OR/15/058 Systematic survey and research: 1966-1977 - Revision history

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	A series of publications arose from the work in the south-east with the overall divisions established by Bell and others (1977)<ref name="Bell 1977">BELL, C M, MAIR, B F, and STOREY, B C. 1977.The geology of part of an island arc–marginal basin system in southern South Georgia. ''British Antarctic Survey Bulletin'', '''46''', 109–127.</ref> and Storey and others (1977)<ref name="Storey 1977">STOREY, B C, MAIR, B F, and BELL, C M. 1977. The occurrence of Mesozoic oceanic floor and ancient continental crust on South Georgia. ''Geological Magazine'', '''114''', 203–208.</ref>. The igneous rocks were divided into the ophiolitic Larsen Harbour Formation (subsequently redefined as a Complex) of submarine basalt lavas and breccias and sheeted basic dykes, and the Drygalski Fjord Complex of mostly gabbroic plutons, with subordinate granitic rocks, intruded into metasedimentary rocks ranging in grade up to siliceous paragneisses. The gabbro bodies were regarded as the root zone of the sheeted dykes and volcanic lavas, intruded into a continental basement of which the metasedimentary units were relics. Storey and Mair (1982)<ref name="Storey 1982">STOREY, B C, and MAIR, B F. 1982. The composite floor of the Cretaceous back-arc basin of South Georgia. Journal of the Geological Society, London, 139, 729–738. </ref> developed these ideas within the marginal basin model for South Georgia describing the ophiolitic Larsen Harbour Formation/Complex, and the pre-Jurassic basement with its gabbroic and granitic intrusions, as remnants of the composite floor of the Cretaceous back-arc basin in which the South Georgia sedimentary successions accumulated. The Larsen Harbour Complex ophiolite comprised pillow lavas and breccias with interbedded tuffs, intruded by mafic and felsic dykes and by gabbro and composite gabbro-plagiogranite plutons. The basement metasedimentary gneisses were intruded by layered gabbro bodies, dioritic and granitic rocks, and by a multitude of mafic dykes.		A series of publications arose from the work in the south-east with the overall divisions established by Bell and others (1977)<ref name="Bell 1977">BELL, C M, MAIR, B F, and STOREY, B C. 1977.The geology of part of an island arc–marginal basin system in southern South Georgia. ''British Antarctic Survey Bulletin'', '''46''', 109–127.</ref> and Storey and others (1977)<ref name="Storey 1977">STOREY, B C, MAIR, B F, and BELL, C M. 1977. The occurrence of Mesozoic oceanic floor and ancient continental crust on South Georgia. ''Geological Magazine'', '''114''', 203–208.</ref>. The igneous rocks were divided into the ophiolitic Larsen Harbour Formation (subsequently redefined as a Complex) of submarine basalt lavas and breccias and sheeted basic dykes, and the Drygalski Fjord Complex of mostly gabbroic plutons, with subordinate granitic rocks, intruded into metasedimentary rocks ranging in grade up to siliceous paragneisses. The gabbro bodies were regarded as the root zone of the sheeted dykes and volcanic lavas, intruded into a continental basement of which the metasedimentary units were relics. Storey and Mair (1982)<ref name="Storey 1982">STOREY, B C, and MAIR, B F. 1982. The composite floor of the Cretaceous back-arc basin of South Georgia. Journal of the Geological Society, London, 139, 729–738. </ref> developed these ideas within the marginal basin model for South Georgia describing the ophiolitic Larsen Harbour Formation/Complex, and the pre-Jurassic basement with its gabbroic and granitic intrusions, as remnants of the composite floor of the Cretaceous back-arc basin in which the South Georgia sedimentary successions accumulated. The Larsen Harbour Complex ophiolite comprised pillow lavas and breccias with interbedded tuffs, intruded by mafic and felsic dykes and by gabbro and composite gabbro-plagiogranite plutons. The basement metasedimentary gneisses were intruded by layered gabbro bodies, dioritic and granitic rocks, and by a multitude of mafic dykes.

	Some compositional and geochemical data were given by Storey and Mair (1982)<ref name="Storey 1982"></ref>, with more detailed, comprehensive descriptions and interpretations provided later: for the Larsen Harbour Formation/Complex by Mair (1983<ref name="Mair 1983">MAIR, B F. 1983. The Larsen Harbour Formation and associated intrusive rocks of southern South Georgia. ''British Antarctic Survey Bulletin'', '''52''', 87–107.</ref>, 1987)<ref name="Mair 1987">MAIR, B F. 1987. The Geology of South Georgia: VI. Larsen Harbour Formation. ''British Antarctic Survey Scientific Reports'', '''111''', 60 pp.</ref> and for the Drygalski Fjord Complex by Storey (1983a)<ref name="Storey 1983a">STOREY, B C. 1983a. The Geology of South Georgia: V. Drygalski Fjord Complex. British Antarctic Survey Scientific Reports, No.107, 88 pp.</ref>. The Larsen Harbour lava succession was shown to be about 2 km thick, dipping moderately towards the west. It forms the upper part of an autochthonous ophiolite sequence with a broad lithostratigraphical zonation. Breccias with subordinate pillow lavas form the base of the succession, where they are cut by multiple mafic dykes, and are overlain by voluminous pillow lavas, with subordinate breccia and interbedded volcaniclastic sedimentary layers. Compositionally most of the rocks resembled oceanic tholeiites. Within the Drygalski Fjord Complex, Storey (1983a)<ref name="Storey 1983a">~~STOREY, B C. 1983a. The Geology of South Georgia: V. Drygalski Fjord Complex. ''British Antarctic Survey Scientific Reports'', No.107, 88 pp.~~</ref> divided the metasedimentary, continental basement rocks into three formations: Salomon Glacier, Cooper Island and Novosilski Glacier. The Salomon Glacier Formation comprised siliceous paragneiss and layered migmatite; the other two formations comprised various metasedimentary clastic rocks. After deformation and metamorphism of this ‘basement’ assemblage, intrusion of a differentiated, tholeiitic magma produced a range of rocks from layered gabbros to granite; other granitic intrusions showed calc-alkaline trends. This intrusive phase was followed by swarms of mafic dykes linked to the generation of the Larsen Harbour Formation ophiolite.		Some compositional and geochemical data were given by Storey and Mair (1982)<ref name="Storey 1982"></ref>, with more detailed, comprehensive descriptions and interpretations provided later: for the Larsen Harbour Formation/Complex by Mair (1983<ref name="Mair 1983">MAIR, B F. 1983. The Larsen Harbour Formation and associated intrusive rocks of southern South Georgia. ''British Antarctic Survey Bulletin'', '''52''', 87–107.</ref>, 1987)<ref name="Mair 1987">MAIR, B F. 1987. The Geology of South Georgia: VI. Larsen Harbour Formation. ''British Antarctic Survey Scientific Reports'', '''111''', 60 pp.</ref> and for the Drygalski Fjord Complex by Storey (1983a)<ref name="Storey 1983a">STOREY, B C. 1983a. The Geology of South Georgia: V. Drygalski Fjord Complex. British Antarctic Survey Scientific Reports, No.107, 88 pp.</ref>. The Larsen Harbour lava succession was shown to be about 2 km thick, dipping moderately towards the west. It forms the upper part of an autochthonous ophiolite sequence with a broad lithostratigraphical zonation. Breccias with subordinate pillow lavas form the base of the succession, where they are cut by multiple mafic dykes, and are overlain by voluminous pillow lavas, with subordinate breccia and interbedded volcaniclastic sedimentary layers. Compositionally most of the rocks resembled oceanic tholeiites. Within the Drygalski Fjord Complex, Storey (1983a)<ref name="Storey 1983a"></ref> divided the metasedimentary, continental basement rocks into three formations: Salomon Glacier, Cooper Island and Novosilski Glacier. The Salomon Glacier Formation comprised siliceous paragneiss and layered migmatite; the other two formations comprised various metasedimentary clastic rocks. After deformation and metamorphism of this ‘basement’ assemblage, intrusion of a differentiated, tholeiitic magma produced a range of rocks from layered gabbros to granite; other granitic intrusions showed calc-alkaline trends. This intrusive phase was followed by swarms of mafic dykes linked to the generation of the Larsen Harbour Formation ophiolite.

