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Trilobite biostratigraphy of the Cambrian 5 and Drumian stages, Series 3 (Laurentian Delamaran, Topazan, and Marjuman stages, Lincolnian Series) of the lower Emigrant Formation at Clayton Ridge, Esmeralda County, Nevada

Published online by Cambridge University Press:  21 May 2018

Frederick A. Sundberg
Frederick A. Sundberg*
Affiliation:
821 E. Pine Ln., Show Low, Arizona 85901, 〈freddeb85@cableone.net〉
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Abstract

The Emigrant Formation at Clayton Ridge, Nevada, consists of 420 m of variably interbedded shale, siltstone, and limestone representing an outer shelf environment. It ranges in age from the youngest portion of the Dyeran Stage (Laurentian Waucoban Series; Cambrian Stage 4, Series 2) to Skullrockian Stage (Ibexian Series; Tremadocian Stage, Lower Ordovician). Consequently, it is condensed compared to other localities. For example, the age-equivalent succession in the House Range and the Wendover Range of Utah and Nevada, respectively, is seven times thicker.

The 100 m thick lower limestone and siltstone member of the Emigrant Formation at Clayton Ridge ranges in age from the Bolbolenellus euryparia/Nephrolenellus multinodus Zone (Laurentian Dyeran Stage) to the Cedaria brevifrons Zone (Laurentian Marjuman Stage; Drumian Stage; this study). The 40 trilobites described herein from two closely spaced sections of the lower member belong to the Glossopleura walcotti/Ptychagnostus praecurrens Zone (Laurentian Delamaran Stage; Stage 5), Ehmaniella Zone (Laurentian Topazan Stage; Stage 5), and Cedaria selwyni to C. brevifrons zones (Laurentian Marjuman Stage; Drumian Stage) zones. The lower Emigrant Formation is <10% as thick as age-equivalent age strata elsewhere in Nevada, California, and Utah. This condensed nature of the lower Emigrant Formation began with the flooding event at the beginning of the Oryctocephalus indicus biochron and the subsequent build-ups of the thick carbonate platforms to the south and northeast.

New species are Pagetia aspinosa, P. claytonensis, and Syspacephalus mccollumorum.

Type
Memoir
Information
Journal of Paleontology , Volume 92 , Supplement S76 , May 2018 , pp. 1 - 44
Copyright
Copyright © 2018, The Paleontological Society 

