The evolution of the early Paleozoic deep-water basin of North Greenland
FINN SURLYK | Geological Survey of Greenland, 0ster Voldgade 10, DK-1350 Kobenhavn K, Denmark JOHN M. HURST
ABSTRACT turbidite basin: turbidite deposition rapidly re- Dawes and Soper, 1973). Significant lateral and sumed, and an elongate submarine fan system vertical movements have occurred along several A major early Paleozoic carbonate shelf- prograded toward the west-southwest parallel major fault zones (see Fig. 1). In contrast, the deep-water basin system is exposed in North to the shelf margin. (8) Middle Wenlockian southern margin adjacent to a major east- Greenland over a length of 800 km, with a max- Caledonian thrusting and conglomerate deposi- west-trending carbonate shelf is essentially un- imum preserved width of about 200 km and a tion: chert-pebble conglomerates prograded disturbed by later tectonic activity. thickness reaching 8 km. The successive south- westward eroded from uplifted Ordovician chert North Greenland thus offers a unique oppor- ern deep-water basin margin was controlled by sequences in the Caledonian nappes. (9) Trans- tunity to study the tectonic and sedimentary evo- four major west-southwest- and east-northeast- pression or gravity sliding related to the advanc- lution of a major carbonate shelf-deep-water trending fault zones or flexures. Nine deep-water ing Caledonian front: a remarkable series of basin couplet. In the present paper, we will focus basin evolutionary stages are recognized. (1) imbricate thrust sheets occurring in the axial, mainly on the nature, provenance, and time The oldest sequence consists of at least 500 m of eastern part of the basin is interpreted as caused trends of the deep-water sequences; the configu- sandstones and mudstones, but little is known by large-scale gravity sliding or by transpression ration of the transition between the two main about the depositional environment. (2) Incipi- due to sinistral transcurrent movements along facies belts; and the interplay between tectonic ent basin: 1 km of (late Precambrian?) Early(?) the Harder Fjord fault zone. A Late Silurian age and eustatic events. Finally, the wider geotec- Cambrian dark gray or yellow limestones, tur- is tentatively suggested for this event. tonic aspects of the depositional system, such as biditic siltstones and mudstones, and resedi- The North Greenland basin may represent a the early evolution of the Arctic and the rela- mented carbonate conglomerates deposited in gradually opening, narrow ocean basin, with the tions to the closing Paleozoic Iapetus Ocean slope and relatively deep-water basin environ- mid-oceanic ridge to the north forming a north- (Proto-Atlantic Ocean), are examined. ments. (3) Narrow turbiditic basin: 2 to 3 km ern barrier to the basin. Conversely, the basin of Early(?) Cambrian turbiditic sandstones, may be fully ensialic and may have formed dur- GEOLOGICAL SETTING deposited on westerly deflected submarine fans, ing the early rifting stages preceding true back- alternating with dark or varigated interfan and arc spreading. Alternatively, the basin may be Due to the remoteness of North Greenland, slope mudstones, deposited following a major an aulacogen extending deeply into an old con- most geological work has been on a reconnais- episode of shelf-margin back-stepping. (4) Basin tinent at a right angle to the Caledonian front to sance level. General reviews of the geology of expansion and initial starvation: about 1 km of the east. North Greenland include Dawes and Soper Cambrian-Ordovician basin-plain anoxic dark (1973), Dawes (1971, 1976), and Dawes and mudstones, black and green cherts, and turbi- INTRODUCTION Peel (1981). The main aspects of the tectonic- dites were deposited. Small borderland fans pro- sedimentologic evolution of the deep-water graded into the deep basin, and upper-slope A major lower Paleozoic deep-water sequence basin have been described by Surlyk and others slumping resulted in a debris sheet of at least is exposed along the north coast of Greenland (1980). 45 km3. Eventual fan abandonment resulted in from Kronprins Christian Land in the east to In early Paleozoic and possibly late Precam- basin starvation and periodic stagnation reflected Washington Land in the west (Fig. 1). This sed- brian times, four important east-west-striking by the fine-grained deposits. The base of slope is imentary basin is approximately 800 km long belts existed, with different structural, environ- dominated by resedimented conglomerates, the and extends into Ellesmere Island, northern mental, and subsidence histories. main sheet about 375 km3. This coincides with Canada (Dawes and Soper, 1973; Dawes, 1976; To the south lay a craton composed of Pre- increased uplift, tilting, nondeposition, and ero- Dawes and Peel, 1981; Hurst and Surlyk, 1980, cambrian basement rocks overlain by late Pre- sion of the eastern carbonate shelf. (5) Longitud- 1982; Surlyk and others, 1980; Surlyk, 1982). cambrian sediments. This was fringed to the inal turbidite basin: an elongate, east-northeast, The maximum preserved width of the deep- north by a shallow-marine carbonate shelf con- west-southwest-sand-rich, longitudinal, turbidite water basin is approximately 200 km and the taining a few intercalations of terrigenous clastic fan-to-basin system developed at the Ordovician- thickness of the sedimentary column may reach sediments (Christie and Peel, 1977; O'Connor, Silurian transition. This was punctuated by sev- 8 km. The main part of the succession is of 1979; Peel, 1979; Ineson and Peel, 1980) eral episodes of lateral conglomerate deposition Cambrian-Silurian age, but it probably extends (Fig. 2). The outer platform margin developed from the southern shelf margin. (6) Basin expan- down into the late Precambrian. The basinal se- as an escarpment to the east (Surlyk and others, sion and starvation: more than 30,000 km2 of quence, although folded, is in general little dis- 1980) but as a broad ramp or drowned shelf to the eastern carbonate shelf foundered at the turbed except in the northern fringe, where the west (Hurst, 1980a; Hurst and Surlyk, 1983 Llandoverian-Wenlockian boundary and a thick deformation is intense and metamorphism lo- and in press). Outside this zone was situated a mudstone unit was deposited on top. (7) Wide cally reaches amphibolite faces (Frankl, 1955; deep-water basin characterized by deposition of
Geological Society of America Bulletin, v. 95, p. 131-154, 36 figs., February 1984.
131
Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/95/2/131/3434444/i0016-7606-95-2-131.pdf by guest on 28 September 2021 Figure 1. Geological sketch map of North Greenland showing place-names and main lineaments, based on Dawes (1976); Map 1 (Rapp. Grönlands geol. Unders., 88,1979); Map 2 (Rapp. Grönlands geol. Unders., 106,1981), and unpublished data.
Figure 2. Stratigraphie scheme of Peary Land, North Greenland. Based on Surlyk and others (1980), Friderichsen and others (1982), Hurst and Surlyk (1982), Christie and Peel (1977), and Ine- son and Peel (1980).
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fine-grained sediments or sandy turbidites and sedimentary infill likewise varied considerably. V. Jensen Land) by Dawes and Soper (1973, conglomerates resedimented from the shelf- Accordingly, we prefer not to use the term 1979). The two schemes were correlated litho- margin zone. A comparable organization is "Hazen Trough" in Greenland. Rather, we stratigraphically and biostratigraphically by recognizable in Arctic Canada (Christie, 1964, recognize a sequential series of deep-water Surlyk and others (1980) and the whole deep- 1979; Kerr, 1967, 1968, 1976, 1981; Morrow basins, each of which has a fairly uniform water sequence was described within the and Kerr, 1977; Trettin, 1971,1979; Trettin and sedimentation history and a stable position. framework of six groups by Friderichsen and Balkwill, 1979; Trettin and others, 1972). The others (1982). Detailed lithostratigraphic and deep-water basin that is the subject of the present STRATIGRAPHIC FRAMEWORK biostratigraphic subdivision of the Silurian paper is termed the Hazen Trough in Arctic rocks was made recently by Hurst (1980b) and Canada (Trettin, 1979). The position of the Two mainly informal sets of lithostratigraphic by Hurst and Surlyk (1982). Figures 2 and 3 basin and, in particular, of its margins in North names were introduced for some of the deep- present stratigraphic schemes of Peary Land Greenland fluctuated widely with time and the water deposits in northern Peary Land (Johannes and western North Greenland, respectively.
Figure 3. Stratigraphic scheme of western North Greenland. The shelf sequence in the left-hand column is based on Washington Land, and the basinal sequence in the two right-hand columns is based on Hall Land and Nyeboe Land. The two schemes show the lithostratigraphy of the main facies belts encountered in a north-south section and are not intended to represent actual geological cross sections. Based on Hurst (1980b) and Hurst and Surlyk (1982).