	Storey’s work extended north-westward to the Ducloz Head area, and north-eastward across the mylonite zone at the margin of the igneous rocks into the Cooper Bay area. At Ducloz Head a succession of volcaniclastic rocks and pillow lava, tuffs and mudstone was defined as the Ducloz Head Formation (Storey 1983b)<ref name="Storey 1983b">STOREY, B C. 1983b. The geology of the Ducloz Head area, South Georgia. ''British Antarctic Survey Bulletin'', '''52''', 33–46.</ref>. The formation had been affected by widespread ductile and brittle deformation and was separated from the adjacent Cumberland Bay Formation by a steep fault zone. Storey recognised similarities with all of the other South Georgia sedimentary divisions, but thought the likely regional association to be as an intermediate between the Annenkov Island and Larsen Harbour formations. At Cooper Bay, Storey (1983a)<ref name="Storey 1983a"></ref> broadly confirmed the lithofacies and polyphase structural interpretation of Stone (1982)<ref name="Stone 1982"></ref>, but thought that the structural history within the mylonite zone was more complicated than previously proposed. In particular, the mylonite zone may have been initiated earlier in the structural history than was indicated in Stone’s interpretation.		Storey’s work extended north-westward to the Ducloz Head area, and north-eastward across the mylonite zone at the margin of the igneous rocks into the Cooper Bay area. At Ducloz Head a succession of volcaniclastic rocks and pillow lava, tuffs and mudstone was defined as the Ducloz Head Formation (Storey 1983b)<ref name="Storey 1983b">STOREY, B C. 1983b. The geology of the Ducloz Head area, South Georgia. ''British Antarctic Survey Bulletin'', '''52''', 33–46.</ref>. The formation had been affected by widespread ductile and brittle deformation and was separated from the adjacent Cumberland Bay Formation by a steep fault zone. Storey recognised similarities with all of the other South Georgia sedimentary divisions, but thought the likely regional association to be as an intermediate between the Annenkov Island and Larsen Harbour formations. At Cooper Bay, Storey (1983a)<ref name="Storey 1983a"></ref> broadly confirmed the lithofacies and polyphase structural interpretation of Stone (1982)<ref name="Stone 1982"></ref>, but thought that the structural history within the mylonite zone was more complicated than previously proposed. In particular, the mylonite zone may have been initiated earlier in the structural history than was indicated in Stone’s interpretation.

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	Storey’s work extended north-westward to the Ducloz Head area, and north-eastward across the mylonite zone at the margin of the igneous rocks into the Cooper Bay area. At Ducloz Head a succession of volcaniclastic rocks and pillow lava, tuffs and mudstone was defined as the Ducloz Head Formation (Storey 1983b)<ref name="Storey 1983b">STOREY, B C. 1983b. The geology of the Ducloz Head area, South Georgia. ''British Antarctic Survey Bulletin'', '''52''', 33–46.</ref>. The formation had been affected by widespread ductile and brittle deformation and was separated from the adjacent Cumberland Bay Formation by a steep fault zone. Storey recognised similarities with all of the other South Georgia sedimentary divisions, but thought the likely regional association to be as an intermediate between the Annenkov Island and Larsen Harbour formations. At Cooper Bay, Storey (1983a)<ref name="Storey 1983a"></ref> broadly confirmed the lithofacies and polyphase structural interpretation of Stone (1982)<ref name="Stone 1982"></ref>, but thought that the structural history within the mylonite zone was more complicated than previously proposed. In particular, the mylonite zone may have been initiated earlier in the structural history than was indicated in Stone’s interpretation.		Storey’s work extended north-westward to the Ducloz Head area, and north-eastward across the mylonite zone at the margin of the igneous rocks into the Cooper Bay area. At Ducloz Head a succession of volcaniclastic rocks and pillow lava, tuffs and mudstone was defined as the Ducloz Head Formation (Storey 1983b)<ref name="Storey 1983b">STOREY, B C. 1983b. The geology of the Ducloz Head area, South Georgia. ''British Antarctic Survey Bulletin'', '''52''', 33–46.</ref>. The formation had been affected by widespread ductile and brittle deformation and was separated from the adjacent Cumberland Bay Formation by a steep fault zone. Storey recognised similarities with all of the other South Georgia sedimentary divisions, but thought the likely regional association to be as an intermediate between the Annenkov Island and Larsen Harbour formations. At Cooper Bay, Storey (1983a)<ref name="Storey 1983a"></ref> broadly confirmed the lithofacies and polyphase structural interpretation of Stone (1982)<ref name="Stone 1982"></ref>, but thought that the structural history within the mylonite zone was more complicated than previously proposed. In particular, the mylonite zone may have been initiated earlier in the structural history than was indicated in Stone’s interpretation.

