Rock magnetic properties across the Paleocene-Eocene Thermal Maximum in Marlborough, New Zealand

V. VILLASANTE-MARCOS, C. HOLLIS, G.R. DICKENS, M.J. NICOLO

Abstract


Rock magnetic properties have been investigated across the Paleocene-Eocene Thermal Maximum (PETM) in three uplifted sections of Paleogene marine sedimentary rocks in Marlborough, South Island, New Zealand. The sections are exposed along Mead Stream, Dee Stream and Muzzle Stream and represent a depth transect up a continental margin from an upper slope to an outer shelf. Sampling was focused on rock beds previously examined for their biostratigraphy and stable carbon isotope (d13C) composition, and where a prominent clay-rich interval referred to as Dee Marl marks the initial 80-100 kyr of the PETM. Measured magnetic properties include bulk magnetic susceptibility, hysteresis cycles and isothermal remanent magnetization (IRM) acquisition and back-demagnetization curves. A strong inverse correlation between magnetic susceptibility and bulk carbonate d13C is found across the PETM such that Dee Marl has low d13C and high magnetic susceptibility. At Mead Stream this interval also contains increased saturation-IRM, and thus ferromagnetic content. Rock magnetic behaviour across PETM is best explained by an increase in terrigenous discharge. This inference has been made previously for PETM intervals in New Zealand and elsewhere, although with different proxies. Increased terrigenous discharge probably signifies an acceleration of the hydrological and weathering cycles. Some changes in magnetic phases could also reflect a drop in redox conditions, which could represent higher sedimentation rates, greater input of organic carbon, dysoxic bottom waters, or a combination of all three. A drop in redox conditions has been inferred for other marine sections spanning the PETM.

Keywords


Magnetic properties; Paleocene-Eocene Thermal Maximum; Terrigenous input; Continental weathering

Full Text:

PDF


DOI: http://dx.doi.org/10.1344/105.000000280

Refbacks

  • There are currently no refbacks.




Geoscience e-Journals

 

Previous

 

Random

 

Next

 

List

 

Creative Commons License
This work is licensed under a Creative Commons Attribution-ShareAlike License.
Geologica Acta (ISSN-1695-6133)
Biblioteca de Geologia (UB-CSIC) | Facultat de Ciències de la Terra, Martí i Franquès s/n 08028 Barcelona | Spain
Phone: +34 93 403 19 89 | Fax: +34 93 402 14 21 | E-mail: geologica-acta@ictja.csic.es
RCUB revistesub@ub.edu Avís Legal RCUB Universitat de Barcelona