38° W 37°30' 37° 36°30' 36° W Scale 1:250 000 Kilometres 0 10 20 30 0 8 16 1:250 000 Scale BIRD Miles ISLAND BAY OF ISLES Bird Island 36 È 54° S 20 54° S 55 È Research station 33 80 43 Geological Map of South Georgia 9 È WILLIS ISLANDS È 55 10 Aptian - Albian È 78 È 65 È Aptian - Albian 70 45 73 BAS GEOMAP 2 Series, Sheet 4, Edition 1 È È È È È 9 22 ICE FJORD 50 30 54 Geological interpretation and map compilation by M.L. Curtis. Geological cross section compiled by M.L. Curtis. Data preparation, digital È cartography, design, and layout by M.L. Curtis and T.R. Riley. Geological mapping and digital mapping production was undertaken as part of 20 the BAS Environmental Change and Evolution (ECE) programme. 60 È Base map data for coastlines, rock outcrops and ice shelves from Landsat ETM+ Path: 206 Row: 098 7 February 2003, Landsat ETM+ Path: 9 È 207 Row: 098 2 May 2002. È È È Leith 42 40 Elevation data from NASA Shuttle Radar Topography Mission (SRTM) February 2000. 60 65 Stromness Aptian È STROMNESS BAY Bathymetry: Fretwell, P.T., Tate, A.J., Deen, T.J. and Belchier, M. (2009). Compilation of a new bathymetric dataset of South Georgia. Antarctic 61 KING HAAKON BAY 9 Aptian Science, 21, 171-174. Husvik Preferred reference for the map: 45 È 52 È CURTIS, M.L. 2011. Geological Map of South Georgia (1:250 000 scale). BAS GEOMAP 2 Series, Sheet 4, British Antarctic Survey, Cambridge, UK. 29 È CUMBERLAND BAY Projection: Lambert Conformal Conic, standard parallels at 54°S and 54°45'S. Aptian - Albian KOHL Horizontal datum: WGS 84. 62 È È PLATEAU Published by BRITISH ANTARCTIC SURVEY, High Cross, Madingley Road, Cambridge, CB3 0ET, United Kingdom. This geological map is 71 78 copyright © British Antarctic Survey, Natural Environmental Research Council, 2011. All rights reserved. 38 È » C Aptian 27 1 62 King Edward Grytviken Point research station 9 Barff PeninsulaÈ A 42 L 9 L B1 A R GEOLOGICAL LEGEND D Geological units are coloured as dark and light tints representing exposed (mountains or nunataks) or Y 10 inferred geology (under ice, snow, vegetation) 43 C Andesitic intrusives: 20 Porphyritic andesite sills and E » irregular intrusions in Upper 40 Glacier Breccia Member. Small quartz Nordenskjöld » C diorite and microdiorite intrusions R 53 »45 on Hauge Reef and Pickersgill Aptian - Albian Late 14 » Cooper Bay Fm: Sequence of highly deformed Islands (Pettigrew, 1981). A » 25 ST ANDREWS volcaniclastic metagreywacke, phyllite and slate, Annenkov Island Fm, Upper N 11 with boudinaged ortho-amphibolite sheets. 36°20'W Breccia Member: 1,200m of BAY Depositional age is uncertain, but considered a predominantly non-stratified, G S A time equivalent of Cumberland Bay Fm. 1 Mt Paget U 14 18 Cumberland Bay Fm: Sandebugten Fm: andesitic conglomerates and 10 5 2934m E O Exhibits a polyphase deformatiol history breccias (Pettigrew, 1981; Tanner » E Scale: 1:75 000 22 9 Andesitic volcaniclastic Quartz-rich sandstone and related to adjacent Cooper Bay Shear ANNENKOV 15 C 13 et al., 1981). 12 A turbidite sequence up to 8km shale turbidite sequence, Zone (Curtis et al. 2010). kilometres » T 13 15 0 4 8 ISLAND E thick. Rare macro fossils derived from a continental, » R 12 Early Cretaceous 52 indicate an Aptian age but felsic volcanic source. A 12 10 C » 35 morainal deposits suggest the Uncertain age, probably a time Ducloz Head Fm: Massive S 26 » 54°30' volcaniclastic breccias and Annenkov Island Fm, Lower 0 2 4 10 Early sequence may extend to Late equivalent of Cumberland Bay 8 » 12 interbedded tuffs and mudstones, Tuff Member: Thinly bedded miles Early Cretaceous Ducloz Jurassic (Thomson et al. Fm. Outcrop restricted to tuffaceous mudstone and tuff. 1982). central northeast coastal areas. derived from a continental margin 200 late Aptian - Albian Head B Fossiliferous upper section on » Moderately deformed into Strongly deformed into containing dacitic to rhyolitic 200 UNDINE » 20 volcanic rocks. Annenkov Island (Thomson et al., » large scale folds with tight-isoclinal folds that are 17 Upper Jurassic to Lower Cretaceous Facies equivalent of 1982). Highly deformed at Ducloz 9 29 Ü HARBOUR Cape associated tectonic foliation. increasingly super-imposed by » Sandebugten Fm. Head (Storey, 1983b). Coeval Ü 39 39 Charlotte a second foliation from NW to » SOUTH 50 Ü 50 Minor pillow basalt minor spilitic subaqueous lavas » SE (Stone, 1980). 