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

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Lower Rinks Dal Member subaqueous lava Upper Rinks Dal Member subaqueous lava subaqueous lava Assoq Member invasive lava 55 m a.s.l. invasive lava Assoq Member invasive lava Fig. 138. Type locality of the Assoq Member at Assoq on the south coast of Disko (for location, see Fig. 124). The brownish black mudstones of the Assoq Member are interbedded with invasive lava flows and overlain by subaqueous lava flows of the lower Rinks Dal Member of the Maligât Formation (see Fig. 131). Sediments and interbedded volcanic rocks are part of a huge landslide, two blocks of which are separated by the dash–dot line. The Assoq Member is also found at higher altitudes away from the coast (A.K. Pedersen et al. 2003). For log, see Fig. 139. dently identified (Fig. 139). The type section is located at 69°19.23´N, 53°09.10´W. Reference sections. Reference sections are exposed on southern Disko east of Assoq (Fig. 139), on northern Disko at Pingu (Figs 124, 128), and on southern Nuussuaq at Qallorsuaq (Keglen). The sediments here were formerly referred to the Aussivik and Point 976 Members of Koch (1959) (Figs 40, 125). Thickness. The Assoq Member is up to c. 200 m thick, but the thickness is difficult to measure in areas where the sediments are interbedded with volcanic or intrusive rocks and are subject to landslides. Lithology. The Assoq Member constitutes a major, coarsening-upward succession with a lower part dominated by brownish black fissile mudstones, and an upper part that is dominated by sands but also includes a single, 3 m thick, coal seam (Figs 126, 128, 138, 140). The mudstones have TOC contents of up to 7%. The dominant clay mineral is kaolinite, but gibbsite is also present in most samples. Thin beds are cemented by siderite. Nume - rous thin tuff layers are interbedded with the mudstones. They are typically a few millimetres to a few centimetres thick, deposited by settling through the water column. Examination of thin sections shows that the tuff is strongly altered diagenetically. The mudstones are interbedded with hyaloclastite breccias and subaqueous lava flows which formed where lava flows of the lower Rinks Dal Member entered the ‘Assoq lake’ (L.M. Larsen et al. 2006). Based on their chemical composition, the invasive lava flows are correlated with various units within the volcanic lower Rinks Dal Member (Figs 131, 139, 140). 156
m 130 125 110 t t invasive lava lower Rinks Dal Mb The upper part of the Assoq Member is dominated by sands, often with comminuted plant debris. In the scree-covered slopes at Tuapaat Qaqqaat and Qallorsuaq (Keglen), the sands are yellow and fine-grained, but rarely well exposed. At Pingu and Gule Ryg, the sedimentary structures suggest deposition from traction currents in a low-energy environment (Fig. 128). A thick coal bed has been observed at the top of the Assoq Member (Fig. 141) which probably correlates to coal beds interbedded with volcanic rocks at several localities west of Gule Ryg, eastern Disko (L.M. Larsen & Pedersen 1990; A.K. Pedersen et al. 2001) (Fig. 131). These sediments are considered part of the Atanikerluk Formation as they can be traced from continuous sedimentary successions into the basal part of the subaerial lava flow succession. The chemistry of these volcanic rocks corresponds to the lower part of the upper Rinks Dal Member. ?Atane Formation Atanikerluk Formation Assoq Member 105 40 35 30 25 10 5 0 t s t s s t t t t t t sill clay si sand invasive lava lower Rinks Dal Mb 8 10 10 10 20 30 12 10 22 30 10 20 3 7 10 10 invasive lava lower Rinks Dal Mb 10 5 Fossils. Plant macrofossils are unevenly distributed in the Assoq Member, but they are generally scarce. From the Atanikerluk area, Koch (1959) reported a leaf of Cercidiphyllum arcticum from the lower part (his Aussivik Member) and pieces of fossil wood of Taxodioxylon type from his Point 976 member. Bedding planes covered by plant remains were observed west of Kingittoq by the present authors. The freshwater bivalve Unio sp. occurs in the upper, sandy part of the Assoq Member (Koch 1959). Fish scales and bones are preserved in a concretion from Akuliarusinnguaq (c. 4 km north of Gieseckes Monument; Fig. 2). The spores and pollen in the Assoq Member were described by Hjortkjær (1991) and differ little from those in the older members of the Atanikerluk Formation. Piasecki et al. (1992) reported finds of marine dinocysts in a few samples from the Assoq Member in southern and eastern Disko. In the inner part of Kvandalen (Fig. 124), the mudstones are found to contain rare bivalves (protobranchs?) and rare dinocysts (Piasecki et al. 1992). A few marine dinocysts were found at Tuapaat Qaqqaat at the top of the Assoq Member just below the basalt conglomerate (Fig. 140). Fig. 139. Type section of the Assoq Member at Assoq on the south coast of Disko (for location, see Fig. 124). The lacustrine mudstones contain numerous millimetre-thick tuff beds. For legend, see Plate 1. 157
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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
Page 105 and 106: 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: Fig. 137. Lower, sharp boundary of
Page 159 and 160: Fig. 141. Upper part of the Assoq M
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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