponds well proposed by McKeever (1991) to get a suitable poten- with the observations on these trackways, where wind tial of preservation in sand-size sediments. Fornos and abrasion reveals a deeper level of tracks, showing their Pons-Moya (1982) equally suppose moistened sand heteropodous nature. conditions during the formation of Myotragus baleari- One important question arises, whether the fore- cus trackways in Pleistocene aeolian dunes. Gevers and shore/backshore environment of the Muth Quartzite, Twomey (1982) considered algal slime and saline surf- at least temporarily dry, was the normal habitat of the spray as other possible binding agents. They regard trailmaker. Interesting observations are two trackways pure water from dew or light rain as insufficient to at the same place of exactly the same size and shape, enable the preservation of trackways. running in the same direction, just separated by two Another possibility for the preservation of trackways foresets, suggesting that exactly the same animal or is probably the early cementation of the fine grained two different individuals of exactly the same size part of a pin-stripe lamination, a lamination of fine walked the same way at least two times. An additional and coarser grained sand common in aeolian sediments observation is a sharply defined beaten track c. 30 cm (Fryberger and Schenk 1988). These early cemented wide and more than 1.5 m visible on a bedding surface layers possibly represent a discontinuity along which consisting of more than a dozen individuals trackways the sediment separates, displaying the trace fossils. of probable eurypterids (Fig. 6).

Fig. Sharply defined beaten track c. 30 cm wide and more than 1.5 m visible on a bedding surface consist .ing more than dozen individuals trackways of probable eurypterids. Single trackways and their walking directions are rd to determine. Discovery of abundant arthropod trackways in the ?Lower Devonian Muth Quartzite 117

Several explanations for the amphibious habit of Workshop in Spiti Valley, Himachal Himalaya, India., ed. D. M. eurypterids exist. Gevers et al. (1971) postulated an Banerjee, pp. 10-36. Field guide book and abstracts. abundant terrestrial food supply as a stimulus for Bhargava O. N. and Bassi U. K. (1986) Silurian reefal buildups: making short-term excursions on land. Briggs and Spiti-Kinnaur, Himachal Himalaya, Indien. Facies 15, 35-52. Rolfe (1983) proposed a seasonal nuptial walk. Braddy Bhargava O. N. and Bassi U. K. (1988) Trace fossils from the Palaeozoic-Mesozoic sequence of Spiti-Kinnaur (Himachal and Dunlop (1997) presented evidence that eurypterids Himalaya) with comments on palaeoenvironmental control on may have acquired sexual maturity as juveniles, which their frequency. J. Geol. Soc. India 32, 227-238. would mean that a seasonal nuptial walk would not Bhargava O. N. and Bassi U. K. Geology of the Spiti-Kinnaur, necessarily have involved only adult individuals and Himachal Himalaya. Mem. Geol. Surv. India 124 (in press). proposed a 'mass-moult-mate' hypothesis, as seen in Braddy S. J. (1995) A new arthropod trackway and associated in- some extant semi-terrestrial crabs, to explain abundant vertebrate ichnofauna from the Lower Hueco Formation accumulations of Eurypterid remains in the Fiddlers of the Robledo Mountains, southern New Mexico. 101-105. In Green Member of the Bertie Formation (Upper Early Permian Footprints and Facies, ed. S. G. Lucas and A. B. Silurian) of Buffalo, State (Andrews et al., Heckert, 6, p. 301. New Mexico Mus. Nat. Hist. Sci. Bull. 1974), and the "veritable stamping grounds" of Gevers Braddy S. J. and Dunlop J. (1997) The functional morphology of mating in the Silurian eurypterid, Baltoeurypterus tetragonophthal- et al. (1971). Trewin and McNamara (1995) suggested mus. Zool. J. Linn. Soc. 121, 435-461. a high predation pressure in small drying up pools Braddy S. J. and Milner A. R. C. A large arthropod trackway from with high population densities as a possible driving the Gaspé Sandstone Group (Middle Devonian) of eastern force behind the colonisation of the land by arthro- Canada. Canad. J. Earth Sci. in review. pods. Bradshaw M. A. (1981) Paleoenvironmental interpretations and sys- The arthropod trackways in the Muth Quartzite are tematics of Devonian trace fossils from the Taylor Group (Lower remarkable for their great number and good preser- Beacon Supergroup), Antarctica. New Zealand J. Geol. Geophys. vation and give us an insight into the habit of these 24, 615-652. animals. The combination of eurypterid and myriapod Brand L. (1979) Field and laboratory studies on the Coconino trackways, sometimes even on the same slab, is a spec- Sandstone (Permian) vertebrate footprints and their paleoecologi- cal implications. Palaeogeogr. Palaeoclimat. Palaeoecol. 