Late Proterozoic(?) to Silurian stratigraphy of southern Wulff Land, North Greenland

No systematic description of the geology of southern Wulff Land (fig. 1) has been published although scattered observations have been made by Koch (1920). Geologists of Greenarctic Consortium visited the area during 1969 in the course of regional exploration and some results of their work have been referred to by Dawes (1976a) in his summary of North Greenland geology, notably the presence of Late Proterozoic(?) and fossiliferous Early Cambrian above the metamorphic basement. With the initiation of the North Greenland Project in 1978, it became practicab!e to briefly visit southern Wulff Land with the aim of estahlishing comparative reference sections through the late Proterozoic(?) Silurian sedimentary sequence overlying the basement. Wulff Land occupies a key position in North Greenland geology with its relatively complete Lower Pa!aeozoic sequence (fig. 2) providing a link between comparatively well known sections in Inglefield Land, Washington Land and Hall Land, to the west (Troelsen, 1950; Dawes 1976a; Henriksen & Peel, 1976) and equivalent, but somewhat dissimilar, sections in Peary Land, to the east (Jepsen, 1971; Christie & Peel, 1977). Crystalline basement outcropping at the head of Victoria Fjord provides the northernmost known exposures of Shield rocks in Greenland. Dawes & Soper (1973) employed the term Victoria Fjord Arch for this tectonically high area, penetrating north toward the North Greenland geosyncline, which has seemingly exerted a profound influence on sedimentary deposition in North Greenland during the late Proterozoic and early Palaeozoic. Two thin sedimentary units of late Proterozoic (or earliest Cambrian) age are recognised in southern Wulff Land and tentatively correlated with strata in Peary Land. Overlying sandstones and shales are assigned to the Buen Formation of Peary Land, and have yielded Early Cambrian fossils from the upper beds. The Buen Formation is followed by doJomites which are grouped

No systematic description of the geology of southern Wulff Land ( fig. 1) has been published although scattered observations have been made by Koch (1920). Geologists of Greenarctic Consortium visited the area during 1969 in the course of regional exploration and some results of their work have been referred to by Dawes (1976a) in his summary of North Greenland geology, notably the presence of Late Proterozoic(?) and fossiliferous Early Cambrian above the metamorphic basement. With the initiation of the North Greenland Project in 1978, it became practicab!e to briefly visit southern Wulff Land with the aim of estahlishing comparative reference sections through the late Proterozoic(?) -Silurian sedimentary sequence overlying the basement.
Wulff Land occupies a key position in North Greenland geology with its relatively complete Lower Pa!aeozoic sequence ( fig. 2) providing a link between comparatively well known sections in Inglefield Land, Washington Land and Hall Land, to the west (Troelsen, 1950;Dawes 1976a;Henriksen & Peel, 1976) and equivalent, but somewhat dissimilar, sections in Peary Land, to the east (Jepsen, 1971;Christie & Peel, 1977). Crystalline basement outcropping at the head of Victoria Fjord provides the northernmost known exposures of Shield rocks in Greenland. Dawes & Soper (1973) employed the term Victoria Fjord Arch for this tectonically high area, penetrating north toward the North Greenland geosyncline, which has seemingly exerted a profound influence on sedimentary deposition in North Greenland during the late Proterozoic and early Palaeozoic.
Two thin sedimentary units of late Proterozoic (or earliest Cambrian) age are recognised in southern Wulff Land and tentatively correlated with strata in Peary Land. Overlying sandstones and shales are assigned to the Buen Formation of Peary Land, and have yielded Early Cambrian fossils from the upper beds. The Buen Formation is followed by doJomites which are grouped together provisionally and referred to as a single unit (Brønlund Fjord Group -Wandel Valley Formation) arter Iithostratigraphical names employed in Peary Land, but probably include strata of Early, Middle and Late Cambrian, and Early and Middle Ordovician ages. Succeeding c1iff-forming, mainly Middle -Upper Ordovician limestones are referred to the Gonioceras Bay, Troedsson Cliff, Cape Calhoun and Aleqatsiaq Fjord Formations on account oftheir similarity with the type area in Washington Land. As in other areas of North Greenland, the Silurian is divisible into two distinct Iithological units -shelf carbonates and basinal clastics. Thus, two composite reference profiles were established near the northern end of the large easternmost lake in southern Wulff Land ( fig. 2). There appears to be a complete succession in the carbonates from the underlying Upper Ordovician to probably at least Upper L1andovery (Telychian). The Silurian carbonate units are complex due to the presence of carbonate buildups at two distinct stratigraphic leveIs. The vertical and horizontal facies changes associated with the carbonate buildups cause difficulties in lithostratigraphic corre1ation along the strike. The shelf carbonates pass abruptly northward into a thick clastic sequence of shales, silts and turbidites, which appears to range in age from at least Late L1andovery (Telychian) to Ludlow. At this contact, but topographically below the platform sediments, a third carbonate buildup horizon occurs. Younger turbidite beds are undoubtedly present to the north, but were not examined.
The Silurian carbonates are about 600 m in thickness and are divided into four formations. At least 650 m of basinal clastics are present, representing three formations. Due to the preliminary nature of this report, formal names are not assigned to the Silurian formations and members and type sections are not designated,
Dawes reports that tlle basement samples fall into two groups. granitic and amphibolitic. Amphibolitcs collected from localities 2. 3 and 4 are all schists containing green hornblende and plagioclase, with ar without biotitc and/ar garnet. The sample from the latter locality is a quartz-bearing garnet amphibolite. The granitic samples (Iocalitics I. 3 and 4) are pink, medium grained and con tai n both plagiodase and potash feldspar, with ar without biotite. The sample from locality l is leucocratic and rat her homogenolIs. the others are biotite foliatcd, granitic gneiss. Mineral assemblages af the samples indicatc metamorphism in the almandine-amphibolile facies.

