The East Greenland Caledonides, which make up an ∼1300-km-long stretch of North-East Greenland, were formed by the collision of Laurentia and Baltica in mid-Silurian time. Geological mapping and research in this remote and poorly accessible segment of the circum-Atlantic Caledonide orogen began in connection with geographical exploration voyages in the early part of the nineteenth century. The first regional geological mapping took place during the long series of “The Danish Expeditions to North-East Greenland” between 1926 and 1958. Modern geological research and regional mapping by the Geological Survey of Denmark and Greenland between 1968 and 1998 have resulted in the publication of a series of 1:500,000 geological maps of the orogen, and an overview geological map at 1:1,000,000 scale, which accompanies this volume. This article reviews the history of geological research and the evolution of interpretations of the orogen. The recent systematic studies by the Geological Survey of Denmark and Greenland supplement and build on the considerable existing published literature and demonstrate that the North-East Greenland segment of the Caledonide orogen consists of a westward-propagating thrust sheet pile, with displacements estimated at 300–500 km. The thrust sheets incorporate major segments of reworked Laurentian gneiss basement, and a thick succession of Neoproterozoic to Ordovician sediments that accumulated in a major basin originally located outboard of the present coastline.

The East Greenland Caledonian orogen can be divided into distinct structurally bound geological domains composed of Archean to Lower Paleozoic lithostrati graphic and lithodemic components derived from the eastern margin of Laurentia. These domains originally evolved as major westward-displaced thrust units in the overriding plate during the collision with Baltica. The western border of the 1300-km-long and up to 300-km-wide segment of the orogen preserved onshore in East Greenland is thrust against the rocks of the Laurentian craton and is largely concealed beneath the Inland Ice. A foreland-propagating thrust pile is well-preserved in the extreme north of the orogen (79°N–82°N), and in the southern half (70°N–76°N), with less-well-preserved remnants in the western nunataks of the intervening region. Between 76°N and 81°N, the outer coastal region is dominated by high-grade Paleoproterozoic orthogneisses that were reworked during the Caledonian orogeny; most of this region is characterized by the presence of eclogitic mafic enclaves, which testify to exhumation from depths in excess of 50 km in late Caledonian time. Caledonian granites are confined to the southern orogen (70°N–76°N), where they intrude rock units now contained within the upper thrust sheet. Devonian continental basins are conspicuous in the southern part of the orogen and occur offshore farther north; their deposition can be linked to syn- to late-orogenic extension. Carboniferous and younger rocks are exposed onshore in the extreme north of the orogen (80°N–81°N) and are widespread in the south between 71°N and 75°N.

The Caledonian orogen of East Greenland contains remnants of Archean, Paleoproterozoic, late Mesoproterozoic, and early Neoproterozoic rocks that occur within far-traveled thrust sheets, and bear witness to a complex polyorogenic history of the region prior to Caledonian orogenesis. Archean and Paleoproterozoic complexes consist mainly of granitoid orthogneisses. A succession of Paleoproterozoic tholeiitic metabasalts is present in some of the foreland windows. A major unit of late Meso-proterozoic metasedimentary rocks (Krummedal supracrustal sequence) contains early Neoproterozoic (ca. 950 Ma) as well as Caledonian granites. There is evidence for Archean (ca. 2800–2600 Ma), Paleoproterozoic (2000–1750 Ma), and late Grenvillian (ca. 950 Ma) deformation and metamorphism, but Caledonian overprinting complicates the study of these events. This paper presents a broad overview of the various rock units with structural, geochemical, and geochronologic data. The Paleoproterozoic metabasaltic rocks from the foreland windows are described in more detail.

