New Zealand Journal of Geology and Geophysics abstracts

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A Cretaceous - early Tertiary macrotidal estuarine-fluvial succession: Puponga Coal Measures in Whanganui Inlet, onshore Pakawau Sub-basin, northwest Nelson, New Zealand

A. BAL
D. W. LEWIS

Geology Department
University of Canterbury
Private Bag 4800
Christchurch, New Zealand

Abstract  Detailed lithofacies analysis of the Puponga Coal Measures Member along the western shore of the Whanganui Inlet, northwest Nelson, is based on five measured sections that incorporate parts of the interfingering and underlying North Cape Formation and overlying Farewell Formation. Two contrasting depositional systems, lithofacies Association A and B, are recognised on the basis of sedimentary structures, textures, paleocurrent data, and the local presence of coal and dinoflagellates.

Association A1-3, North Cape Formation, which includes the Puponga Coal Measures Member (Haumurian - Lower Teurian), represents a progradational sequence of estuarine, fluvial, floodplain, and mire deposits. Subenvironments include: high energy subtidal channels, upper-flow regime subtidal to intertidal sand shoals or flats, intertidal mixed sand/mud and mud flats, salt marsh, mires, fluvial distributary or crevasse channels and levees, and open/closed bays. The overall setting is a macrotidal estuary over which mires and fluvial deposits prograded.

An abrupt basinward shift in the depositional system is implied by lithofacies Association B, the Farewell Formation (Paleocene), that represents alluvial plain deposits. Association B is separated from the underlying Association A by an erosional (Lower Teurian) unconformity. This unconformity marks the Pakawau Group and Kapuni Group contact.

Keywords  Taranaki Basin; Pakawau Group; Kapuni Group; Puponga Coal Measures Member; Farewell Formation; North Cape Formation; sedimentology; stratigraphy; coal; facies associations; fluvial environments; estuarine environments; tidal environments; paleocurrents; Cretacteous-Tertiary boundary

New Zealand Journal of Geology and Geophysics, 1994, Vol. 37: 287-307

0028-8306/94/3703-0287 $2.50/0 (c) The Royal Society of New Zealand 1994

PDF file of entire paper: medium quality (8081K); (scanned from paper original: notes about this process)

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