Age and corre/arion
The age af the crystalline basement is as yet unknowll. although overlying sediments are uf Late Proterozoic(?) ar carlicst Cambrian agc. Dawcs comments that amphiboJitic and granitic rocks make up parts af the crystal1ine basement compkx in Jnglefield Land. some 500 km to the south-west. Pink and red granitcs af the Etah meta-iglleous camplex in Inglefield Land arc similar to rocks in the present collection. The crystal1inc basement af tlle IngJefield Land -Thule region was afTected by a high-grade regional mctamorphic event af Hudsonian age. wilh K-Ar dales ranging from about J880 to 1610 m.y. (Larsen & Dawcs, 1974). althougll alder material is undoubtcdly present.
It was not possibIe to ascertain the tllickness af the breccia or the prescnce of ovcrlying sediments. Howcvcr, it is eonsidered likely that tile sediments form thc lowest bcds ortlle UI1-llamed dolornite formation, described belo\\'.

Un-namcd dolornite formation
This formation \Vas only cxamincd at locality 5 ( fig. 2) although similar carbonate cemented breccia directly overlying the rnetamorphic base ment at locality 4 may belong here. Between 20 and JO m af dolomitic rocks are exposed. but the outcrops are disturbed by so!ifluxioll and are drift plastered.

Litha!ogy
The lowest exposures cansist of 2 -3 nI af paie thin bedded dolomites followed by a 50 cm tllick dolomitic breccia. AboUI 10 m af overlying dolomites are generally laminated. sometimes shaly, paie \Veatilering, grey ar paIe hulT in colour with same llodules or lcntides of black and while cherts. The highest exposed beds cansist af 5 -IO m ol" do\omilic breccia in which roor1y sorted, angular to subrounded cJasts (coarse grains to J In boulders) af quartz, granitic bascment, various dolomites (including oolites) and sand stones are supported by a bufT coJoured matrix of dolomitie sand (lig. 4).

Age and Corre!arion
A satisfactory correlation of the un-named dolomitc formation with other units elsewhere in Nonh GreenJand is not firmly established. However. the Port fJeld Formation af Peary Land (Jepsen, 1971) is mainly do[omites and includes a brcccia in its upper part not unlikc the WulfT Land breccia, aJthough withoUl the metamorphic bJock s. The PonfjeJd Formation. af unccrtain late Proterozoic to carliest Cam brian agc, is ovcrlain scemingly conformably by clastics af the Bucn Formation in Peary land and thi s unit is 31so recognised in WultT land in a somewhat modified form. In Peary land. tlle Portfjeld Formation overlies lhe Moraenesø Formation. a thin series of sandstones, some stromatolitic dolomites and breccias interpreted as tillite. The Moraenesø Formation lies on the eroded surface of the Proterozoic Inuiteq Sø Formation (Jepsen, 1971) which is dominated by large-scale cross-bedded, reddish weathering sandstones. Blocks of similar sandstone have been observed in the calcareous breccia overlying the metamorphic basement at locality 4.
On the basis of available evidence, a tentative correlation of the un-named dolomite formation with the upper part ofthe Portfjeld Formation of Peary Land is considered the most appropriate.