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TECTONIC LINEAMENTS present-day net result is downfaulting to the directly into the Nyeboe Land fault zone south by about 2,000 m. An area of intense (Dawes, 1982). The middle portion of the fault One of the most remarkable geologic features westward-directed thrust faulting occurs imme- seems to show sinistral en echelon displacement. of North Greenland is a system of east- diately south of the fault zone and the thrusts are Orientation: linear, east-west. west-trending lineaments, some of which can be truncated by the fault, leaving no traces north of Nature: the zone is developed as a trans- followed throughout the entire region (Fig. 1). the fault (see Fig. 36 below). This has been in- gressed escarpment in Lauge Koch Land and The lineaments are characteristically straight or terpreted by Pedersen (1980, 1981a, 1981b) as Freuchen Land. In the J. P. Koch Fjord area it is slightly curved with occasional splays. When due to later strike-slip faulting along the fault associated with major, parallel shear zones (Figs. studied in detail, some or parts of the lineaments zone. An alternative interpretation suggested 4, 5). can be shown to represent faults cutting through here is that the thrust belt was directly caused by Movement: normal, down-to-north. the sedimentary sequence. Other parts of the sinistral, up-to-north, oblique-slip faulting along Facies boundary: the zone constitutes one of lineaments represent buried linear escarpments the Harder Fjord fault zone. The fault zone the main facies boundaries in North Greenland or faults transgressed by nonfaulted sediments. seems in different places or at different times to as it separates Ordovician-Silurian shelf car- Still other parts correspond to flexures and have been influenced by both compressional and bonates and basinal chert, mudstones, and aligned reefs and ramp hinge lines. extensional forces, probably associated with turbidites. The lineaments seem generally to represent transpression and transtension. Nonmarine Timing: the zone was active from a least the surface expression of major zones of crustal Upper Permian and marine Cretaceous and Ter- Cambrian times. The undisturbed draped nature weakness. tiary sediments thus are preserved in small grab- of the sediments transgressing the escarpment When the lineaments are compared to facies ens within the fault zone (Higgins and others, precludes post-Lauge Koch Land Formation patterns, it immediately becomes clear that the 1981). The amount of net lateral movement is, movement; that is, the fault zone controlling the underlying tectonic features exerted a strong however, considered relatively insignificant, position of the escarpment became structurally control over sedimentation and delineated and as Higgins and others (1981) succeeded in trac- dead in latest Llandoverian time (Fig. 2). defined the main facies belts. In some cases, this ing the main Cambrian-Ordovician lithostrati- 3. Nyeboe Land Fault Zone (Dawes, 1982) control was sharp, as where faulting caused the graphic boundaries across the western part of the fault zone without noting significant strike- development of an escarpment bordering the Location: the zone extends from Hall Land in slip displacement. Strike-slip on one part of the carbonate shelf. In other cases, the control was the west to the western Peary Land, where it main fault is estimated at about 20 km (A. K. more indirect, as where lines of weakness or probably passes into the northern splay of the Higgins, 1982, personal commun.). Further- fault splays determined the position of ramp Navarana Fjord fault zone. West of Nares Strait, more, the sequences on each side of the fault hinge lines. it possibly extends into the Judge Daly Promon- zone in the central part of Johannes V. Jensen This notion of tectonic control of the shape tory fault zone. It is associated with a number of Land (Figs. 1 and 2) can be lithostratigraphi- and evolution of the deep-water basin was in- splays at high angles to the main fault. cally correlated with reasonable accuracy (Sur- troduced by Surlyk and others (1980). Nature: the tectonic features occurring in this lyk and others, 1980). There was a pronounced tendency for an east- zone include major faults, and in Wulff Land a to-west transition from escarpment-type shelf Facies boundary: possibly in the late Precam- large anticline. The zone in most places consists margins to ramps or more diffuse types of shelf brian(?)-Early Cambrian during deposition of of several parallel faults. margins where the main faults splay and die out. the Portfjeld Formation and Paradisfjeld Group Movement: normal. The fault zone seems to The same pattern can be seen in Arctic Canada (Fig- 2). have had a rather complex history and the direc- (Trettin and Balkwill, 1979, Fig. 5). Timing of movement: late Precambrian(?), tion of relative movement seems to have been The most important of the North Greenland Cambrian-Recent. Probably normal down-to- reversed several times. The net result is more lineaments are named the Harder Fjord fault north in the early Paleozoic followed by a rela- than 1 km of down-to-south movement. The zone, the Navarana Fjord fault, the Nyeboe tively small amount of sinistral oblique slip in the faulting was accompanied by brecciation, crush- Land fault zone, and the Permin Land flexure latest Silurian-Devonian. Major down-to-south ing, and intense hydrothermal veining, as well as (Fig. 1). They are described in turn and their movement took place in the late Mesozoic- by mylonitization and folding (Dawes, 1982). detailed nature documented as much as possible. Cenozoic, probably accompanied by some These features together with the nature of the This is difficult because most of the zones have a oblique slip. The zone is associated with vol- fault splays suggest the existence of compressive complex origin. canic centers and intrusions of uncertain, oblique-slip movement during one or more pe- possibly Late Cretaceous, age (see Fig. 36 riods. The fault seems to die out toward the east 1. The Harder Fjord Fault Zone below) (Parsons, 1981). and the net amount of lateral displacement is (Frankl, 1955) probably insignificant. 2. Navarana Fjord Fault Facies boundary: the northern margin of the Location: northeastern Peary Land to eastern (Surlyk and others, 1980) zone probably acted as a simple down-to-north Johannes V. Jensen Land and possibly eastern shelf-basin boundary at least during the Cam- Nansen Land (Fig. 1). Location: the fault zone is well known from brian (see Dawes, 1982), and possibly also dur- Orientation: east-west. Lauge Koch Land and Freuchen Land imme- ing the Ordovician and Early Silurian. The Splays: the fault zone is characterized by nu- diately west of Peary Land (Surlyk and others, southern margin seems, on the other hand, to merous splays, especially on the north side. 1980). It probably extends eastward to the east- have acted as a down-to-south carbonate horst Sense of movement: complex zone where di- ern end of Peary Land. The fault zone tends to (compare Hurst and Kerr, 1982) to deep clastic rection of relative movement has changed sev- break down when approaching the Victoria shelf-facies boundary in the Early Silurian eral times during the existence of the zone. The Fjord Arch. The northern branch may continue (Llandoverian) (Hurst and Surlyk, 1982).
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ure is represented by a linear reef belt or a ramp hinge line (Hurst, 1980a). There is thus a general tendency for the lineament to break down in a westward direction as the shelf margin changes from a scarp to a ramp. Movement: synsedimentary down-to-north faulting along the eastern part. Differential sub- sidence to the west. Facies boundary: to the east, the lineament marks a rather abrupt boundary between the Silurian carbonate shelf and the deep-water clas- tic basin. To the west, the boundary is more diffuse and marks the transition from ramp to deep-water basin apparently formed by drown- ing of an earlier shelf segment (Hurst and Kerr, 1982). Timing: Early Silurian probably extending into the Ludlovian. BASIN EVOLUTION The late Precambrian to early Paleozoic basin evolution is examined with reference to the main structural elements. A sequential series of Figure 4. Buried Early Silurian shelf-margin scarp, Navarana Fjord. C, platform carbonates. deep-water basins is defined on the basis of sed- ST1, Lower Silurian turbidites of the basin sequence. SC, buried scarp, partly scree-covered. imentary infill and position and structural style MB, Megabed transgressing the scarp; the bed has not been inspected on the ground but is of the shelf-basin boundary. These are described thought to be a major turbidite or resedimented conglomerate. SM, Lower Silurian mudstone below in ascending stratigraphic order. Each of sequence (phase 6 in the basin evolution) deposited in the transgressive phase following the main stages in basin evolution corresponds platform foundering. ST2, Middle Silurian turbidites of the wide turbidite basin (phase 7 in to one of the lithostratigraphic groups described basin evolution). The height of the section is about 800 m. View is toward the northwest at an by Friderichsen and others (1982). oblique angle to the east-west-trending scarp. The light shelf carbonates (C) in the right foreground thus do not underlie the turbidites (ST1) but occur immediately adjacent to them. Enigmatic Sequence (Stage 1) The oldest sedimentary sequence recognized in the basin area corresponds to the Skagen Group of presumed late Precambrian-Early Cambrian age (Friderichsen and others, 1982) (Fig. 2). It crops out in the eastern and western core region of the foldbelt in Peary Land (Fig. 1). The rocks are tightly folded quartzitic sand- stone and mudstone and little is known about the depositional environment. The Skagen Group is at least 500 m thick and is found only north of the Harder Fjord fault zone. The con- tact relations to this fault are obscure. This early, little-known phase of deposition Figure 5. Shelf-basin boundary in J. P. Koch Fjord, view to the east. ST, Lower Silurian may have been contemporaneous with the early turbidites. C, shelf carbonates, including Ordovician limestones and dolomites, overlain by stages of sedimentation of shallow-marine Silurian dolomites, and at the top Silurian limestone; at the very base of the cliff, some carbonates of the PortQeld Formation (Fig. 2). Cambrian carbonates probably crop out. SC, scarp. Dashed lines: shear zones in shelf Nevertheless, it is still possible that it belongs to carbonates, parallel to scarp. a much older sedimentary sequence. Several different presumed Precambrian(?) clastic units Timing: the fault zone was active in several Orientation: east-west. Bends toward the with unclear contact and age relations were episodes from at least Cambrian to Tertiary southwest in the Nares Strait region. described from eastern Peary Land by Christie times. Nature: probably fault-controlled escarpment and Ineson (1979). in Wulff Land, Warming Land, and eastern Incipient Basin (Stage 2) 4. Permin Land Flexure (New) Nyeboe Land. Due to present-day erosion, it cannot be seen whether the scarp was draped by The first well-known basin evolution stage is Location: Wulff Land to Washington Land. later sediments. From western Nyeboe Land represented by the sediments of the Paradisfjeld Seems to extend into Ellesmere Island. into Hall Land and Washington Land the flex- Group (Fig. 2).
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The group is probably considerably more E than 1 km thick. In Peary Land, it is not found south of the Harder Fjord fault zone, but to the west in Nansen Land it transgresses the southern- most splay of the zone (Higgins and others, 1981). An along-strike, east-west facies zonation as well as an across-strike, north-south facies zonation can be recognized. To the west in Nansen Land, and on islands west of Peary Land, the succession consists of uniform dark gray to black, impure carbonate rocks, commonly conglomeratic at the top. These pass eastward into more varied sequences made up of dark gray limestone, yellow lime- stone, turbiditic siltstone, and mudstone (now phyllites due to later metamorphism) (Dawes and Soper, 1973; Higgins and others, 1981; Friderichsen and others, 1982). At the far eastern end of Johannes V. Jensen Land, the sequence consists of massive dark gray limestone and cal- careous shale, followed by white, black, orange, and gray limestone (Soper and others, 1980), topped by fine-grained lime turbidites and resed- Figure 6. Block diagram showing a reconstruction of stage 2 in basin evolution, incipient imented carbonate conglomerates (personal ob- basin. The depositional environment of the preceding stage 1 is not sufficiently well known to servation, 1979). form the basis of a diagram. Stage 2 corresponds to the (Precambrian?)-Lower Cambrian A south-to-north transect across central Paradisfjeld Group (Fig. 3). HFFZ = Harder Fjord fault zone. Johannes V. Jensen Land appears to show a relative increase in the proportion of terrigenous a strong overprint of tectonic deformation. The facies association of mainly gray lime- mud to the north. Much more important is the Transport directions have not been measured. stones with turbidites and related deposits points occurrence of resedimented conglomerates in The lithology and distribution clearly indicate, toward a relatively deep-water slope and basin the top parts of the sequence in a broad belt over however, a source area of the conglomerates in environment. The southward transition into a length of 200 km along the southern outcrop the southern carbonate platform area. shallow-marine sediments of the carbonate shelf margin (Higgins and others, 1981; personal ob- servations, 1979). Resedimented conglomerates are virtually absent from the northern areas of the foldbelt. The conglomerates are clast- supported and consist mainly of light gray car- bonate pebbles and (in some cases) abundant, deformed rip-up clasts set in a fine-grained car- bonate matrix. The highest conglomerate char- acteristically has a sandy matrix. Grading is common. The beds are planar, with sharp, often erosive, boundaries. Bed thickness normally varies between 15 cm and 3 m, but composite units as much as 15 m thick have been observed (A. K. Higgins, 1982, personal commun.). The sum of sedimentary features suggests transport by high-density turbidity currents and debris flows. The original pebble fabric commonly has
Figure 7. A. Section through outer-fan-lobe turbidites and related deposits of the Narrow turbidite basin stage, Polkorri- doren Group (Fig. 2). Note the abundance of nongraded beds and of water-escape structures such as dish and pillar structures. B. Mud-rich sequence with thin-bedded turbidites of the Narrow turbidite baisin stage, Polkorridoren Group (Fig. 2). The sequence overlies outer-fan-lobe turbidites and probably represents a lobe abandonment facies. Horizontal grain-size scale in these and fol- lowing logs: cl = claystone; si = siltstone; ss = sandstone; f = fine-grained; m = medium-grained; c = coarse-grained; p = peb- bles; c = cobbles; b = boulders.