The crystalline basement within the northern parts of the Caledonian orogen, and in the adjacent foreland, is overlain by a several-kilometer-thick succession of sedimentary and volcanic rocks, the Paleoproterozoic–Mesoproterozoic Independence Fjord Group and the Mesoproterozoic Zig-Zag Dal Basalt Formation. The lowermost strata of the Independence Fjord Group, composed of quartzitic and feldspathic sandstones and conglomerates with interbedded volcanic rocks, occur within the Caledonian orogen and are strongly deformed. These strata were deposited around 1740 Ma ago, and they were associated with a period of rifting that succeeded a long sequence of Paleoproterozoic orogenic events. Similar sandstones, interbedded with siltstone units but without volcanic rocks, are widespread in the Caledonian foreland, where they are virtually undeformed. These foreland deposits were laid down in a continental sag basin under semiarid conditions. Sedimentary structures indicate a largely fluvial origin, with intermittent eolian transport. The siltstones were deposited in extensive shallow lakes. Desiccated bedding surfaces show that these periodically dried out. The sandstones of the Independence Fjord Group are cut by a multitude of doleritic sheets and dikes, the ca. 1380 Ma Midsommersø Dolerites, and more silicic intrusions, most of which show evidence of hydrothermal alteration and variable contamination with components derived from the crystalline basement and the sandstones. Some intrusions consist almost entirely of crustally derived material. The Zig-Zag Dal Basalt Formation conformably overlies the Independence Fjord Group. Compositional similarities suggest a genetic relationship with the Midsommersø Dolerites, but the basalts appear to be less crustally contaminated. The basalts were deposited within a basin that underwent subsidence during and after volcanic activity. The Zig-Zag Dal Basalt Formation is unconformably overlain by Neoproterozoic sedimentary successions. The unconformity represents a stratigraphic hiatus of some 500 m.y., for which no information is available from North Greenland.

Two major Neoproterozoic sedimentary basins that probably formed in response to an early pulse of Iapetan rifting along the Laurentian margin are well exposed in the East Greenland Caledonides. The Hekla Sund Basin is exposed at the northern termination of the East Greenland Caledonides, and it is represented by the Rivieradal and Hagen Fjord Groups, which attain a cumulative thickness of 8–11 km. The evolution of this basin reflects deposition during active rifting and a postrift thermal equilibration stage. The Eleonore Bay Basin of East Greenland includes the deposits of the Eleonore Bay Supergroup of early Neoproterozoic age overlain by Cryogenian (mid-Neoproterozoic) glacial deposits of the Tillite Group, which have a combined thickness in excess of 14 km. Four stages of basin evolution may be distinguished based on paleogeographic reorganizations of the shelf and a change from siliciclastic to carbonate deposition, and the final stage was dominated by glacigenic deposition. Major regional stratigraphic breaks seem to be absent, as is other evidence of rift-related sedimentation, suggesting deposition in one or a series of connected ensialic basins. A comparison with other Neoproterozoic basins along the Laurentian margin of the Iapetus Ocean shows similarities between the Eleonore Bay Basin and coeval deposits on Svalbard and the Central Highlands of Scotland. The development of an extensive carbonate platform during the later stages of both the Eleonore Bay and Hekla Sund Basins testifies to a period of tectonic stability prior to onset of Iapetus rifting. The extent of this carbonate platform may have been even larger, since similar successions are present in the Caledonides of Scotland and Ireland.

The Iapetus margin of Laurentia is preserved, with varying degrees of deformation, along a belt that extends for 1300 km along the eastern coast of Greenland, from Scoresby Sund in the south to Kronprins Christian Land at the northernmost extent of the Caledonian–Appalachian orogen. Along the length of the Greenland Caledonides, deformation is restricted to a single orogenic phase, the Scandian, at around 425 Ma, which represents the continent-continent collision of Laurentia and Baltica. The Lower Paleozoic stratigraphy can be closely correlated with the palinspastically contiguous terranes of NE Spitsbergen, Bjørnøya, and NW Scotland, and, farther to the south, that of western Newfoundland. In Greenland itself, Lower Paleozoic sediments are present in the foreland, parautochthon, and the highest allochthonous sheet of the orogen, the Franz Joseph allochthon. In the Franklinian Basin of eastern North Greenland, unconformity-bounded Lower Cambrian sediments can be correlated with the Sauk I sequence of cratonic North America. These Cambrian sediments are separated from younger units by a significant hiatus, the sub–Wandel Valley unconformity, but above that surface, the succession extends without major breaks from the major flooding event at the base of Sauk IV (Early Ordovician) through to the early Wenlock. The carbonate platform in this region foundered from late Llandovery time onward due to loading by thrust sheets, and turbidite deposition replaced platform carbonate deposition. Caledonian thrusts truncate the youngest preserved sediments, which are of early Wenlock age. The punctuated, attenuated stratigraphy seen in Kronprins Christian Land continues southward along the length of the parautochthon, through Lambert Land, Nørreland, and Dronning Louise Land, to a series of tectonic windows in the southern part of the Greenland Caledonides. In contrast to the stratigraphy seen in the parautochthon, the Franz Joseph allochthon contains one of the thickest Cambrian–Middle Ordovician successions in Laurentia, including a complete succession from Sauk I to Tippecanoe II.

