New Zealand Journal of Geology and Geophysics abstracts

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Paleoenvironmental changes across the Cretaceous/Tertiary boundary at Flaxbourne River and Woodside Creek, eastern Marlborough, New Zealand

C. J. Hollis¹
C. P. Strong¹
K. A. Rodgers²
K. M. Rogers¹

¹Institute of Geological & Nuclear Sciences
P.O. Box 30 368
Lower Hutt, New Zealand
email: c.hollis@gns.cri.nz

²Australian Museum
College St
Sydney, NSW, Australia

Abstract  An integrated study of variation in siliceous microfossils, lithofacies, and other geochemical guides to environmental conditions through the Cretaceous/Tertiary (K/T) boundary transition at Flaxbourne River and Woodside Creek, coastal eastern Marlborough, indicates that the K/T impact disrupted oceanic conditions along the continental margin of eastern New Zealand for c. 1 m.y. Initial effects of the K/T event were a major reduction in carbonate production, associated with calcareous plankton extinctions, and significant increases in terrigenous clay and biogenic silica content. An absence of radiolarian extinctions or significant negative excursions in paleo-productivity indicators (Ba, δ¹³C) at the boundary, followed by rapid increases in the abundance of diatoms and spumellarian radiolarians, indicate that biogenic silica production partly compensated for the collapse in calcareous plankton. The earliest Paleocene recovery of calcareous plankton was short-lived, giving way to a progressive increase in siliceous plankton abundance over c. 500 000 yr, which culminated in a c. 400 000 yr episode of peak biogenic silica production. The dominance of siliceous facies, coupled with the abundance of diatoms and spumellarian radiolarians, indicates climatic or oceanic conditions were significantly cooler than in the Late Cretaceous. Stepped increases in biogenic silica production show c. 100 000 yr periodicity, suggesting that early Paleocene lithofacies changes were influenced by climate forcing agents at the eccentricity bandwidth.

Keywords  Mead Hill Formation; Paleocene; K/T boundary; radiolarians; diatoms; foraminifera; biostratigraphy; paleoecology; geochemistry; silica; barium; carbon isotopes

G02029 Received 14 June 2002; accepted 6 March 2003; published 30 June 2003
New Zealand Journal of Geology & Geophysics, 2003, Vol. 46: 177-197
0028-8306/03/4602-0177 $7.00/0 © The Royal Society of New Zealand 2003

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