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has not been directly observed, as it is covered The Polkorridoren Group is widely exposed The southern limit of the deep-water basin is by younger rocks. The top of the group has north of the Harder Fjord fault zone. The high- not well known and it must be stressed that the yielded inarticulate brachiopod fragments and a est unit in the group is formed by the variegated possibility of later, lateral movements on the spicule of Chancelloria, suggesting a Cambrian Frigg Fjord mudstone, which is distributed Harder Fjord fault zone complicates direct com- age for that part of the sequence (Peel and Hig- chiefly in the northern part of the area between parisons across the fault zone. Surlyk and others gins, 1980; Friderichsen and others, 1982). Sur- the Harder Fjord fault zone and the Navarana (1980) proposed that the shelf margin was con- lyk and others (1980) proposed on regional Fjord fault. The lower turbidites and mudstones trolled by the Navarana Fjord fault and that an grounds and on the basis of facies resemblance that have their main distribution north of the episode of back-stepping of the shelf margin that the obvious southern correlative is the Harder Fjord fault zone are found only south of heralded the beginning of deep-water turbidite stromatolitic limestones and dolomites of the the zone toward the west in the Nansen Land deposition. It was also suggested, mainly on Portfjeld Formation (O'Connor, 1979). This is area (Higgins and others, 1981). The total thick- lithological grounds, that the southern shelf supported by the limited fossil evidence. The ness of the group is estimated to be at least 1 km sequence, correlative to the deep-water deposits, precise nature of the boundary between the two and possibly as much as 2 to 3 km (Higgins and was the sediments of the Buen Formation. This depositional regimes is not known. At the north- others, 1981). formation consists of black, sandy mudstones eastern tip of Peary Land, the Portfjeld Forma- The Polkorridoren Group consists of two and represents the only phase of dominantly ter- tion and the Paradisfjeld Group crop out main alternating facies associations, black, green, rigenous clastic deposition within the shelf area immediately south and north of the Harder and purple mudstone and sandy turbidites (Fig. until a major phase of shelf foundering in late Fjord fault zone, respectively. This outcrop area 7). This alternation has made it possible to make Llandoverian time. The northernmost outcrop is limited by northwest-southeast-trending faults rather detailed local lithostratigraphic schemes of the Buen Formation is in northeastern Peary to the southwest. The rapid transition across the (Dawes and Soper, 1973; Soper and others, Land, immediately south of the Harder Fjord fault zone, which in this area merges with the 1980). The main part of the turbidite sequences fault zone. According to Christie and Ineson Navarana Fjord fault, suggests a strong tectonic consists of thick, commonly structureless beds (1979) and J. R. Ineson (1980, personal com- control of the carbonate shelf margin, possibly deposited in a submarine-fan environment in mun.), it is here characterized by more varie- even in the form of an escarpment. The possibil- outer fan lobes and in the outer part of the mid- gated colors and is somewhat reminiscent of a ity remains, however, that the juxtaposition was fan. About 70 paleocurrent readings show 3 dis- fine-grained, thin-bedded turbidite sequence. It caused by sinistral strike-slip movement along tinct modes toward the west, north, and, less may thus pass directly into the variegated northwest-southeast-trending faults, limiting the commonly, east. The longitudinal transport to- deeper-water Frigg Fjord mudstone. The main outcrop of the Portfjeld Formation toward the ward the west is interpreted as representing a mudstone units in the Polkorridoren Group are southwest. To the west, where the Harder Fjord combination of westerly directed submarine fans interpreted as representing basin-plain and inter- fault zone splays, the Paradisfjeld Group occurs and deflection of the outer parts of northerly fan channel deposits that to the south merge into on both sides of the faults. directed fans along the basin axis. The bed lower-slope mudstones. The slope-and-rise en- vironment is most likely represented by the This may be seen as the first indication of a thickness and grain size seem to increase toward Frigg Fjord mudstone, which expands drasti- general theme in the structural configuration of the north and northwest (Higgins and others, cally in thickness south of the Harder Fjord fault the platform-basin transition, both in North 1981; personal observations, 1979), whereas zone. Greenland and in Arctic Canada. To the east, there is a general decrease in the two parameters the facies boundary is sharp, an fault control of toward the west in the outcrop area crossing the The passage from the second to the third stage the shelf margin, commonly resulting in forma- Harder Fjord fault zone. The interbedded mud- in basin evolution is thus characterized by pro- tion of an escarpment, can be demonstrated. stone units normally contain thin-bedded turbi- nounced increase in basinal subsidence, leading Westward along the margin, the facies boundary dites and starved ripples. The basal unit is to the development of a deep-water turbidite is more transitional, and the main controlling mainly black and increases in thickness toward basin. This is accompanied by the southward faults die out or splay, resulting in the develop- the east. The highest mudstone units are greenish shift of the shelf-basin boundary to a position ment of a ramp. In the same place, the thickness and purple. They contain thin-bedded turbidites, probably controlled by the Navarana Fjord and grain sizes of the basinal sediments decrease. and abundant trace fossils occur at some hori- fault. This, in turn, resulted in a southward shift The platform-basin transition was, in the case zons (Pickerill and others, 1982). The thickness in facies belt so that slope and basin margin of the Paradisfjeld Group, most likely developed of the highest mudstone unit, the Frigg Fjord deposits of the Paradisfjeld Group are overlain as a wide zone of uniform slope deposits imper- mudstone, has been estimated at 750 to 1,000 m by true basinal deposits of the Polkorridoren ceptibly passing into the shallow-marine car- in the Nansen Land area (Higgins and others, Group, whereas the slope area moved south- bonates of the Portfjeld Group toward the south 1981); it appears to be much thinner north of ward to occupy a broad belt between the Nava- (Fig. 6). the Harder Fjord fault zone in central Johannes rana Fjord fault and the Harder Fjord fault V. Jensen Land. zones. The last now occupied an intrabasinal Narrow Turbidite Basin (Stage 3) The Polkorridoren Group is poor in con- position but still seems to have been active in The transition from the slope and basin car- glomeratic rocks compared to the sequences of that it appears to have controlled the base- bonate of the Paradisfjeld Group to the turbi- the previous basin stage. However, Higgins and of-slope position. The marked increase in ditic sandstone and terrigenous mudstone of the others (1981) noted the presence of two levels of subsidence correlates with an interruption of oveflying Polkorridoren Group represents a limestone boulder conglomerates in the south- carbonate shelf deposition if the correlation of major step in the evolution of the deep-water western outcrop area in Nansen Land and the deep-water sediments with the mudstones of basin of North Greenland. Subsidence increased MacMillan 0. The conglomerates were most the Buen Formation is correct. The water depth drastically, resulting in deposition characterized probably resedimented from the shelf margin over the shelf was, however, not very great, and by terrigenous sandstone turbidites and mud- and deposited in a base-of-slope environment. It the area still formed a well-defined shelf con- stones, whereas carbonates occur only as con- thus appears that the base-of-slope has moved trasting with the deeper slope and basin en- glomerates resedimented from the southern southward, when compared to the underlying vironments. The correlation of shelf-margin shelf. Paradisfjeld Group. back-stepping and drowning of large shelf areas
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also can be seen in the late Llandoverian, but in that case, foundering continued, and the sub- merged shelf area eventually became part of the turbidite basin. The tectonic-sedimentologic set- ting at this stage thus can be visualized as follows (Fig. 8). Outside a shelf area receiving terrige- nous mud and sand, a wide slope was formed, characterized by deposition in a well-oxygenated environment of red and green mudstones with occasional thin turbidites. Coarse clastic mate- rial was funneled across the shelf into submarine canyons that still remain to be found. This mate- rial was deposited by turbidity currents onto one or more submarine fans that were deflected westward following the east-west axis of the basin. An additional source for the longitudinally derived turbidites may be uplifted areas to the east. The Buen Formation is absent in Kronprins Christian Land (Fig. 1). This is tentatively inter- preted as due to Early Cambrian uplift in the easternmost shelf region corresponding to the deepest, eastern part of the major angular un- Figure 8. Block diagram showing a reconstruction of stage 3 in basin evolution: Narrow conformity described from Peary Land (see Fig. turbidite basin, corresponding to the Lower Cambrian Polkorridoren Group (Fig. 2). HFFZ = 18 below). The unconformity was probably Harder Fjord fault zone. NFF = Navarana Fjord fault. The black dots in the block diagram caused by bulging that was propagating to the indicate the position of the immediately preceding block diagram. west away from a subduction zone at the west- ern margin of the lapetus Ocean (compare Jacobi, 1981). If this interpretation is correct, the narrow turbidite basin represented by the Polkorridoren Group is a good analogue to the Silurian turbidite basin (stages 5 and 7 in basin evolution). Erosion and collapse of the shelf margin resulted in occasional deposition of car- bonate conglomerates in the base-of-slope en- vironment (see Fig. 13 below). The petrographic composition of the conglomerates indicates that the margin had considerable relief and that ap- preciable erosion took place, because the con- temporaneous shelf deposits were made up primarily of terrigenous mud and sand. a The along-strike variation in the configura- 3 o tion of the shelf-basin transition follows the pat- h. tern presented in the description of the preceding O basinal stage. The controlling structural features -o t> tend to lose their identity toward the west. The _> Harder Fjord fault zone splays widely, and the >a
Figure 9. A. Turbidites overlain by thick sequence of resed- imented conglomerates from the upper parts of basin evolu- tion substage 4a, corresponding to the Velvedal Group. The clasts of the conglomerates are cherts and gray limestones derived from the shelf-slope break and upper slope. The con- glomerates crop out immediately below the section shown in Figure 10. B. Section through the boundary between sub- stages 4a and 4b in the basin evolution stage: basin expansion and starvation, corresponding to the Cambrian-Ordovician Velvedal and Amundsen Land Groups (Fig. 2). The Valvedal Group shows upward-fining turbidites of channelized midfan origin; the Amundsen Land Group is represented by thin-bedded basin-plain turbidites. 1,1 I f'm'cl l'm'cl I I 1 J II mcl I m< cl s ss o c b cl s ss p
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south-to-north transition from platform to basin is very gradual. This is clearly shown by Figure 10. Top of turbidite sequence of (he Vohedal Group (FIES. 2. 9), cor- the dramatic westward increase in width and responding
Figure 11. Fan fringe and basin-plain tur- bidites, cherts and black mudstones of basin evolution stage 4a (Velvedal Group, Figs. 2, 12), Valvedal, Johannes V. Jensen Land. Thickness of the very consistent light beds in middle of section about 10 cm.
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derivation of the turbidites, and a canyon-fan model is thus suggested (Fig. 12). The turbidite fan sequence crops out only in a 25-km-wide strip between the Harder Fjord fault zone and Frederik E. Hyde Fjord. The youngest rocks in the northern parts of the foldbelt in Johannes V. Jensen Land (north of the Harder Fjord fault zone) belong, however, to the same sequence, but they represent only the most distal fan sedi- ments interbedded with basin-plain mudstones. Along strike, the fan turbidites pass into slope and possibly interfan mudstones. All mudstones and fine-grained, thin-bedded turbidites are chertified to varying degrees. In many cases, the chertification is so intense that the original tur- bidite features are completely masked, and only ghosts of cross-lamination can be seen. Toward the termination of submarine-fan deposition, the upper slope underwent slumping of large dimensions. A composite debris sheet in total up to about 20 m thick thus can be traced along strike for about 75 km from O. B. Beggild Fjord in the west to the inner reaches of Frigg Figure 12. Block diagram showing a reconstruction of stage 4a in basin evolution, cor- Fjord in the east (Figs. 1, 9B). The sheet consists responding to the Cambrian Velvedal Group (Fig. 2). HFFZ = Harder Fjord fault zone. NFF = to the west of a series of amalgamated conglom- Navarana Fjord fault. erates. The thickest individual bed measures 5 m (Figs. 9B, 13). To the east, somewhat farther down the slope, the sheet consists of 4 con- glomerates, the thickest of which is about 5 m. The conglomerates are composed of black chert and flat, angular clasts of laminated limestone that range in size from pebbles to boulders. Both clast types show varying degrees of plastic deformation, indicating that the parent rock was only partially lithified at the time of slumping and subsequent mass-flow transport. The clasts are set in a muddy lime matrix, and the conglomerates are mainly clast-supported. The texture is rather unusual, in that the elongate clasts are arranged in a wavy pattern that can easily be mistaken for imbrication in cases where it is not possible to examine the section from some distance. The wavy texture occurs ubiquitously in the resedimented conglomerates of the starved-basin phase. It is interpreted as reflecting an original orientation pattern formed in response to the development of internal waves within high-density debris flow during transport.
