We have investigated the variability of the magnetic properties of surface sediments across eight Minnesota lake basins. The measured magnetic properties are controlled by the competing fluxes of allochthonous and autochthonous magnetic particles, and differ according to location in the basin. Shoreline sediments are dominated by detrital magnetic particles, whereas littoral and profundal sediments are characterized by a combination of bacterial

Both terrestrial and aquatic ecosystems should respond to abrupt climate changes such as those that affected the mid-continent of North America during the Holocene. A variety of paleorecords indicate that the onset of prolonged dry conditions in this region occurred as rapidly as 300 years during the early Holocene, with a subsequent increase in moisture occurring rapidly in the late Holocene. Here, we report a 9500 year multiproxy sediment record

Droughts are recurrent features in sedimentary records at the prairie-forest ecotone of northern U.S.A. It is therefore important to understand the duration of such events, as well as their severity and consequences beyond the century-scale instrumental record. The existing drought records can be complemented with additional proxies that clearly document the interactions between external factors and the depositional environment. Here we attempt to

The magnetic recordings preserved in calcite speleothems and the nature of their constituent magnetic minerals hold enormous potential for paleomagnetic and paleoenvironmental reconstructions. Speleothems lock in magnetization instantly, are not affected by post-depositional effects, and can be dated with high precision. The natural remanence in speleothems is carried mainly by magnetite, and the main remanence acquisition mechanism is depositional,

We have developed a quantification method that uses mainly room temperature rock-magnetic measurements to calculate concentrations of ferrimagnetic particles in sediments. Our method uses saturation magnetization (Ms) as a total ferrimagnetic concentration proxy, the saturation remanence ratio (Mrs/Ms) as a magnetic grain-size proxy, the anhysteretic remanence ratio (Xa/Mrs) to estimate inter-particle magnetostatic interactions, and the normalized

We explore the effects of sampling density, signal/noise ratios, and position-dependent measurement errors on deconvolution calculations for u-channel magnetometer data, using a combination of experimental and numerical approaches. Experiments involve a synthetic sample set made by setting hydraulic cement in a 30-cm u-channel and slicing the hardened material into ~2-cm lengths, and a natural lake-sediment u-channel sample. The cement segments can

A major challenge in groundwater and petroleum modeling is how to represent the diagenesis effect "sensu lato" and its associated features (e.g., karst cavities, porosity and permeability characteristics). Both geometrical descriptions and genesis are necessary for modeling diagenetic features, because they allow the restitution of phenomenon in subsurface settings where they cannot be fully observed. This study focuses on flank-margin caves developed