	By the time that Mair and Storey published, the first radiometric dates (Rb–Sr) had become available from granite within the Drygalski Fjord Complex and from a granitic intrusion coeval with the later episodes of dyke intrusion in the Larsen Harbour Formation/Complex (Tanner and Rex 1979). The former gave ages in the approximate range 180–200 Ma, the latter gave an age of 127 ± 4 Ma. Storey (1983a)<ref name="Storey 1983a"></ref> and Mair (1987)<ref name="Mair 1987"></ref> incorporated these results, and Storey also described the heterogeneous migmatite aureole that surrounded the intrusive plutonic rocks — but note that Storey (1983b)<ref name="Storey 1983b"></ref> and Mair (1983)<ref name="Mair 1983">~~MAIR, B F. 1983. The Larsen Harbour Formation and associated intrusive rocks of southern South Georgia. British Antarctic Survey Bulletin, 52, 87–107.~~</ref> were received for publication in August 1978 and October 1976 respectively, before the radiometric dates were available.		By the time that Mair and Storey published, the first radiometric dates (Rb–Sr) had become available from granite within the Drygalski Fjord Complex and from a granitic intrusion coeval with the later episodes of dyke intrusion in the Larsen Harbour Formation/Complex (Tanner and Rex 1979). The former gave ages in the approximate range 180–200 Ma, the latter gave an age of 127 ± 4 Ma. Storey (1983a)<ref name="Storey 1983a"></ref> and Mair (1987)<ref name="Mair 1987"></ref> incorporated these results, and Storey also described the heterogeneous migmatite aureole that surrounded the intrusive plutonic rocks — but note that Storey (1983b)<ref name="Storey 1983b"></ref> and Mair (1983)<ref name="Mair 1983"></ref> were received for publication in August 1978 and October 1976 respectively, before the radiometric dates were available.

	In addition to his work on the Larsen Harbour Formation/Complex Mair also investigated the geology in the Moraine Fjord area of Cumberland East Bay during a short period in 1977. He described a number of small, pre-tectonic, dioritic and gabbroic sheets intruded into strata of the Cumberland Bay Formation, and traced out the structural contact and contrasts between that formation and the structurally subjacent Sandebugten Formation (Mair 1981)<ref name="Mair 1981">MAIR, B F. 1981. Geological observations in the Moraine Fjord area, South Georgia. ''British Antarctic Survey Bulletin'', '''53''', 11–19.</ref> to the south of Dartmouth Point (the promontory now known as Greene Peninsula). This was the area from which Dalziel and others (1975)<ref name="Dalziel 1975"></ref> had described a thrust contact between the two formations.		In addition to his work on the Larsen Harbour Formation/Complex Mair also investigated the geology in the Moraine Fjord area of Cumberland East Bay during a short period in 1977. He described a number of small, pre-tectonic, dioritic and gabbroic sheets intruded into strata of the Cumberland Bay Formation, and traced out the structural contact and contrasts between that formation and the structurally subjacent Sandebugten Formation (Mair 1981)<ref name="Mair 1981">MAIR, B F. 1981. Geological observations in the Moraine Fjord area, South Georgia. ''British Antarctic Survey Bulletin'', '''53''', 11–19.</ref> to the south of Dartmouth Point (the promontory now known as Greene Peninsula). This was the area from which Dalziel and others (1975)<ref name="Dalziel 1975"></ref> had described a thrust contact between the two formations.

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	Some compositional and geochemical data were given by Storey and Mair (1982)<ref name="Storey 1982"></ref>, with more detailed, comprehensive descriptions and interpretations provided later: for the Larsen Harbour Formation/Complex by Mair (1983<ref name="Mair 1983">MAIR, B F. 1983. The Larsen Harbour Formation and associated intrusive rocks of southern South Georgia. ''British Antarctic Survey Bulletin'', '''52''', 87–107.</ref>, 1987)<ref name="Mair 1987">MAIR, B F. 1987. The Geology of South Georgia: VI. Larsen Harbour Formation. ''British Antarctic Survey Scientific Reports'', '''111''', 60 pp.</ref> and for the Drygalski Fjord Complex by Storey (1983a)<ref name="Storey 1983a">STOREY, B C. 1983a. The Geology of South Georgia: V. Drygalski Fjord Complex. British Antarctic Survey Scientific Reports, No.107, 88 pp.</ref>. The Larsen Harbour lava succession was shown to be about 2 km thick, dipping moderately towards the west. It forms the upper part of an autochthonous ophiolite sequence with a broad lithostratigraphical zonation. Breccias with subordinate pillow lavas form the base of the succession, where they are cut by multiple mafic dykes, and are overlain by voluminous pillow lavas, with subordinate breccia and interbedded volcaniclastic sedimentary layers. Compositionally most of the rocks resembled oceanic tholeiites. Within the Drygalski Fjord Complex, Storey (1983a)<ref name="Storey 1983a">STOREY, B C. 1983a. The Geology of South Georgia: V. Drygalski Fjord Complex. ''British Antarctic Survey Scientific Reports'', No.107, 88 pp.</ref> divided the metasedimentary, continental basement rocks into three formations: Salomon Glacier, Cooper Island and Novosilski Glacier. The Salomon Glacier Formation comprised siliceous paragneiss and layered migmatite; the other two formations comprised various metasedimentary clastic rocks. After deformation and metamorphism of this ‘basement’ assemblage, intrusion of a differentiated, tholeiitic magma produced a range of rocks from layered gabbros to granite; other granitic intrusions showed calc-alkaline trends. This intrusive phase was followed by swarms of mafic dykes linked to the generation of the Larsen Harbour Formation ophiolite.		Some compositional and geochemical data were given by Storey and Mair (1982)<ref name="Storey 1982"></ref>, with more detailed, comprehensive descriptions and interpretations provided later: for the Larsen Harbour Formation/Complex by Mair (1983<ref name="Mair 1983">MAIR, B F. 1983. The Larsen Harbour Formation and associated intrusive rocks of southern South Georgia. ''British Antarctic Survey Bulletin'', '''52''', 87–107.</ref>, 1987)<ref name="Mair 1987">MAIR, B F. 1987. The Geology of South Georgia: VI. Larsen Harbour Formation. ''British Antarctic Survey Scientific Reports'', '''111''', 60 pp.</ref> and for the Drygalski Fjord Complex by Storey (1983a)<ref name="Storey 1983a">STOREY, B C. 1983a. The Geology of South Georgia: V. Drygalski Fjord Complex. British Antarctic Survey Scientific Reports, No.107, 88 pp.</ref>. The Larsen Harbour lava succession was shown to be about 2 km thick, dipping moderately towards the west. It forms the upper part of an autochthonous ophiolite sequence with a broad lithostratigraphical zonation. Breccias with subordinate pillow lavas form the base of the succession, where they are cut by multiple mafic dykes, and are overlain by voluminous pillow lavas, with subordinate breccia and interbedded volcaniclastic sedimentary layers. Compositionally most of the rocks resembled oceanic tholeiites. Within the Drygalski Fjord Complex, Storey (1983a)<ref name="Storey 1983a">STOREY, B C. 1983a. The Geology of South Georgia: V. Drygalski Fjord Complex. ''British Antarctic Survey Scientific Reports'', No.107, 88 pp.</ref> divided the metasedimentary, continental basement rocks into three formations: Salomon Glacier, Cooper Island and Novosilski Glacier. The Salomon Glacier Formation comprised siliceous paragneiss and layered migmatite; the other two formations comprised various metasedimentary clastic rocks. After deformation and metamorphism of this ‘basement’ assemblage, intrusion of a differentiated, tholeiitic magma produced a range of rocks from layered gabbros to granite; other granitic intrusions showed calc-alkaline trends. This intrusive phase was followed by swarms of mafic dykes linked to the generation of the Larsen Harbour Formation ophiolite.

