Palaemagnetism Current Projects
The researchers in the lab are actively conducting research projects, some of which are listed below:
Further Refinement of India? Proterozoic Paleogeography and Geochronology. (J. Meert)
This project will both complement and expand our current knowledge of Proterozoic paleogeography and, in particular, the supercontinents of Gondwana, Rodinia and Columbia. It will provide first order constraints for snowball earth climate models, the Ediacaran Cambrian radiation and the loci of non-renewable mineral deposits that typically form during continental collision and breakup. It targets two of the so-called Purana basins in India along with dikes intruding the Dharwar, Singhbhum and Bundelkhand cratons.
Ediacaran Paleomagnetism and geochronology of eastern Baltica: A key to paleogeography and climatic history of the continent. (J. Meert)
This project aims to partially solve one of the major conundrums of Neoproterozoic paleogeography. It targets Neoproterozoic sequences from the margins of Baltica in the central and southern Ural mountains. These sequences are either well-dated or potentially dateable and contain suitable targets for paleomagnetic study. The work will provide a near continuous record of motion for the 650-530 Ma interval and allow us to assess myriad climatic, evolutionary and magnetic field models.
Time-averaged Earth Magnetic Field During the Last 2 Ma on Equatorial Africa. (N.D. Opdyke)
This project is part of the Time-averaged Field Initiative (TAFI). It is a follow-up to work on equatorial lavas from Ecuador, South America.
Geomagnetic variability, paleoenvironmental change, and a tuned geologic timescale from Pacific Eocene-Paleocene sediments, IODP Expedition 320-321. (J.E.T. Channell)
Integrated Ocean Drilling Program (IODP) Expeditions 320 and 321 were part of a single drilling program that was designed to core thick sedimentary sections along a Pacific Equatorial Age Transect (PEAT). Each of the eight sites (Sites U1331–U1338) was selected to recover a portion of the interval spanning the Eocene through the Pleistocene. Multiple holes were cored at each site ensuring complete stratigraphic coverage and resulting in the recovery of over 6 km of core. The shipboard magnetic records from these sites indicate that the sediments have recorded the paleomagnetic field with high fidelity, and the shipboard data indicate the potential of these sediments for studies of geomagnetic field variability, paleoenvironmental change, chronostratigraphy, and Pacific plate kinematics and geodynamics. This project aims at addressing each of these topics through a collaborative effort. It will (1) refine the shipboard magnetostratigraphies by improving the placement of polarity reversal boundaries and resolving brief polarity subchrons and excursions; (2) generate long continuous relative geomagnetic intensity (RPI) and directional paleosecular variation (PSV) records; (3) construct high-resolution environmental magnetic records; (4) tune the geologic timescale over much of the Cenozoic by combining astronomical variations in physical and magnetic properties with the magnetostratigraphy and biostratigraphy constraints; and (5) improve the Pacific Plate apparent polar wander path (APWP) by integrating paleolatitudes estimated from PEAT sites with other Pacific paleomagnetic data.
Correlation of millennial-scale climate variability in the North Atlantic beyond the last glacial cycle. (J.E.T. Channell)
Age models for North Atlantic IODP sites (mainly from IODP Expedition 303) are built by tandem matching of relative paleointensity (RPI) and oxygen isotope data (δ18O) to reference records. Sedimentation is characterized by detrital layers that are detected by higher than background gamma-ray attenuation (GRA) density, peaks in X-ray fluorescence (XRF) indicators fordetrital carbonate (Ca/Sr) and detrital silicate (Si/Sr), and an ice-rafted debris (IRD) proxy (wt% >106 µm). The age model enables correlation of Site U1302/03 to IODP Site U1308 in the heart of the central Atlantic IRD belt where an age model and a similar set of detrital-layer proxies have already been derived. Ages of Heinrich (H) layers H1, H2, H4, H5 and H6 are within ~2 kyr at the two sites (H0, H3 and H5a are not observed at Site U1308), and agree with previous work at Orphan Knoll within ~3 kyr. At Site U1308, Brunhes detrital layers are restricted to peak glacials and glacial terminations back to marine isotope stage (MIS) 16 and have near-synchronous analogs at Site U1302/03. Detrital layers at Site U1302/03 are distributed throughout the record in both glacial and most interglacial stages. We distinguish Heinrich-like layers associated with IRD from detrital layers marked by multiple detrital-layer proxies (including Ca/Sr) but usually not associated with IRD, that may be attributed to lofted sediment derived from drainage and debris-flow events funneled down the nearby Northwest Atlantic Mid-Ocean Channel (NAMOC). The prominent detrital layers at Sites U1302/03 and U1308 can be correlated to millennial scale features in the Chinese speleothem (monsoon) record over the last 400 kyr, implying a link between monsoon precipitation and Laurentide Ice Sheet (LIS) instability. The detrital-layer stratigraphy at Site U1302/03 provides a long record of LIS dynamics against which other terrestrial and marine records can be compared.
Magnetic properties of Arctic sediments: implications for magnetic stratigraphy. (J.E.T. Channell)
Inclination patterns of natural remanent magnetization (NRM) in Quaternary sediment cores from the Arctic Ocean have been widely used for stratigraphic correlation and to determine age models, however, shallow and negative NRM inclinations in sediments deposited during the Brunhes Chron in the eastern Arctic Ocean appear to have a partly diagenetic origin. Rock magnetic and mineralogical studies demonstrate the presence of titanomagnetite and titanomaghemite. Thermal demagnetization of the NRM indicates that shallow and negative inclination components are largely “unblocked” below ~300°C, consistent with a titanomaghemite remanence carrier. Following earlier studies on the Mendeleev-Alpha Ridge, shallow and negative NRM inclination intervals in cores from the Lomonosov Ridge and Yermak Plateau are attributed to partial self-reversed chemical remanent magnetization (CRM) carried by titanomaghemite formed during sea-floor oxidation of host (detrital) titanomagnetite grains. Distortion of paleomagnetic records due to sea-floor maghematization appears to be important in the perennially ice covered western (Mendeleev-Alpha Ridge) and central Arctic Ocean (Lomonosov Ridge) and, to a lesser extent, near the ice edge (Yermak Plateau). On the Yermak Plateau, magnetic grain size parameters mimic the global benthic oxygen isotope record back to at least marine isotope stage 6, implying that magnetic grain size is sensitive to glacial-interglacial changes in bottom-current velocity and/or detrital provenance.