Shackleton Limestone

Taylor Formation quartzite, hornfels, marble Shackleton Limestone Selborne Marble Archaeocyatha limestone, marble, conglomerate, quartzite... 

All investigators agree that the rocks of the Byrd Group were deposited during the Cambrian Period because the Shackleton Limestone as well as the Taylor Formation (in the Shackleton Glacier area) contain fossils of Cambrian age (Laird and Waterhouse 1962 Hill 1964a, b Palmer and Gatehouse 1972 Yochelson and Stump 1977 Debrenne and Kruse 1986). 

Rowell et al. (1988a) published excellent photographs of the shelly fauna and of eodiscoid and polymeroid trilobites of the Shackleton Limestone in the Churchill Mountains and at the head of the Beardmore Glacier where outcrops of the Shackleton Limestone were desaibed by RoweU and Rees (1989) from an area south of Ml Bowers (85°00 S, 164°05 E) on Buckley Island. 

The Selbome Marble in Table 5.1 consists of highly deformed and metamorphosed scapolite-bearing marbles interbedded with biotite schist and homfels that occur only at Cape Selbome and at the north side of Couzens Bay, both of which are located south of the mouth of the Byrd Glacier. The relation of the Selbome Marble to the Shackleton Limestone is uncertain because the two units are not in contact. Skinner (1964, 1965) suggested that the Selbome Marble is either a highly altered part of the Shackleton Limestone or is a marble-amphibolite complex of the Precambrian Nimrod Group. Stump (1980) who worked on the Shackleton Limestone at nearby Mount Madison favored the explanation that the Selbome Marble is a highly metamorphosed member of the Shackleton Limestone. 

The Shackleton Limestone is overlain by clastic sedimentary rocks that have been assigned to the Dick, Douglas, and Starshot formations. The Dick Formation is composed of siltstone, argillite, sandstone, and silty limestone. Rees et al. (1988) reported that sandstones of the Dick Formation are ripple-marked and cross-bedded and that interbedded shales contain rare mud-cracks. In addition, an outcrop of the Dick Formation located east of Mt. Dick (89°49 S, 159°32 E) and about 20 km south of the Byrd Glacier contains a lava flow that is 9 m thick and is composed of spilite (Skinner 1964, 1965). Rees et al. (1988) later interpreted this lava flow as a pillow basalt and noted that the contact between it and sedimentary rocks of the Byrd Group was covered by snow. They also reported that they had obtained a whole-rock K-Ar date of 586 20 Ma (Neoproterozoic), which is incompatible with the presence of Early Cambrian fossils in the underlying Shackleton Limestone. Therefore, Rees et al. (1988)... 

In addition, the U-Pb date of zircons in the gabbro of the Cotton Plateau (668 1 Ma) implies that Rodinia broke up somewhat later and that the rift valley between Laurentia and the East Antarctic craton began to trap sediment later than the previous interpretation of the evidence had indicated. The reassignment of the bulk of the Goldie Formation to the Starshot Formation of the Byrd Group also means that the contact between the inboard part of the Goldie Formation and the over-lying Shackleton Limestone is now presumed to be an unconformity. 

According to Myrow et al. (2002), the transition from the carbonate rocks of the Shackleton Limestone to the clastic rocks of the uppCT Byrd Group in the Holyoake-Cotton Plateau area (i.e., the Douglas, Dick, and Starshot formations) records the change from sedimentation along a passive continental margin to... 

The Shackleton Limestone of the Churchill Mountains south of the Byrd Glacier is tightly folded and was intruded by ... small plutons of hornblende granite, pyroxene-hornblende diorite or gabbro, and dikes of quartz porphyry, all probably related to the Hope Granite (Grindley and Laird 1969). Faure and Felder (1984) described and sampled a complex pegmatite that intruded the Shackleton Limestone on one of two... 