28, 25-38. tacular indication of early terrestrialization. Brand L. (1996) Variations in Salamander trackways resulting from substrate differences. J. Paleont. 70, 1004-1010. Briggs D. E. G. and Rolfe W. D. I. (1983) A giant arthropod track- way from the Lower Mississippian of . J. Paleont. 57, Acknowledgements-Financial support to ED and BG was 377-390. provided by FWF (Fond zur Forderung der wissenschaftli- Buatois L. A. and Mangano M. G. (1993) Ecospace utilization, chen Forschung) through project number P- 11765 -Geo. SJB paleoenvironmental trends, and the evolution of early nonmarine is funded by Leverhulme Trust grant F/182/AZ on biotas. Geology 21, 595-598. Palaeozoic terrestrial ichnofaunas awarded to D.E.G. Briggs Chatterji G. C. (1967) Devonian of India. International symposium (University of Bristol). Christa-Charlotte Hofmann stimu- on the Devonian system 1, 557-563. lated much thought on the environment of deposition. Hugh Copper P. and Brunton F. (1991) A global review of Silurian reefs. Rice, Fritz Steininger, Werner Piller, Christian Meyer and Spec. Paper in Pal. 44, 225-259. Peter Pervesler provided much helpful discussion and sup- Dasgupta P. K. (1971) On textural characteristics of the Muth port. The drawings were made by Leo Leitner. Thanks to Quartzite of Spiti and Kuti regions, central Himalayas. J. geol. Christine Miller and Gerhard Wiesmayr, who assisted ED Soc. India 12, 152-1 58. and BG in their field studies. The thorough and constructive Davis R. A. (1992) Depositional systems: an introduction to sedi- review by N.H. Trewin was much appreciated and improved mentology and stratigraphy, p. 604. Prentice-Hall, London. both content and style. Dongarrá G. and Francofonte S. (1995) Quality of rainwater: A geo- chemical process of water-air-rock-life interaction. Environ. Geol. 25, 149-155. REFERENCES Flügel H. W. and Tintori A. (1993) Late Devonian (Frasnian) Corals from Central Dolpo, Nepal. Riv. It. Paleont. Strat. 99(1), 3-26. Allen J. R. L. (1965) Scour marks in snow. J. Sed. Petr. 35, 331- Fornos J. J. and Pons-Moya J. (1982) Icniteas de Myotragus baleari- 338. cus del yacimiento de Ses Piquetes (Santanyi, Mallorca). Bolleti de Andrews H. E., Brower J. C., Gould S. J. and Reyment R. A. (1974) la Societat de Historia Natural des les Balears 26, 135-144. Growth and variation in remipes Dekay. Bull. Geol. Fryberger S. G. and Schenk C. J. (1988) Pin stripe-lamination: a dis- Inst. Univ. Upsala 4, 81 -1 14. tinctive feature of modern and ancient eolian sediments. Sed. Geol. Bagati T. N. (1990) Lithostratigraphy and facies variation in the 55, 1-15. Spiti Basin (Tethys), Himachal Pradesh, India.. J. Himal. Geol. 1, Fuchs G. (1977) The geology of the Karnali and Dolpo regions, 35 -47. Western Nepal. Jahrbuch der Geologischen Bundesanstalt 120(2), Banerjee D. M. (1974) Stratigraphy and depositional characteristics 165-217. of Tethyan sediments in Kuti-Kalapani area, Kumaun, India. Fuchs G. (1982) The geology of the Pin valley in Spiti, H.P., India. Himalayan Geol. 4, 296-322. Jahrbuch der Geologischen Bundesanstalt 124/2, 325-359. Bassi U. K. (1988) Orthis aff. rustica from the Devonian quartz-are- Gaetani M., Casnedi R., Fois E., Garzanti E., Jadoul F., Nicora A. nite of the Muth Formation, Khimokul La (Kinnaur), Himachal and Tintori A. (1986) Stratigraphy on the Tethys Himalaya in Himalaya. Current Science 57, 329-33 1. Zanskar, Ladakh. Riv. It. Paleont. Strat. 91(4), 443-478. Baud A., Gaetani M., Garzanti E., Fois E., Nicora A. and Tintori Gaetani M. and Garzanti E. (1991) Multi cyclic History of the A. (1984) Geological observations in southeastern Zanskar and Northern India Continental Margin (Northwestern Himalaya). adjacent Lahul area (northwestern Himalaya). Eclogae Geol. Helv. Am. Ass. Petr. Geol. Bull. 75, 1427-1446. 77, 171-197. Gansser A. (1964) Geology of the Himalayas, p. 289. Wiley & Sons, Bhargava O. N. (1997) Tethyan Sequence in the Spiti Valley, New York. Himachal Himalaya. In Response of the ocean/atmosphere system Garzanti E., Angiolini L. and Sciunnach D. (1996) The Mid- to the past global changes, IGCP-386. 1st International Field Carboniferous to lowermost Permian succession of Spiti (Po 118 E. Draganits et al.