Figure 13. Boundary between outer and midfan turbidites (V) with conglomerate (1) at base of section (basin evolution stage 4a, Velvedal Group), and thin-bedded turbidites, black cherts and mudstones, and occasional conglomerates (A) (basin evolution stage 4b, Amundsen Land Group). At the top of the mountain slope, light-colored outer-fan and basin-plain turbidites (P) (basin evolution stage 5, Peary Land Group). North side of O. B. Beggild Fjord. Sections in Figures 9 and 10, located in same wall.
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This texture was then enhanced by loading caused by expulsion of pore water shortly after deposition. The lithology of the conglomerates shows that they were derived from the upper slope rather than from the carbonate shelf. The position of the shelf margin was probably controlled by the Navarana Fjord fault (Fig. 1), the eastward ex- tension of which runs on average 40 km south of the Harder Fjord fault zone. As the source area of the debris sheets is located somewhat down- slope to the north of the shelf margin, the maximum travel distance of the flows was prob- ably of the order of about 30 km (conservative estimate). The minimum volume of the compos- ite sheet is thus on the order of (30 x 75 x 0.020 km3) = 45 km3,20 m being the thickness of the sheet in the southernmost basinal locality. Due to extensive east-west shortening of the sequence as a result of thrusting (see Fig. 34 below), the original along-strike extension of the sheet was considerably more than 75 km, and the actual volume accordingly was probably several times larger than the calculated 45 km3. Figure 14. Green, bedded cherts from basin evolution stage 4b, upper part of Amundsen Starved Basin (b). The relatively small-sized Land Group, section shown in Figure 13. borderland fans of the Valveldal Group (Fig. 12) eventually were abandoned and a long period of basin starvation and, at times, also facies are dominated by black and green radio- conforms with a mainly lateral south-to-north stagnation was initiated. This period corresponds larian cherts and by black and greenish mud- fill of coarse clastic material, as was also ob- approximately to the Lower Ordovician-Lower stones and include thin-bedded turbidites and a served for the preceding phase of small-sized Silurian Amundsen Land Group (see Frider- thick sequence of resedimented conglomerates submarine-fan and starved-basin deposition ichsen and others, 1982). From now on, age with interbedded turbidites (Figs. 13-17). All of (Fig. 11). Approaching the southern outer slope, control is much better because good graptolite the fine-grained sediments are chertified to vary- the sedimentary facies become more varied, and data exist for the Amundsen Land Group ing degrees. bioturbation becomes increasingly important. (Friderichsen and others, 1982; Surlyk and oth- The northernmost localities around Sydglet- Finally, conglomerates and thick turbidites ers, 1980) and the overlying Peary Land Group scher (Fig. 1) are characterized by fine-grained dominate the sequence completely in the base- (Hurst and Surlyk, 1982). The sedimentary mudstones with rare thin-bedded turbidites. This of-slope environment. The thickness and grain size
Figure 15. A. Disorganized matrix-supported flat-pebble conglomerate from the chert-mudstone sequence of the Amundsen Land Group (Fig. 2). Gray clasts are carbonates, and black, slightly deformed clasts are chert, O. B. Baggild Fjord. B. Clast-supported flat-pebble conglomerate. Subhorizontal clast fabric. Clasts consist of carbonates. Top part of Amundsen Land Group (Fig. 2), Freuchen Land.
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Figure 16. Huge sheet of redeposited carbonate conglomerates. Individual beds are as much as 10 m thick. Height of the wall is about 100 m. Lower part of Amundsen Land Group (basin evolution stage 4a, Figs. 2,19).
of the coarse clastic sediments show a general about 75 km (Fig. 1). Their main development decrease upward in the Amundsen Land Group. occurs in the eastern part of this transect. The The dominant clast composition in the con- group is covered by Silurian turbidites east of glomerates changes upward from flat pebble Midtkap (Fig. 1) and, accordingly, nothing is carbonates to black chert, reflecting a change in known about its composition in eastern Peary source area from mainly upper slope and shelf Land. Down the paleoslope, the sheets are ex- margin to lower parts of the slope. The con- posed from Harebugt in the south approxi- I II If mclf mcl I I glomerates are commonly graded, with weak mately to the Harder Fjord fault zone in the cl s ss p c b imbrication or subhorizontal orientation of north, that is, over a distance of about 35 km. Figure 17. Section through turbidite-domi- clasts (Fig. 17). Other varieties are nongraded The shelf margin was similar to the preceding nated part of the debris sheet shown in Figure and disorganized (Fig. 15). Boulder and cobble turbiditic phase and probably was controlled by 16. grades dominate the lower conglomerates, the Navarana Fjord fault. This again implies that whereas pebble grades become dominant in the the shelf-slope break was situated about 25 km Figs. 16, 17). The unconformity is markedly an- higher parts of the sequence. south of the southernmost outcrop. Assuming an gular with an east-to-west increasing strati- In the southernmost localities at Harebugt average thickness of 100 m of the main debris graphic hiatus (Fig. 18). According to Peel and Kap Mjelner (Fig. 16), the conglomerates sheet, a minimum volume can be calculated to (1979) and Ineson and Peel (1980), it appears 3 3 reach a thickness of about 100 m. They are in- about 262 km (35 x 75 x 0.1) km , which were that in the easternmost locality about 1,000 m of terbedded with thick-bedded, medium sand tur- stripped off the outer shelf and upper slope Middle and Upper Cambrian and Lower Ordo-
bidites of the ta, tab, and t^ types (Fig. 17). The mainly in Early Ordovician time. It is, however, vician rocks has been eroded or was never de- conglomerate beds often form the base of fining- clear that the conglomerates have a wider distri- posited prior to the deposition of the Wandel thinning upward cycles (Fig. 17). Although the bution in both up- and down-slope directions Valley Formation. Examination of the sche- sequences are strongly folded and thrust, it is than present-day exposure shows. The conglom- matic sections presented by Ineson and Peel clear that the conglomerates form huge sheets erate belt probably has a total width of about (1980, Fig. 17) (Fig. 18) reveals, however, that a that can be followed for many kilometres along 50 km rather than the exposed 35 km, giving a general shallowing upward and eastward trend 3 strike. The cycles consequently are not inter- unit volume of 375 km . The original distance is present in the preunconformity sequence. This preted as representing filling and abandonment was much larger but was reduced by later thrust- strongly suggests that the eastern portion of the of channels. Rather, they reflect waning activity ing, and the real volume thus was considerably shelf underwent gradual uplift in the Middle and of the deposition resulting from major phases of larger than is the calculated volume. Late Cambrian and that much of the hiatus slumping and successive development of mass The enormous amount of redeposited mate- (Fig. 18) is due to nondeposition rather than to flows and turbidity currents. rial fits remarkably well with conditions on the Early Ordovician erosion. If all of the hiatus The huge debris sheets can be traced along shelf where an unconformity at the late Early were due to Early Ordovician tilting and ero- strike from the O. B. Boggild Fjord area in the Ordovician base of the Wandel Valley Forma- sion, the sedimentary sequences should be more west, where they have almost wedged out, to tion is known to be the principal structural fea- uniformly developed along strike. Frigg Fjord in the east, that is, over a distance of ture (Peel, 1979, p. 38; Ineson and Peel, 1980, Accordingly, we interpret the dramatic angu-
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A B C E F G H
Localities E,F
< Berglum River Formation Ö > M O Wandel Valley Formation O oc o "XIXDTD
Tavsens fm. T3 fm. T4
Iskappe fm.T2 fm. T3 fm. T7 Group fm. T1 fm.T1 fm.T5 z fm.T6 < M fm.4 Bronlund 5 fm.3 CO Fjord S fm.2 < Group fm.6 O fm.1
Buen Formation
Portfjeld Formation
Figure 18. Cambrian-Ordovician shelf sequence in southern Peary Land. Modified from Ineson and Peel (1980). Note the impressive sub-Wandel Valley Formation hiatus. Eroded Middle-Upper Cambrian and lowermost Ordovician carbonates formed the source of the debris sheets (Fig. 16) redeposited in a deep-water base-of-slope environment outside the platform (Fig. 19).
lar unconformity as being due to increasing shelf prograded across the shelf as cross-bedded sand and increase in proportion of chert and black uplift and tilting resulting in combined nondepo- bodies. mudstones reflect the increasing starvation and sition and erosion to the east in Middle and Late Thé geologic record offers only rare examples stagnation of the deep-water basin. This again Cambrian to Early Ordovician times. The of a progressively uplifted or tilted, eroded shelf may be a result of mid-Late Ordovician eustatic eroded carbonate material was transported preserved adjacent to the base-of-slope and sea-level rise that gradually drowned the outer across the outer shelf and shelf-slope break in a basin-plain margin, where the off-stripped mate- parts of the shelf and prevented coarser clastics series of remarkable debris flows, whereas the rial was redeposited (Fig. 19). from being transported downslope via subma- sand represented by the base-of-slope turbidites The upward disappearance of conglomerates rine canyons or as line-sourced debris sheets.
