Volcanic stratigraphy of Hannah Point, Livingston Island, South Shetland Islands, Antarctica

• Main Authors: Pallàs i Serra, Raimon, Soriano, C., Zheng, X., Sàbat i Montserrat, Francesc, Casas Tuset, Josep Maria
• Format: Article in Journal/Newspaper
• Language: English
• Published: Universitat de Barcelona (UB). Institut de Cièncias de la Terra Jaume Almera (ICTJA) 1999
• Subjects: Roques volcàniques; Estratigrafia; Livingston (Shetland del Sud : Illa); Antàrtida; Volcanic rocks; Stratigraphic geology; Livingston Island (South Shetland Islands); Antarctica; Antarctic; The Antarctic; Antarctic Peninsula; South Shetland Islands; Livingston Island; Hannah; Hannah Point; Antarc*
• Online Access: http://hdl.handle.net/2445/33154

The Upper Cretaceous volcanic succession of Hannah Point is the best exposure of the Antarctic Peninsula Volcanic Group on L ivingston Island. The aim of the present paper is to contribute to the characterisation of the stratigr a p hy and petrogr a p hy of this little studied succession, and briefly discuss some aspects of the eru p t ive style of its volcanism. The succession is about 470 m thick and is here subdivided into five lithostratigraphic units (A to E from base to top). Unit A, approximately 120 m thick, is mainly composed of polymict clast-supported volcaniclastic breccias and also includes a dacitic lava laye r. Interstratified in the breccias of this unit, there is a thin laminated devitrified layer which shows some degree of welding. Unit B, approx imately 70 m thick, is almost entirely composed of volcaniclastic breccias, and includes a volcaniclastic conglomerate laye r. Breccias in this unit can be subdivided into two distinct types; polymict clast-supported breccias, and monomict matrix-supported breccias rich in juvenile components and displaying incipient welding. Unit C, about 65 m thick, is mainly composed of basaltic lavas, which are interlayered with minor vo lcaniclastic breccias. Unit D, approximately 65 m thick, is lithologically similar to unit B, composed of an alternation of polymict clasts upported breccias and matrix-supported breccias, and includes a volcaniclastic conglomerate laye r. Unit E, about 150 m thick, is mainly formed of thick andesitic lava layers. Minor basaltic dykes and a few normal faults cut the succession, and the contact betwe e n units A and B can be interpreted both as an unconformity or a fault. The matrix-supported breccias included in the succession of Hannah Point have high contents of juvenile components and incipient welding, which suggest that part of the succession is the result of pyroclastic fragmentation and emplacement from pyroclastic flows. In contrast, the polymict clast-supported breccias suggest reworking of previous deposits and deposition ...