A magnetostratigraphic calibration of Middle Miocene through Pliocene dinoflagellate cyst and acritarch events in the Iceland Sea (Ocean Drilling Program Hole 907A)

Abstract

A detailed dinoflagellate cyst investigation of the almost continuous Middle Miocene through Pliocene of Ocean Drilling Program Hole 907A in the Iceland Sea has been conducted at 100-kyr resolution. The investigated section is well constrained by magnetostratigraphy, providing for the first time an independent temporal control on a succession of northern high-latitude dinoflagellate cyst bioevents. Based on the highest/lowest occurrences (HO/LO) and highest common occurrence (HCO) of 20 dinoflagellate cyst taxa and one acritarch species, 26 bioevents have been defined and compared with those recorded at selected DSDP, ODP, and IODP sites from the North Atlantic and contiguous seas, and in outcrops and boreholes from the onshore and offshore eastern U.S.A., and the North Sea and Mediterranean basins. Comparisons reveal near-synchronous HOs of the dinoflagellate cysts Batiacasphaera micropapillata (3.8-3.4 Ma, mid-Pliocene) and Reticulatosphaera actinocoronata (4.8-4.2 Ma, Lower Pliocene) across the Nordic Seas and North Atlantic, highlighting their value on a supraregional scale. This probably applies also to Hystrichosphaeropsis obscura (upper Tortonian), when excluding ODP Hole 907A where its sporadic upper stratigraphic range presumably relates to cooling in the early Tortonian. Over a broader time span within the upper Tortonian, the HO of Operculodinium piaseckii likely also permits correlation across the Nordic Seas and North Atlantic, and the HO of Labyrinthodinium truncatum appears useful in the Labrador and Nordic Seas. Biostratigraphic markers useful for regional rather than supraregional correlation are the HOs of Batiacasphaera hirsuta (c. 8.4 Ma, upper Tortonian) and Unipontidinium aquaeductus (c. 13.6-13.9 Ma, upper Langhian), the HCO of the acritarch Decahedrella martinheadii (c. 6.7-6.3 Ma, Messinian), and possibly the LO of Cerebrocysta irregulare sp. nov. (c. 13.8 Ma, uppermost Langhian) across the Nordic Seas. Since Habibacysta tectata, B. micropapillata, R. actinocoronata and D. martinheadii have been observed in the Arctic Ocean, they are potentially useful for high latitude correlations in the polar domain. The LOs of Habibacysta tectata and Unipontidinium aquaeductus suggest a mid-to late Langhian age (15.1-13.7 Ma) for deposits at the base of Hole 907A, thus providing new constraints on the age of basalts at the base of ODP Hole 907A. The stratigraphically important dinoflagellate cysts Cerebrocysta irregulare sp. nov., and Impagidinium elongatum sp. nov. are formally described.

Batiacasphaera bergenensis and Lavradosphaera elongata — New dinoflagellate cyst and acritarch species from the Miocene of the Iceland Sea (ODP Hole 907A)

“…Black stars: indicating the position of silicoflagellate events used for the interpretation of the paleomagnetic record by Channell et al (1999). Dashed black line: indicating the extrapolation of average sedimentation rates down-core (see Schreck et al, 2012 for details). Symbols: ①Epoch/subepoch, ②Age, ③lithological units and subunits identified (Shipboard Scientific Party, 1995).…”

“…The revised age model for Site 907 is based on magnetic polarity stratigraphy (Shipboard Scientific Party, 1995;Channell et al, 1999), but is independently supported by four silicoflagellate datums in the Miocene interval ( Fig. 2; see Channell et al, 1999;and Schreck et al, 2012 for detailed discussion of the age model). The ages of the polarity chron boundaries given by Channell et al (1999) have been updated to the ATNTS 2012 (Hilgen et al, 2012), and therefore, this age model allows assigning numerical ages for each sample and bioevent.…”

“…The residue has been mounted with glycerine jelly on microscope slides. The results of the detailed palynological investigation are published by Schreck et al (2012, and all slides are stored at the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany. The slides containing all illustrated specimens of Batiacasphaera bergenensis sp.…”

“…During a detailed palynological investigation on Neogene sediments of Iceland Sea ODP Hole 907A, more than 40 undescribed dinocyst and acritarch taxa have been recognized , and two potentially useful new dinocyst species have been described previously (Schreck et al, 2012). Herein we describe a new dinocyst species, Batiacasphaera bergenensis sp.…”

“…Bujak and Matsuoka, 1986;Head et al, 1989a;Manum et al, 1989;De Schepper et al, 2011;Schreck et al, 2012), whereas acritarchs have only been recently recognized as a useful microfossil group to tighten Neogene biostratigraphy in the high northern latitudes (e.g. Matthiessen et al, 2009b;Schreck et al, 2012;De Schepper and Head, 2013;Verhoeven et al, 2013).…”