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the O. B. Boggild Fjord area (Fig. 1), there was a gradual increase in grain size in the latest Ordo- vician, leading to the sandy turbidite facies. Farther to the north in the Sydgletscher area (Fig. 1), turbidite deposition started very abruptly, probably in early Llandoverian time with the incoming of extremely thick turbidite beds (Fig. 20). A well-organized sand-rich depositional sys- tem was, however, rapidly developed (Fig. 21). The turbidite beds are sheetlike, with great lat- eral continuity. Mudstone is restricted mainly to thin divisions on top of many turbidites (Fig. 22). Paleocurrents are extremely uniform toward the west-southwest, parallel to the margin of the carbonate shelf (Fig. 23). The Peary Land Group shows a crude tripartite di- vision into lower and upper sandy turbidite units separated by a middle mudstone unit (Fig. 2 and SM in Fig. 4). The main part of the lower turbidite sequence (Merqujóq Formation) represents deposition in the outer-fan environment in a highly elongate Figure 19. Block diagram showing a reconstruction of stage 4b in basin evolution, corre- east-west submarine fan system (Figs. 21, 24). sponding to the Amundsen Land Group (Fig. 2). HFFZ = Harder Fjord fault zone. NFF = The top part of the formation is characterized by Navarana Fjord fault. The gradually tilted and uplifted shelf formed a source area for the huge complex channeling and scouring interpreted as debris sheets deposited in the base-of-slope environments (Figs. 16-18). representing a braided midfan environment (Fig. 25). Some channels show point-bar-like features suggestive of lateral migration and meandering. The largest observed channels ob- tained widths of several hundred metres and depths of about 50 m. Turbidite sedimentation was punctuated by several episodes of conglomerate deposition. In contrast to the longitudinally derived turbidites, the conglomerates were resedimented from the southern shelf area. The conglomerates range in thickness from 0.5 m to about 50 m and vary from well-sorted pebble beds to totally disorga- nized boulder beds with individual clasts often reaching a diameter of several metres (Fig. 26). The clasts are mainly carbonates, many of which can be matched directly with shelf lithologies. Virtually all conglomerates are clast-sup- ported, and coarse-tail grading is often observed. The matrix is mainly lime mudstone, but some of the well-sorted pebbly conglomerates are to- tally devoid of a matrix. Transport mechanisms were mainly high-density debris flows and occa- sional pure grain flows. The thicker conglomer- ates are almost everywhere overlain by char- Figure 20. Block diagram showing a reconstruction of stage 5 in basin evolution: longitudi- acteristic sequences of thin-bedded muddy tur- nal turbidite basin, corresponding to the lower part of the Peary Land Group (Fig. 2). NFF = bidites resulting from overflow over the local Navarana Fjord fault. topographic highs formed by the conglomerates (Fig. 27). Longitudinal Turbidite Basin (Stage 5) veloped following the Ordovician starved-basin The shelf margin seems to have been con- phase. Turbidite deposition continued through- trolled by the Navarana Fjord fault, as in the The most dramatic paleoceanographic change out the Silurian, and the resulting sequence is preceding phases of basin evolution. Good expo- in the deep-water basin took place at the placed in the Peary Land Group (Fig. 2). sures in the J. P. Koch Fjord area show that the Ordoyician-Silurian transition when a major, The initiation of major turbidite deposition actual shelf margin was developed as a steeply sand-rich, longitudinal turbidite basin was de- was diachronous (Surlyk and others, 1980). In dipping fault-controlled escarpment (Figs. 4, 5).
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15
Figure 22. A. Section through sand-rich outer-fan-lobe turbidites of basin evolution stage 5: longitudinal turbidite basin, Peary Land Figure 21. Turbidites of basin evolution stage 5: longitudinal tur- Group (Fig. 2). B. Section across the boundary between basin evolu- bidite basin. The extremely low content of mudstones is characteristic. tion stages 5 and 6: longitudinal turbidite basin. Basin expansion and Encircled hammer for scale. East coast of Freuchen Land. starvation, Peary Land Group (Fig. 2).
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foundering of the outer-shelf region, and western North Greenland seems for the first time to have become part of the deep-water basin. It is, however, possible that the Upper Ordo- vician-Llandoverian shelf carbonates exposed along the north coast of Hall Land actually re- present an east-west elongated horst or sea- mount limiting an enclosed deeper-water clastic basin to the south, as suggested by Hurst and Kerr (1982) and Hurst and Surlyk (1982). This question is at present difficult to solve, as the area exposes virtually no sediments of pre-late Llandoverian age. The southern margin of the basin from Hall Land to Wulff Land became well established at a position immediately north of the Inland Ice (Fig. 1). The shelf-basin transition was devel- oped either as a ramp or as an impressive east-west-trending reef belt (Hurst, 1980a; Hurst and Surlyk, 1983 and in press). Basin- ward, the reefs are flanked by mudstone with thick redeposited clastic debris sheets and iso- lated blocks of reef limestone. This belt passes Figure 24. Thick, structureless, nongraded gravity-flow deposits. Ghosts of horizontal load gradually into slope mudstone and finally into cast system show that the thick bed actually consists of three amalgamated units. Interpreted as basin-plain turbidites derived from the east. deposited in the outer-fan-lobe environment of basin evolution stage S: longitudinal turbidite East of a major structural high, the Victoria basin. Same locality as Figure 25. Fjord Arch, the margin was developed differ- ently. In this area, corresponding to Peary Land Turbidite deposition seems to have taken place Basin Expansion and Starvation (Stage 6) and the adjacent southern area, all of the shelf not only in the basinal region but virtually to the foundered and became part of the deep-water scarp, and it may be speculated that the scouring A dramatic phase of southward basin expan- basin. The foundering and deep submergence of activity of the turbidity currents played an active sion occurred at the Llandoverian-Wenlocxian more than 30,000 km2 of carbonate shelf east of role in maintaining the escarpment topography. boundary. This took place by collapse and the Victoria Fjord Arch are probably caused in
Figure 25. Margin of large turbidite-filled channel cut into sand-rich turbidites of basin evolution stage 5: longitudinal turbidite basin (Fig. 20). The channel is part of large, complex system of nested channels interpreted as representing a braided midfan environment. Immediately south of Frederick E. Hyde Fjord approximately opposite Kap Mjelner.
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Figure 26. A. Boulder conglomerate deposited in a base-of-slope environment immediately outside the scarp formed by the Navarana Fjord fault at basin evolution stage 5 (Fig. 20). The blocks consist of carbonates, and the lithologies can for the most part be matched with specific units in the shelf. South coast of Frederick E. Hyde Fjord opposite Kap Mjolner. B. Carbonate pebble conglomerate associated with conglomerate unit shown in Figure 27. The lack of matrix indicates a grain-flow origin of the conglomerate, which again suggests transport down a very steep
part by the combined effects of shelf back- outer-fan origin. This difference in development and deep submergence, the turbidite deposi- stepping, eustatic drowning, and the loading ef- is explained as being due to the strong overprint tional systems rapidly built up again. Transport fect of Caledonian nappes advancing from the of nappe loading in the east on a general phase was still westward parallel to the shelf margin east and southeast (Hurst and others, 1983). The of shelf-margin collapse and back-stepping. and the western reef belt. A huge, elongate sub- northern shelf margin was inundated by clastic marine fan system prograded westward, and the sediments in the latest Llandoverian, whereas Wide Turbidite Basin (Stage 7) whole region from the eastern tip of Peary Land the southern part first started to receive terrigen- to the Victoria Fjord Arch was occupied by ous clastics during the Wenlockian, indicating Following the late Llandoverian-Wenlockian outer-fan and fan-fringe environments (Fig. 30). that shelf foundering was associated with flexur- phase of basin starvation caused by transgression Complex channel systems characteristic of a ing. The extensive transgression resulted in dep- osition of a thick, uniform sequence of black mudstone with thin-bedded turbidites on top of the carbonates all along the new shelf margin (Figs. 28, 29). Slumping phenomena are com- mon, and the depositional regime can be charac- terized as a slope and rise system northward passing into the deep-water basin. In western North Greenland, the muddy slope-rise se- quence reaches a thickness of as much as 500 m (Fig. 28), whereas the thickness east of the Vic- toria Fjord Arch reaches only about 100 m. Another difference is that in western North Greenland, the slope-rise mudstone belt occu- pied a fairly stable position during the remaining part of the Silurian and did not show any marked northward progradation or southward encroachment by the turbidite basin except to the east in Wulff Land, where the turbidite facies spreads far to the south. Rather, the boundary between the two facies belts remained in a rela- tively stable position although showing pro- nounced small-scale interfingering. In eastern North Greenland, the slope mud- Figure 27. Thin-bedded muddy turbidites resulting from overflow over the topographic stones, on the other hand, pass vertically rather highs formed by the thick conglomerates shown in Figure 26A. South coast of Frederick E. abruptly into sandy turbidites of basin-plain and Hyde Fjord.
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midfan environment occur only in the highest ^ERin, ' OP Pi part of the sequence. The easternmost localities are characterized by thick, upward-fining cycles  composed of thick, locally pebbly, structureless sandstones passing upward into dark turbiditic mudstones. The cycles are interpreted as repre- senting a system of parallel, very wide inner fan valleys where the upper muddy part indicates channel abandonment. West of the Victoria Fjord Arch, the sandstone/mudstone ratio, sand grain size, and turbidite thickness decreased in a downcurrent direction, and sandy turbidite units alternate with mudstone units rich in thin- bedded turbidites, starved ripples, and silt and sand laminae (Fig. 31). These fine-grained units that show over-all thickening- or thinning- upward trends display all of the features taken as characteristic of overbanking by dilute turbidity currents and are tentatively interpreted as thick levee sequences. The intervening sand units con- sequently are taken as representing channel deposits. The entire depositional setting is interpreted Figure 28. Block diagram showing a reconstruction of basin evolution stage 6: basin expan- as an extremely elongate submarine fan imper- sion and starvation. This corresponds to the upper Llandoverian-lower Wenlockian mudstone ceptibly passing into a basin plain with wide sequence that overlies shelf carbonates (Fig. 2). deep-sea channels limited by depositional levees (Fig. 30). Lateral migration of the channel sys- tem resulted in cyclicity in the fine-grained units.
Figure 29. Block diagram showing a reconstruction of basin evolution stages 7 and 8: wide turbidite basin and Caledonian uplift and conglomerate deposition. The rocks representing prograding conglomerate lobes crop out in eastern Peary Land (see also Fig. 2). The nappes had probably reached Kronprins Christian Land. The western reef belt is exposed from WulfT Land to Washington Land. The buried horstlike feature indicated at the right-hand margin of the diagram represents the northern margin of Hall Land and Nyeboe Land.
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It should, however, be noted that bedding tic material carried out in deep water by turbid- currents (Stow and Lowell, 1979), is invalid in geometry is sheetlike and that channels have not ity currents. The huge dimensions of the fan longitudinal turbidite basins, where the two been observed in outcrop. This is to be expected, system, the elongate shape, and the absence of paleocurrent systems are parallel. as present-day deep-sea channels have widths of distinct fan segments and of a clearly defined fan In the period following the late Llandoverian- about 5 to 10 km or more and depths of several apex make it difficult to describe it within the Wenlockian shelf collapse, the amount of clastic hundred metres (Nelson and Kulm, 1973). currently fashionable fan models (Normark, material eroded in Caledonian mountains to the Furthermore, the main undisturbed, long sec- 1978; Mutti and Ricci-Lucchi, 1975). It seems, east and redeposited in deep water during the tions of the basin-plain turbidite sequences trend however, to compare rather well with the Ben- Silurian longitudinal-basin phases (phases 5, 6, east-west, that is, parallel to the paleocurrents, gal fan (Curray and Moore, 1971). The up- 7) can be estimated at about 300,000 km3. This whereas undisturbed north-south sections, current eastern part of the turbidite basin is is a minimum figure because the northern limit which could reveal large-scale channel shapes, unusually sand rich compared to other fans of of the deep-water basin is unknown. The prox- are virtually lacking, as they cut faults, thrusts, comparable size. It may be speculated that geo- imal southeastern part of the fan system in and fold axes at a high angle. strophic currents prevented the mud from Kronprins Christian Land has also been ex- The total preserved length of the system of fan settling and carried it in suspension along the cluded from the calculation, as it may have a and basin plain with deep-sea channels is 600 east-west-trending contours to the distal western different source area (compare Fig. 30). There is km in North Greenland. The marginal part of end of the basin, where both slope-rise system no indication that the northern limit was situ- the basin is preserved in the down-current ter- and the basin plain are mud rich (we owe this ated close to the north coast of Peary Land, and mination in Washington Land (Fig. 1), which suggestion to E. Mutti, 1981). There is evidence the basin thus may have been considerably adds another 200 km to the basin length so that for reworking of thin-bedded turbidites by con- wider than the exposed part. Furthermore, the the total preserved length is about 800 km. The tour currents in the distal parts of the basin basin probably extended westward, occupying inner-fan regions were situated in eastern Peary (Fig. 32). It is important in this connection to the areas to the north of Wulff Land, Nyeboe Land and farther toward the east. In this region, note that one of the main criteria for recog- Land, and Hall Land (see Fig. 1). The total vol- the rising Caledonian mountain belt formed the nizing contour current activity, that is, paleocur- ume of turbidites and associated sediments thus source region for the enormous amount of clas- rents at a right angle to the down-slope turbidity is probably more of the order of about
Figure 30. Thin-bedded Wenlockian turbidites with abundant starved ripples and rapid lateral wedging indicating deposition by overflow. Interpreted as representing proximal levee sediments of deep-sea channels. Northern Nyeboe Land.
