Geological Survey of Denmark and Greenland Bulletin 19 ... - Geus

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Atanikerluk Formation Assoq Member m 510 500 450 400 380 280 250 200 150 100 invasive lava flows correlate to the lower Rinks Dal Member invasive lava flows correlate to the Akuarut unit of the lower Rinks Dal Member Depositional environment. At Skarvefjeld (Fig. 2), the lower, shaly part of the Assoq Member is interbedded with hyaloclastite breccias that are traced laterally into the lower Rinks Dal Member (Heinesen 1987; L.M. Larsen & Pedersen 1990). Water depths of 80−100 m are calculated from the height of the foresets of the hyaloclastite breccias. Similar interbedding of Assoq Member mudstones and hyaloclastite breccias is also known from Sorte Hak on central Disko, slightly east of the Disko Gneiss Ridge (Fig. 124). The Assoq Member is interpreted as lacustrine in origin, deposited within the ‘Assoq lake’. At present it is not possible to demonstrate whether this was one huge lake or several smaller lakes. Scarce marine dinocysts indicate that the Assoq lake was subject to marine inundations. The dinocysts were found in samples from eastern and south-eastern Disko, but were not recorded from Nuussuaq. This distribution, coupled with a south-eastward tilting of an originally nearly horizontal magmatic boundary (L.M. Larsen & Pedersen 1992) suggests that the marine inundations were from the south. The upward transition from mudstones to sandstones reflects shallowing and gradual fill of the lake. During a break in clastic sediment input, peat accumulated in a large swamp in eastern Disko, and resulted in a thick coal bed (Fig. 141). Boundaries. The lower boundary of the Assoq Member is placed at the base of the mudstone succession, and is interpreted as a lacustrine drowning surface (Figs 128, 137). On north-east Disko, the lower boundary overlies a coal bed. The upper boundary is placed where the sediments are overlain by subaerial lava flows of the Rinks Dal Member. Note that locally thin tongues of sediment within the lower Rinks Dal Member are assigned to the Assoq Member; such sediment wedges are bounded abruptly beneath and above by volcanic strata. At Tuapaat Qaqqaat, the uppermost bed in the Assoq Member is a conglomerate with clasts of basaltic rocks derived from lava flows of the Akuarut unit of the Rinks Dal Member (Fig. 140; L.M. Larsen & Pedersen 1990, 2009). Atane Formation Skansen Member 50 0 Covered by scree vf f m c vc f m c clay silt sand pebbles Fig. 140. Composite reference section of the Assoq Member at Tuapaat Qaqqaat, south-eastern Disko (for location, see Fig. 124). Note the occurrence of marine dinocysts at the top of the lacustrine section, indicating a brief marine inundation. Colour coding of volcanic rocks follows Fig. 131. For legend, see Plate 1. 158
Fig. 141. Upper part of the Assoq Member including a 5.1 m thick coal bed. South side of Blåbærdalen, eastern Disko (for location, see Fig. 124). Correlative coal beds are seen at several widely spaced outcrops indicating the development of large swamps. The sediments are overlain by subaerial lava flows of the volcanic Rinks Dal Member (see Fig. 131). upper Rinks Dal Member coal Assoq Member Geological age. The age of the Assoq Member lies within the age range of the Atanikerluk Formation (i.e. early to mid-Paleocene, see p. 146). Correlation. On southern Disko, the lower, shaly, part of the Assoq Member is interbedded with subaqueous lava flows and hyaloclastite breccias, which continue westwards into the Skarvefjeld unit (formerly Pahoehoe unit) of the lower Rinks Dal Member (Fig. 131; Heinesen 1987; L.M. Larsen & Pedersen 1990, 2009; A.K. Pedersen et al. 2003; L.M. Larsen et al. 2006). On north-eastern Disko (Akunneq and Pingu), the earliest volcanic rocks are thick invasive lava flows with columnar jointing, which invaded the uppermost part of the Umiussat Member and the Assoq Member. The composition of these volcanic rocks tie them to the uppermost lower Rinks Dal Member and the Akuarut unit (formerly FeTi unit) (Fig. 131; A.K. Pedersen et al. 2005; L.M. Larsen et al. 2006; L.M. Larsen & Pedersen 2009). On Nuussuaq, lava flows of the Akuarut unit invaded mudstones of the Assoq Member and increased markedly in thickness due to ponding of the lavas in the ‘Assoq lake’. Throughout eastern Disko and southern Nuussuaq the Assoq Member is thus interbedded with invasive flows of the Rinks Dal Member, and the various volcanic facies (breccias, invasive lavas or ponded subaerial lava flows) are thought to reflect different extrusion rates. In most of its area of distribution, the Assoq Member is overlain by subaerial lava flows of the upper Rinks Dal Member (Fig. 131). It is concluded that the Assoq Member generally correlates with the Rinks Dal Member. On easternmost central Nuussuaq, however, an outcrop of mudstones interbedded with invasive lava flows of the younger Niaqussat Member is also referred to the Assoq Member (A.K. Pedersen et al. 2002). Acknowledgements The work reported on in this publication was carried out with considerable financial support from the Danish Energy Research Programme (EFP), the Danish Natural Science Research Council (SNF), the Bureau of Minerals and Petroleum, Government of Greenland, the Carlsberg Foundation and the Arktisk Station, University of Copen - hagen. Their support is gratefully acknowledged. The authors are greatly indebted to the three referees: Dr. T. Christopher R. Pulvertaft, now retired from GEUS, has taken a keen interest in the manuscript from its early stages and has encouraged the authors throughout. He has corrected the English language and has used his great knowledge of the area to ensure that details in descriptions and illustrations are correct. Dr. J. Christopher Harrison of the Geological Survey of Canada and Dr. Robert Knox of the British Geological Survey have read the manuscript very carefully and offered a large number of helpful suggestions for the improvement of text and figures. With few exceptions, the illustrations have been prepared by Jette Halskov, GEUS, without whom the manuscript would not have been completed. 159
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GEOLOGICAL SURVEY OF DENMARK AND GR
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Contents Abstract . . . . . . . . .
