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). 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 EVOLUTION OF DEEP-WATER BASIN, GREENLAND 133 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). 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 134 SURLYK AND HURST 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.