The 1300-km-long, up to 300-km-wide onshore segment of the East Greenland Caledonian orogen is divided into distinct structurally bound geological domains that originally evolved as major westward-displaced thrust units during collision with Baltica. The thrust systems accommodated contraction of an already complex Laurentian assembly of Archean to Neoproterozoic and Cambrian to Silurian lithostratigraphic units and are a consequence of the convergence, and final collision, of Baltica with Laurentia in the mid- to late Silurian Scandian orogeny. The transition from undisturbed foreland to orogen is perfectly preserved in the extreme north of the East Greenland Caledonides, where a younger lower (Vandredalen) thrust sheet carrying older thrust sheets (Western thrust belt) is displaced westward across a thin-skinned fold-and-thrust belt. In the southern half of the orogen, a pile of far-traveled thrust sheets (from youngest to oldest, Gemmedal, Niggli Spids, Hagar Bjerg thrust sheets) is displaced WNW across parautochthonous foreland windows, and the intact foreland is only intermittently exposed at the margin of the Inland Ice in the far west. These westward- and foreland-propagating systems are distinct from the Nørreland thrust sheet, the coastal region between 76°N and 79°N, in which Paleoproterozoic basement gneiss lithologies host enclaves of Devonian and Carboniferous eclogite-facies rocks. These rocks must have been exhumed from the roots of the collisional orogen, and their age suggests that the Nørreland thrust may be out of sequence relative to the main WNW foreland-propagating systems.

The Greenland Caledonides have a tectonic architecture built of Laurentian-margin Precambrian crystalline complexes and younger sedimentary successions that were metamorphosed during the Paleozoic collision with Baltica. Caledonian metamorphic patterns correspond to the gross structural levels of the orogen. The patterns are superimposed on earlier metamorphic histories in the Precambrian crystalline complexes, but they account for the sole metamorphism of Neoproterozoic to early Paleozoic sedimentary units. We describe the Caledonian metamorphism by dividing the orogen into two parts, a northern and a southern segment separated at 76°N by Bessel Fjord. North of Bessel Fjord, metamorphic grade increases eastward toward the hinterland in progressively higher thrust sheets, where it ultimately reaches ultrahigh-pressure conditions. The metamorphic pattern in the southern segment is complicated by regional extensional detachment faults. Very low-grade sedimentary rocks of the foreland are overlain by the deepest structural level, the Niggli Spids thrust sheet, which contains widespread relicts of high-pressure metamorphism. The overlying Hagar Bjerg thrust sheet is composed of a midcrustal-level migmatite complex that records high temperatures in the amphibolite to granulite facies. The Neoproterozoic to Ordovician sedimentary rocks of the uppermost unit, the Franz Joseph allochthon, reached greenschist- and locally amphibolite-facies conditions (garnet + staurolite) at their base. The Devonian and younger sedimentary basins are not significantly metamorphosed. Each of the main structural levels has a characteristic pressure-temperature path. Three main periods of metamorphism are currently recognized. The oldest, ca. 440–415 Ma, relates to the formation of migmatites and granites at midcrustal levels. This was followed by widespread high-pressure granulite- and eclogite-facies metamorphism from 410 to 390 Ma. A very late pulse of ultrahigh-pressure metamorphism occurred at 360–350 Ma and marked the end of the Caledonian collision.

Caledonian (435–425 Ma) and “Grenvillian” (950–900 Ma) S-type leucogranites and augen gneisses are prominent in the thrust units that form the southern half of the East Greenland Caledonian orogen, south of 76°N. Such rocks do not occur further north (76°N–81°N), where the bedrock is dominated by Paleoproterozoic orthogneisses and metagranitoid rocks (2000–1750 Ma). More mafic Caledonian granitoid rocks (quartz diorites, granodiorites, quartz monzonites, syenites, etc.) are found only in the southernmost parts of the orogen (∼71°N), side by side with S-type leucogranites. The S-type granites were formed by partial fusion of “fertile” lithologies within the late Mesoproterozoic Krummedal supracrustal sequence prior to or during emplacement of the thrust units and subsequent collapse of the orogen. The lack of similar granites north of 76°N is probably related to the absence of major units of metasedimentary rocks in that area. Among the granitoid rocks in the southernmost area, an early quartzdioritic to granodioritic intrusion was dated at 466 ± 9 Ma; this is ∼35 m.y. older than most Caledonian S-type granites. Quartzmonzonitic, granitic, and syenitic intrusions have yielded ages of 444–432 Ma. These rocks are geochemically similar to Caledonian granites in Scotland and may be related to subduction of oceanic lithosphere underneath East Greenland. The north-south variation in the occurrence of granites in the East Greenland Caledonides is the expression of an original (pre-thrusting) west-east zonation. It is envisaged that the orogen consists of a number of parallel belts, now telescoped by thrusting: a southeastern belt containing supracrustal rocks (Krummedal sequence) with leucogranites, with more mafic granitoids in the southeast, and a northwestern belt where these rocks do not occur. These belts are envisaged to run from Scotland over the southern parts of the East Greenland Caledonides and, obliquely to the Greenland coast, over the North-East Greenland shelf to Svalbard and Norway, where similar rock units also occur.