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Preface The onshore Cretaceous-Pale
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Introduction The Nuussuaq Basin bel
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chemistry of the Nuussuaq Basin hav
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Fig. 5. Plant fossils from the Atan
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Peak 2010 m Peak 1900 m Peak 1760 m
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A lithostratigraphy for the marine
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to provide further funding for stud
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DGR Geological setting As a result
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TSS 8 Agatdal Fm Eqalulik Fm Kangil
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A Svartenhuk Halvø 50 km B Hinterl
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Nuussuaq Group new group History. T
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ley (Figs 2, 40, 65). The section a
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Central Nuussuaq Agatdalen South co
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3 10 4 6 5 Qorlortorssuaq Slibesten
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volcanic sediments are referred to
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Fig. 20. View from Uummannaq toward
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In the Kuuk area, the sediments ove
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m m 15 14 14 13 12 11 10 9 8 7 6 5
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Kome Formation m 40 30 20 D tial re
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Fig. 28. Reference locality of the
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Vaigat Fm Vesterfjeld Slibestensfje
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Gilbert delta in the Ikorfat area (
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150 300 450 100 250 400 m 550 50 20
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Fig. 36. Outcrop of the Upernivik N
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Correlation. The Upernivik Næs flo
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12’ 09’ 15’ 06’ 03’ Saqqa
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m 0 GGU 247801 200 400 247815 ★
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wave-rippled sand streaked mudstone
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the formation in the marine mudston
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d d Fig. 47. Type locality of the S
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Fig. 49. Cross-bedded medium- to co
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and Qaarsut (Fig. 22). Its wider di
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Fig. 52. Two closely spaced section
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Type section. The type section of t
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Fig. 56. Delta front succession of
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Fig. 59. The Kingittoq Member at Ki
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sh L sh ch delta front Vaigat Forma
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Fig. 63. Type locality of the Itivn
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782 Quaternary cover 54° 888 Malig
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Kuugannguaq-Qunnilik Fault and is o
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and include clasts of intraformatio
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deposited in a base-of-slope and ba
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VK 53°30’ 53°15’ Niaqornat Tu
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Umiivik-1 m Overburden ★ ★ No p
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76). Heavily bioturbated interbedde
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Fig. 78. Type locality of the Kussi
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A B Itilli Formation Kussinerujuk M
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160 140 120 100 Vaigat Formation Eq
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Fig. 85. Mudstones and conglomerati
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Fig. 87. Type section of the Kangil
Page 107 and 108: m 150 140 130 120 110 100 90 Kangil
Page 109 and 110: channellised, high-density currents
Page 111 and 112: Thickness. The Annertuneq Conglomer
Page 113 and 114: Fig. 96. A: Type locality of the Oy
Page 115 and 116: On Svartenhuk Halvø, on the east s
Page 117 and 118: Fig. 100. Reference locality of the
Page 119 and 120: Tupaasat Member Atane Formation Fig
Page 121 and 122: ever, have a fluvio-lacustrine orig
Page 123 and 124: etween Tupaasat and Nuuk Qiterleq a
Page 125 and 126: Vaigat Formation sill Quikavsak For
Page 127 and 128: Fig. 112. The sharp boundary betwee
Page 129 and 130: Agatdal Formation Eqalulik Formatio
Page 131 and 132: Fig. 116. Basal conglomerate unit o
Page 133 and 134: heterolithic deposits of the Kangil
Page 135 and 136: GANE#1 Vaigat Fm Anaanaa Mb m Hyalo
Page 137 and 138: Fig. 121. Well reference section of
Page 139 and 140: Pedersen 1978). The beds are usuall
Page 141 and 142: In detail, however, the boundary be
Page 143 and 144: Fig. 126. Composite type section of
Page 145 and 146: m m 240 340 m Pingu Member 230 230
Page 147 and 148: Naujât Member Atane Formation, Kin
Page 149 and 150: The TOC [Total Organic Carbon] cont
Page 151 and 152: Fig. 133. Correlation of the member
Page 153 and 154: Fig. 135. Type locality of the Ping
Page 155 and 156: Fig. 137. Lower, sharp boundary of
Page 157: m 130 125 110 t t invasive lava low
Page 161 and 162: Brown, R. 1875: Geological notes on
Page 163 and 164: a rosetted spreite trace fossil: Da
Page 165 and 166: ing bark from the Nûgssuaq peninsu
Page 167 and 168: 1998: The syn-volcanic Naajaat lake
Page 169 and 170: Appendix: Place names and localitie
Page 171: Place name Place name P Paatuut sou
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Geological Survey of Denmark and Greenland Bulletin 19 ... - Geus

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