Magnetic anomalies in Bahia Esperanza: a window of magmatic arc intrusions and glacier erosion over the northeastern Antarctic Peninsula

• Published in: Tectonophysics
• Main Authors: Galindo Zaldívar, Jesús, Ruiz Constán, Ana, Pedrera Parias, Antonio, Ghidella, Marta, Montes Santiago, Manuel Jesús, Nozal Martín, Francisco de Borja, Rodríguez Fernández, Luis Roberto
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2012
• Subjects: basic and intermediate intrusive rocks; Pacific Margin Anomaly; field magnetic observations; glacier erosion; Bahía Esperanza; Antártida; Antarctic; The Antarctic; Antarctic Peninsula; Pacific; Esperanza; Nobby; bahía Esperanza; Mount Flora; Basement Glacier; Nobby Nunatak; Antarc*
• Online Access: http://hdl.handle.net/10261/276859; https://doi.org/10.1016/j.tecto.2012.09.008

Bahia Esperanza, constituting the NE tip of the Antarctic Peninsula, is made up of Paleozoic clastic sedimentary rocks overlain by a Jurassic volcano-sedimentary series and intruded by Cretaceous gabbros and diorites. The area is located along the southern part of the Pacific Margin magnetic anomaly belt. Field magnetic researches during February 2010 contribute to determining the deep geometry of the intermediate and basic intrusive rocks. Moreover, the new field data help constrain the regional Pacific Margin Anomaly, characterized up to now only by aeromagnetic and marine data. Field magnetic susceptibility measurements of intrusive intermediate and basic rocks, responsible for magnetic anomalies, ranges from 0.5 × 10− 3 SI in diorites to values between 0.75 × 10− 3 SI and 1.3 × 10− 3 SI in gabbros. In addition, a significant remanent magnetism should also have contributed to the anomalies. The regional magnetic anomaly is characterized by a westward increase from 100 nT up to 750 nT, associated with large intrusive diorite bodies. They probably underlie most of the western slopes of Mount Flora. Gabbros in the Nobby Nunatak determine local residual rough anomalies that extend northwards and westwards, pointing to the irregular geometry of the top of the basic rocks bodies below the Pirámide Peak Glacier. However, the southern and eastern boundaries with the Buenos Aires Glacier are sharp related to deep glacier incision. As a result of the glacier dynamics, magnetic anomalies are also detected north of the Nobby Nunatak due to the extension of the anomalous body and the presence of gabbro blocks in the moraines. The Bahia Esperanza region is a key area where onshore field geological and magnetic research allows us to constrain the shape of the crustal igneous intrusions and the basement glacier geometry, providing accurate data that complete regional aeromagnetic research Departamento de Geodinámica, Universidad de Granada, España Instituto Andaluz de Ciencias de la Tierra, Consejo Superior de ...