The North-East Greenland Caledonides record a complex history of crustal thickening and extension during the Paleozoic collision of Baltica with Laurentia. We divide the southern portion of the orogen (70°N–76°N) into three plates separated by low-angle fault systems that are interpreted as extensional detachments superimposed on, and perhaps coeval with, the thrust geometry of the orogen. From structurally lowest to highest, the plates include amphibolite-facies Archean to Paleoproterozoic orthogneiss and lesser paragneiss that retain relics of Devonian high-pressure metamorphism, migmatitic Mesoproterozoic metasedimentary rocks with Silurian leucogranites and lesser orthogneiss at amphibolite-facies conditions, and low-grade Neoproterozoic to Ordovician sedimentary rocks. Individual detachments are characterized by superposition of cataclastic features on mylonitic fabrics, and they record progressive deformation that accommodated exhumation. The extensional faults define two detachment systems that evolved at different crustal levels during two episodes of movement. The upper detachment system, which separates the upper and middle plates, exhumed the midcrustal rocks after ca. 420 Ma. Extension was contemporaneous with crustal thickening and closely followed leucogranite emplacement. The structure may be analogous to the South Tibetan detachment system in the present-day Himalayas. Continental Old Red Sandstone deposition began in the Eifelian, closely following high-pressure metamorphism in the lower plate at ca. 405 Ma. The lower detachment was probably active at some depth below the evolving Devonian basins. The lower detachment system brought lower-plate metamorphic rocks to shallower crustal levels after 400 Ma, excising the overlying extensional system. This second period of extension was similar in timing and style to extension in the Scandinavian Caledonides. Displacement on the younger detachments, which exhumed lower-plate rocks, was broadly syncollisional, as indicated by the overlap in age with ultrahigh-pressure metamorphism in the north at 365–350 Ma, and it may have been synchronous with young thrusts that emplaced high-pressure lower-plate rocks over the foreland and with strike-slip faults in the hinterland. Conversion to extension, accommodated by high-angle brittle faulting in the Carboniferous (after 345 Ma), may mark the final transition to plate divergence that ultimately led to continental rifting.

From Middle Devonian times, the continental Old Red Sandstone Basin in NorthEast Greenland has accumulated more than 8 km of mainly coarse clastic sediments. These sediments have been studied for more than 100 yr, and they became world famous prior to the Second World War for the discovery of the earliest four-legged vertebrates, the tetrapods later assigned to the genus Ichthyostega . Basin initiation in East Greenland was caused mainly by extensional collapse of an overthickened Caledonian crustal welt accommodated by SE-NW–oriented dip-slip faulting and, subordinately, by N-S–oriented sinistral wrench faulting due to late Caledonian shear displacements along plate boundaries. Four main tectonostratigraphic basin stages have been recognized in the succession. The stages of basin development are separated by subregional to basinwide unconformities and represent depositional episodes punctuated by major tectonic events. Each basin stage is built up of one or several depositional complexes that share roughly similar drainage patterns, measured on a basinwide scale. The four basin stages indicate initial eastward drainage, followed by southward drainage, northward drainage, and finally southwestward drainage. In this paper, we review previous research on the dynamics of Devonian basin initiation, its filling, and the tectonic and climatic controls on sedimentary processes. The successive vertebrate faunal assemblages of the different basin stages are also reviewed, with some consideration of the preservational, ecological, and wider faunal contexts of the components of those faunas. Some remaining problems of correlation and precise dating are noted, and suggestions are made for further work.