	Storey’s work extended north-westward to the Ducloz Head area, and north-eastward across the mylonite zone at the margin of the igneous rocks into the Cooper Bay area. At Ducloz Head a succession of volcaniclastic rocks and pillow lava, tuffs and mudstone was defined as the Ducloz Head Formation (Storey 1983b)<ref name="Storey 1983b">STOREY, B C. 1983b. The geology of the Ducloz Head area, South Georgia. ''British Antarctic Survey Bulletin'', '''52''', 33–46.</ref>. The formation had been affected by widespread ductile and brittle deformation and was separated from the adjacent Cumberland Bay Formation by a steep fault zone. Storey recognised similarities with all of the other South Georgia sedimentary divisions, but thought the likely regional association to be as an intermediate between the Annenkov Island and Larsen Harbour formations. At Cooper Bay, Storey (1983a)<ref name="Storey 1983a"></ref> broadly confirmed the lithofacies and polyphase structural interpretation of Stone (1982)<ref name="Stone 1982">~~STONE, P. 1982. Geological observations in the Cooper Bay – Wirik Bay area, South Georgia. ''British Antarctic Survey Bulletin'', '''51''', 43–53.~~</ref>, but thought that the structural history within the mylonite zone was more complicated than previously proposed. In particular, the mylonite zone may have been initiated earlier in the structural history than was indicated in Stone’s interpretation.		Storey’s work extended north-westward to the Ducloz Head area, and north-eastward across the mylonite zone at the margin of the igneous rocks into the Cooper Bay area. At Ducloz Head a succession of volcaniclastic rocks and pillow lava, tuffs and mudstone was defined as the Ducloz Head Formation (Storey 1983b)<ref name="Storey 1983b">STOREY, B C. 1983b. The geology of the Ducloz Head area, South Georgia. ''British Antarctic Survey Bulletin'', '''52''', 33–46.</ref>. The formation had been affected by widespread ductile and brittle deformation and was separated from the adjacent Cumberland Bay Formation by a steep fault zone. Storey recognised similarities with all of the other South Georgia sedimentary divisions, but thought the likely regional association to be as an intermediate between the Annenkov Island and Larsen Harbour formations. At Cooper Bay, Storey (1983a)<ref name="Storey 1983a"></ref> broadly confirmed the lithofacies and polyphase structural interpretation of Stone (1982)<ref name="Stone 1982"></ref>, but thought that the structural history within the mylonite zone was more complicated than previously proposed. In particular, the mylonite zone may have been initiated earlier in the structural history than was indicated in Stone’s interpretation.

	By the time that Mair and Storey published, the first radiometric dates (Rb–Sr) had become available from granite within the Drygalski Fjord Complex and from a granitic intrusion coeval with the later episodes of dyke intrusion in the Larsen Harbour Formation/Complex (Tanner and Rex 1979). The former gave ages in the approximate range 180–200 Ma, the latter gave an age of 127 ± 4 Ma. Storey (1983a)<ref name="Storey 1983a"></ref> and Mair (1987)<ref name="Mair 1987"></ref> incorporated these results, and Storey also described the heterogeneous migmatite aureole that surrounded the intrusive plutonic rocks — but note that Storey (1983b)<ref name="Storey 1983b"></ref> and Mair (1983)<ref name="Mair 1983">MAIR, B F. 1983. The Larsen Harbour Formation and associated intrusive rocks of southern South Georgia. British Antarctic Survey Bulletin, 52, 87–107.</ref> were received for publication in August 1978 and October 1976 respectively, before the radiometric dates were available.		By the time that Mair and Storey published, the first radiometric dates (Rb–Sr) had become available from granite within the Drygalski Fjord Complex and from a granitic intrusion coeval with the later episodes of dyke intrusion in the Larsen Harbour Formation/Complex (Tanner and Rex 1979). The former gave ages in the approximate range 180–200 Ma, the latter gave an age of 127 ± 4 Ma. Storey (1983a)<ref name="Storey 1983a"></ref> and Mair (1987)<ref name="Mair 1987"></ref> incorporated these results, and Storey also described the heterogeneous migmatite aureole that surrounded the intrusive plutonic rocks — but note that Storey (1983b)<ref name="Storey 1983b"></ref> and Mair (1983)<ref name="Mair 1983">MAIR, B F. 1983. The Larsen Harbour Formation and associated intrusive rocks of southern South Georgia. British Antarctic Survey Bulletin, 52, 87–107.</ref> were received for publication in August 1978 and October 1976 respectively, before the radiometric dates were available.

