GEUS Bulletin no 5.pmd

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m 50 40 30 20 10 0 102 Mud Sand Gravel 360400, 401 360399 360398 360397 360396 360395 360394 360393 360392 360700 360699 360698 360697 360696 360695 360694 360692, 693 360691 Lithology Sand Sand with gravel Mud Structure Fossils 360691 GEUS Bulletin no 5.pmd 102 29-10-2004, 11:14 31 31 26 19a 16 16 Lamination Lenticular lamination Planar cross-bedding Shell bed Clay clasts Calcareous concretions Hardened bed Thalassinoides isp. Curvolithos isp. Monocraterion isp. Diplocraterion isp. Planolites isp. Boreal ammonite fauna horizon Belemnite Bivalve Pinna sp. Wood Serpulid Oyster GGU sample numbers Fig. 2. Sedimentological log of the exposed Middle Jurassic succession at Ravn Pynt. Levels of the analysed palynological samples are indicated.
may indicate a hiatus in the sedimentary succession or simply no preservation of fauna and flora in that specific part of the section. Some of the absent ammonite faunas, however, have been collected just south of Ravn Pynt on Store Koldeway. Ammonites The Jurassic succession contains abundant ammonites in well-separated faunal horizons and the stratification is generally preserved despite some solifluction. The sedimentological succession was studied in a ravine at Ravn Pynt and four ammonite horizons were collected here in situ and directly correlated with the fine-grained palynological samples (Fig. 2). These ammonites represent the Arcticoceras ishmae Zone (horizon 16), the Arcticoceras cranocephaloide Zone (horizon 19a including topotypes of Kepplerites tychonis Ravn), the Cadoceras apertum Zone (horizon 26) and the Proplanulites koenigi Zone (horizon 31) of the standard Boreal ammonite biostratigraphy of Jameson Land (Callomon 1993). The age of the succession is then mid- Bathonian to Callovian based on the ammonite faunas. Dinoflagellate cysts The organic matter in the Middle Jurassic succession is dominated by black and brown woody material. The abundance of dinoflagellate cysts is generally low but the diversity is fair (65 recorded species, including a few acritarchs). The assemblages are dominated by proximate cysts accompanied by few cavate cysts but are basically barren of chorate cysts. Specimens from the Pareodinia/Paraevansia/Evansia and the Escharisphaeridium/Sentusidinium groups are the most abundant cysts. Successive species appear regularly upwards in the succession but the highest number of appearances is in GGU sample 360698 at 19.60 m (Fig. 4) at the base of a 13 m thick fine-grained interval (Fig. 2). This may reflect a hiatus in the succession below the sample and/or a shift to a more open marine depositional environment. Since the Middle Jurassic succession is dated in detail by ammonites, the distribution of the dinoflagellate cysts can be used to increase the precision of their ranges in the Boreal Jurassic as previous recorded in other regions in East Greenland (Jameson Land and Hold with Hope). Sirmiodinium grossii, Gonyaulacysta pectinigera, Paragonyaulacysta retiphragmata and GEUS Bulletin no 5.pmd 103 29-10-2004, 11:14 Chytroeisphaeridia hyalina are the stratigraphically important species that occur throughout the investigated succession. S. grossii appears in the Arctocephalites arcticus Chronozone in Milne Land (Larsen et al. 2003) and becomes more frequent from approximately the Arctocephalites cranocephaloide Chronozone and upwards to the Cadoceras apertum Chronozone (Milner & Piasecki 1996). This increase in abundance of S. grossii is not observed here because no samples were collected from this part of the section. In Milne Land, G. pectinigera is recorded as becoming abundant from the A. cranocephaloide Chronozone upwards into the C. apertum Chronozone but again, this increase in abundance is not represented in the present section. In Jameson Land, P. retiphragmata has its earliest appearance in the A. cranocephaloide Chronozone but at Store Koldewey it clearly appears already in the Arcticoceras ishmae Chronozone. C. hyalina appeared earliest in the Cadoceras calyx Chronozone in Jameson Land (Milner & Piasecki 1996). The present material, in combination with new data from Jameson Land, show that C. hyalina is present already in the A. ishmae Chronozone and becomes abundant from the C. apertum Zone. Aldorfia aldorfensis appears in the A. cranocephaloide Chronozone precisely where it is expected from its range in Jameson Land (Milner & Piasecki 1996). The morphologically variable species Ctenidodinium thulium is recorded throughout the succession, having a much more extensive range than that recorded elsewhere in East Greenland. Towards the south, in Milne