Determination of basinwide paleocurrent patterns in a shale succession from anisotropy of magnetic susceptibility (AMS): A case study of the Mid-Proterozoic Newland Formation, Montana

Journal Article · Wed Sep 01 00:00:00 EDT 1993 · Journal of Sedimentary Petrology; (United States)

OSTI ID:6054115

Schieber, J; Ellwood, B B ^[1]

---

1. Univ. of Texas, Arlington, TX (United States). Dept. of Geology

In shales of the Mid-Proterozoic Newland Formation, magnetic fabrics can be used as indicators of paleoflow direction. The long axis of the anisotropy of magnetic susceptibility (AMS) ellipsoid parallels paleoflow and is inclined in the upcurrent direction (Schieber and Ellwood 1988). To apply the AMS paleocurrent method to shales on a basinwide scale, oriented samples from the two members of the Newland Formation and its lateral equivalents were collected over the entire southeastern Belt basin. For the lower member of the Newland Formation the data show a parallel-bipolar and north-south-oriented paleoflow pattern. The pattern for the upper member of the Newland Formation is more complex: it indicates the presence of a northern and southern shoreline from where sediment is transferred deeper into the basin (parallel-unimodal pattern), as well as a central zone of overlap with a parallel-bipolar pattern. The results of the study show that AMS-based paleocurrent patterns support paleogeographic reconstructions based on stratigraphic and sedimentologic studies, and that tectonic deformation did not significantly alter primary fabrics. In the upper member of the Newland Formation, shore-normal vs. shore-oblique sediment transport for sandy and muddy storm deposits, respectively, is in agreement with a recently opposed depositional model for storm deposits.

• OSTI ID: 6054115
• Journal Information: Journal of Sedimentary Petrology; (United States), Vol. 63:5; ISSN 0022-4472
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
GEOLOGIC FORMATIONS
DEPOSITION
PALEOMAGNETISM
STRATIGRAPHY
MONTANA
GEOLOGIC HISTORY
GEOLOGIC MODELS
MAGNETIC SUSCEPTIBILITY
PRECAMBRIAN ERA
SHALES
DEVELOPED COUNTRIES
GEOLOGIC AGES
GEOLOGY
MAGNETIC PROPERTIES
MAGNETISM
NORTH AMERICA
PHYSICAL PROPERTIES
ROCKS
SEDIMENTARY ROCKS
USA
580000* - Geosciences