Planktonic foraminiferal biostratigraphy (Altonian‐Tongaporutuan Stages, Miocene) at DSDP Site 593, Challenger Plateau, Tasman Sea

Abstract

The planktonic foraminiferal biostratigraphy of cores 22-45 from DSDP Site 593 (Challenger Plateau, Tasman Sea) is related to New Zealand onshore Miocene stages (Altonian-Tongaporutuan). An excellent succession of Altonian events at the site allows the stage to be divided into three informal zones. Upper Clifdenian and some lower Lillburnian horizons are highly condensed, or missing; this possible hiatus near 393.5 m is at a prominent lithostratigraphic boundary. A pronounced increase in representation of dextrally coiled Globorotalia miotumida immediately above the base of Tongaporutuan Stage in two onshore sequences is also recorded at Site 593. It may provide a useful criterion for the boundary in oceanic sequences lacking the Bolivinita quadrilatera group, as well as defining a basal Tongaporutuan zone. The highest occurrence of Globoquadrina dehiscens near the top of core 28 is well defined and possibly provides a useful intrastage event.

Integrated stratigraphy of the lower Altonian (Early Miocene) sequence at Tangakaka Stream, East Cape, New Zealand

“…It is rare in most Tangakaka collections in which Globorotalia incognita or Globorotalia zealandica is common. Scott et al (1990) placed the FAD of Paragloborotalia bella in upper Altonian, above the FAD of Globorotalia zealandica; however, Scott (1992) recorded P. cf. bella from core 45, section 3, 70-72 cm in the lower Altonian Globorotalia incognita Zone at DSDP Site 593.…”

“…However, when associated with Globorotalia praescitula, its occurrence usefully identifies horizons below the FAD of Globorotalia zealandica. This relationship defines the lower boundary of the Globorotalia incognita Zone of Scott (1992).…”

“…However, the high sediment flux at the site greatly magnifies the record of bioevents, particularly in the Globorotalia incognita Zone, and about its boundary with the Globorotalia zealandica Zone. This facilitates detailed study of the nature and position of foraminiferal bioevents in the lower Altonian Stage and assessment of the precision at which the boundary between the two lower zones (Scott 1992) is resolvable. The diverse deep-water assemblages in the Tangakaka sequence also allow an evaluation of the stratigraphy of some benthic foraminiferal events that Hornibrook et al (1989) cited as significant near the base of the Altonian Stage.…”

“…From a study of planktonic foraminiferal assemblages at DSDP Site 593 (Tasman Sea), Scott (1992) subdivided the Altonian Stage into three zones. The lower and middle units (Globorotalia incognita and Globorotalia zealandica Zones) are recognised in Tangakaka Stream (Fig.…”

Early Miocene magnetostratigraphy and a new palaeomagnetic pole position from New Zealand

“…Most samples yielded abundant quantities of foraminifera. The Altonian Stage was subdivided into three planktic foraminiferal zones by Scott (1992), the lower Altonian (Globorotalia incognita zone) is represented by the interval from the base of the stage to the entry of Globorotalia zealandica. The lowest sample examined in the section (f29) from the hard layer at the top of the limestone yielded no biostratigraphically useful taxa.…”