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References

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Locality register

The Split Mountain East Section is 1.6 km NE of Split Mountain, Clayton Ridge, NW 1/4 Sec. 31, T2S, R41E, on the Split Mountain 7.5’ topographic quadrangle map (U.S. Geological Survey, 1970, 1:24,000 scale); at ~37°43'27''N, 117°26'18''W, Esmeralda County, Nevada.Google Scholar
USNM locality 44109: 22 m above base of formation. Glossopleura walcotti/Ptychagnostus praecurrens Zone. Thin to medium bedded, laminated, dark gray (N3), silty limestone with yellowish gray (5Y7/2) to grayish orange (10YR7/4) silty beds. Collected June 1999. Pagetia aspinosa.Google Scholar
USNM locality 44110: 0.75 m above base of secondary section, 22.5 m above base of formation. Glossopleura walcotti/Ptychagnostus praecurrens Zone. Limestone, 20 cm bed, laminated, dark gray (N3) with yellowish gray (5Y7/2) to grayish orange (10YR7/4) silt layers. Collected November 2007. Pagetia aspinosa.Google Scholar
USNM locality 44111: 1.0 m above base of secondary section, 22.75 m above base of formation. Glossopleura walcotti/Ptychagnostus praecurrens Zone. Limestone, 10 cm lenticular bed, laminated, dark gray (N3) with yellowish gray (5Y7/2) to grayish orange (10YR7/4) silt layers. Collected November 2007. Pagetia aspinosa.Google Scholar
USNM locality 44112: 1.3 m above base of secondary section, 23.0 m above base of formation. Glossopleura walcotti/Ptychagnostus praecurrens Zone. Limestone, 10 cm bed, laminated, dark gray (N3) with yellowish gray (5Y7/2) to grayish orange (10YR7/4) silt layers. Pagetia aspinosa.Google Scholar
USNM locality 44113: 23.5 m above base of formation. Glossopleura walcotti/Ptychagnostus praecurrens Zone. Thin to medium bedded, laminated, dark gray (N3), silty limestone with yellowish gray (5Y7/2) to grayish orange (10YR7/4) silty beds. Collected June 1999 and July 2015. Achlysopsis brighamensis, Chancia maladensis, Pagetia aspinosa n. sp., Pentagnostus bonnerensis, Pentagnostus brighamensis, Syspacephalus mccollumorum n. sp.Google Scholar
USNM locality 44114: 24.0 m above base of formation. Glossopleura walcotti/Ptychagnostus praecurrens Zone. Thin to medium bedded, laminated, dark gray (N3), silty limestone with yellowish gray (5Y7/2) to grayish orange (10YR7/4) silty beds. Collected June 1999. Achlysopsis brighamensis, Glossopleura walcotti, Pagetia aspinosa n. sp., Pentagnostus brighamensis, Syspacephalus mccollumorum n. sp., Zacanthoides sp. indet.Google Scholar
USNM locality 44115: 2.5 m above base of secondary section, 24.25 m above base of formation. Glossopleura walcotti/Ptychagnostus praecurrens Zone. Limestone, 10 cm bed, laminated, dark gray (N3) with yellowish gray (5Y7/2) to grayish orange (10YR7/4) silt layers. Collected November 2007. Achlysopsis brighamensis, Chancia maladensis, Pagetia aspinosa n. sp.Google Scholar
USNM locality 44116: 24.5 m above base of formation. Glossopleura walcotti/Ptychagnostus praecurrens Zone. Thin to medium bedded, laminated, dark gray (N3), silty limestone with yellowish gray (5Y7/2) to grayish orange (10YR7/4) silty beds. Collected June 1999. Pagetia aspinosa n. sp., Zacanthoides sp. indet.Google Scholar
USNM locality 44117: 3.3 m above base of secondary section, 25.0 m above base of formation. Glossopleura walcotti/Ptychagnostus praecurrens Zone. Limestone, 10 cm lenticular bed, laminated, dark gray (N3) with yellowish gray (5Y7/2) to grayish orange (10YR7/4) silt layers. Collected November 2007. Achlysopsis brighamensis, Chancia maladensis, Pagetia aspinosa n. sp., Pentagnostus brighamensis, Syspacephalus mccollumorum n. sp., ?Zacanthoides sp. indet.Google Scholar