Lithology
About 10 m of large-scale cross-bedded sandstone forms a conspicuous red weathering stripe above the dolomites at locality 5, at the foot ofthe clitT. The sandstone is unfossiliferous, poorly sorted, medium to coarse grained with small subangular to rounded quartz pebbles and scattered feldspar. The contact with the underlying dolomites, see above, was not observed.

Age and Correlation
The unit may represent the basal beds of the overlying Buen Formation of Early Cambrian age, examined at locality 6 across the lake, but some tens of meters of unexposed section intervene. A second, but less likely possibility is that the sandstone unit correlates with a thin sandstone near the top of the Portfjeld Formation (Late Proterozoic or Early Cambarian) of Peary Land (Jepsen, 1971). In westernmost Peary Land, field work during 1978 demonstrated a largescaie cross-bedded grit similar to the WultT Land deposit in this stratigraphic position. In the former area, dolomites overlie the grit but on account of poor exposure no evidence of their occurence in WultT Land was noted. Jepsen (1971) gave the name Buen Formation to a unit of sandstones and shales of probable Early Cambrian age in the Jørgen Brønlund area of Peary Land. Field work during 1978, confirmed the brief report by Dawes (1976b), that established that the formation extends westwards beyond Peary Land into Freuchen Land. A substantial thickness (c. 550 -600 m) of sandstones and overlying black shales and silts in southern WultT Land can be readily assigned to the Buen Formation. Early Cambrian fossils have been collected from the upper levels of the formation in both areas.

Definition
The Buen Formation outcrops extensively in southern WultT Land, a reconnaissance section being measured at locality 6 ( fig. 2). The lower hill slopes are drift covered but there seems little doubt that the formation overlies the feldspathic sandstone unit examined across the lake at locality 5. The formation can be divided into a lower resistant unit (c. 450 -550 m) predominantly composed of various sandstones and subordinate silts, and a poorly exposed upper recessive unit (c. 100 -150 m) of mainly shales, silts and thin sandstones, with a thin limestone bed near the top.

Lithology
The sandstones ef the lower member range from white or grey, COarse graincd. massive weathering, large-scaJe cross-bedded and congfomeratic in character, to (iner. grecnish weathering. cross-bedded, micaceous, bioturbatcd sandstones with silty parlings. Paie gre)'. orange-brown weathcring, medium to coarse grained quartzitcs are conspicuous in the upper part af thc mernber and are loealty rich in Skoli{hos (fig. 5). Hillsides formed by thc wcathered sandstones ofthc lower mcmber are often conspicuously coloured with reds, ycllows and greens the dominant tones.
Tbe overlying recessive member af the Buen Formation in Wulff Land is apparently rich in simles and siltstones although these are poarly exposed in tlte section at locality 6. The hardness contrast with tlte undcrJying rcsistant sandstones has resulted in the shalc bcing stripped away to produce characteristisc flat, damp. well vegetated tops ro hills in the soulhern part of the area. with !he lawer, sand.slOne member formjng the sleep hill .sides.
Thin, cross-beddcd quartzites aeeur in the lower part af the mcmber. while a 1.5 m thick bcd of bioclastic limestone forms a bench around the hill tops adjacent to section 6. about 35 m belaw the top. The limestone is a coquina composed of pagetid trilobitcs. brok en fragments of oleneIIids, hyolithids, and inarticuJate brachiopods.
Thc upper con laet af lhe formation with the over1ying dolomiles was not examined in WuJfT Land, but it is apparcntly well exposed along the lak e shorc to the norlh-east of loeatity 6 (fig. 6. Incalily 7 in fig. 2).