Land, it is restricted to the interval above the A. cranocephaloide Chronozone and below the Paltoceras athleta Chronozone (Larsen et al. 2003). This upper range is confirmed in these northern regions by data from Hold with Hope where it is recorded in strata just below the P. athleta Chronozone (Piasecki et al. 2004, this volume). Many of the less frequent species seem to occur in a rather random way that makes their presence and especially their absence less stratigraphically useful. Crussolia perireticulata is a good example of this. In Milne Land, it occurs in the Bathonian A. arcticus Chronozone and again higher in the Callovian part of the succession (Larsen et al. 2003). In Jameson Land, it appears one ammonite zone higher than in Milne Land, the Bathonian Arctocephalites greenlandicus Chronozone and is then not recorded again until it reappears in the basal Callovian, top C. apertum Chronozone. There are no records of this species from the Bathonian or the Callovian of Store Koldewey and Hold with Hope. This could indicate a southern affinity of this 103
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GEOLOGICAL SURVEY OF DENMARK AND GR
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GEUS Bulletin no 5.pmd 3 29-10-2004
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Contents Preface . . . . . . . . .
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(Alsen & Surlyk 2004, this volume).
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Jurassic syn-rift sedimentation on
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NW SE m 1000 500 0 NW SE m 1000 500
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grained than the lower parasequence
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the Pelion Formation. The mudstone-
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The fluviatile Bristol Elv Formatio
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Name. After the river Bristol Elv i
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edded, and display both sheet-like
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N S Fig. 5. Coarse-grained sandston
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Fig. 7. Lacustrine deposits from th
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deposition of peat and coal. Journa
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Maximum Middle Jurassic transgressi
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834 N Lycett Bjerg Barrikade Gletsc
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SW NE Lycett Bjerg Parnas Member Be
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Cadoceras cf. nordenskjoeldi Callom
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4 C B 1 2 GEUS Bulletin no 5.pmd 41
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Fig. 1. Sketch-map of the Jameson L
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Table 1. Measurement of dimensions
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1 2 GEUS Bulletin no 5.pmd 49 29-10
Page 51 and 52: A new Middle-Upper Jurassic success
Page 53 and 54: 74º00'N ■■ ■■ ■■ 73º5
Page 55 and 56: System Ma 159.4 154.1 164.4 169.2 1
Page 57 and 58: Sedimentary structures Biota Struct
Page 59 and 60: wards units is biogenic carbonate d
Page 61 and 62: Fig. 7. Log panel giving a broadly
Page 63 and 64: SPM LU to medium-grained and consis
Page 65 and 66: and mudstone drapes reflects varyin
Page 67 and 68: with the presence of a minor angula
Page 69 and 70: the north-east and south-west, resp
Page 71 and 72: elly mass-flow deposits. In: Koster
Page 73 and 74: Jurassic dinoflagellate cyst strati
Page 75 and 76: 74°00'N ■■ ■■ ■■ 73°5
Page 77 and 78: Bernbjerg Formation Payer Dal Forma
Page 79 and 80: Depositional environment. The prese
Page 81 and 82: GEUS Bulletin no 5.pmd 81 29-10-200
Page 85 and 86: Metres 30 20 10 Hold with Hope, Loc
Page 87 and 88: Correlations The Pelion Formation o
Page 89 and 90: Jurassic dinoflagellate cysts from
Page 91 and 92: Fig. 2. Sedimentological log of the
Page 93 and 94: LITHOSTRATIGRAPHY BIOSTRATIGRAPHY F
Page 95 and 96: ALPHABETICAL SPECIES LIST 41 Adnato
Page 97 and 98: References Alsgaard, P.C., Felt, V.
Page 99 and 100: Jurassic dinoflagellate cyst strati
Page 101: parties from the Geological Survey
Page 105 and 106: Metre 50 25 0 Store Koldewey Ravn P
Page 107 and 108: Fig. 6. Schematic stratigraphical c
Page 109 and 110: Chronozone) to the earliest Kimmeri
Page 111 and 112: The Upper Jurassic succession is co
Page 115 and 116: 185 Greenland from Archaean to Quat
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GEUS Bulletin no 5.pmd

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