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	Farther south, in the Cooper Bay area, deformation proved to be more intense, with an apparently thinly-bedded turbidite succession converted into a series of schistose rocks, slates and cataclasites. Within the metasedimentary succession were widespread boudinaged sheets of a pervasively altered, but originally doleritic intrusive rock. Stone (1982)<ref name="Stone 1982">STONE, P. 1982. Geological observations in the Cooper Bay — Wirik Bay area, South Georgia. ''British Antarctic Survey Bulletin'', '''51''', 43–53.</ref> — a paper submitted for publication in October 1975 — defined the metasedimentary succession as the Cooper Bay Formation and described its polyphase deformation. The earliest small-scale folds, with an associated slaty cleavage, were identified from their interference patterns with a series of tight, minor folds with an axial planar crenulation cleavage. The latter was then folded into large-scale, upright folds to which a steeply inclined, second crenulation cleavage was axial planar; all of these structures were cross-cut by a range of minor, late and locally developed folds and crenulations. At the south-western margin of its outcrop, the structures affecting the Cooper Bay Formation merged into a polyphase, mylonitic shear zone that separated the metasedimentary rocks from Trendall’s (1959)<ref name="Trendall 1959">TRENDALL, A F. 1959. The Geology of South Georgia: II. ''Falkland Islands Dependencies Survey Scientific Reports'', No.19, 47 pp, 5 plates, fold-out map.</ref> South-eastern Igneous Complex.		Farther south, in the Cooper Bay area, deformation proved to be more intense, with an apparently thinly-bedded turbidite succession converted into a series of schistose rocks, slates and cataclasites. Within the metasedimentary succession were widespread boudinaged sheets of a pervasively altered, but originally doleritic intrusive rock. Stone (1982)<ref name="Stone 1982">STONE, P. 1982. Geological observations in the Cooper Bay — Wirik Bay area, South Georgia. ''British Antarctic Survey Bulletin'', '''51''', 43–53.</ref> — a paper submitted for publication in October 1975 — defined the metasedimentary succession as the Cooper Bay Formation and described its polyphase deformation. The earliest small-scale folds, with an associated slaty cleavage, were identified from their interference patterns with a series of tight, minor folds with an axial planar crenulation cleavage. The latter was then folded into large-scale, upright folds to which a steeply inclined, second crenulation cleavage was axial planar; all of these structures were cross-cut by a range of minor, late and locally developed folds and crenulations. At the south-western margin of its outcrop, the structures affecting the Cooper Bay Formation merged into a polyphase, mylonitic shear zone that separated the metasedimentary rocks from Trendall’s (1959)<ref name="Trendall 1959">TRENDALL, A F. 1959. The Geology of South Georgia: II. ''Falkland Islands Dependencies Survey Scientific Reports'', No.19, 47 pp, 5 plates, fold-out map.</ref> South-eastern Igneous Complex.

	In summing up the deformation history seen on the north-east coast of South Georgia, Stone (1980)<ref name="Stone 1980">STONE, P. 1980. The Geology of South Georgia: IV. Barff Peninsula and Royal Bay areas. ''British Antarctic Survey Scientific Reports'', No.96, 45 pp + 8 plates.</ref> built on the marginal basin model of Dalziel and others (1975)<ref name="Dalziel 1975">~~DALZIEL, I W D, DOTT, R H, WINN, R D, and BRUHN, R L. 1975. Tectonic Relations of South Georgia Island to the Southernmost Andes. ''Geological Society of America Bulletin'', '''86''', 1034–1040.~~</ref>, envisaging its sedimentary fill experiencing diachronous, supra-subduction zone deformation as the basin closed. In modern terms this would be described as accretionary tectonics.		In summing up the deformation history seen on the north-east coast of South Georgia, Stone (1980)<ref name="Stone 1980">STONE, P. 1980. The Geology of South Georgia: IV. Barff Peninsula and Royal Bay areas. ''British Antarctic Survey Scientific Reports'', No.96, 45 pp + 8 plates.</ref> built on the marginal basin model of Dalziel and others (1975)<ref name="Dalziel 1975"></ref>, envisaging its sedimentary fill experiencing diachronous, supra-subduction zone deformation as the basin closed. In modern terms this would be described as accretionary tectonics.

	The 1973–74 austral summer marked a turning point in the BAS South Georgia geology programme as specialist studies began in parallel with the final phase of the regional mapping work. The structural geology and overall tectonic regime were investigated in particular by P W G Tanner, who spent that summer and the subsequent 1975–76 summer on a wide-ranging field programme. His work, and the rest of the specialist research theme, will be returned to in a later section of this account.		The 1973–74 austral summer marked a turning point in the BAS South Georgia geology programme as specialist studies began in parallel with the final phase of the regional mapping work. The structural geology and overall tectonic regime were investigated in particular by P W G Tanner, who spent that summer and the subsequent 1975–76 summer on a wide-ranging field programme. His work, and the rest of the specialist research theme, will be returned to in a later section of this account.
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	By the time that Mair and Storey published, the first radiometric dates (Rb–Sr) had become available from granite within the Drygalski Fjord Complex and from a granitic intrusion coeval with the later episodes of dyke intrusion in the Larsen Harbour Formation/Complex (Tanner and Rex 1979). The former gave ages in the approximate range 180–200 Ma, the latter gave an age of 127 ± 4 Ma. Storey (1983a)<ref name="Storey 1983a"></ref> and Mair (1987)<ref name="Mair 1987"></ref> incorporated these results, and Storey also described the heterogeneous migmatite aureole that surrounded the intrusive plutonic rocks — but note that Storey (1983b)<ref name="Storey 1983b"></ref> and Mair (1983)<ref name="Mair 1983">MAIR, B F. 1983. The Larsen Harbour Formation and associated intrusive rocks of southern South Georgia. British Antarctic Survey Bulletin, 52, 87–107.</ref> were received for publication in August 1978 and October 1976 respectively, before the radiometric dates were available.		By the time that Mair and Storey published, the first radiometric dates (Rb–Sr) had become available from granite within the Drygalski Fjord Complex and from a granitic intrusion coeval with the later episodes of dyke intrusion in the Larsen Harbour Formation/Complex (Tanner and Rex 1979). The former gave ages in the approximate range 180–200 Ma, the latter gave an age of 127 ± 4 Ma. Storey (1983a)<ref name="Storey 1983a"></ref> and Mair (1987)<ref name="Mair 1987"></ref> incorporated these results, and Storey also described the heterogeneous migmatite aureole that surrounded the intrusive plutonic rocks — but note that Storey (1983b)<ref name="Storey 1983b"></ref> and Mair (1983)<ref name="Mair 1983">MAIR, B F. 1983. The Larsen Harbour Formation and associated intrusive rocks of southern South Georgia. British Antarctic Survey Bulletin, 52, 87–107.</ref> were received for publication in August 1978 and October 1976 respectively, before the radiometric dates were available.

	In addition to his work on the Larsen Harbour Formation/Complex Mair also investigated the geology in the Moraine Fjord area of Cumberland East Bay during a short period in 1977. He described a number of small, pre-tectonic, dioritic and gabbroic sheets intruded into strata of the Cumberland Bay Formation, and traced out the structural contact and contrasts between that formation and the structurally subjacent Sandebugten Formation (Mair 1981)<ref name="Mair 1981">MAIR, B F. 1981. Geological observations in the Moraine Fjord area, South Georgia. ''British Antarctic Survey Bulletin'', '''53''', 11–19.</ref> to the south of Dartmouth Point (the promontory now known as Greene Peninsula). This was the area from which Dalziel and others (1975)<ref name="Dalziel 1975">~~DALZIEL, I W D, DOTT, R H, WINN, R D, and BRUHN, R L. 1975. Tectonic Relations of South Georgia Island to the Southernmost Andes. Geological Society of America Bulletin, 86, 1034–1040.~~</ref> had described a thrust contact between the two formations.		In addition to his work on the Larsen Harbour Formation/Complex Mair also investigated the geology in the Moraine Fjord area of Cumberland East Bay during a short period in 1977. He described a number of small, pre-tectonic, dioritic and gabbroic sheets intruded into strata of the Cumberland Bay Formation, and traced out the structural contact and contrasts between that formation and the structurally subjacent Sandebugten Formation (Mair 1981)<ref name="Mair 1981">MAIR, B F. 1981. Geological observations in the Moraine Fjord area, South Georgia. ''British Antarctic Survey Bulletin'', '''53''', 11–19.</ref> to the south of Dartmouth Point (the promontory now known as Greene Peninsula). This was the area from which Dalziel and others (1975)<ref name="Dalziel 1975"></ref> had described a thrust contact between the two formations.