Age and Correlatioll
Well preserved pagetid triolobites from the eoquina ncar the (OP af the shale are eomparablc to IIebedisclis marginalus Rasetti. 1967 from the Early C<tmbrian af New York. referred to Ekwipagetia by Fritz (1973) who reported a simi1ar. bul slightly alder species from the Sekwi Formation in north-western Canada. A.R. Palmer (pers. eomm. 1979) has idcntified Labradoria, O/eneJlus, Wallneria?, Hyolithus, l-1)'olilhellus, Pelagiella and Obo/ella from the same collcction. Geologists af Greenarctic Consortium (Dawes, 1976a) reportcd Qlenellus, Calla via, Wimanel/a and BOfs/ordia from Early Cam brian rocks in southcrn Wulff Land but the precise locality(s) and horizon(s) arc unknown to the authors. Skulithos occurs in the lower sandstones af the Buen Formation in Wulff Land and il is assumcd that the emire formation is af Early Cam brian age.
The Buen Formation has not been recogniscd to the west af WulfT Land. Early Cam brian sandstones in Washington Land informally rcferred to as the HumbolcIt formation by Peel (1978) and Jepsen & Dueholm (1978, fig. 50) include a lower cross-bedded sandstone unit with Skolithos and higher si1ts and fine sandstones with Cruziana. Early Cam brian fossils have been reeovered from a thi n dolomitic eonglomerate near the top af the formation.

Brønlund Fjord Group -Wandel Valley Formalion
Direct examination af this composite unit was restricted to the small outlier forming the hill top at locality 6 ( fig. 2) where a few meters af paIe, mottled, vuggy, recrystalliscd dolomitc near to the base of the unit are exposed. These lower dolamitcs, lying above the Buen Formation, ean be compared to basal beds af the Brønlund Fjord Group (Earl}' -Middle Cambrian) af Peary Land, in terms af bath Iithology and stratigraphic position (Christie & Peel. 1977: Peel. 1979. Upper beds af the unit are distinctively black and white banded (figs 6-8) and are readily corre\aled \\'llh Ihe do\omites af the Wande\ Vaney Formation (Ear\y -Middle Ordavician) in Peary Land. 1mervening strata expased along the lake sides include grey and reddish weathering units but the presence or absence af sandstones in the othcf\.vise apparently largely dolomite formation is not known. It is probable, but unsubstantiated, that these intervel1ing red and grey strata correlate in part with Middle and Uppcr Cam brian rocks in western Peary Land ol" Lhe Brønlund Fjord and Tavsens (skappe Groups (Peel, 1979).

Troedsson Cliff Formation
Definition Koch (1929) originall}' defined thi s unit in south-wes( Washingwn Land. but il is here applied in the rcdefined sense of Peel & Hurst (in press). Koch (1929) did not rcport the presence of this formation outside Washington land alrhough hc did intimalC ehal ehe c10scJy comparable.
underlying. Gonioceras Bay Formation should be present in Peary Land. However. the work of Thc Troedsson Cliff Formation is a thick unit which forms the lower part af the clin's and valley floor at the northern end af the major lakc (figs 2, 7). As with all the Palaeozoic units. it dcscencts gcntly northwards due to the regional dip. The total thickness is unknown and only thc top 30 m were examined in detail ( fig. 9).

Lilila/ogy
The upper part af the limestone ( fig. 2, locality l t) appears uniformly medium bedded in units 50 to 100 cm thick. On fresh surfaces thc sediments are genera Ily dark grey with occasional pinkish tinges. but on weathered surfaces the general dark brown colouration is broken by faitH yellowish brown mottling. Some of the mottling is related to burrowing. Most beds are massive with no internal stratification but occasionally a thin unit (50 cm) develops a nodular crinkly texture which wedges out. These units tend to be of a lighter grey colour. The sediments are predominantly wackestones (90-95 per cent) but very thin packestone beds up to 10 cm thick generally eontain the highest faunal content.

Fauna
The upper part is richly fossiliferous and large Mac!uriles sp. and orchocone cephatopods are panicularly canspicuaus, the latter aften containing many borings and epizoans. Corals inc1uding SajJorciophy/lum sp., Calenipora sp., Calapoecia sp., LobocoraJlium(?) sp. and strepteiasmatids are abundant. Othcr fauna includes the brachiopod Zygospira sp., bivalves. the gastropod Murchisonia sp., bumastine and other trilobite debris and crinoid fragments. As the topmost part of this formation is recessive, bedding plane surfaces exhibiting imperfect surface silicification of fossils are common.

