Geological development of Heard Island, Central Kerguelen Plateau

• Published in: Australian Journal of Earth Sciences
• Main Authors: Duncan, RA, Quilty, PG, Barling, J, Fox, JM
• Format: Article in Journal/Newspaper
• Language: English
• Published: Taylor & Francis 2016
• Subjects: Earth Sciences; Geology; Geology not elsewhere classified; Kerguelen; Heard Island; Indian; Drygalski; McDonald Island; Big Ben; Laurens Peninsula; Mawson Peak; Mount Dixon
• Online Access: https://doi.org/10.1080/08120099.2016.1139000; http://ecite.utas.edu.au/111803

We report 40 Ar- 39 Ar laser step-heating age determinations on 15 stratigraphically controlled lava flows and intrusive rocks from Heard Island, Central Kerguelen Plateau (Indian Ocean). The island history began with uplift of pelagic limestone intruded by 22 Ma gabbro sills. Subaerial and wave erosion levelled the early island, producing an unconformity onto which pillow lavas, tuffaceous sediments and shallow-water, fossiliferous marine siltstone (Drygalski Formation) were deposited, beginning in late Miocene time. Two volcanic systems then formed in the late Quaternary. Big Ben dominates the larger southeast part of the island, while Mount Dixon occupies the northwest Laurens Peninsula. Feeder dykes and the early lava flows in both systems are 400200 ka. Lava flows with evolved compositions (trachytes, trachyandesites) erupted 10020 ka. Well-preserved parasitic cones exposed at low elevations are 1510 ka and younger. Mawson Peak, near the summit of Big Ben, has erupted lava flows as recently as 2007. Heard Island, and nearby active McDonald Island, are subaerial features of a larger Neogene volcanic region of Central Kerguelen Plateau that includes several large sea knolls and recently identified submarine fields of small cones. This broadly distributed volcanic activity is linked to incubation of plume material at the base of the nearly stationary overlying Central Kerguelen Plateau.