Figure 31. A. Section through relatively thick-bedded turbidite se- quence from the distal part (Nyeboe Land) of the longitudinal turbidite basin (basin evolution stage 7): wide turbidite basin, Peary Land Group (Fig. 2). B. Section through thin-bedded turbidites from same locality as A.
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Figure 32. A. Nongraded bioturbated sandstones with sharp upper and lower boundaries. Interpreted as contourites formed by reworking of turbidites by geostrophic currents. Wenlockian, northern Nyeboe Land. B. Trace fossils on sole of thin sandstone bed of the type shown in A.
1,000,000 km3. The down-current termination The conglomerates differ markedly from all conglomerates were also deposited in the Jo- of the basin in Ellesmere Island is also excluded of the earlier deep-water conglomerates de- hannes V. Jensen Land area, the original volume from the estimate, as new source areas are intro- scribed above. The latter are all derived from of the unit that extends westward to Hendrik 0 duced (Surlyk, 1982). In comparison, the south- the upper slope and carbonate shelf to the south. was probably about three to four times greater. ern margin of the expanded deep-water basin is They are often of chaotic disorganized types The generally well-rounded and sorted ap- not preserved in Peary Land, due to later ero- with lime mud matrix, poor clast sorting, arid a pearance of the chert pebbles indicates that the sion. West of Freuchen Land, the outer part of variety of clast lithologies. Transport mecha- parent rock was lithified at the time of erosion the shelf foundered at approximately the same nisms were mainly debris flows, in some cases and that considerable transport and sorting had time as in Peary Land, and deposition of the transitional to grain flows. In contrast, the new taken place in the coastal zone before redeposi- overlying slope and basinal mudstones and tur- conglomerates are more organized, with rela- tion into deeper water by high-density turbidity bidites was initiated in latest Llandoverian time. tively thin, sheetlike beds; sandy matrix identical currents. The chert pebbles probably were from Toward the south and southwest, the Llandover- to the interbedded sandy turbidites; and well- an uplifted thick cherty sequence of mainly Or- ian carbonate ramp (Hurst, 1980a; Hurst and sorted and rounded pebble-sized clasts of green, dovician age (Volvedal and Amundsen Land Surlyk, 1983, and in press) subsided slowly. On black, and gray chert (Figs. 33, 34, 35). The Groups and their correlatives, Fig. 2), as no other this ramp, carbonate build-ups and top-of-slope cherts have yielded radiolarian remains sugges- known units contain sufficient volumes of cherts mudstones with resedimented conglomerates tive of an Ordovician age (D. L. Jones, 1981, to function as provenance for the conglomerates. were deposited. In Washington Land, this subsi- personal commun.). The beds often show grad- The uplift probably was caused by thrusting in dence phase was initiated earlier in the lower to ing and occur intimately interbedded with nor- connection with the advancing Caledonian middle Llandoverian, and slope mudstones and mal sandy turbidites lithologically identical to nappes (Fig. 30). Deposition of the conglomer- hemipelagic lime mudstones developed with the conglomerate matrix (Fig. 33). The con- ates took place in the inner and middle fan and carbonate build-ups (Hurst, 1980a; Hurst and glomerate/sandy turbidite ratio decreases to- in base-of-slope environments in eastern Peary Surlyk, 1983). ward the west. The transport mechanism of the Land, whereas the western localities probably pebbly beds was probably mainly high-density represent outer-fan lobes. Caledonian Thrusting and Conglomerate turbidity currents with basal grain-flow carpets However, the generally waning turbidity- Deposition (Stage 8) (Figs. 34, 35). current activity continued. The youngest unit in The conglomeratic unit forms the top stratum the western part of the basin (Nyeboe Land and At some time during the middle Wenlockian of the lower Paleozoic deep-water sequence in Hall Land) is of latest Silurian and possibly a major phase of conglomerate deposition was eastern Peary Land and its original thickness Devonian age. It consists of laminated, light initiated at the eastern, proximal end of the thus is not known. The maximum preserved gray, nonbioturbated mudstones deposited from basin. The conglomeratic depositional system thickness is at least 100 m and because of the muddy contour currents, very dilute turbidity prograded rapidly westward, and a feather edge sheetlike geometry the minimum volume of the currents, or nepheloid layers in a distal basin reached Hendrik 0 in later Wenlockian or early unit in Peary Land can be tentatively estimated plain that toward the south passed imperceptibly Ludlovian times (Hurst and Surlyk, 1982). at about 1,000 km3. If it is assumed that the into the continental rise.
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Figure 34. Chert-pebble conglomerate from the conglomerate lobes (Fig. 29). Note the excellent rounding and relatively good sorting of the pebble population. Pebble in center is 3.5 cm in diameter. Eastern Peary Land.
Figure 33. Pebbly sandstone with diffuse laminae of chert granules and pebbles in a sandy matrix, eastern Peary Land. Represents the first indications of the prograding conglomerate lobes (Fig. 29).
Transpression or Gravity Sliding Related to tional mega-sliding downslope along the axis of rana Fjord fault (Figs. 3A, 12, 19). In contrast, the Advancing Caledonian Front (Stage 9) the basin away from the Caledonian front. He contemporaneous rocks south of the fault are furthermore suggested that the carbonate shelf dominated by thick competent carbonates. A remarkable series of imbricate thrust sheets margin to the south acted as a "side land" for the The abrupt southern limitation of the thrust characterizes the area between the Harder Fjord thrust-fault deformation. This hypothesis can be belt (Fig. 34) thus can be interpreted as due to fault zone and Frederick E. Hyde Fjord (Figs. 1, rejected, as the shelf margin after the late Llan- the abrupt disappearance at the old shelf-margin 34) (Pedersen, 1980, 1981a, 1981b). The de- doverian episode of basin expansion (phase 6) fault zone of thick sequences of fine-grained in- formation is distinguished by imbricated thrust was situated at least 100 km south of the thrust- competent sequences that could act as décolle- sheets 100 to 500 m thick (Fig. 36). Displace- faulted area (Figs. 30, 34). There are no indica- ment zones or accommodate major thrusting. ment along the thrust faults ranges from 1 to 10 tions in the turbidite sequence of any changes Thrusting is of post-Llandoverian age, and the km toward the west or west-southwest, as indi- across the older Llandoverian shelf margin that deformed sediments all seem to have been lithi- cated by the north-south-oriented axial direc- could reflect the existence of a marked paleo- fied before thrusting. There are, furthermore, no tion of the anticlines at the nose and the topographic gradient. An alternative explanation signs within the whole turbidite sequence of the synclines at the rear of the sheets. The total pre- of the abrupt southward termination of thrusting Peary Land Group immediately to the south of served length of the sheets is about 100 km and is proposed here. Thrusting did not take place the thrust belt to indicate that dramatic, large- the width about 30 km. The thrust sheets incor- south of the trace of the buried Navarana Fjord scale events took place during turbidite deposi- porate basinal sediments belonging mainly to fault (compare Figs. 1A and 34). The thick var- tion. These features all point toward a post- the Ordovician Velvedal and Amundsen Land iegated Frigg Fjord mudstones that acted as a Peary Land Group age of the thrusting. The Groups, whereas the youngest sediments are of décollement zone during emplacement of the thrusted sequence is, however, strongly affected Llandoverian age and belong to the Peary Land thrust sheets occur only north of the Navarana by north-south compression of the Ellesmerian Group. They almost everywhere rest on the in- Fjord fault (Figs. 3A, 8). The dark mudstones orogenic phase. The age of this phase is consi- competent Frigg Fjord mudstones. Pedersen and cherts of the Volvedal and Amundsen Land dered to be between late Silurian and Carbonif- (1980, 1981a, 1981b) interpreted the thrust- Groups in which most of the thrusting took erous in North Greenland (Dawes and Soper, fault deformation as resulting from gravita- place are also limited to the south by the Nava- 1979; Surlyk and others, 1980). Springer (1981)
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recently demonstrated that an important struc- was probably a direct result of oblique plate tural metamorphic episode in the North Green- collision in the northern Iapetus Ocean in Late land foldbelt took place approximately at the Silurian time. Devonian-Mississippian boundary. Although the individual thrust sheets are only CALEDONIAN EVENTS IN 100 to 500 m thick (Pedersen, 1980, 1981a, NORTH GREENLAND 1981b), the thrusted sequence is several kilome- tres thick. Thrusting was interpreted by Pedersen The evolution of the early Paleozoic basin of (1980,1981a, 1981b) as a result of gravitational North Greenland is not directly related to Cale- sliding downslope away from the Caledonian donian events in the Iapetus region. The basin front to the east. This is not considered very came to an end during the Devonian and Early likely, as the sliding would have had to cross an Mississippian when the North Greenland fold- approximately north-south-trending narrow belt was formed by north-south compression ocean, trench, or deep basin in front of the during the Ellesmerian orogenic phase. Never- Caledonides. theless, a number of events during basin evolu- An alternative interpretation is that the thrust- tion can be related to the progressive closure of ing is caused by transpression in connection with the Iapetus Ocean and the formation of the Cal- sinistral, up-to-north oblique-slip movements on edonian mountain belt. the Harder Fjord fault zone (compare Harding The relation of the youngest events to the and Lowell, 1979). This hypothesis immediately Caledonides is comparatively evident, whereas explains the absence of the thrust belt in the the connection of the oldest is speculative. The relatively uplifted area north of the fault zone earliest and most conjectural event was the uplift (Fig. 34). It also explains the southwesterly di- of the eastern shelf areas in Cambrian and Early rected curvature of the thrusts and the absence Ordovician times (Figs. 12, 18, 19). The first Figure 35. Section through the distal west- of thrusting along the east coast of Frederick E. phases of uplift may be interpreted as resulting ern part of the prograding chert conglomerate Hyde Fjord (Fig. 34). As a consequence, it is not from upwarp along a peripheral bulge formed lobes (basin evolution stage 8): Caledonian necessary to invoke large-scale strike-slip trans- when the continental plate and its shelf area uplift and conglomerate deposition, Peary lations to account for the missing northern part drifted eastward toward an east-dipping subduc- Land Group (Fig. 2). Hendrik 0. of the thrust belt. Sinistral oblique-slip faulting tion zone. This phase was followed by the late
Figure 36. Map of area characterized by west- to west-southwest-directed thrusting (modified from Pedersen, 1980, 1981b). The upper fine-grained unit of the Polkorridoren Group (Frigg Fjord mudstones, Fig. 2) is the main décollement zone, whereas much of the thrusting occurred in the mudstone and chert sequences of the Valvedal and Amundsen Land Groups. The southern limit of thrusting corresponds to the southern limit of these fine-grained basinal facies (see Figs. 8,12,19).