Definition
The complicated history of nomenc1atorial changes surrounding the naming and subsequent recognition of this unit is discussed in detail by Peel & Hurst (in press). Essential1y, the Cape Calhoun Formation as defined by Koch (1929) was embracive and he traced it across North Greenland into Peary Land. In the restricted sense of Peel & Hurst the formation cannot be traced into Peary Land, but is replaced by the Børglum River Formation. Even in the expanded sense of Koch (1929), partially including the underlying Troedsson ClitT Formation and the overlying Aleqatsiaq Fjord Formation, the unit is not present in Peary Land. Thus, its presence in WultT Land again underlines the stratigraphic similarity with Washington Land and the dissimilarity with Peary Land, during this time interval.

Lithology
The Cape Calhoun Formation as defined by Peel & Hurst (in press) is a thin succession of generally recessive, thinly bedded limestones with very thin shale interbeds which conformably follows the Troedsson ClitT Formation (figs 9, 10). Some 40 m are present in WultT Land of which the lowest 10 m in the measured section were scree covered. The limestone beds (5 to 20 m thick) are crinkly or nodular packstones and the interbedded shale wraps around the harder more competent lime beds. The whole unit has a distinctive green colour due mainly to staining caused by the breakdown of the millimetre thick shale interbeds.

Fauna and Age
Many fossils of the so-called Arctic Ordovician fauna abound in the Cape Calhoun Formation. Large corals e.g. Catenipora sp. and Calapoecia sp., numerous orthocone cephalopods and the gastropod Mac!urites sp. are characteristic. The whole faunal assemblage is typical of the Cape Calhoun Formation elsewhere and probably ranges in age from Upper Eden, Maysville to possibly lowest Richmond (Actonian, Onnian and Pusgillian).

Aleqatsiaq Fjord Formation
Definition This formation, erected by Peel & Hurst (in press) in Washington Land, is represented by 130 m of sediments in WultT Land. The Aleqatsiaq Fjord Formation is a massive unit which weathers dark brown in marked contrast to the underlying, recessive, green Cape Calhoun Formation upon which it conformably lies (figs 9, 10).

Lithology
The contact between the Cape Calhoun Formation and the Aleqatsiaq Fjord Formation is fairly abrupt. The loss of the shaly interbeds of the former formation imparts a thicker stratified and therefore bedded nature to the succeeding formation, although the lower 5 m are still nodular. Above the basal 5 m the formation is medium bedded (c. 50 cm to 2 m) and on weathered surfaces it is generally faintly mottled light yellowish brown. The sediments are mainly lime mudstones and wackestones, although in places weak patchy dolomitisation occurs.

Fauna and Age
The fauna af thi s unit is poor. Large, aften recrystallised tabulatc coral colonics and <lClinoceratid cephalopods are the most conspicuous elements. Mac!urilcs sp. is present up to [00 m from the formation base indicating a probable Ordovician (Richmond) age for that part uf thc formation. Thc top 30 m uf tbe formation may be Silurian (Early Llandovery. Rhuddanian) although there is 110 unequivoca! cvidcnce to indicate this.

Silurian carbonatc formation]
A very variable sequence af limestones and dolomiles, some l R5 m thick. conformably overlies the Aleqatsiaq Fjord Formation (figs 9. IO). The limeslones me mainly massive. forming  imprcssive bluffs, and are generaily light to medium grey in co lour. Thc first level af carbonate buildups occurs wilhin this unit and il is composed af bright yellow vuggy dolomile (figs 11, 12).
The base ofthe formation is marked by a 20 m thick very thin bedded (c. IO cm) dark grey, mottled, lime mudstone (flg. 10). Out af thi s level grows a 100 m thick carbonate buildup ( fig.  11) mainly composed af fenestral dolomites ( fig. 12). The relief af the mound varies from near horizontal, an the nanks. to verticaL and the mound interfingers with the surrounding nat bedded light grey lime mudslones and wackcstoncs. The carbonate buildup is flanked hy thick massive bio-breccia beds composed af coral and slromatoporoid debris which is not thoroughly dolomitised. Carbon atc buiJdups at this stratigraphic level are nOL common. possibly onl)' anc other being observed in thc immediate vicinity. Their environmemal position is intriguing in that they are set back som e 5 to IO km from the carbonate shelf edge.
Away from the buildup. the normal nat beddcd sediments which completely overlap the feature eonsisr of massive bedded light grey lime wackestoncs and subordinate floatstones.
The whole unit is not very fossilifcrous. Stromatoporoids and tabulate corals are commonly associated with the flank beds af the carbonate buildups and are rarer in thc flat bcdded carbonares. The basal beds contain a new virgianiid brachiopod possibly indicating an Early to Middle L1andovery (Rhuddanian -ldwian) age. This further suggests that the top ol' the Aleqatsiaq Fjord Formation is SiJurian.

