Role of lithology in the complex structure of Dromedary Massif, Antarctica
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Dromedary Massif of Southern Victoria Land, Antarctica is an anomalously complex area situated at the southern margin of the regionally simple, Bonney Pluton dominated, structure of the Dry Valleys area. A detailed structural study of Dromedary Massif has highlight the importance of lithological effects deformation under amphibolite facies conditions.
Dromedary Massif basement rocks are dominated by metasediment in which three mappable units are identified: Psammitic unit, Interlayered unit and Marble unit. The nomenclature is based on lithological content rather than the previous nomenclature which infers the presence of primary sedimentary structures. Metasediment was intruded first by a series of mafic plutons, Dromedary gabbro, Renegar diorite, Glee hybrid intrusives, and nepheline syenite. Felsic plutons intruded later (Camp One foliated-granite, Penny Hill foliated-grained, Gloomy Hill foliated-granite). All the major lithological groups have been subjected to upper amphibolite fades metamorphism. Numerous granitic dikes intruded the massif at all stages of its structural history and have also been subjected to varying degrees of deformation.
Three phases of deformation are recognizable in metasediment using structural elements such as the overprinting of lineations and foliation. The first phase produced a pervasive foliation in the metasediments. The Dromedary Massif is dominated by phase two structures the onset of which second phase is marked by intrusion of mafic plutons during a phase of regional flattening. This was followed by intrusion of a suite of felsic plutons. During regional deformation, metasediment behaved as an incompetent material flowing around relatively competent igneous plutons to produce complex macroscopic and mesoscopic structure. Dromedary Basement structure was further complicated later by intrusion of the Bonney pluton to the north. Flow between two closely spaced plutons on the eastern side of the massif during the same phase as the Bonney pluton intrusion resulted developement of an 8km long by lkm wide NW-SE trending high strain zone. Strain in Dromedary gabbro was locally accommodated along granite dike horizons and produced a spectacularly and complexly deformed granite-dike mylonite. The third deformation phase is recorded by localised crenulation development. Two late-stage major northeast trending faults cross-cut the central and western part of the massif respectively.
The complex macroscopic structures of Dromedary Massif predate the generally simpler structures of the northern Dry Valleys area which are related to the intrusion of the Bonney pluton. The complex structure is due to macroscopic inhomogeneous flow during regional deformation.
Dromedary Massif basement rocks are dominated by metasediment in which three mappable units are identified: Psammitic unit, Interlayered unit and Marble unit. The nomenclature is based on lithological content rather than the previous nomenclature which infers the presence of primary sedimentary structures. Metasediment was intruded first by a series of mafic plutons, Dromedary gabbro, Renegar diorite, Glee hybrid intrusives, and nepheline syenite. Felsic plutons intruded later (Camp One foliated-granite, Penny Hill foliated-grained, Gloomy Hill foliated-granite). All the major lithological groups have been subjected to upper amphibolite fades metamorphism. Numerous granitic dikes intruded the massif at all stages of its structural history and have also been subjected to varying degrees of deformation.
Three phases of deformation are recognizable in metasediment using structural elements such as the overprinting of lineations and foliation. The first phase produced a pervasive foliation in the metasediments. The Dromedary Massif is dominated by phase two structures the onset of which second phase is marked by intrusion of mafic plutons during a phase of regional flattening. This was followed by intrusion of a suite of felsic plutons. During regional deformation, metasediment behaved as an incompetent material flowing around relatively competent igneous plutons to produce complex macroscopic and mesoscopic structure. Dromedary Basement structure was further complicated later by intrusion of the Bonney pluton to the north. Flow between two closely spaced plutons on the eastern side of the massif during the same phase as the Bonney pluton intrusion resulted developement of an 8km long by lkm wide NW-SE trending high strain zone. Strain in Dromedary gabbro was locally accommodated along granite dike horizons and produced a spectacularly and complexly deformed granite-dike mylonite. The third deformation phase is recorded by localised crenulation development. Two late-stage major northeast trending faults cross-cut the central and western part of the massif respectively.
The complex macroscopic structures of Dromedary Massif predate the generally simpler structures of the northern Dry Valleys area which are related to the intrusion of the Bonney pluton. The complex structure is due to macroscopic inhomogeneous flow during regional deformation.
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101 p. : ill. (some col.), maps (some col.) ; 30 cm.
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1990Walcott
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Walcott, Rachel Clare, 1966-, “Role of lithology in the complex structure of Dromedary Massif, Antarctica,” Otago Geology Theses, accessed July 20, 2026, https://theses.otagogeology.org.nz/items/show/249.