Review of Greenland Avtivities 2001 - Geus

More documents

Recommendations

Info

Seismic interpretation The grid of seismic reflection data used in this interpretation is shown in Fig. 1. The data are all multichannel lines, acquired in 1990, 1991, 1992 and 1995, with the addition of some reprocessed regional lines acquired in 1977. Twenty-nine seismic sequences have been recognised within the studied sediment package, and these seismic sequences have been grouped into 11 third-order depositional sequences (Chalmers et al. 2001a). The seismic stratigraphic interpretations have been used to infer two distinct episodes of tectonism. During the Late Paleocene, coinciding with the stage of sea-floor spreading in the Labrador Sea between magnetochrons 27 and 25, tectonism was predominantly extensional. During the Early to Middle Eocene, extension continued in most of the region, but became transpressional along the Ikermiut Fault Zone. Major tectonism ceased during the Middle Eocene at the same time as sea-floor spreading in the Labrador Sea slowed substantially (Chalmers et al. 2001a). A seismic sequence has been identified that is equivalent in age to the sediments that include the Marraat source rock in the Nuussuaq Basin (Bojesen-Koefoed et al. 1999). If this seismic sequence also includes a source rock facies, it will be mature for oil generation in the region between the Maniitsoq High and the Kangâmiut-1 well (Chalmers et al. 2001a). In the distal parts of many of the seismic sequences, it is possible to recognise and map discrete seismic facies interpreted as basin-floor fans, syn-tectonic wedges and turbidite channel complexes that could act as hydro- 0 N A 1000 2000 3000 Sea bed 4000 5000 S.P. A' S 500 1000 TWT (msec) TWT (msec) 1500 2000 2500 0 500 1000 1500 1000 2000 3000 4000 5000 S.P. Quaternary SS150 SS100 SS250 Sea bed SS500 SS4500 SS2500 SS4000 SS3750 SS3600 SS3000 SS2000 SS5000 SS1000 SS3500 SS6000 'Mid-Eocene unconformity' SS10000 SS9500 SS9000 SS7000 Quaternary SS7500 SS8500 20 km SS8000 SS7750 SS8250 2000 2500 Brackish to inner neritic palaeoecology Neritic to bathyal palaeoecology Mounded mass flows – possibly slumps or basin floor fans Mass flows – possibly turbidites Offlap break GGU/92-03 Fig. 2. North–south seismic line GGU/92-03 across the Sisimiut Basin showing the maximum thickness of the seismic sequences. This line illustrates many of the relationships between the seismic sequences, their internal seismic facies and interpretation of palaeoenvironments. For location, see Fig. 1. 92
carbon reservoirs, sealed by surrounding mudstone (Figs 1, 2). Based on thickness variation throughout the basin it is suggested that sediment input was dominantly from the north, probably representing a continuation of the Cretaceous drainage system from the Nuussuaq Basin, as described by Pedersen & Pulvertaft (1992). Lesser amounts of sediments came from the mainland of Greenland to the east and minor amounts from highs to the west. The sediments were deposited in environments that ranged from freshwater/marginal marine to upper bathyal. Proximal environments are probably generally sand-prone, whereas distal environments probably contain larger amounts of mud, some of which could contain a mature source rock for oil. Well log interpretation Sedimentological and palaeoenvironmental interpretations are based on well log interpretation, cuttings and sidewall core descriptions, and palynological and microfossil studies. A lithostratigraphic and biostratigraphic correlation of the five wells from the 1970s offshore West Greenland has been achieved and a log panel displaying correlation of the palyno- and microfossil zonation and seismic sequences is presented here (Fig. 3). Sixteen sequences have been described and dated using log motifs, lithology, microfossils and palynomorphs, and a depositional