USNM locality 44118: 25.0–26.0 m above base of formation. Glossopleura walcotti/Ptychagnostus praecurrens Zone. Thin to medium bedded, laminated, dark gray (N3), silty limestone with yellowish gray (5Y7/2) to grayish orange (10YR7/4) silty beds. Collected July 2015. Achlysopsis brighamensis, Chancia maladensis, Glossopleura walcotti, Pagetia aspinosa n. sp., Pentagnostus brighamensis, Syspacephalus mccollumorum n. sp., ?Zacanthoides sp. indet.Google Scholar
USNM locality 44119: 27 m above base of formation. Glossopleura walcotti/Ptychagnostus praecurrens Zone. Thin to medium bedded, laminated, dark gray (N3), silty limestone with yellowish gray (5Y7/2) to grayish orange (10YR7/4) silty beds. Collected July 2015. Achlysopsis brighamensis, Chancia maladensis, Glossopleura walcotti, Pagetia aspinosa n. sp., Pentagnostus brighamensis, Syspacephalus mccollumorum n. sp., Zacanthoides sp. indet.Google Scholar
USNM locality 44120: 7.75 m above base of secondary section, 28.0 m above base of formation. Glossopleura walcotti/Ptychagnostus praecurrens Zone. Limestone, 10 cm lenticular bed, laminated, dark gray (N3) with yellowish gray (5Y7/2) to grayish orange (10YR7/4) silt layers. Collected November 2007. Achlysopsis brighamensis, Pagetia aspinosa n. sp., Syspacephalus mccollumorum n. sp., Zacanthoides sp. indet.Google Scholar
USNM locality 44121: 23–27 m above base of formation, collected as loose blocks from slope, assigned to this stratigraphic interval based on position on slope and lithology. Glossopleura walcotti/Ptychagnostus praecurrens Zone. Thin to medium bedded, laminated, dark gray (N3), silty limestone with yellowish gray (5Y7/2) to grayish orange (10YR7/4) silty beds. Collected June 1999. Achlysopsis brighamensis, Chancia maladensis, Glossopleura walcotti, Oryctocephalites sp. indet., Pagetia aspinosa n. sp., Pentagnostus brighamensis, Syspacephalus mccollumorum n. sp., Zacanthoides sp. indet.Google Scholar
USNM locality 44122: float material probably from the 29–30 m above base of formation based on lithology and position on slope. Glossopleura walcotti/Ptychagnostus praecurrens Zone. Thin to medium bedded, laminated, dark gray (N3), silty limestone with yellowish gray (5Y7/2) to grayish orange (10YR7/4) silty beds. Collected June 1999. Pagetia fossula, Pagetia rugosa, Syspacephalus mccollumorum n. sp.Google Scholar
USNM locality 44123: 29 m above base of formation. Glossopleura walcotti/Ptychagnostus praecurrens Zone. Thin to medium bedded, laminated, dark gray (N3), silty limestone with yellowish gray (5Y7/2) to grayish orange (10YR7/4) silty beds. Collected June 1999. Achlysopsis liokata, Bathyuriscus sp. indet., Glossopleura walcotti, Kistocare sp. indet., Pagetia fossula, Pagetia rugosa, ptychopariid pygidium unidet., Zacanthoides cf. Z. longipygus.Google Scholar
USNM locality 44124: 29.75 m above base of formation. Glossopleura walcotti/Ptychagnostus praecurrens Zone. Thin to medium bedded, laminated, dark gray (N3), silty limestone with yellowish gray (5Y7/2) to grayish orange (10YR7/4) silty beds. Collected June 1999. Achlysopsis liokata, Pagetia rugosa.Google Scholar
USNM locality 44125: 36.5 m above base of formation. Ehmaniella Zone. Thin to medium bedded limestone, medium gray (N5). Collected June 1999. Kootenia? sp. indet., Pagetia claytonensis n. sp.Google Scholar
USNM locality 44126: 37.5 m above base of formation. Ehmaniella Zone. Thin to medium bedded limestone, medium gray (N5). Collected June 2000. Alokistocare cf. A. paranotatum, Bathyuriscus terranovensis, Elrathina marginalis, Oryctocephalus cf. O. reynoldsi, Parkaspis cf. P. drumensis, Thoracocare cf. T. minuta, Zacanthoides divergens.Google Scholar
USNM locality 44127: 38.5 m above base of formation. Ehmaniella Zone. Collected June 1999 and June 2000. Bathyuriscus terranovensis, Elrathina? wheelera, Zacanthoides divergens.Google Scholar
USNM locality 44128: 51.5 m above base of formation. Cedaria selwyni Zone. Medium gray (N5) limestone and black (N1) chert. Collected June 1999 and June 2000. Cedaria selwyni, Coosella sp. indet., Crepicephalus sp. indet., Meteoraspis sp. indet., Tricrepicephalus sp. indet.Google Scholar
