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A British Antarctic Survey (BAS) geological field party (Teal Riley – geologist; Catrin Thomas – field assistant) were put ashore on Joinville Island, at the northern tip of the Antarctic Peninsula for 3 weeks in February – March. The purpose of the visit was to make a geological map of the southern coast of Joinville Island as part of a broader programme to update the geological map of the Scotia Sea area. The geology of Joinville Island is akin to the northern part of the Antarctic Peninsula (Graham Land) and distinct to the islands to the east of the Antarctic Peninsula.
Washing up
Inside the pyramid tent drying boots and gloves
The BAS field party worked from a fixed camp site on the Mount Alexander peninsula and mapped the geology of the local area. The geology is dominated by granite-type rocks, which intrude sedimentary and volcanic rocks of Mesozoic age. The oldest rocks of the area are metamorphosed sedimentary rocks of the Trinity Peninsula Group. Volcanic rocks are also common, which are Middle Jurassic in age (170 million years old). The volcanic rocks include lavas and pyroclastic ash deposits and point to the existence of highly explosive volcanic eruptions. The youngest sedimentary rocks of the area are a thick (minimum 700 feet) succession of laminated mudstones and siltstones, which are Cretaceous in age. The sediments would have formed in a deep basin and are marked by rare fragments of ammonite and bivalve fossils.
Mount Alexander camp site
Looking towards camp site from Mount Alexander
The granite intrudes all the sedimentary-volcanic rocks of the area and is therefore the youngest geological event on Joinville Island.
Geologist Teal Riley checking out his rocks!
The weather on Joinville Island was generally cloudy and characterised by local katabatic winds, but for much of the 3 weeks the weather was good enough for geological survey work.
The BAS field party were extracted from Joinville Island on the 9th March in difficult conditions, but efficient helo tasking involving four loads led to a smooth and rapid return to ship.
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