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Shaly Packstone
Krause and Meyer (2004) reported a coarse, crinoidal, shaly packstone in many of Kentucky's Fort Payne buildups. Packstones are a type of limestone. They have less mud then a wackestone, but are grain supported like grainstones. Knox and Stapor (2003) did not treat this as a separate facies in Tennessee buildups, but it likely encompasses some of their heterolithic shale and limestone facies. Where present, the shaly packstone facies is generally thin, (0 to 1.5 ft) and drapes the green core shale (or heterolithic shale and limestone) facies (Fig. 1). The shaly packstone thickens downslope and pinches out upslope. It may contain very thin (inches) coarse, crinoidal wackestone beds or layers (Fig. 2) similar to those of the green core shale as defined here, or to the heterolithic shale and limestone facies of Knox and Stapor (2003). Rather than being part of the same bedding within the mound core, however, the base of this facies always has a sharp contact with the underlying green shales. Also, bedding within the facies is parallel to the scour and drape of the beds, rather than to the internal structure of the mound core. In fact, the shaly packstone facies may laterally truncate bedding in the underlying green core shale facies. The upper contact is always sharp, and in some places may be erosional, with the overlying massive wackestone facies.
Figure 1. Typical appearance of heterolithic shale and thin limestone in the shaly packstone facies of Fort Payne buildups.
GSC=Green core shale facies, SP= Shaly packestone facies, MW=Massive wackestone facies.
Echinoderms are the dominant faunal component of the shaly packstone facies, especially crinoid columnals in thin interbedded wackstone and packstone layers. Intact calyces and partially articulated arms and stalks are often encountered, but complete disarticulation is common as well (Krause and Meyer, 2004).
Picture under construction
Figure 2. Shaly packstone facies in Fort Payne buildups.
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