Silurian carbonate formation 2
Thc sccond un-named formation is a variable sequcncc af limestones up to 180 m thick which inciudes the second carbonate buildup level (figs 9 & IO). Generally. the unit is massive bedded in the immediate vicinity ol' the buildups but thc surrounding level bedded carbonates are thi n beddcd and recessive. The nature of exposurc of the buildups. with vcrtical cliff-faces. precludes examinarioll; the only accessibie parts are the flank beds.
The base ol' tile formation is well marked by a 5 m thid unit ar dark grey to blad, very thin bedded (1-2 cm), nodular, mottled lime mudstone. One examined carbonate buildup originates at this level and, in the core region, reaches at least 100 m thick. The flank beds consist entire1y of graded crinoidal rudstones and stromatoporoid, tabulate coral rudstones. Proximal deposits of the buildup appear to contain talus breccia beds. Three kilometers along strike, away from the carbonate buildup the sediments consist entirely of a monotonous sequence of thiniy bedded (5-10 cm), dark weathering, black lime mudstones, mottied yellowish brown. The whole sequence is nodular and some horizons consist entirely of small spherical nodules (c. 1 cm) imparting a honeycombed look to the rock. This facies interfingers with the carbonate buildup and its flank beds but it does not overwhelm the buildup.
In the area studied on1y two carbonate buildups were seen. Both were situated 5 to 6 km to the south of the edge of the carbonate shelf and the base of the overlying formation rests directly on them. Due to differential compaction, and initial relief associated with the buildup of carbonate, the contact with the overlying formation is undulating.
The fauna in the flat Iying carbonates is poor and consists of a few disarticulated pentamerids (Harpidium sp.?) tabu1ate cora1s and stromatoporoids. Nearer the buildup the fauna is more abundant but it is essentially the same. The presence of Harpidium sp.? suggests a Late Llandovery (Fronian -Telychian) or younger age.

Silurian carbonate formation 3
This monotonous formation is 200 m thick and forms the prominent cliffs at the top of the Silurian carbonate sequence ( fig. 9, 10). It is generally massive bedded (c. 5 to 10 m) with little internal stratification. The whole unit weathers light grey with a yellowish tinge but on outcrop, the rock is seen to be mott1ed light medium grey. Small ca1cite vugs and patches are scattered throughout the sediment which is mainlyalime mudstone or packstone. Some pockets of crinoidal rudstone occasionally occur as do very thin intraformational conglomerates.
The base of the formation was only accessibie at the transition from the level bedded carbonates below. Here, an abrupt facies change from dark grey to black lime mudstones to light grey lime mudstones was observed. The base of Silurian carbonate formation 3 is marked by a thick intraformationa1 conglomerate.
A rich fauna of trilobites, corais, stromatoporoids, brachiopods and crinoid debris occurs. The who1e faunal aspect is suggestive of Late Llandovery (Fronian -Telychian) or younger, an assignment which is consistent with the presence of Harpidium sp.

Silurian shale and breccia formation
This formation is 240 m thick and comprises two members, here informally designated A and B ( fig. 9).
Member A consists of an alternation of laminated black graptolitic muds and limestone breccia beds up to 20 m thick. The shales are bituminous and account for 10 per cent ofthe succession. Many of the breccia beds are graded and laminated ( fig. 13). The thicker ones contain boulders up to 5 m across and have erosive bases. Their structure is chaotic, without any sedimentary structures.

Member A (c. 60 m).
Member A is a fine to medium graincd micaceous siltsLOne. which is medium grey to dark grey in colour. The silts are finely laminatcd and inlcrbcdded with thi n (c. 5 cm) lime mudstone horizons. Sporadie thill calcareous sandstonc brcccia (C. 1·5 cm) with calcareous debris account for 2 per cent of the facies. On weathered surfaces the silts have a slight green tinge. The only fossils noted were vcry rare graptolites.