Group and Ganmachidam Formation; Tethys Himalaya, Northern Ranga Rao A., Dhar C. L., Ram J., Rao S. V. and Shah S. K. India): glaciation and rifting of Neo-Tethys. (1984) Contributions to the stratigraphy of Spiti. Him. Geol. 12, Geodinamica Acta 9(2), 78-100. 98-113. Gevers T. W., Frakes L. A., Edwards L. N. and Marzolf J. E. Selden P. A. (1984) Autecology of Silurian Eurypterids. 39-54. In (1971) Trace fossils in the lower Beacon sediments (Devonian), Autecology of Silurian organisms, ed. M. G. Bassett and J. D. Darwin Mountains, Southern Victoria land, Antartica. J. Paleont. Lawson, 32, p. 295. Spec. pap. Palaeont. 45, 81-94. Srikantia S. V. (1981) The lithostratigraphy, sedimentation and Gevers T. W. and Twomey A. (1982) Trace Fossils and their structure of Proterozoic-Phanerozoic formations of Spiti Basin in Environment in Devonian (Silurian?) Lower Beacon Strata in the the Higher Himalaya of Himachal Pradesh, India. In Asgard Range, Victoria Land Antarctica. In Antarctic geoscience, Contemporary Geoscientific Researches in Himalaya, ed. A. K. ed. C. Craddock, pp. 639-648. University of Wisconsin Press, Sinha, pp. 31-48. Bishen Singh Mahendra Pal Singh, Dehra Dun. Madison. Stoliczka F. (1865) Geological section across the Himalayan moun- Goldring R. and Seilacher A. (1971) Limulid undertracks and their tains of Wangtu Bridge on the river Sutlej to Sungdo on the sedimentological implications. Neues Jahbuch fur Geologie Palaont. Indus: with an account of formation of Spiti, accompanied by a Abh. 137, 422-442. revision of all known fossils from the district. Mern. Geol. Surv. Griesbach C. L. (1891) Geology of the Central Himalayas. Mem. India 5, 1-173. Geol. Surv. Ind. 23, 1-232. Taira A. and Scholle P. A. (1979) Origin of bimodal sands in some Hanken N-M. and Stormer L. (1975) The trail of a large Silurian modern environments. J. Sed. Petrol. 49, 777-786. eurypterid. Fossils and Strata 4, 255-270. Talent J. A., Goel R. K., Jain A. K. and Pickett J. W. (1988) Hayden H. H. (1904) The geology of Spiti with parts of Bashahr and Silurian and Devonian of India, Nepal and Bhutan: Rupshu. Mem. Geol. Surv. India 36, 1-129. Biostratigraphic and Palaeobiogeographic Anomalies. Cour. Johnson E. W., Briggs D. E. G., Suthren R. J., Wright J. L. and Forsch.-Inst. Senckenberg 106, 1-57. Tunnicliff S. P. (1994) Non-marine arthropod traces from the sub- Trewin N. H. (1994) A draft system for the identification and aerial Ordovician Borrowdale Volcanic Group, English Lake description of arthropod trackways. Palaeontology 37, 8 11-823. District. Geol. Mag. 131, 395-406. Trewin N. H. and McNamara K. J. (1995) Arthropods invade the Kumar S., Singh I. B. and Singh S. K. (1977) Lithostratigraphy, land: trace fossils and palaeoenvironments of the Tumblagooda structure, depositional environment, palaeocurrent and trace fossils Sandstone (?late Silurian) of Kalbarri, Western Australia. of the Tethyan sediments of Malla Johar area, Pithoragarh- Transact. Royal Soc. Edinburgh 85, 177-210. Chamoli Districts, Uttar Pradesh, India. J. Palaeont. Soc. India Twiss R. J. and Moores E. M. (1992) Structural Geology, p. 532. 20, 396-435. Freeman and Company, New York. McKeever P. J. (1991) Trackway preservation in aeolian Vannay J-C. (1993) Geologie des chaines du Haut-himalaya et du from the Permian of Scotland. Geology 19, 726-729. Pir Panjal au Haut-Lahul (NW-Himalaya, Inde. Palkogeographie Mukherjee B. and Dasgupta P. K. (1972) Depositional Environment et tectonique. Mémoires de Géologie (Lausanne) 16, 148. of the Upper Member of "Muth Quarzite" from Spiti and Kuti Walter H. (1984) Zur Ichnologie der Arthropoda. Freiberger Regions, Central Himalayas, India. 24th Intern. Geol. Congress 6, Forschungshefte C391, 58-94. 424-43 1. Woolfe K. J. (1990) Trace fossils as paleoenvironmental indicators Oldham R. D. (1888) The Geology of Northwest Himalayas. Rec. in the Taylor Group (Devonian) of Antarctica. Palaeogeogr. Geol. Surv. India 21, 145-165. Palaeoclimat. Palaeoecol. 80, 301-310.