Major Projects at the Paleomagnetics Laboratory

 

Crustal Accretion within Icelandic Flexure Zones: Analog for Fast-Spread Oceanic Ridges

Jeff Karson (Duke University) and I initiated a new study during Summer 2003 within the Blödous flexure zone in northern Iceland. There we are studing the interplay between magmatic and structural events related to flexure formation. Iceland's flexure zones may represent near-axis structure preserved through ridge jumping. Paradoxically, given Iceland's position on the slow-spread Mid Atlantic Ridge, these flexure zones are similar to the structure seen at some cross sectional exposures of fast-spread crust produced at magmatically robust ridges, such as the East Pacific Rise. Much like our studies in Cyprus and at Hess Deep, we are using paleomagnetic and structural techniques to determine the relative timing of intrusive events and structural tilting within the flexure zones.

 

Paleomagnetic Constraints on Generation of Ocean Crust at Overlapping Spreading Centers and Microplate Rotations, Pito Deep, South Pacific

In 2005, we used the submersible Alvin and remotely operated robot Jason II to collect 69 fully oriented blocks from the steep escarpments bounding the Pito Deep, located along the eastern margin of the Easter microplate. With this sample set we will be able to assess the relative role of structural rotations at this superfast spreading segment of the East Pacific Rise as well as the role of vertical axis rotations implied by current models for microplate development. Addtionally, we are using anisotropy of magnetic susceptibility to determine the possible contribution of horizontal flow of magma near ridge segment boundaries.

 

 Paleomagnetic, Geochemical and Chronological Distinction of ~17-20 Ma Tuffs of the Colorado River Extensional Corridor, Western Arizona, Southeastern California and Southern Nevada

We are using paleomagnetism as part of a much larger study to understand the stratigraphic relationships between various regionally exposed ash flow tuff units in and around the Colorado River extensional corridor.

 

 

Paleomagnetic Evidence for Deformation of Macquarie Island and Its Relationship to the Indian Ocean Crust

We are currently conducting a survey of magnetic remanence in lava flows and dikes exposed on Macquarie Island in the Indian Ocean. We hope to be able to use these data to comment on deformation models for the ophiolite and its relationship to surrounding Indian Ocean crust.

 

Paleomagnetic Constraints on Tectonic Tilting of Young Ocean Crust at the Hess Deep,Equatorial Pacific

In March-April, 1999, we collected a large suite of oriented dikes and gabbros exposed along the steep cliff faces of the Hess Deep. The samples were collected in situ, using the mechanical arms of the submersible ALVIN and its GEOCOMPASS. In this study, we are attempting to assess the role of tectonic tilting at oceanic ridges.

 

 

 

 

Ridge Crest Magmatic and Structural Development of the Troodos Ophiolite, Cyprus

For many years, we have used paleomagnetism as an important tool in deducing the relative role of magmatic, structural and alteration events within the Troodos ophiolite, Cyprus. Through this work, we have been able to figure out the magnitudes of extensional tilting, the timing of this tilting, the relative timing between structural development and black smoker activity at the fossil ridge crest and the dynamics of dike injection. Much of this work has been done in conjuction with Dr. Jeff Gee of Scripps Institution of Oceanography..

 

Some Recent Related Publications:

Varga, R.J., Faulds, J.E., Snee, L.W., Harlan, S.S. and Bettison-Varga, L., 2004, Miocene extension and extensional folding in an anticlinal segment of the Black Mountains accommodation zone, Colorado River extensional corridor, southwestern United States: Tectonics, v. 23, 19 p.

Varga, R.J., Karson, J.A., and Gee, J.S., 2004, Paleomagnetic constraints on deformation models for uppermost oceanic crust exposed at the Hess Deep Rift: Implications for Axial Processes at the East Pacific Rise: Journal of Geophysical Research, v. 109, 22 p.

Varga, R.J., 2004, The sheeted dike complex of the Troodos ophiolite and its role in understanding mid-ocean ridge processes, in Ophiolite Concept & the Evolution of Geological Thought, edited by Y. Dilek, and S. Newcomb, Geological Society of America Special Paper 173.

Welty, N. and Varga, R., 2003, Paleomagnetic investigations of Peach Springs Tuff (PST) and other Pre-Extensional Ignimbrites in the Colorado River Extensional Corridor, Laughlin, NV to Kingman, AZ: Geological Society of America Abstracts with Programs, Cordilleran Section Meeting.

Bagocius, S., Wiles, G. and Varga, R.J., 2002, The environmental magnetic record of the last glacial-interglacial transition from Ekurd's Pond, Urbana, Ohio: Geological Society of America Abstracts with Programs

Varga, R.J., Myers, E., Biga, J., Haverkamp, F., Faulds, J. and Snee, L., 2001, Paleomagnetic constraints on the stratigraphic and tectonic development of the Black Mountains accommodation zone in the Grasshopper Junction-western Cerbat Mtns. region: Geological Society of America Abstracts with Programs

Varga, R.J., Gee, J.S., Bettison-Varga, L., *Anderson, R.S. and *Johnson, C.L., 1999, Early establishment of seafloor hydrothermal systems during structural extension: Paleomagnetic evidence from the Troodos ophiolite, Cyprus: Earth & Planetary Science Letters, v. 171, p. 221-235.

Karson, J.A., Hurst, S.D., Klein, E.M., Gillis, K., Miller, J., Varga, R.J., et al., 1999, Large-scale ARGO II digital images of upper crustal structures at Hess Deep: Ridge Events, v. 10, n. 1, p. 29-32.

Varga, R.J. and Karson, J.A., 1999, Paleomagnetic investigation of tectonic tilting in upper oceanic crust, North Wall of the Hess Deep, Equatorial Pacific: EOS Transactions of the American Geophysical Union.

Faulds, J.E. and Varga, R.J., 1998, The role of accommodation zones and transfer zones in the regional segmentation of extended terranes: a review: in Faulds, J.E. and Stewart, J.H. (eds.), Accommodation zones and transfer zones: the significance and nature of large-scale segmentation in the Basin and Range: Geological Society of America Special Paper 323, p. 1-57.

Varga, R.J., Bettison-Varga, L., *Haverkamp, F., *Murrey, R., *Spring, S., *Wilds, N., Harlan, S. and Snee, L., 1998, Tertiary extensional and magmatic development of the Grasshopper Junction segment of the Black Mountains accommodation zone, W. Arizona: Geological Society of America Abstracts with Programs, v. 30, n. 7, p. 241.

Varga, R.J., Gee, J. and Staudigel, H., 1998, Dike surface lineations as magma flow indicators within the sheeted dike complex of the Troodos ophiolite, Cyprus: Journal of Geophysical Research, v. 103, p. 5241-5256.

*Selkin, P., Varga, R., and Crowley, P., 1997, Petrologic and structural constraints on the origin of foliated gabbro near Khandria, Troodos ophiolite, Cyprus: Geological Society of America Abstracts with Programs, v. 29, n. 1, p. 78.

*denotes student co-author