I recently finished my PhD at the IRM working on the magnetic properties of lake sediments from Illinois and Minnesota. Interpreting sediment-magnetic variations in terms of climate change involves a three step process:First one has to characterize the magnetic component of the sediment in terms of abundance, particle size and mineralogy. Since most lake sediments contain only very low concetrations (often ppm-range) of iron-bearing minerals and most of the particles of interest are quite small (smaller than 1 micron), this task is best accomplished by a combination of indirect magnetic measurements. I have my set of personal favorites, that are fast, cheap and can give you a general idea of whats going on (sometimes). Based on these initial results it is often possible to concentrate on a few samples to figure out what's going on.
Next, it helps to understand the processes that caused the observed changes. Some of them, such as erosion rates, reductive dissolution, dilution by organic matter etc., are probably fairly obvious. Others, such as the differences between slopewash and eolian dust input are harder to figure out (but those are the ones that keep us in business). It often helps - I hate to admit it - to have some non-magnetic data too. That's where collegues come in handy with all their knowledge about water chemistry, sedimentology, palynology, the life cycles of Physocypria globula etc..
Finally, once all this is figured out, one can think about the climatic changes that could be the reason for all the variations observed in the sediments, and then it might be the time to publish some wiggles.
More details about magnetic variations, climatic change and why magnetite knows about the climate you can check out my thesis or the papers we published on the sediment-magnetic records of Pittsburg Basin and Kirchner Marsh. If you still don't have enough you can have a look at some of my abstracts.