5 25 » 9 10 66 25 13 11 8 (Storey, 1983b). and sills (Pettigrew, 1981). » 10 » 9 15 Early Cretaceous È » 12 C 52 50 86 33 7 S 26 » » 22 400 83 Smaaland Cove Intrusive Larson Harbour Complex: » » » U Late Drygalski Fjord Complex (DFC): 40 A Suite: Small composite plutons » 61 400 42 Granitoid intrusions: Predominantly tholeiitic pillow 69 » Predominantly gabbroic plutons (4a) 7 M 36 of plagiogranite to quartz gabbro 47 57 » Variable composition basalts (Larson Harbour 6c L and small bodies of diorite and quartz » 200 400 including granodiorite, cutting Larson Harbour Fm lavas Formation) associated with » B » diorite (4b) intruding the pre-Jurassic 43 9 50 V È tonalite, trondhjemite, and and contemporaneous with mafic dyke hyloclastite, pillow breccias, plus » metasedimentary basement rocks. 4c »82 » E 12 78 12 C 6 emplacement (Mair, 1987). Intrusion age I rare tuff and chert units. Minor 66 22 undifferentiated DFC (Storey, 1983a). granophyre. 6a calc » S 78 15 E R » 4a 2 alkaline Trendall Crag of Smaaland Cove pluton is 150±1 Ma component of silicic lavas, dykes 54 31 S The percentage volume of mafic A Ü » (Mukasa & Dalziel, 1996). 6c S Middle granodiorite,6b Cooper Island and small intrusions. Mafic L »55 Godthul PICKERSGILL R dykes increases from 25 - 80% from » 72 69 U granophyre, cogenetic with dykes form up to 80% of the 200 J east to west across the DFC’s outcrop. A 7 E 77 400 47 ISLANDS tholeiitic mafic rocks of DFC, 6c lower part of the volcanic » Age of mafic plutons is poorly 83 » N 5 N 39 o v o undifferentiated granitoids stratigraphy. s i l s 6c N constrained. k i 4a including mylonitic granodiorite Structural depth of exposure D » G l a 6c 27 c i e r within the Cooper Bay Shear Zone, increases from north to south (Mair, 1987). » 28 6c » 5 R dated at 162±2 Ma (Curtis et al., » 72 Early E 72 43 2010). 6c A 4 A 78 N S » Ü Moraine 13 T 63 G Salomon Glacier Fm: Amphibolite grade Novosilski Glacier Fm: Similar to Cooper Cooper Island Fm: 50m thick, tectonically » C Fjord 42 48 10 6c 2 I paragneiss, banded gneiss and migmatites, Island Fm. comprising sub-arkosic sandstones inverted, sequence of laminated mudstone and » 600 S E D1 S exhibiting a polyphase deformation history to sub-quartzose greywackes derived from a siltstone with massive arkosic sandstone and B 4c A Ü 6c 11 R (Storey, 1983a). plutonic and metamorphic terrane. Outcrops greywacke derived from a plutonic and metamor- »12 A Salomon Glacier U 1 2 3 È J within the Cooper Bay Shear Zone reveal a phic terrane. The sequence exhibits low regional B 49 4b Y E gradation from clastic to volcaniclastic composition. metamorphic grade with localised contact thermal 600 75 »18 22 A 6c R 1 P 62 » Drygalski Fjord Generally exhibits a low regional metamorphic grade metamorphism (Storey, 1983a). 54°20'S » Ü R 54°20'S 4b (low greenschist) (Storey, 1983a). 200 » »50 1 4a »42 F 44 G 38 Cooper Bay Ü » F 45 53 R » » 34 64 » 400 » 39 E 8 P 30 4a 5 400 5 » E E Ü 6a 6b 21 75 N Ü N 4c E Larsen Harbour COOPER »31 I GEOLOGICAL SYMBOLS N 38 3 ISLAND » P S 33 È 43 » 57 E »51 U N Ü L 200 Downward structural facing Fold axial plane with dip » Stratigraphic boundary 75 I 14 400 A » Sörling Valley 7 Ü 76 » 25 40 60 »N m S »36 Shear zone boundary 53 » » 35 U 600 29 D » » Ü 52 L 82 Shear zone inferred 70 Inclined bedding with dip Stretching lineation » Cove 29 8 7 » Ü Smaaland Ü with plunge 400 A 25 200 Ü » 14 m 10 Fault (tick on downthrown side) » 62 30 m Ü 29 Ü Hound S1 cleavage or metamorphic foliation Ü Mylonite lineation 600 35 » Bay Fault inferred 36 m 55 with dip 33 »14 600 19 600 Thrust (teeth in hanging wall) » S cleavage or metamorphic foliation » »22 2 Cumulate layering 800 » 73 with dip 64 200 »26 60 400 » 18 14 Mafic dyke trends in the Larson Harbour 9 » Ü 400 and Drygalski Fjord complexes Ü 56 S 200 55° S Nordenskjöld Glacier » 13 Presence of fossils 53 Age range provided where fossils are indicative 38°0'0"W 37°30'0"W 36°20'W 37° W 36°30' 36° W Gastropod Belemnite Ammonite Belemnite Bivalve Fish scales in moraine debris A A1 GEOLOGICAL CROSS SECTIONS 1 REFERENCES Metres Annenkov Is. Horizontal scale 1:250 000 15 2 3 1. Macdonald, D.I.M. 1982. The sedimentology, structure and palaeogeography of the 12. Storey, B.C. 1983b. The geology of the Ducloz Head area, South Georgia. British Antarctic 1000 Hauge Reef Cumberland Bay Formation, South Georgia. PhD thesis, University of Cambridge, 155pp. Survey Bulletin, 52, 33-46. 0 2 1 1 2. Clayton, R.A.S. 1983. The geology of north-western South Georgia: IV. Structural Geology. 13. Tanner, P.W.G., Storey, B.C.