	==References==		==References==
	<References/>		<References/>
	[[category: OR/15/058 The geological exploration of the sub-Antarctic island of South Georgia: a review and bibliography, 1871-2015 \| 07]]		[[category: OR/15/058 The geological exploration of the sub-Antarctic island of South Georgia: a review and bibliography, 1871-2015 \| 07]]

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	The 1972–73 austral summer saw the involvement of an American team led by I W D Dalziel and funded by the United States Antarctic Research Program, whilst the BAS geological survey programme was continued by T H Pettigrew and R A S Clayton. Accompanying Dalziel were R L Bruhn, R H Dott and R D Winn: Dalziel and Bruhn were based at Columbia University, New York; Dott and Winn were based at the University of Wisconsin.		The 1972–73 austral summer saw the involvement of an American team led by I W D Dalziel and funded by the United States Antarctic Research Program, whilst the BAS geological survey programme was continued by T H Pettigrew and R A S Clayton. Accompanying Dalziel were R L Bruhn, R H Dott and R D Winn: Dalziel and Bruhn were based at Columbia University, New York; Dott and Winn were based at the University of Wisconsin.

	Early in 1973 the American team made detailed observations in the Cumberland Bay and Stromness Bay areas, supplemented by brief visits to the Bay of Isles and Bird Island. In Cumberland East Bay, on the Dartmouth Point promontory (now Greene Peninsula) they located a thrust contact between the Cumberland Bay and Sandebugten formations and from structural analyses showed that the deformation in the two divisions was broadly contemporaneous, despite the differences in style (Dalziel and others 1975)<ref name="Dalziel 1975">DALZIEL, I W D, DOTT, R H, WINN, R D, and BRUHN, R L. 1975. Tectonic Relations of South Georgia Island to the Southernmost Andes. ''Geological Society of America Bulletin'', '''86''', 1034–1040.</ref>. An assessment of palaeocurrent indicators showed dispersal towards the north-west in the Cumberland Bay Formation, but a more complicated pattern in the Sandebugten Formation dominated by a south-directed component; the structural restoration of the data was detailed by Dott (1974)<ref name="Dott 1974">DOTT, R H. 1974. Paleocurrent analysis of severely deformed flysch-type strata — A case study from South Georgia island. ''Journal of Sedimentary Petrology'', '''44''', 1166–1173.</ref>. From a regional perspective, the American team brought the advantage of direct familiarity with the likely correlative geology in the extreme south of South America. This allowed the development of a regional model for the origin of South Georgia (and the South American correlatives) in a marginal basin lying between the continental margin and a rifted continental sliver carrying a calc-alkaline volcanic arc. Sediment was derived from both sides of the basin, with deformation initiated by basin closure and the resulting arc-continent collision (Dalziel and others 1975<ref name="Dalziel 1975">~~DALZIEL, I W D, DOTT, R H, WINN, R D, and BRUHN, R L. 1975. Tectonic Relations of South Georgia Island to the Southernmost Andes. ''Geological Society of America Bulletin'', '''86''', 1034–1040.~~</ref>; Winn 1978).<ref name="Winn 1978">WINN, R D. 1978. Upper Mesozoic flysch of Tierra del Fuego and South Georgia Island: A sedimentological approach to lithosphere plate restoration. ''Geological Society of America Bulletin'', '''89''', 533–547.</ref> This interpretation brought South Georgia geology squarely into the plate tectonic era.		Early in 1973 the American team made detailed observations in the Cumberland Bay and Stromness Bay areas, supplemented by brief visits to the Bay of Isles and Bird Island. In Cumberland East Bay, on the Dartmouth Point promontory (now Greene Peninsula) they located a thrust contact between the Cumberland Bay and Sandebugten formations and from structural analyses showed that the deformation in the two divisions was broadly contemporaneous, despite the differences in style (Dalziel and others 1975)<ref name="Dalziel 1975">DALZIEL, I W D, DOTT, R H, WINN, R D, and BRUHN, R L. 1975. Tectonic Relations of South Georgia Island to the Southernmost Andes. ''Geological Society of America Bulletin'', '''86''', 1034–1040.</ref>. An assessment of palaeocurrent indicators showed dispersal towards the north-west in the Cumberland Bay Formation, but a more complicated pattern in the Sandebugten Formation dominated by a south-directed component; the structural restoration of the data was detailed by Dott (1974)<ref name="Dott 1974">DOTT, R H. 1974. Paleocurrent analysis of severely deformed flysch-type strata — A case study from South Georgia island. ''Journal of Sedimentary Petrology'', '''44''', 1166–1173.</ref>. From a regional perspective, the American team brought the advantage of direct familiarity with the likely correlative geology in the extreme south of South America. This allowed the development of a regional model for the origin of South Georgia (and the South American correlatives) in a marginal basin lying between the continental margin and a rifted continental sliver carrying a calc-alkaline volcanic arc. Sediment was derived from both sides of the basin, with deformation initiated by basin closure and the resulting arc-continent collision (Dalziel and others 1975<ref name="Dalziel 1975"></ref>; Winn 1978).<ref name="Winn 1978">WINN, R D. 1978. Upper Mesozoic flysch of Tierra del Fuego and South Georgia Island: A sedimentological approach to lithosphere plate restoration. ''Geological Society of America Bulletin'', '''89''', 533–547.</ref> This interpretation brought South Georgia geology squarely into the plate tectonic era.

