Gymnosperm woods from the Cretaceous (mid-Aptian) Cerro Negro Formation, Byers Peninsula, Livingston Island, Antarctica: the arborescent vegetation of a volcanic arc

Abstract

Silicified gymnosperm trunks usually more than 30cm in diameter and several metres in length occur abundantly in the lower part of the mid-Aptian Cerro Negro Formation, which crops out on Byers Peninsula, Livingston Island, northern Antarctic Peninsula. These fossil woods are found within silicic ignimbrites, tuffs and lapilli-tuffs interpreted as the product of hot pyroclastic flows, and in silicic and andesitic conglomerates interpreted as fluvially-reworked volcanic sediments. A detailed quantitative study of the wood taxonomy has revealed the presence of three form genera, Araucarioxylon,Podocarpoxylon , and Sahnioxylon. The former two genera represent the conifer families Araucariaceae and Podocarpaceae respectively and the latter probably belongs to the extinct gymnosperm order Bennettitales. These wood genera represent the remains of the arborescent vegetation, which grew on the margins of an active pyroclastic volcanic cone near the edge of the mid-Cretaceous Antarctic Circle (palaeolatitude 62°S).