The Caledonian orogen of North-East Greenland hosts numerous mineral occurrences related to (1) pre-Caledonian crystalline complexes (Pb-Zn skarn type); (2) Neoproterozoic basins (strata-bound copper); (3) Caledonian granites (vein-type gold, silver, tungsten, arsenic, and antimony); and (4) late Caledonian extensional structures (vein base metal ± silver). Sr, Pb, and Sm-Nd isotope analyses of scheelite (CaWO 4 ) indicate a heterogeneous, probably local, source for tungsten, and Sr isotopic data support a genetic link to Caledonian magmatic activity. Pb isotopes indicate mixing of Pb derived from late waning-stage fluids from the granites and from interaction with wall rocks. Sm-Nd isotopic data for the investigated scheelites indicate that a portion of the rare earth elements was derived from fluids that had interacted with both Archean-Paleoproterozoic crystalline basement and Mesoproterozoic-Neoproterozoic sedimentary rocks. Mineral occurrences associated with fault zones and late Caledonian veins all show a genetic relationship with Caledonian granite emplacement. Sm-Nd isotopic data from scheelite define an errorchron with a slope corresponding to 382 ± 39 Ma (mean square of weighted deviates [MSWD] = 2.6) and an initial 143 Nd/ 144 Nd value of 0.511642 ± 0.000049. This indicates emplacement during the latest stages or even subsequent to emplacement of most Caledonian granites around 425 Ma. The initial Nd isotopic ratio defined by the scheelite Sm-Nd isotopic correlation line is identical within error to the values of S-type granitoids. The multi-isotope studies indicate that tungsten may have been deposited from fluids associated with Caledonian granites, which provided heat sources for local hydrothermal circulation cells. Forced into faults, thrusts, and fractures, the fluids were trapped by dominantly Ca-rich sediments.

The orthotectonic Scottish Caledonides constitute only a small fragment of the Neoproterozoic to Paleozoic margin of Laurentia, albeit one which lies at a prominent bend in that margin. Sequences exposed in the Scottish outcrop include Mesoproterozoic, Neoproterozoic, and Cambrian-Ordovician strata that record sedimentation, volcanism, and deformation related to the latter stages of the amalgamation of Rodinia, the subsequent breakout of Laurentia, and growth of the Iapetus Ocean. Metamorphic and tectonic overprints then record the destruction of that ocean through Ordovician arc accretion and mid-to-late Silurian collision of Laurentia, Baltica, and Avalonia and the final closure of Iapetus by end-Silurian time. New isotopic data and recent advances in the understanding of the late Mesoproterozoic (Stenian) to Cambrian-Ordovician stratigraphic framework now better constrain the sequence and timing of events across the “Scottish Corner” and invite a dynamic comparison with the current research into the East Greenland Caledonides summarized in this volume. Although many broad similarities exist, the comparisons described here reveal for the first time a number of significant contrasts in the spatial arrangement of depocenters, location of rifting, and patterns and timing of magmatism, metamorphism, and contractional deformation. This expanded understanding of the late Neoproterozoic evolution of these adjacent sectors of Laurentia provides an important basis for reconstructions of the subsequent early Paleozoic Caledonian orogenic evolution of the present North Atlantic region.

A geological map of the Caledonian orogen in East Greenland at the scale of 1:1,000,000 accompanies this volume. The map sheet is a compilation of lithostructural data, and it includes cross sections and inset synoptic tectonic maps with profiles. The ∼1300 km length of the N-S–trending Caledonian orogen in East Greenland is divided into three lithostructural domains—the Caledonian foreland, which is partly exposed in the west, a western marginal thrust belt with foreland windows exposed in anticlinal culminations, and an eastern thick-skinned thrust belt that incorporates major segments of reworked Laurentian gneiss basement in major thrust sheets. Caledonian migmatites and granite intrusions are widespread in the southern part of the orogen. Transport directions of the major thrusts are to the west-northwest, and restoration indicates total displacements on the order of 200–400 km, with estimated shortening of 40%–60%. Archean and Paleoproterozoic gneiss complexes, reworked during Caledonian orogenesis, are widespread. In the south, they are overlain by late Mesoproterozoic metasedimentary rocks. Overlying Neoproterozoic and Lower Paleozoic sediments laid down at the margin of Iapetus reach ∼20 km in thickness. In the north, the Paleoproterozoic basement gneisses are overlain by late Paleoproterozoic to early Mesoproterozoic quartzites interbedded with basaltic rocks and cut by doleritic dikes and sills. Overlying Neoproterozoic and Lower Paleozoic sedimentary rocks relate to developments on the south side of the Franklinian Basin, which extends across North Greenland and into Arctic Canada.