Fig. 5.10a Mt. Madison (80°27 S, 160°02 E) is located on the south side of the mouth of the Byrd Glacier. Its north-facing slope contains three small cirques that are separated from each other by two bedrock spurs which are composed of the Shackleton Limestone of the Byrd Group. Fig. 5.10b The crest of the western spur contains an outcrop of pegmatite composed of spodumene, lepidolite, bismuthinite, and tourmaline (Faure and Felder, 1984). The spur on which the pegmatite is located is marked by an x. This map is an excerpt of the topographic map Cape Selborne, Antarctica (SU 56-60/2) published in 1963 by the US Geological Survey in Washington, DC Photo G. Faure...

The Sr concentration of the Shackleton Limestone adjacent to the pegmatite is 179.3 ppm and its Sr/ Sr ratio is 0.70996 0.00031. The comparatively high value of the Sr/ Sr ratio of the Shackleton Limestone is consistent with the increase in this ratio in the oceans during the Cambrian Period which peaked during the late Middle Cambrain at about 0.7093 (Faure and Mensing 2005). 

Burgess CJ, Lammerink W (1979) Geology of the Shackleton Limestone (Cambrian) in the By rd Glacier area. New Zealand Antarctic Record 2(1) 12-16... 

Debrenne F, Kruse PD (1986) Shackleton Limestone archaeo-cyathids. Alcheringa 10 235-278... 

Hill D (1964b) Archaeocyatha from the Shackleton Limestone of the Ross System, Nimrod Glacier area, Antarctica. Roy Soc New Zealand Trans, Geol 2 137-146 lUGS (2002) International stratigraphic chart. Commission on the Geologic Map of the World, UNESCO, United Nations, New York... 

Rees MN, Pratt BR, RoweU AJ (1989) Early Cambrian reefs, reef complexes, and associated Uthofacies of the Shackleton Limestone, Transantarctic Mountains. Sedimentology 36 341-361... 

Rowell AJ, Rees MN (1989) Early Paleozoic history of the upper Beardmore Glacier area ImpUcations for a major Antarctic structural boundary within the Transantarctic Mountains. Antarctic Sci 1 249-260 Rowell AJ, Rees MN (1991) Setting and significance of the Shackleton Limestone, central Transantarctic Mountains. In Thomson MRA, Crame JA, Thomson JW (eds) Geological evolution of Antarctica. Cambridge University Press, Cambridge, pp 171-175... 

The isotope compositions of oxygen and carbon identify this specimen as amarine limestone of Cambrian age most likely derived from the Shackleton Limestone (Veizer and Hoefs 1976). However, the Sr/ Sr ratio is lower than Sr/ Sr ratio of marine strontium of... 

A large deposit of till at the base of Mt. Tuatara on the south side of the Byrd Glacier in Fig. 19.14 a few tens of meters above the present level of the glacier extends up the side of the mountains for about 100 m. The glacial polish of the Shackleton Limestone on Mt. Tuatara indicates that the level of the glacier in the past was several hundred meters above its present level. The elevation of the base of the deposit is about 300 m a.s.l. 

Fig. 19.13 The valley of the Byrd Glacier is a fault zone that separates two blocks of the Transantarctic Mountains. The northern block includes the Britannia Range which is composed of the Granite Harbor Intrusives overlain by sedimentary rocks of the Beacon Supergroup. The southern block is part of the Churchill Mountains which consist of the Shackleton Limestone and of the overlying Beacon Supergroup. The Byrd Glacier is about 30 km wide at Cape Selbourne and extends more than 200 km onto the polar plateau beyond the range of...

Fig. 19.14 A large deposit of yellowish till is exposed along the north-facing slope of Mt. Tuatara on the south side of the Byrd Glacier. The deposit extends from the present level of the glacier to about 100 m up the polished and striated slope of the Shackleton Limestone. The till was deposited by the Byrd Glacier at a time when it was several hundered meters thicker than it is at the present time. The glacier was wet-based at the time because the till displays features of soft-sediment deformation and includes a lenticular deposit of clasts at the base of the exposure indicating the action of glacial meltwater. The site was visited by G. Faure and R. Felder in December of 1978 (Photo by G. Faure)...

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