environment has been suggested for each. The sediments are predominantly sandstones in the basin-marginal wells (Hellefisk-1, Nukik-1, Nukik-2) and shales in the basin-centre wells (Ikermiut-1, Kangâmiut-1). Based on the re-interpretation of the log data, the sand/shale ratio and facies distributions have been modified from that presented by Rolle (1985). Most of the Palaeogene sediments in Hellefisk-1, Nukik-1, and to a certain degree Nukik-2, were deposited in a littoral to inner neritic environment, whereas most Palaeogene sediments in Kangâmiut-1 and Ikermiut-1 were deposited in an outer neritic to bathyal turbiditic environment (Dalhoff et al. 2001). Biostratigraphy A new Palaeogene dinoflagellate cyst stratigraphy from offshore West Greenland has been described based on data from the Hellefisk-1, Ikermiut-1, Kangâmiut-1, Nukik-1, Nukik-2 and Qulleq-1 wells (Nøhr-Hansen 2001). The dinoflagellate cyst stratigraphy has been correlated with the microfossil zonation and previously established zonations in the North Sea. Twenty-one stratigraphic intervals are defined from the upper Lower Paleocene to the Upper Eocene. The stratigraphy and well correlation are based on last appearance datum events and abundances of stratigraphically important species from 355 samples, 148 of which are sidewall core samples. A nannofossil study has been carried out in the Kangâmiut-1 and Nukik-2 wells (Sheldon 2001). The stratigraphy has been correlated with previously established nannofossil zonation schemes and, where possible, used to indicate palaeoenvironmental changes during the Early and Middle Eocene. The stratigraphy and dating are based on stratigraphically important species, and palaeoenvironmental signals are based on species influxes. A total of 69 samples (26 sidewall cores and 43 ditch cuttings samples) were examined and compared with findings from nearby DSDP and ODP sites. A microfossil-based biostratigraphy of the Paleocene and Lower Eocene sediments of the Hellefisk-1, Ikermiut-1, Kangâmiut-1, Nukik-1 and Nukik-2 wells has been established (Rasmussen & Sheldon 2001). In general, the five wells contain fairly well-preserved, diverse microfossil faunas and floras consisting mainly of foraminifera, radiolaria, ostracods, bivalves and fish remains, together with diatom and palynomorph floras. Nannofloras (mainly coccoliths) occur in relatively low numbers (Sheldon 2001). The biozones are more easily recognised in the two basinal wells (Ikermiut-1 and Kangâmiut-1) than in the three more nearshore wells (Nukik-1, Nukik-2 and Hellefisk-1) due to a higher microfossil diversity and abundance. The Middle Eocene and upper Lower Eocene intervals of the Hellefisk-1 well in particular are poorly represented by microfauna, with samples often being barren or only containing coal fragments. Concluding remarks The new interpretation of seismic and well data suggests that an equivalent to the Marraat oil source rock may be present – and mature – in large parts of the Sisimiut Basin. The Marraat oil, one of the oils that have been discovered seeping to the surface in the Nuussuaq Basin, has been attributed to a source rock not older than the latest Cretaceous (Bojesen-Koefoed et al. 1999). The source rock appears to have been encountered in the GRO#3 well (Christiansen et al. 1999), and this interval is dated as belonging to the Early Paleocene (Nøhr- Hansen et al. in press). Only the lower part of sequence 93
Page 1:
GEOLOGY OF GREENLAND SURVEY BULLETI
Page 4:
Geology of Greenland Survey Bulleti
Page 7 and 8:
Contents Numbers of articles corres
Page 9:
■ ■ ■ ■ ■ ■ ■ ■ ■
Page 12 and 13:
Canada Pituffik O 1 Thule Air Base
Page 14 and 15:
Publications A complete list of geo
Page 16 and 17:
Canada Greenland Greenland Inland I
Page 18 and 19:
northern Nagssugtoqidian orogen (SN
Page 20 and 21:
western to the north-eastern corner
