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Carbonate-argillaceous laminate lithofacies, Nonesuch Formation.

Detailed Description

Photomicrographs and cathodoluminescence (CL) images of the carbonate-argillaceous laminite lithofacies, Nonesuch Formation, Wisconsin.

Figure 8 from Stewart, E.K., and Mauk, J.L., 2017,

Photomicrographs and cathodoluminescence (CL) images of the carbonate-argillaceous laminite lithofacies. The sedimentary matrix is made up of silty clay and carbonate laminae. Clay is dark and platy. Molar-tooth (MT) spar infills molar-tooth cracks, is present as laminae within the sedimentary matrix, and forms blobs within the sedimentary matrix. A. Vertical crack infilled by MT spar. Note the ptygmatic folds of the crack align with laminae boundaries and changes in laminae lithology and thickness. laminae deflect both up and down around the edges of the crack, and a fine clay layer is aligned tangential to the crack boundary. Silt grains are locally mixed with MT spar within the crack. Scale bar is ∼100 µm. B. Vertical crack filled with MT spar. Note deflection of the surrounding sedimentary matrix around the crack and sharp boundary between the MT spar and surrounding matrix. Scale bar is ∼100 µm. C. Horizontal carbonate (light colored) and silty clay (dark colored) laminae. Carbonate laminae include fine-grained carbonate, MT spar, and lesser silt and clay. Clay laminae include patches of MT spar, indicated by white arrows labeled 1. Notice the prominent carbonate lamination with abundant MT spar in the center of the image appears to load down into underlying laminae, deflecting clay, indicated by black arrow labeled 2. Scale bar is ∼200 µm. Box locates image shown in (D) D. Close-up of carbonate lamination shown in (C). The prominent carbonate lamination includes fine-grained carbonate, smaller, equigranular MT spar, and lesser silt-sized quartz. Scale bar is ∼200 µm. E. Arrow points to MT spar forming blobs within the sedimentary matrix. Note uniform size and shape of spar. Scale bar is ∼100 µm. F. MT spar. Note the uniform size and planar boundaries of the crystals. Scale bar is ∼50 µm. G - H. CL image of MT calcitespar within sedimentary matrix (G) and within crack (H). Note MT calcite spar is characterized by a luminescent, subrounded core with uniform shape and size, and dull, angular overgrowths. I. Line drawing of MT spar within box show in (H). Outlines show subrounded MT cores.


Public Domain.

Stewart, E.K., and Mauk, J.L., 2017, doi:10.1016/j.precamres.2017.03.023.
Stewart, K.L., and Mauk, J.L., 2017, Sedimentology, sequence-stratigraphy, and geochemical variations in the Mesoproterozoic Nonesuch Formation, northern Wisconsin, USA: Precambrian Research, 294, 111-132,