Geology and palaeontology of the Hindon Maar Complex: A Miocene terrestrial fossil Lagerstätte in southern New Zealand

Highlights • Hindon Maar Complex is a new mid-Miocene Fossil-Lagerstatte in New Zealand. • Anoxia in maar lakes allowed exquisite preservation of plant and animal fossils. • The biota is from a lake and Nothofagus/podocarp/mixed broadleaf forest ecosystem. • Fossils record high diversity at humid, warm Southern Hemisphere mid-latitudes. Abstract This paper highlights the geology, biodiversity and palaeoecology of the Hindon Maar Complex, the second Miocene Konservat-Lagerstatte to be described from New Zealand. The Lagerstatte comprises four partly eroded maar-diatreme volcanoes, with three craters filled by biogenic and highly fossiliferous lacustrine sediments. The exceptionally well-preserved and diverse biota from the site is derived from a mid-latitude Southern Hemisphere lake-forest palaeoecosystem, including many fossil taxa not previously reported from the Southern Hemisphere. The most common macrofossils are leaves of Nothofagus, but the flora also includes conifers, cycads, monocots (such as Ripogonum and palms), together with Lauraceae, Myrtaceae and Araliaceae leaves and flowers. The small maar lakes were surrounded by Nothofagus/podocarp/mixed broadleaf forest growing under humid, warm temperate to subtropical conditions. The fossil fauna comprises insects in the orders Odonata, Hemiptera, Thysanoptera, Coleoptera, Diptera, Hymenoptera and Trichoptera, and the fish assemblage includes a non-migratory species of the Southern Hemisphere Galaxias (Galaxiidae) and a significant new record of the freshwater eel Anguilla (Anguillidae). The fossil assemblage also includes the first pre-Quaternary bird feathers from New Zealand and abundant coprolites derived from fish and volant birds, presumably waterfowl. Palynomorph analysis and a 40Ar/39Ar age of 14.6 Ma obtained from basanite associated with the maar complex indicate that the Hindon Maar Complex is of mid-Miocene age (Langhian; New Zealand local stage: Lillburnian). It thus provides a new and unique perspective on Neogene terrestrial biodiversity and biogeography in the Australasian region, around the end of the mid-Miocene thermal optimum and prior to late Miocene–Pleistocene climate cooling episodes when many warm-temperate and subtropical forest components became extinct in New Zealand.