Crimites elkoensis Miller et al

Crimites elkoensis Miller et al., 1957, is an adrianitid goniatite from the Lower Permian (Wolfcampian = Sakmarian) of eastern Nevada. The genus Crimites has a cosmopolitan distribution in the Permian (Sakmarian to Kazanian). Several species of this genus occur in Lower Permian deposits in Nevada (Miller et al., 1957). Although other ammonoids are more common at this site, Crimites elkoensis is the most abundant goniatite.

The shell of Crimites elkoensis is relatively small, globular, and involute, with reticulate ornament and four or five constrictions per whorl (Fig. 9.1A). The whorl width is commonly greater than the whorl height. The suture is relatively simple, with about 14 lobes (Fig. 9.1B).

Specimens were collected near Buck Mountain in east-central Nevada (Figs. 9.2, 9.3). The strata containing ammonoids are part of the Lower Permian Arcturus Formation and are located on the south side of the mountain in three

Fig. 9.1 Crimites elkoensis Miller et al., 1957, SUI39000, Rib Hill-Arcturus Formation, Lower Permian, Buck Mountain, Nevada. A. Apertural view and right side. Maximum diameter = 8.8mm. B. Partial suture of the same specimen at shell diameter = 8.8mm. From Lee (1975: 105).
Fig. 9.2 Localities of Crimites elkoensis Miller et al., 1957, and Cravenoceras fayettevillae Gordon, 1965. Map of the USA with asterisks indicating the sites at Buck Mountain, Nevada, and Fayetteville, Arkansas.

PERIOD

N. AMERICAN SERIES

EUROPEAN SERIES

EASTERN NEVADA

northwest

ARKANSAS

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Ely Group

Tomera Formation

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Moorefield Formation

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Ctiainman Formation

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Boone Formation

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Fig. 9.3 Stratigraphie column for Buck Mountain, Nevada, and Fayettevillae, Arkansas. The specimens of Crimites elkoensis Miller et al., 1957, are from the Areturus Group (Permian). The Areturus Group has been referred to by various names, as shown. The specimens of Cravenoceras fayettevillae Gordon, 1965, are from the lower Fayetteville Shale (Mississippian). Modified From Tomastik (1981:18) and Manger (2004: 5, 14).

ridges just east of Beck Springs. The fossils, which include marine invertebrates and vertebrates, occur in carbonate and phosphate concretions. Prolecanitid ammo-noids are the most abundant fossils, followed by goniatites and nautiloids. During deposition of these strata, the lower part of the water column may have been anoxic and slightly acidic (Landman et al., 2006). These conditions would have allowed for rapid phosphatization of cameral membranes in ammonoids very early in diagenesis (Briggs, 2003; Landman et al., 2006). The originally aragonitic shell material of the goniatites was transformed into calcite, while the originally organic membranes were replaced by phosphate.

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