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Llandoverian shelf foundering interpreted as in low and increases very gradually northward. In remarkable feature of the basin is the longitudi- part caused by nappe loading (Hurst and others, northernmost Johannes V. Jensen Land, the nal east-to-west transport of the Silurian turbi- 1983) when the continental crust was rapidly main metamorphism reaches low-amphibolite dites parallel to the continental margin (Surlyk, downdropped into the subduction zone facies. An important structural-metamorphic ep- 1982) (Fig. 23). This indicates the presence of a (Fig. 30). The third and most remarkable phase isode occurred at the Devonian-Carboniferous northern barrier of some sort. If the presence of is represented by the incoming of the enormous boundary (Springer, 1981). This event falls a narrow ocean basin is accepted, the mid- amount of turbiditic sandstone derived from the within the Late Devonian-earliest Carbonifer- oceanic ridge would have been situated fairly east (phases 5 and 7). The total volume of the ous age of the Ellesmerian orogeny of the Cana- close to the present-day north coast of Green- turbiditic units is estimated above as more than dian Arctic (Trettin and Balkwill, 1979). The land. The elevated topography of the ridge 1,000,000 km3. The monotonous lithology, rocks included in the foldbelt all belong to the would imply a southerly directed topographic eastern provenance, huge volume, and mainly lower Paleozoic deep-water sequence. The gradient away from the ridge, changing to a Silurian age of the units indicate that the Silurian north-south compressive nature and the regional northward-dipping continental slope and rise orogenic phases in the northern end of the type of metamorphism suggest that the foldbelt outside the shelf. The intervening basinal axis Atlantic Caledonian mountain belt resulted in originated with closure of a narrow ocean or probably followed the east-west axis of Jo- uplift of enormous landmasses that became the transitional type of basin by convergent plate hannes V. Jensen Land in Cambrian-Early Silu- subject of erosion (Surlyk, 1982). The fourth movement. Wrench faulting in the region was rian time and may have been shifted southward phase was characterized by the incoming in mid- probably of much younger age. in later Silurian time. If this general hypothesis is Wenlockian time of the westward-prograding, The deformed sequence is overlain with angu- correct, the basin can be seen as a close analogue chert-pebble conglomerates, probably originat- lar unconformity by a thick Carboniferous- to the deep turbidite basins described by Pilkey ing from upthrust Ordovician chert units to the Tertiary sequence described collectively under and others (1980) from the Atlantic coast of the east. Finally, a major thrust belt was formed in the term of the "Wandel Sea basin." These de- United States. the axial region of the basin south of and adja- posits have themselves been severely block- An alternative hypothesis is that sea-floor cent to the Harder Fjord fault zone (Pedersen, faulted in a tectonic setting unrelated to the late spreading never occurred and that the basin was 1981a). It is here interpreted as caused by trans- Paleozoic diastrophism (Dawes and Soper, formed by rift-controlled subsidence of the area pression in connection with sinistral and up-to- 1973; Dawes, 1976; Surlyk and others, 1980; situated between the carbonate shelf and a north oblique-slip movements along the fault Hakansson, 1979; Hakansson and others, 1981). northern landmass. If this landmass represented zone. The thrust event cannot be precisely dated, a volcanic arc, the basin was formed during the but it was probably related to thrusting and up- PLATE-TECTONIC INTERPRETATION early rifting stages preceding true back-arc lift of the basinal sediments to the east along the spreading. A landmass termed "Pearya" existed Caledonian front at a time when the nappes The tectonic setting of the deep-water basin is in northern Ellesmere Island. It contains a Pro- reached their westernmost position in the Kron- not fully understood, as the northern margin is terozoic gneissic basement, thick sequences of prins Christian Land area (Hurst and McKer- unknown in North Greenland (Surlyk, 1982). It Proterozoic-early Paleozoic shelf sediments, row, 1981; Hurst and others, 1983). A probable is, of course, tempting to extrapolate the setting volcanics of arc and extensional origin, and a age for this event is latest Silurian. known from Ellesmere Island (Trettin and collision orogen of essentially Middle Ordovi- The Caledonian events in North Greenland as Balkwill, 1979) into North Greenland. It must, cian age with large amounts of syntectonic and here interpreted have many features in common however, be emphasized that there is no direct post-tectonic clastic sediments. If, on the other with contemporaneous sequences along eastern evidence for the existence of an exposed north- hand, this hypothetic northern landmass is of North America from the southern Appalachians ern landmass throughout the existence of the normal continental nature, the basin compares (Shanmugam and Lash, 1982) to New Found- basin. There is, furthermore, no a priori reason well with the aulacogen model, as it was formed land (Jacobi, 1981). to accept the idea that a specific configuration of by rifting and extends deeply into the old a continental margin extends unchanged for continental landmass at a right angle to the ELLESMERIAN (DEVONIAN) about 1,000 km. One possibility is that the shelf- Caledonian front to the east (Surlyk, 1982). OROGENY IN NORTH GREENLAND basin transition represents a normal, passive margin of an ocean basin. ECONOMIC GEOLOGY The deep-water lower Paleozoic sediments The general setting, as visualized by Surlyk and the marginal northern parts of the carbonate and others (1980), suggests the presence of The present paper is the first systematic shelf were deformed and metamorphosed during highly attenuated crust, possibly of transitional treatment of the lower Paleozoic deep-water the Ellesmerian orogenic phase (Trettin and type, beneath the basin. This is supported by the sediments of North Greenland. It is mainly the Balk will, 1979; Christie, 1979) and form the tentative interpretation (Parsons, 1981) of the result of work done during a mapping program North Greenland foldbelt. spilite-serpentinite assemblage found in volcanic by the Geological Survey of Greenland in The degree of deformation and metamor- centers adjacent to the intrabasinal Harder Fjord 1979-1980. Systematic collection of samples for phism increases from south to north. The bound- fault zone (Figs. 2, 36) as representing a margin- source-rock analysis was done in 1980 (Rolle, ary between undeformed and deformed strata al oceanic crust beneath the deep-water depos- 1981; Rolle and Wrang, 1982). Sampling was coincides approximately with the pre-Llando- its. Continental-type rocks are known to under- concentrated in the Peary Land region. Sampling verian shelf-basin margin controlled by the lie the shelf carbonates, but the only direct of western North Greenland is planned for Navarana Fjord fault. evidence of the type of crust underlying the 1984-1985. A few Lower Silurian samples Farther toward the north, the Harder Fjord deep-water basin is the occurrence of exotic from Washington Land have, however, been fault zone approximately represents the bound- gneiss blocks from a dike in the northern part of analyzed, and they qualify as mature potential ary between rather mild deformation without the foldbelt and in the volcanic centers (Fig. 34), oil-source rocks. According to Rolle (1981; metamorphism and more severe folding and and on this basis Soper and others (1980) sug- Rolle and Wrang, 1982), mature source rocks metamorphism. Metamorphic grade is generally gested that the deep-water basin was ensialic. A for oil exist at several levels in the shelf se-
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glum Elv. Peary Land, eastern North Greenland: Grönlands Geologiske Devonian: Geological Survey of Canada Bulletin, v. 260. 55 p. quence, particularly in formation 2 (Ineson and Undersogelse Rapport, v. 82, 42 p. 1981, Evolution of the Canadian Arctic Islands: A transition between Peel, 1980) of the Brönlund Fjord Group (Fig. Curray, J. R„ and Moore, D. G.. 1971, Growth of the Bengal deep-sea fan and the Atlantic and Arctic Oceans, in Nairn. A.E.M., Churkin, M„ and denudation in the Himalayas: Geological Society of America Bulletin, Stehli. F. G., eds.. The ocean basins and margins. Volume 5: The Arctic 18). Good indications for source rocks have v. 82, p. 563- 572. Ocean: New York and London, Plenum Press, p. 105-199 been found within the Silurian shale unit, which Dawes, P. R., 1971, The Noah Greenland fold belt and environs: Geological Morrow, D. W„ and Kerr. J. W„ 1977, Stratigraphy and sedimentology of Society of Denmark Bulletin, v. 20, p. 197-239. lower Paleozoic formations near Prince Alfred Bay, Devon Island: Geo- overlies the shelf carbonates (Fig. 3A). 