	Pettigrew spent the 1972–73 austral summer on a detailed investigation of the geology of Annenkov Island, submitting his report (Pettigrew 1981)<ref name="Pettigrew 1981">PETTIGREW, T H. 1981. The geology of Annenkov Island. ''British Antarctic Survey Bulletin'', '''53''', 213–254. </ref> for publication in July 1975. Two members of an Annenkov Island Formation were recognized and had experienced only very minor deformation, allowing a sedimentary thickness of about 2000 m to be measured. A Lower Tuff Member comprised mostly interbedded tuff and tuffaceous mudstone; an Upper Breccia Member comprised mostly volcaniclastic breccia and sandstone. The lower member is the most fossiliferous although preservation is not good. The assemblage of bivalves, ammonites, fish fragments plant fossils etc., as described by Wilckens (1932<ref name="Wilckens 1932">WILCKENS, O. 1932. Fossilien und Gesteine von Süd Georgien. ''Scientific Results of the Norwegian Antarctic Expedition 1927–1928'', '''8'''. I Kommisjon Hos Jacob Dybwad, Oslo.</ref>, 1937<ref name="Wilckens 1937">WILCKENS, O. 1937. Geologische Ergebnisse der Deutschen Süd Georgien Expedition Dr Kohl-Larsen 1928–29. ''Geologische Rundschau'', '''28''', 127–128.</ref>, 1947)<ref name="Wilckens 1947">WILCKENS, O. 1947. Paläontologische und geologische Ergebnisse der Reise von Kohl-Larsen (1928–29) nach Süd Georgien. Abhandlungen der Senckenbergischen Naturforschenden Gesellschaft, 474, 66 pp.</ref> was confirmed, with an additional Early Cretaceous belemnite fauna recovered from the upper member (Pettigrew and Willey (1975)<ref name="Pettigrew and Willey 1975">PETTIGREW, T H, and WILLEY, L E. 1975. Belemnite fragments from Annenkov Island. ''British Antarctic Survey Bulletin'', '''40''', 33–36.</ref>. Both members contain rare interbedded basaltic lavas and are cut by a range of basaltic and andesitic minor intrusions. Pettigrew described the Annenkov Island succession as representing parts of a volcanic island arc and marginal basin and, in collaboration with M. Suarez (Instituto de Investigaciones Geológicas de Chile), developed a regional model in those terms incorporating South Georgia and the southern Andes (Suarez and Pettigrew 1976)<ref name="Suarez and Pettigrew 1976">SUAREZ, M, and PETTIGREW, T H. 1976. An Upper Mesozoic island-arc–back-arc system in the southern Andes and South Georgia. ''Geological Magazine'', 113, 305-328.</ref>.		Pettigrew spent the 1972–73 austral summer on a detailed investigation of the geology of Annenkov Island, submitting his report (Pettigrew 1981)<ref name="Pettigrew 1981">PETTIGREW, T H. 1981. The geology of Annenkov Island. ''British Antarctic Survey Bulletin'', '''53''', 213–254. </ref> for publication in July 1975. Two members of an Annenkov Island Formation were recognized and had experienced only very minor deformation, allowing a sedimentary thickness of about 2000 m to be measured. A Lower Tuff Member comprised mostly interbedded tuff and tuffaceous mudstone; an Upper Breccia Member comprised mostly volcaniclastic breccia and sandstone. The lower member is the most fossiliferous although preservation is not good. The assemblage of bivalves, ammonites, fish fragments plant fossils etc., as described by Wilckens (1932<ref name="Wilckens 1932">WILCKENS, O. 1932. Fossilien und Gesteine von Süd Georgien. ''Scientific Results of the Norwegian Antarctic Expedition 1927–1928'', '''8'''. I Kommisjon Hos Jacob Dybwad, Oslo.</ref>, 1937<ref name="Wilckens 1937">WILCKENS, O. 1937. Geologische Ergebnisse der Deutschen Süd Georgien Expedition Dr Kohl-Larsen 1928–29. ''Geologische Rundschau'', '''28''', 127–128.</ref>, 1947)<ref name="Wilckens 1947">WILCKENS, O. 1947. Paläontologische und geologische Ergebnisse der Reise von Kohl-Larsen (1928–29) nach Süd Georgien. Abhandlungen der Senckenbergischen Naturforschenden Gesellschaft, 474, 66 pp.</ref> was confirmed, with an additional Early Cretaceous belemnite fauna recovered from the upper member (Pettigrew and Willey (1975)<ref name="Pettigrew and Willey 1975">PETTIGREW, T H, and WILLEY, L E. 1975. Belemnite fragments from Annenkov Island. ''British Antarctic Survey Bulletin'', '''40''', 33–36.</ref>. Both members contain rare interbedded basaltic lavas and are cut by a range of basaltic and andesitic minor intrusions. Pettigrew described the Annenkov Island succession as representing parts of a volcanic island arc and marginal basin and, in collaboration with M. Suarez (Instituto de Investigaciones Geológicas de Chile), developed a regional model in those terms incorporating South Georgia and the southern Andes (Suarez and Pettigrew 1976)<ref name="Suarez and Pettigrew 1976">SUAREZ, M, and PETTIGREW, T H. 1976. An Upper Mesozoic island-arc–back-arc system in the southern Andes and South Georgia. ''Geological Magazine'', 113, 305-328.</ref>.