Abstract Greenland, the largest island in the world, is situated at the northeast corner of the North American plate. Nares Strait, a channel in places as narrow as 20 km, separates western North Greenland from Ellesmere Island. Geologi- cally the are as on the two sides of the strait have much in common, and there is little evidence to support the large sinistral strike-slip movements proposed along the strait in response to seafloor spreading farther south (see Dawes and Kerr, 1982; Okulitch et al., 1990). Baffin Bay and Labrador Sea, which separate the coast of West Greenland from the coasts of Baffin Island and Labrador, developed by seafloor spreading that began at about the Cretaceous- Tertiary boundary and terminated by the Early Oligocene. East of Greenland the North Atlantic Ocean opened during the Tertiary, and fragmented the Caledonide Orogen (Fig. 12.1). In East Greenland the Caledonides can be traced from latitude 70° to 82°N. Predrift reconstructions produce a variety of configurations for the reassembled Caledonide Orogen, but there is a general consensus that parts of Spitsbergen represent the northern extension of the East Greenland Caledonides, whereas the Southern extension is to be seen in the Caledonides of the British Isles and the Appalachians of eastern North America (Harland and Gayer, 1972; Harland, 1985; Ziegler, 1985). General reviews of the East Greenland Caledonides are given by Haller (1971), Henriksen and Higgins (1976), Higgins and Phillips (1979), and Henriksen (1985). The East Greenland Caledonides form a coastal belt 1200 km long and up

Abstract The Franklinian Basin extended from northern Ellesmere Island across North Greenland, where its sedimentary infill is exposed from Inglefield Land and Washington Land in the west to Kronprins Christian Land in the east (Fig. 7.1–7.3). The segment of the basin exposed in North Greenland is approximately 800 km long and has a maximum preserved north-south width of 200 km. The thickness of the sedimentary column reaches about 8 km; the main part of the succession is of Cambrian-Silurian age, but it may extend down into the latest Precambrian and up into the earliest Devonian. A distinction into a shelf sequence and deep water trough sequence can be recognized in northern Ellesmere Island and in North Greenland, and the variations in facies with time in the two regions show close parallels. Correlation on group or formation level is often possible across Nares Strait (Peel and Christie, 1982; Peel et al., 1982). Detailed knowledge of the North Greenland sequences, however, permits an integrated account of shelf and trough development in the North Greenland segment of the Franklinian Basin. A craton composed of Archean and Upper Proterozoic crystalline basement rocks, overlain by Middle and Upper Proterozoic sedimentary and volcanic rocks, lies to the south of the Franklinian Basin (Chapter 6). This is now exposed intermittently along the margin of the Inland Ice, and more extensively in eastern North Greenland (Fig. 7.1). In the early Paleozoic, this craton was fringed to the north by an east-west trending shallow marine shelf, Two main facies belts

Abstract As outlined above (Chapters 7, 8), the sedimentary subprovince of the Franklinian deep water basin (Hazen Trough) extends eastward from the Canadian Arctic Islands (Chapter 8C) into northern Greenland (Chapter 7), and the pulses of deformation which affected the Canadian sector (Hazen Fold Belt) in Late Silurian or Devonian to Early Carboniferous time (Chapter 12) likewise extended into Greenland producing an east-west striking mobile zone, known traditionally as the North Greenland fold belt. The fold belt has an exposed width of up to 100 km on the north coast of Greenland and is flanked to the south by the weakly deformed lower Paleozoic platform sequence described in Chapter 7. Figure 11.1 shows that several distinct tectonic zones can be recognized in the fold belt, and Figure 11.2 illustrates how these are spatially related to the geometry of the deep water basin (Hazen Trough). A southern fold and thrust zone coincides with a region which was transitional between the platform and trough for much of the Cambrian and Ordovician. It is bounded to the south by the Navarana Fjord lineament, which represents the position to which the platform margin had retreated by Early Silurian time. The structure of the southern zone is of thin skinned fold and thrust type, with an approximately east-west strike and southerly vergence. A northern orthotectonic zone is developed on the site of the trough proper with its thick fill of dominantly Lower Cambrian turbidites. It forms the mountainous regions of Johannes V. Jensen Land, Nansen Land,