The geology of eastern and central Alexander Island, Antarctica
A brief history of the discovery of Alexander
Island, Antarctica, is given.
The physiography in the area is consistent with
the present polar environment superimposed on an ancient
The LeMay Formation was deposited in a deep
water environment and forms a low-grade metamorphic
"basement" for younger rocks. Within this formation a
neritic fossil assemblage, possibly deposited in an
accretionary basin in an arc-trench gap, dates at least
part of the formation as late Triassic in age. Polyphase
deformation affects most of the LeMay Formation, with
non-sequence ophiolites and stratigraphical relationships
suggesting that subduction processes were active in the
area in pre-Upper Jurassic times.
The fossiliferous Upper Jurassic Fossil Bluff
Formation is unconformable on the LeMay Formation, but
the two formations are usually separated by a large fault
zone. A southerly-prograding delta system depositing
sediment into a longitudinally-elongated basin is envisaged
for the Fossil Bluff Formation. Additionally, large
slump structures provide evidence of palaeoslopes within
the basin. Both slu~ps and clastic dykes within this thick
formation point to an unstable depositional environment.
A volcanic sequence of ?Upper Cretaceous age in
the Walton Mountains is also unconformable on the LeMay
Formation. Calc-alkaline intrusive rocks also exposed in
the Walton Mountains may represent plutonic equivalents of
the volcanic sequence.
Local stratigraphical correlation is possible but
correlation with more distant localities is tenuous. The
Alexander Island-Palmer Land area gives a good crosssection
through a Mesozoic--Cenozoic volcanic arc--fore arc