Page 22 and 23:
group consists of conjugate sets of
Page 24 and 25:
y pure shear. Coincidence of the or
Page 26 and 27:
The Precambrian supracrustal rocks
Page 28 and 29:
68°25′ 52° 68°25′ BIF 0 3 km
Page 30 and 31:
Fig. 4. Dolomitic marble in the sou
Page 32 and 33:
Bugt (Fig. 1; Henderson 1969). The
Page 34 and 35:
Keto, L. 1962: Aerial prospecting b
Page 36 and 37:
▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲
Page 38 and 39:
increases towards the south. We obs
Page 40 and 41:
Kalsbeek, F. & Taylor, P.N. 1999: R
Page 42 and 43:
Canada Nuussuaq 0 50 km PROTEROZOIC
Page 44 and 45: deposit. Descriptions of the differ
Page 46 and 47: Pegmatites The gneisses throughout
Page 48 and 49: tacts with quartzo-feldspathic coun
Page 50 and 51: Geological correlation of magnetic
Page 52 and 53: Fig. 2. The hand-held magnetic susc
Page 54 and 55: Susceptibility distribution (%) Sus
Page 56 and 57: have a reducing effect, which hinde
Page 58 and 59: ancy between the susceptibility val
Page 60 and 61: 67° Sisimiut • 53° 52° 51° 50
Page 62 and 63: Table 1. Range of Nb concentrations
Page 64 and 65: chemical composition - may indicate
Page 66 and 67: Concentration/C1 chondrite 100.00 1
Page 68 and 69: Menzies, M.A. & Hawkesworth, C.J. (
Page 70 and 71: 72°30´ Aeromag 2001 50 km Upernav
Page 72 and 73: 56° 54° 52° 72° 72° nT 71°30
Page 74 and 75: Conclusions The aeromagnetic survey
Page 76 and 77: 53° 51° Inland Ice Greenland 72°
Page 78 and 79: On the south coast of Nuussuaq, wes
Page 80 and 81: Fig. 5. Blocks and boulders in the
Page 82 and 83: 2000 SW NE 1500 Surface trace 1985
Page 84 and 85: 1979). Along other sections of the
Page 86 and 87: Petroleum geological activities in
Page 88 and 89: Seismic acquisition during summer 2
Page 90 and 91: Other petroleum geological work Alt
Page 92 and 93: A multidisciplinary study of the Pa
Page 96 and 97: Middle Eocene Lower Eocene Upper Pa
Page 98 and 99: Chalmers, J.A., Dahl, J.T., Bate, K
Page 100 and 101: 95-06 ▲ ▲ 58° 95-12 95-10 56°
Page 102 and 103: 70° 71° 60° 2000 2000 2400 400 1
Page 104 and 105: Storey, M., Duncan, R.A., Pedersen,
Page 106 and 107: 24° 100 km 30° 27° 21 ° Jameson
Page 108 and 109: Oligocene Krabbedalen Fm Eocene Bop
Page 110 and 111: grading. Bivalve shell material is
Page 112 and 113: References Birkenmajer, K. 1972: Re
Page 114 and 115: B A 72° Palaeogene basalts Gl 50 k
Page 116 and 117: a b c d e f g h 20 µm i j k l Fig.
Page 118 and 119: offshore South-East Greenland, onsh
Page 120 and 121: ▲ Albert Heim Bjerge Wordie Gletc
Page 122 and 123: T D A CW NS placed the lowermost c.
Page 124 and 125: is abundant and highly diverse, and
Page 126 and 127: The Heimbjerge Formation comprises
Page 128 and 129: Late Permian carbonate concretions
Page 130 and 131: m 25 20 15 B3 L2 B2 Fig. 3. Simplif
Page 132 and 133: (2001), who pointed out the restric
Page 134 and 135: Piasecki, S. 1984: Preliminary paly
Page 136 and 137: 66° 68° • • • • • • 7
Page 138 and 139: absent at Tikeraussaq where a postu
Page 140 and 141: 72° 70° 68° 66° Sample locality
Page 142 and 143: Table 2. Summary of selected elemen
Page 144 and 145:
Concluding remarks Observations dur
Page 146 and 147:
Lake-catchment interactions with cl
Page 148 and 149:
lakes. As in earlier reports (e.g.
Page 150 and 151:
Discussion Global climate models pr
Page 152 and 153:
Glaciological investigations on ice
Page 154 and 155:
Fig. 2. The new one-mast design of
Page 156 and 157:
A B N 20 km 1993 1995 Fig. 5. Satel
Page 158 and 159:
Krabill, W., Frederick, E., Manizad
Page 160 and 161:
2001/47: Calibration of stream sedi
Page 162 and 163:
Hanghøj, K., Kelemen, P., Bernstei
Page 165 and 166:
Danmarks og Grønlands Geologiske U
Page 167:
GEOLOGY OF GREENLAND SURVEY BULLETI
show all

Review of Greenland Avtivities 2001 - Geus

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?