Brooks B. Ellwood1,
Rex E. Crick2
(1) Louisiana State University, Baton Rouge, LA
(2) University of Texas at Arlington, Arlington, TX
Abstract: The MagnetoSusceptibility Event and Cyclostratigraphy (MSEC) method used in high-resolution chronocorrelation
We have been using magnetic susceptibility (MS) measurements of Paleozoic marine rocks, in conjunction with biostratigraphic control, for high-resolution chronocorrelation and have named the method MagnetoSusceptibility Event and Cyclostratigraphy (MSEC). MS is a measure of the concentration of magnetic grains that have been eroded and brought into the marine system as part of the detrital fraction of lithogenic material. This process is due primarily to eustasy, climate and sea floor/basin subsidence. In those sections we have examined, MSEC trends of increasing MS magnitudes correlate well with episodes of regression, while trends of decreasing MS magnitudes correlate with episodes of transgression. Exceptions are individual event, thinly bedded silt or sand layers that have several possible origins but usually show high MS values.
The data presented will show the initial development of MSEC within the sub-Sahara region of southern Morocco. These results will be correlated with sections located in Europe and North America, including both pelagic and neritic environments. With high-resolution data sets, it now appears that MSEC provides better resolution than the associated biostratigraphy upon which it is dependent for temporal control. MSEC has the important advantage of being measurable in the field, on unoriented core or using cuttings, thus helping geologists to resolve ambiguities while on the outcrop or to establish correlations between wells where correlations may be ambiguous. One significant aspect of this work is the clear indication that MSEC results are facies independent. Note that MSEC can be applied to rocks of any age.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana