Mr Mark Bourne

Postgraduate Student

Email:	mark.bourne@earth.ox.ac.uk
TEL:	+44 (1865) 282112
FAX:	+44 (1865) 272072
Homepage:	http://www.earth.ox.ac.uk/~markb

Research Profile

My research attempts to understand how the Earth's field has behaved in the past and the implications of such behaviour on our understanding of the processes that control its generation.

Geomagnetic excursions mark periods when the variation in the direction and intensity of the Earth's magnetic field greatly exceeds that of normal secular variation, and at times the field approaches a 'reversed state' before returning to a 'normal state'. Approximately 12 excursions of the Earth's magnetic field have been claimed to have occurred since the last full geomagnetic reversal at 780 ka, though the absolute chronology of these is uncertain.

Most recently I have been working on obtaining high-resolution records of the Laschamp (41 ka) and Blake (125 ka) excursions from Ocean Drilling Program (ODP) Sites 1061 & 1062 from Leg 172 on the Blake-Bahama Outer Ridge.

To understand the temporal behaviour of the geomagnetic field from palaeomagnetic records, the sedimentation rate must be determined. Therefore, part of my work has been to develop a method by which sedimentation rate can be constrained. This uses the concentration of the isotope ²³⁰Th in the sediment as a proxy for sedimentation rate. This uses the assumption that ²³⁰Th is supplied at a constant rate from the water column to the sea-floor.

In the future, I hope to investigate the possibility of using magnetic excursions as a correlatory tool for climatic records from terrestrial, marine and ice cores.

Teaching Profile

Demonstrating

Practical Sessions

3rd Year Atmosphere & Hydrosphere
(Prof. Gideon Henderson)

Field-Trips

1st year field-course in Pembrokeshire, Wales, UK
(Dr Conall Mac Niocaill)

Tutoring

Palaeomagnetism & Geomagnetism

Electricity and Magnetism (1st year course)
(Prof. Barry Parsons)

Selected Publications

Pre-prints and data available on personal homepage.

Bourne, MD, Thomas, AL, Mac Niocaill, C, Henderson GM, (2012) Improved determination of marine sedimentation rates using ²³⁰Th_xs, Geochemistry, Geophysics, Geosystems, 13, Q09017, DOI:10.1029/2012GC004295

Bourne, M, Mac Niocaill, C, Thomas, AL, Knudsen, MF, Henderson GM, (2012) Rapid directional changes associated with a 6.5 kyr-long Blake geomagnetic excursion at the Blake-Bahama Outer Ridge, Earth and Planetary Science Letters, 333-334, pp21-34, DOI:10.1016/j.epsl.2012.04.017

Other Information

Member of the Oxford Palaeomagnetism & Rock Magnetism and Climotope Research Groups