Paleomagnetic dating of burial diagenesis in Mississippian carbonates, Utah

Abstract

[1] The objective of this study is to test models for the origin of widespread secondary magnetizations in the Mississippian Deseret Limestone. The Delle Phosphatic Member of the Deseret Limestone is a source rock for hydrocarbons, and modeling studies indicate that it entered the oil window in the Early Cretaceous during the Sevier orogeny. Paleomagnetic and rock magnetic results from the Deseret Limestone and the stratigraphically equivalent Chainman Shale in central and western Utah indicate that the units contain two ancient magnetizations residing in magnetite. Burial temperatures are too low for the magnetizations to be thermoviscous in origin, and they are interpreted to be chemical remanent magnetizations (CRMs) 18 O) and petrographic analyses suggest that externally derived fluids did not alter these rocks. This CRM was acquired at the beginning of the oil window and is interpreted to be the result of burial diagenesis of organic matter. A second younger CRM in western central Utah is apparently postfolding and is probably Late Cretaceous to early Tertiary in age. On the basis of the thermal modeling, the timing overlaps with the oil window. These results are consistent with a connection between organic matter maturation and remagnetization. Modeling of the smectite-to-illite transformation in the Deseret Limestone suggests a mean age prior to acquisition of both CRMs, although the range for illitization overlaps with the Triassic to Jurassic CRM. The results of this study support the hypothesis that pervasive CRMs can be related to burial diagenetic processes. In addition, paleomagnetism can be used to determine the timing of such processes, which can benefit hydrocarbon exploration efforts.

Magnetic inference of in situ open microcracks in sandstone samples from the Taiwan Chelungpu Fault Drilling Project (TCDP)

“…Two hypotheses are commonly put forward to explain chemical magnetic remagnetizations (CRM). Diagenetic reactions that destabilize clay minerals or organic matter during burial temperature increase and release Fe in solution (Katz et al, 1998;Katz et al, 2000;Blumstein et al, 2004). The second hypothesis appeals for more exotic fluids associated to large-scale migrations of orogenic fluids (Oliver, 1992) or water table fluids (Garven, 1995).…”

The Timing of Diagenesis and Thermal Maturation of the Cretaceous Marias River Shale, Disturbed Belt, Montana

“…Katz et al, 2000) or maturation of organic matter (e.g. Banerjee et al, 1997;Blumstein et al, 2004) by burial alone. Several models for the origin of the CRM may be considered, including the migration of externally derived orogenic fluids (Oliver, 1992;Sears, 2001).…”

Remagnetization and chemical alteration of sedimentary rocks

“…Lu et al 1991;Hirt et al 1993;Katz et al 1998Katz et al , 2000Gill et al 2002;Woods et al 2002;Zegers et al 2003;Blumstein et al 2004;Moreau et al 2005;Tohver et al 2008). Many of these studies incorporated presence/absence tests (e.g.…”

“…7) is not related to syndeformational orogenic fluids (Fruit et al 1995). A study of the Mississippian Desert Limestone and Chainman Shale (Blumstein et al 2004), source rocks in western Utah, found a Jurassic CRM that was interpreted to have formed as a result of the maturation of organic matter based on the overlap between the timing of CRM acquisition and the timing of oil generation from modelling studies (Fig. 8).…”