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	During the 1972–73 austral summer Clayton worked around the Bay of Isles, in the north-west of South Georgia; during the following summer, 1973–74, he extended his mapping across to the south coast of the island, in the Ice Fjord to King Haakon Bay area, accompanied by R N Mortimore. All of this area comprised part of the outcrop of the Cumberland Bay Formation. Detailed sedimentological analysis of the turbidite succession focussed particularly on relative proximality indicators (Mortimore 1979<ref name="Mortimore 1979">MORTIMORE, R N. 1979. Distal and proximal turbidites at Nilse Hullet, western South Georgia. ''British Antarctic Survey Bulletin'', 47, 117–128.</ref>; Clayton 1982a)<ref name="Clayton 1982a">CLAYTON, R A S. 1982a. The geology of north-western South Georgia: II. Sedimentology. ''British Antarctic Survey Bulletin'', '''51''', 55–78.</ref>, with a qualitative assessment of the detrital composition and subsequent alteration of the wacke-type sandstones during diagenesis and low-grade metamorphism (Clayton 1982b). Large-scale close to open folds were shown to be asymmetric and locally overturned towards the north, with a pervasive axial planar cleavage (Clayton 1983)<ref name="Clayton 1983">CLAYTON, R A S. 1983. The geology of north-western South Georgia: IV. Structural Geology. British Antarctic Survey Bulletin, 52, 187–204.</ref>. Stereographic analysis suggested that a second phase of open folding had affected the main structures and cleavage, whilst subsequent minor structures were recognised locally. In a more wide-ranging study, Clayton (1982c)<ref name="Clayton 1982c">CLAYTON, R A S. 1982c. A preliminary investigation of the geochemistry of greywackes from South Georgia. ''British Antarctic Survey Bulletin'', 51, 89–109.</ref> compared the whole-rock geochemistry of the Cumberland Bay Formation sandstones in the north-west of South Georgia, to that found in other parts of its outcrop, and extended the comparison to the Sandebugten Formation and Cooper Bay area, utilising specimens collected by Skidmore and Stone. All four of Clayton’s papers had been submitted for publication between November 1975 and July 1976.		During the 1972–73 austral summer Clayton worked around the Bay of Isles, in the north-west of South Georgia; during the following summer, 1973–74, he extended his mapping across to the south coast of the island, in the Ice Fjord to King Haakon Bay area, accompanied by R N Mortimore. All of this area comprised part of the outcrop of the Cumberland Bay Formation. Detailed sedimentological analysis of the turbidite succession focussed particularly on relative proximality indicators (Mortimore 1979<ref name="Mortimore 1979">MORTIMORE, R N. 1979. Distal and proximal turbidites at Nilse Hullet, western South Georgia. ''British Antarctic Survey Bulletin'', 47, 117–128.</ref>; Clayton 1982a)<ref name="Clayton 1982a">CLAYTON, R A S. 1982a. The geology of north-western South Georgia: II. Sedimentology. ''British Antarctic Survey Bulletin'', '''51''', 55–78.</ref>, with a qualitative assessment of the detrital composition and subsequent alteration of the wacke-type sandstones during diagenesis and low-grade metamorphism (Clayton 1982b). Large-scale close to open folds were shown to be asymmetric and locally overturned towards the north, with a pervasive axial planar cleavage (Clayton 1983)<ref name="Clayton 1983">CLAYTON, R A S. 1983. The geology of north-western South Georgia: IV. Structural Geology. British Antarctic Survey Bulletin, 52, 187–204.</ref>. Stereographic analysis suggested that a second phase of open folding had affected the main structures and cleavage, whilst subsequent minor structures were recognised locally. In a more wide-ranging study, Clayton (1982c)<ref name="Clayton 1982c">CLAYTON, R A S. 1982c. A preliminary investigation of the geochemistry of greywackes from South Georgia. ''British Antarctic Survey Bulletin'', 51, 89–109.</ref> compared the whole-rock geochemistry of the Cumberland Bay Formation sandstones in the north-west of South Georgia, to that found in other parts of its outcrop, and extended the comparison to the Sandebugten Formation and Cooper Bay area, utilising specimens collected by Skidmore and Stone. All four of Clayton’s papers had been submitted for publication between November 1975 and July 1976.

	Stone had also returned to South Georgia for the 1973–74 austral summer, extending his work on the north–east coast southwards to Iris Bay and Cooper Bay; some additional infill work was completed at St Andrews Bay and on the south side of Royal Bay. The polyphase folding of the Cumberland Bay Formation to the south-east of Royal Bay was established (Stone 1980)<ref name="Stone 1980">~~STONE, P. 1980. The Geology of South Georgia: IV. Barff Peninsula and Royal Bay areas. ''British Antarctic Survey Scientific Reports'', No. 96, 45 pp + 8 plates.~~</ref>, with an early suite of minor folds thought to pre-date the main, large scale structures that continued the trends seen elsewhere in the island, here with hinges trending NW–SE. The two fold sets were axially co-planar so that a slaty cleavage was cut by a closely sub-parallel micro-crenulation cleavage. A second, locally cross-cutting crenulation cleavage was associated with minor overturned folds.		Stone had also returned to South Georgia for the 1973–74 austral summer, extending his work on the north–east coast southwards to Iris Bay and Cooper Bay; some additional infill work was completed at St Andrews Bay and on the south side of Royal Bay. The polyphase folding of the Cumberland Bay Formation to the south-east of Royal Bay was established (Stone 1980)<ref name="Stone 1980"></ref>, with an early suite of minor folds thought to pre-date the main, large scale structures that continued the trends seen elsewhere in the island, here with hinges trending NW–SE. The two fold sets were axially co-planar so that a slaty cleavage was cut by a closely sub-parallel micro-crenulation cleavage. A second, locally cross-cutting crenulation cleavage was associated with minor overturned folds.

	Farther south, in the Cooper Bay area, deformation proved to be more intense, with an apparently thinly-bedded turbidite succession converted into a series of schistose rocks, slates and cataclasites. Within the metasedimentary succession were widespread boudinaged sheets of a pervasively altered, but originally doleritic intrusive rock. Stone (1982)<ref name="Stone 1982">STONE, P. 1982. Geological observations in the Cooper Bay — Wirik Bay area, South Georgia. ''British Antarctic Survey Bulletin'', '''51''', 43–53.</ref> — a paper submitted for publication in October 1975 — defined the metasedimentary succession as the Cooper Bay Formation and described its polyphase deformation. The earliest small-scale folds, with an associated slaty cleavage, were identified from their interference patterns with a series of tight, minor folds with an axial planar crenulation cleavage. The latter was then folded into large-scale, upright folds to which a steeply inclined, second crenulation cleavage was axial planar; all of these structures were cross-cut by a range of minor, late and locally developed folds and crenulations. At the south-western margin of its outcrop, the structures affecting the Cooper Bay Formation merged into a polyphase, mylonitic shear zone that separated the metasedimentary rocks from Trendall’s (1959)<ref name="Trendall 1959">TRENDALL, A F. 1959. The Geology of South Georgia: II. ''Falkland Islands Dependencies Survey Scientific Reports'', No.19, 47 pp, 5 plates, fold-out map.</ref> South-eastern Igneous Complex.		Farther south, in the Cooper Bay area, deformation proved to be more intense, with an apparently thinly-bedded turbidite succession converted into a series of schistose rocks, slates and cataclasites. Within the metasedimentary succession were widespread boudinaged sheets of a pervasively altered, but originally doleritic intrusive rock. Stone (1982)<ref name="Stone 1982">STONE, P. 1982. Geological observations in the Cooper Bay — Wirik Bay area, South Georgia. ''British Antarctic Survey Bulletin'', '''51''', 43–53.</ref> — a paper submitted for publication in October 1975 — defined the metasedimentary succession as the Cooper Bay Formation and described its polyphase deformation. The earliest small-scale folds, with an associated slaty cleavage, were identified from their interference patterns with a series of tight, minor folds with an axial planar crenulation cleavage. The latter was then folded into large-scale, upright folds to which a steeply inclined, second crenulation cleavage was axial planar; all of these structures were cross-cut by a range of minor, late and locally developed folds and crenulations. At the south-western margin of its outcrop, the structures affecting the Cooper Bay Formation merged into a polyphase, mylonitic shear zone that separated the metasedimentary rocks from Trendall’s (1959)<ref name="Trendall 1959">TRENDALL, A F. 1959. The Geology of South Georgia: II. ''Falkland Islands Dependencies Survey Scientific Reports'', No.19, 47 pp, 5 plates, fold-out map.</ref> South-eastern Igneous Complex.

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