USNM locality 44129: 53.5 m above base of formation. Cedaria brevifrons Zone. Medium gray (N5) limestone and black (N1) chert. Collected September 1999. Cedaria cf. C. brevifrons, Agnostoid sp. 2.Google Scholar
USNM locality 44130: 54.5 m above base of formation. Cedaria brevifrons Zone. Medium gray (N5) limestone and black (N1) chert. Collected September 1999. Cedaria cf. C. brevifrons.Google Scholar
USNM locality 44131: 54 m above base of formation. Cedaria brevifrons Zone. Medium gray (N5) limestone and black (N1) chert. Collected June 1999. Cedaria cf. C. brevifrons.Google Scholar
Split Mountain West Section is 1.5 kilometers E of Split Mountain, Clayton Ridge, unsurveyed area T3S and between R40E and R41E, on the Split Mountain 7.5’ topographic quadrangle map (U.S. Geological Survey, 1970, 1:24,000 scale) and 3.3 km SW from the East Section; at ~37°42'38''N, 117°28'16''W, Esmeralda County, Nevada.Google Scholar
USNM locality 44132: 35.5 m above base of formation. Medium bedded, medium dark gray (N4) limestone, 30 cm from base of ridge forming unit. Ehmaniella Zone. Collected July 2015. Agnostoid sp. 1, Bathyuriscus terranovensis, Elrathina? wheelera, Oryctocara sp. indet., Pagetia claytonensis n. sp., Parkaspis cf. P. drumensis, Thoracocare cf. T. minuta, Zacanthoides divergens.Google Scholar
USNM locality 44133: 36.5 m above base of formation. Thin bedded, silty limestone to limy siltstone, poorly exposed. Ehmaniella Zone. Collected July 2015. Bathyuriscus terranovensis, corynexochid pygidium indet., Elrathina? wheelera, Pagetia claytonensis n. sp., Parkaspis cf. P. drumensis, Thoracocare cf. T. minuta, Zacanthoides divergens.Google Scholar
USNM locality 44134: 39 m above base of formation. Thin bedded, silty limestone to limy siltstone, poorly exposed. Ehmaniella Zone. Collected September 2000. Amecephalus? sp. indet., Bathyuriscus terranovensis, corynexochid pygidium indet., Elrathina? wheelera, Pagetia claytonensis n. sp., Thoracocare cf. T. minuta, Zacanthoides divergens.Google Scholar
USNM locality 44135: 40 m above base of formation. Thin bedded, silty limestone to limy siltstone, poorly exposed. Ehmaniella Zone. Collected September 2000. Bathyuriscus terranovensis, Elrathina marginalis, Elrathina? wheelera, Pagetia claytonensis n. sp., Thoracocare cf. T. minuta, Utia curio?, Zacanthoides divergens.Google Scholar
USNM locality 44136: 42.5 m above base of formation. Micropeloidal to lime mudstone, medium bedded; 37°42’37”N, 117°28’18”W. Ehmaniella Zone. Collected September 2000. Bathyuriscus terranovensis, Elrathina? wheelera, Oryctocephalus cf. O. reynoldsi, Pagetia claytonensis n. sp., Thoracocare cf. T. minuta, Zacanthoides divergens.Google Scholar
USNM locality 44137: 44.5 m above base of formation. Near the base of a mostly covered 4 m interval with thin bedded, silty limestones to limy siltstones; 37°42'37''N, 117°28'18''W. Ehmaniella Zone. Collected June and September 2000. Bathyuriscus terranovensis, Oryctocephalus cf. O. reynoldsi, Pagetia claytonensis n. sp., Zacanthoides divergens.Google Scholar
USNM locality 44138: 96 m above base of formation. Within the 1 m interval of rubble below a 70 cm chert bed with a flat pebble conglomerate and above 30 cm interbedded chert and limestone horizon, 1.6 m above shale interval, 37°42'36''N, 117°28'15''W. Cedaria selwyni Zone. Collected June 2000. Cedaria selwyni, Cedaria sp. 1, Cedaria sp. 2, Coosella sp. indet., Coosia sp. indet., Tricrepicephalus sp. indet.Google Scholar
Northern Groom Range, White Blotch Springs SE 7.5’ quadrangle, Nevada, near center of unsurveyed Sec. 25, T4S, R55E. Approximately 9.3 km SSW from the town or Rachel and 1.1 km WNW of the Andies Mine; ~37°34'4''N, 115°47'18'' W, 1879 m (6530 ft.), Lincoln County, Nevada.Google Scholar
USNM locality 44139: 22 m above the base of the Rachel Limestone; medium bedded, medium dark gray. Albertella Zone. Chancia maladensis.Google Scholar