Member B (c. 110 m)
This consists mainly of fine to medium grained. laminatcd. micaccous siltstone. The whole unit is a distinctivc green colour wilh. rarely. thin stringers of grey silt. Yel10wish green c\aystone units are occasionaJly present. while thin calcarcous sandstones up to 5 cm thick account for 5 per cent of the facies. Similarly, thin shelly coquinas with 'e/oril/da' dormilzeri and fragmcntcd orthoconc ccphalopods occur. Graptolites are rare but still the most consistcntly present fauna.  . 2). b, lime mud carhonate buildup with lang axis pcrpcndicular to tile shelf slape contact; c. downslope carhonatc brcccias dipping from the huildup iota shales, siltstoncs (s) and turbidites (t).

Member C (c. 130 m)
Member C cornprises a sequcncc af dark grcy. micaccous siltstones. Mica flakes over 3 mm wide afe common and, rarely, thin micaceous sandstones occur. There are no coquinas and no fauna was locared.

Silurian turbiditc formation
In the seelian presented in fig. 9 only the basa170 m ofthis formation was cxamincd, although rcconnaissancc indicates that the formation is at leas! 500 m [hick. The basal beds consist af very coarseJy laminated sandy silt, intcrbcddcd with fine grained. massive ar laminated. sole marked, sandstones up to IO cm lhick. The sand stones are almast white and appear quartzitic. The tllrbidites weathcr brown and are generally not as recessive as tlle underlying units. thus forming sJightly stepped hills ( fig. ]5). The upper part ofthe unit consists ofthicker. slightly coarser and darker sandstones. with thinner silt interbeds. The fauna is very infrequent although a few graptolitcs were found in the basal part of the sequence.

Age ofthe Silurian clastic sequenccs
Preliminary identification of graptolit e faunas from the Silurian clastic scqllences has been undertaken by M. Bjerreskav (written communicatian. 1978

Basinshelf contact
In other areas of North Greenland the basin-shelf contacts are aften characterised by the presence af carbonate buildups (Dawes, 1971(Dawes, , 1976aChristie & Peel, 1977;Mayr, 1976). Dawes (1971Dawes ( , 1976a inferred such buildups to be present in WulfT Land an the basis of regional photographic interpretation and the present study substantiates his inferrence ( fig. 14). In WulfT Land the cantact between basin and shelr is abrupt. The nat bedded carbonales of the shelf sequence abruptly pass northward into slightly inclined basinal clas tics (figs. 14 & 15). The carbonates form topographically high features against which the basinal clastics abut. In the easternmost cantact seen ( fig. 2, locality 12; fig. 15) the bedded carbanates are anly partially in cantact with the basin clastics. The actual carbon atc contact with the clastic sequence is marked by mound-likc structures which are interpreted as downfau1ted carbonate bioeks.
A similar setting was examined at a nearby point ( fig. 2, locality 13; fig. 14). Here, an an isolated knoll of flat to steeply bedded and slumped blue grey lime mudstone, with pockets af crinoidal and stromatoporoida1 rudslOne, passes northward into shales and siltstones ( fig. 14). Breccia beds in the basinal clastics are derived from the carbonate areas and indicate a primary slope to the north (flg. 13). The knoll is separated from the flat bedded shelf carbonates to the south by a valley, but it is noticeably below the highest carbonate formation. The nature of the contact between the flat bedded carbonates and the carbonate buildup is unknown. These carbonate buildups appear very similar to the foreslope mud mounds of Wilson (1974).
The uppermost thick chaotic breccia marking the top of member A of the Silurian shale and breccia formation correlates with the uppermost beds of the carbonate buildup at locality 13 (fig. 2). Thus, from preliminary identification of graptolite faunas in the shale, it appears as if the top of the carbonate buildup is no younger than Early Wenlock (Centrifugus -Riccartonensis Zones). Thin calcareous breccia and shelly coquina beds still occur above this level in the shale and breccia formation. They possibly indicate that the carbonate buildup was still a positive feature, providing a source of carbonate for erosion and also areas for benthie animal colonisation. However, carbonate sedimentation had probably ceased.
Topographic relationships suggest that the age of the flat bedded Silurian carbonate formation 3 may be younger than the carbonate buildup ( fig. 15). Further, carbonate formation 3 is closely comparable to a group of sediments which cap carbonate buildups of late Llandovery to early Wenlock age in western Hall Land and northern Washington Land. From structural and stratigraphic relations in WulfT Land, and regional geological considerations, it is thought unlikely that carbonate formation 3 predates the late Llandovery and may possibly be Wenlock or Ludlow.