SPOILT FOR CHOICE: A GEOLOGY FIELD CAMP ON AN ACTIVE PLATE BOUNDARY

The New Zealand geology field camp is spoilt for choice. It is located on an active plate boundary that changes character progressively along strike from west-directed subduction in the north, through strike-slip in South Island to east-directed subduction in the south. Compression from the subduction trench close offshore on the eastern side of North Island shows as uplifting shorelines, growing folds and strike-slip faulting. To the west, back-arc extension results in active volcanism and related geothermal phenomena. In north-eastern South Island, a zone of sub-parallel strike-slip faults has resulted from the oblique collision of the Pacific Plate with the Indo-Australian Plate and this transpressional character continues along the 600-km length of the Alpine Fault plate boundary. Faulting and uplift associated with large earthquakes has produced a range of progressively-displaced geomorphic features the most spectacular of which are flights of offset river terraces. On the eastern, uplifted side of the Alpine Fault, the Triassic-Jurassic greywackes of the Southern Alps reach their greatest elevation near Mt Cook where the uplift rate peaks at about 11 m/kyr.

The philosophy of this field camp is that geological education is not complete without field-based, practical training and experience: no text or virtual reality conveys the same understanding as straddling an active plate boundary or walking on a glacier. Thus, this field camp is designed to give students practical experience in as many geological environments as possible while still maintaining the basic aim of a thorough training in structural geological mapping.

Before tackling mapping projects in complexly folded and faulted rocks, students spend a week of basic mapping in a fragment of ancient Gondwanaland where Paleozoic terranes are overlain by less-deformed Cretaceous-Tertiary rocks. The major part of tectonic geomorphology is in North Island with surveys to determine the geometry and rates of uplift and tilting of raised Holocene shorelines (quantitative) and observations of active folding and strike-slip faulting effects. Volcanic geology includes and concentrates on tephrostratigraphy to the stage that students are able to identify composition, eruptive types and history by detailed examination of tephra sections.