1976, Precambrian to Tertiary of northern Greenland, in Escher, A., logical Survey of Canada Bulletin, v. 254, p. 1 222, and Watt, W. S., eds., Geology of Greenland: Copenhagen. Geological Mutti, E., and Ricci-Lucchi, F.. 1975. Turbidite facies and facies associations: Source rocks for natural gas and condensate Survey of Greenland, p. 248 303. International Congress on Sedimentology, 9th, Nice, Guidebook A-l I, 1982, The Nyeboe Land fault zone: A major dislocation on the Green- p. 21-36. have been found in the Ordovician starved-basin land coast along northern Nares Strait, in Dawes, P. R., and Keir, J. W.. Nelson, C. H., and Kulm, L. D.. 1973, Submarine fans and deep-sea channels deposits of the Volvedal and Amundsen Land eds., Nares Strait and the drift of Greenland: A conflict in plate tecton- Turbidites and deep water .sedimentation: Society of Economic Paleon- ics: Meddelelser om Grönland, Geoscience, v. 8, p. 177 193. tologists and Mineralogists, Pacific Section, Short Course, p. 39 78. Groups (Fig. 3A). The great thickness and large Dawes, P. R., and Peel, J. S„ 1981, The northern margin of Greenland from Normark, W. R., 1978, Fan valleys, channels, and depositional lobes on mod- Baffin Bay to the Greenland Sea. in Nairn, A.E.M., Churkin, M„ and ern submarine fans: Characters for recognition of sandy turbidite envi- areal extent of oil source rocks are worth noting. Stehli, F. G., eds.. The ocean basins and margins, Volume 5: The Arctic ronments: American Association of Petroleum Geologists Bulletin, Possible reservoir rocks occur throughout the Ocean: New York and London. Plenum Press, p. 201 264. v. 62, p. 912 931. Dawes, P. R., and Soper, N. J„ 1973, Pre-Quaternary history of North Green- O'Connor, B.. 1979, The Portfjeld Formation (? early Cambrian) of eastern sequence of shelf carbonates, but they have not land, in Pitcher, M. G., ed.. Arctic geology: American Association of North Greenland: Grönlands Geologiske Undersogelse Rapport, v. 88, Petroleum Geologists Memoir 19. p. 117-134. p. 23-28. yet received any detailed study. Particularly in- 1979. Structural and stratigraphic framework of the North Gieenland Parsons, I., 1981. Volcanic centres between Frigg Fjord and Midtkap. eastern teresting in this connection is the regional un- fold belt in Johannes V. Jensen Land, Peary Land: Grönlands Geolo- North Greenland: Grönlands Geologiske Undersogelse Rapport, giske Undersogelse Rapport, v. 93, 40 p. v. 106, p. 69-75. conformity in the shelf sequence (Fig. 18) and Fränkl, E.. 1955, Rapport über die Durchquerung von Nord Peary Land Pedersen, S.A.S.. 1980, Regional geology and thrust fault tectonics in the (Nordgrönland) im Sommer 1953: Meddelelser om Grönland, v. 103, southern part of the North Greenland fold belt of North Peary Land: the Silurian reefs that in some areas are buried 61 p. Grönlands Geologiske Undersogelse Rapport, v. 99, p. 79-87. under younger turbidites. Traps can also be ex- Friderichsen, J. D., Higgins, A. K., Hurst, J. M., Pedersen, S.A.S., Soper, N. J., 1981a, Thrust fault tectonics along the Palaeozoic continental margin of and Surlyk, F., 1982, Lithosiratigraphic framework of the uppei Proter- North Greenland: The westernmost structural effect of the Caledonian pected along the fault zones, especially where ozoic and lower Palaeozoic deep water clastic deposits of North orogenesis: Terra Cognita, v. I. p. 72 only. Greenland: Grönlands Geologiske Undersogelse Rapport, v. 103. 1981b, The application of computer-assisted photogram metric methods they controlled the shelf-basin boundary, in Harding, T. P., and Lowell. J. D., 1979, Structural styles, their plate tectonic in the structural analysis of part of the North Greenland Fold Belt: these cases, fringes of often highly porous con- habitats, and hydrocarbon traps in petroleum provinces: American As- Journal of Structural Geology, v. 3, p. 253- 264. sociation of Petroleum Geologists Bulletin, v. 63, p. 1016 1058. Peel, J. S„ 1979, Cambrian Middle Ordovician stratigraphy of the Adams glomerate sheets occur, which may act as con- Higgins, A. K., Friderichsen. J. D.. and Soper. N. J.. 1981, The North Gletscher region, southwest Peary Land, North Greenland: Grönlands Greenland fold belt between central Johannes V. Jensen Land and Geologiske Undersogelse Rapport, v. 88, p. 29 39. duits between basinal source rocks and shelf or eastern Nansen Land: Grönlands Geologiske Undersogelse Rapport, Peel, J. S„ and Higgins, A. K„ 1980, Fossils from the Paradisfjeld Group. North reef reservoirs. v. 106, p. 35 45. Greenland fold belt: Grönlands Geologiske Undersogelse Rapport, Hurst. J. M., 1980a, Paleogeographic and stratigraphic differentiation of Silu- v. 101, p. 28. Regional maturity patterns and the time rela- rian carbonate buildups and biostromes of North Greenland: American Pickerill, R. K., Hurst. J. M.. and Surlyk. F., 1982, Notes on lower Palaeozoic Association of Petroleum Geologists Bulletin, v. 64, p. 527- 548. flysch trace fossils from Hatl Land and Peary Land, North Greenland: tions between hydrocarbon generation and mi- 1980b, Silurian stratigraphy and fades distribution in Washington Land Grönlands Geologiske Undersogelse Rapport, v, 108, p. 25 29. and western Hall Land, North Greenland: Grönlands Geologiske Un- Pilkey, O. H.. Locker, S. D.. and Cleary, W. J.. 1980, Comparison of gration are still not known, and it is thus too dersogelse Bulletin, v. 138,95 p. sand-layer geometry on flat doors of 10 modern depositional basins: early to attempt a more precise regional Hurst, J. M., and Kerr, J. W„ 1982, Upper Ordovician to Silurian facies American Association of Petroleum Geologists Bulletin, v. 64. patterns in eastern Ellesmere Island and western North Greenland and p. 841-856. assessment. their bearing on the Nares Strait lineament, in Dawes, P. R., and Kerr, Rolle, F., 1981, Hydrocarbon source rock sampling in Peary Land 1980: Grön- J. W., eds., Nares Strait and the drift of Greenland: A conflict In plate lands Geologiske Undersogelse Rapport, v. 106, p. 99- 103. tectonics: Meddelelser om Grönland, Geoscience, v. 8, p. 137-145. Rolle, F., and Wrang, P., 1982. En forelobig oliegeologisk vurdering af Peary Hurst. J. M., and McKerrow. W. S., 1981, The Caledonian nappes of eastern Land omridet i Nordgronland: Geological Survey of Greenland. Inter- ACKNOWLEDGMENTS North Greenland: Nature, v. 290, p. 772-774. nal report. Hurst, J. M, and Surlyk, F., 1980, Notes on the Lower Palaeozoic clastic Shanmugam, G.. and Lash, G. G., 1982, Analogous tectonic evolution of the sediments of Peary Land, East Greenland: Grönlands Geologiske Un- Ordovician foredeeps. southern and central Appalachians: Geology, We direct our thanks to D. L. Jones, R. J. dersogelse Rapport, v. 99, p. 73- 78. v. 10, p. 562-566. 1982, Stratigraphy of the Silurian turbidite sequence of North Green- Soper, N. J., Higgins, A. K„ and Friderichsen, J. D„ 1980, The North Green- Moiola, H. P. Trettin, and A. K. Higgins for land: Grönlands Geologiske Undersogelse Bulletin, v. 145, 121 p. land fold belt in eastern Johannes V. Jensen Land: Grenlands Geolo- constructive criticism of the manuscript during 1983, Depositional environments along a carbonate ramp to slojie tran- giske Undersogelse Rapport, v. 99, p. 89-98. sition in the Silurian of Washington Land, North Greenland: Canadian Springer, N., 1981, Preliminary Rb-Sr age determinations from the North various stages of its preparation. D. L. Jones Journal of Earth Sciences, v. 20, p. 473-499. Greenland fold belt, Johannes V. Jensen Land, with comments on the in press. Carbonate shelf margin configuration and facies in the Silurian metamorphic grade: Grönlands Geologiske Undersogelse Rapport, kindly processed chert samples for radiolaria. of North Greenland: American Association of Petroleum Geologists v. 106, p. 77-84. This paper is the outcome of field work under- Bulletin. Stow, D.A.V., and Lowell, J.P.B., 1979, Contourites: Their recognition in mod- Hurst. J. M , McKerrow, W. S., Soper, N. J., and Surlyk. F., 1983. The ern and ancient sediments: Earth-Science Reviews, v. 14, p. 251-291. taken during the Geological Survey of Green- relationship between Caledonian nappe tectonics and Silurian turbidite Surlyk, F., 1982, Nares Strait and the down-current termination of the Silurian deposition in North Greenland: Journal of the Geological Society of turbidite basin of North Greenland, in Dawes, P. R„ and Kerr, J. W., land North Greenland activities, and we are London, v. 140, p. 123 132. eds., Nares Strait and the drift of Greenland: A conflict in plate tecton- especially thankful to N. Henriksen for organiza- Häkansson, £., 1979, Carboniferous to Tertiary development of the Wandel ics: Meddelelser om Grönland. Geoscience, v. 8, p. 147-150. Sea Basin, eastern North Greenland: Grönlands Geologiske Underso Surlyk, F., Hurst, J. M., and Bjerreskov, M., 1980, First age-diagnostic fossils tion of the logistic aspects. Technical assistance gelse Rapport, v. 88, p. 73 83. from the central part of the North Greenland foldbelt: Nature, v. 286, Häkansson, IL, Heinberg, C.. and Stemmerik, L„ 1981, The Wandel Seit Basin p. 800-803. was provided by E. Glendal, B. Sikker Hansen, from Holm Land to Lock wood 0, eastern North Greenland: Grenlands Trettin, H. P., 1971, Geology of lower Paleozoic formations, Hazen Plateau and J. Lautrup, and N. Turner. The paper is pub- Geologiske Undersogelse Rapport, v. 106, p. 47-63. southern Grant Land Mountains, Ellesmere Island, Arctic Archipelago: Ineson. J. R , 1980, Carbonate debris flows in the Cambrian of south-west Geological Survey of Canada Bulletin, v. 203, 134 p. lished with the permission of the Director of the Peary Land, eastern North Greenland: Grönlands Geologiske Underso 1979, Middle Ordovician to Lower Devonian deep-water succession at gelse Rapport, v. 99, p. 43 49. southeastern margin of Hazen Trough, Canon Fiord, Ellesmere Island: Geological Survey of Greenland. Ineson, J. R , and Peel, J. S.. 1980, Cambrian stratigraphy in Peary Land, Geological Survey of Canada Bulletin, v. 272, 84 p. eastern North Greenland: Grönlands Geologiske Undersogelse Rap- Trettin, H. P., and Balkwill, H. R., 1979, Contributions to the tectonic history port, v. 99, p. 33-42. of the Innuitian Province. Arctic Canada: Canadian Journal of Earth REFERENCES CITED Jacobi, R. D., 1981, Peripheral bulge—A causal mechanism for the Lower/ Sciences, v. 16, p. 748-769. Middle Ordovician unconformity along the western margin of the Trettin, H. P., Frisch, T. O., Sobczak. L. W„ Weber, J. R., Niblett, E. R., Uw, Christie, R. L., 1964, Geological reconnaissance of northeastern Ellesmere northern Appalachians: Earth and Planetary Science Letters, v. 56. L. K„ DeLaurier, J. M.. and Whitham, K., 1972, The Innuitian Island, District of Franklin: Geological Survey of Canada Memoir, p. 245-251. Province, in Price, R. A. and Douglas, R.J.W., eds.. Variations in v. 331,79 p. Kerr, J. W., 1967, Nares submarine rift valley and the relative rotation of North tectonic styles in Canada: Geological Association of Canada Special 1979, The Franklinen geosyncline in the Canadian Arctic and its rela- Greenland: Canadian Petroleum Geology Bulletin, v. 15, p. 483 520. Paper, v. 11, p. 83-179. tionship to Svalbard: Norsk Polarinstitutt Skrifter, v. 167, p. 263-314. 1968, Stratigraphy of central and eastern Ellesmere Island. Arctic Christie, R. L., and Ineson, J. R.. 1979, Precambrian-Silurian geology of the G. Canada—Part II, Ordovician: Geological Survey of Canada Paper, B. Schley Fjord region, eastern Peary Land, North Greenland: Grön- v. 67-27, 2, 92 p. MANUSCRIPT RECEIVED BY THE SOCIETY JUNE 28, 1982 lands Geologiske Undersogelse Rapport, v. 88, p. 63-71. 1976, Stratigraphy of central and eastern Ellesmere Island. Arctic REVISED MANUSCRIPT RECEIVED JANUARY 17,1983 Christie, R. L.. and Peel, J. S„ 1977, Cambrian-Silurian stratigraphy of Bo- Canada—Part III, Upper Ordovician (Richmondian). Silurian and MANUSCRIPT ACCEPTED FEBRUARY 1, 1983
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