Trilobite zone

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Trilobites are used as index fossils to subdivide the Cambrian period. Assemblages of trilobites define trilobite zones. [1] The Olenellus -zone has traditionally marked the top of the Lower Cambrian, [2] and is followed by the Eokochaspis zone. [3]

Contents

The last two zones of the Middle Cambrian are the Bathyuriscus – Elrathina -zone (contemporaneous with the Burgess Shale) and the subsequent Bolaspidella -zone (starting at the base of the Drumian stage [4] ). These are overlain by the lowermost Upper Cambrian Cedaria -zone. [5]

Alternative zoning names place the Burgess Shale in the Peronopsis bonnerensis-zone, which is underlain by the Oryctocephalus indicus -zone (e.g. Spence Shale) and overlain (perhaps not directly) by the Ptychagnostus punctuosus-zone. [6]

The lower Middle Cambrian [7] Glossopleura -zone (Spence Shale) is above the Albertella -zone. [8]

The Elvinia -zone is upper Cambrian. [9]

SeriesStageTrilobite zoneTrilobite GSSP
Furongian Stage 10 Saukia-zone (upper part), Eurekia apopsis-zone, Tangshanaspis-Zone, Parakoldinioidia-zone, Symphysurina-zone [10] Lotagnostus americanus (undecided)
Jiangshanian Ellipsocephaloides-zone, Saukia-zone (lower part) [10] Agnostotes orientalis
Paibian  ? (?) Glyptagnostus reticulatus
Cedaria
Miaolingian Guzhangian Bolaspidella ( / Ptychagnostus praecurrens ?? ). [6] Lejopyge laevigata
Drumian Ptychagnostus atavus
Wuliuan Bathyuriscus – Elrathina (?) Oryctocephalus indicus
Eokochaspis
Series 2 Stage 4 Olenellus Olenellus or Redlichia (undecided)
Stage 3
Fallotaspis , Nevadella First appearance of trilobites (undecided)
Terreneuvian (Pre-Trilobitic Cambrian) Stage 2  ?
Fortunian

Subdivision of the Olenellus-zone

Recently, it has been proposed to subdivide the Olenellus-zone. [11] The following zones have been proposed to replace the Upper Olenellus-zone. Each lower boundary is defined by the first occurrence of the naming species. Each upper boundary is defined by the first occurrence of the naming species of the overlying zone. In case of the youngest zone, this is Eokochaspis nodosa, that also marks the base of the Wuliuan.

Species: Nephrolenellus multinodus (lower half), Mesonacis fremonti , Olenellus terminatus s.l. , Olenellus puertoblancoensis s.l., Olenellus fowleri s.l., Olenellus gilberti , Bolbolenellus brevispinus (not the lower part), Olenellus chiefensis (upper half), Olenellus sp.1 (upper half), Nephrolenellus geniculatus (upper part), Olenellus sp.2 (upper part), Olenellus howelli (very uppermost part).

Species: Bolbolenellus euryparia (lower half), Mesonacis fremonti, Bristolia fragilis s.l. (lower half), Olenellus terminatus s.l., Olenellus fowleri s.l., Olenellus puertoblancoensis s.l., Olenellus gilberti (uppermost part), Biceratops nevadensis (uppermost part), Bristolia brachyomma (very uppermost part).

Species: Peachella iddingsi (lower half), Mesonacis fremonti, Olenellus nevadensis (lower part), Bristolia anteros (lowest half), Bristolia fragilis s.l., Olenellus terminatus s.l., Paranephrolenellus besti (very short period in the late lower part), Peachella brevispina (middle part).

Species: Bristolia insolens (lower half), Mesonacis fremonti, Olenellus nevadensis, Olenellus clarki , Olenellus sp.3, Paranephrolenellus klondykensis (lowest part), Bristolia harringtoni (middle part), Bristolia bristolensis (lower half), Bristolia anteros (not lowest part), Bristolia fragilis s.l. (upper half), Paranephrolenellus inflatus (very short interval in the middle), Eopeachella angustispina (uppermost part).

Species: Bristolia mohavensis (lower half), Mesonacis fremonti, Olenellus nevadensis, Olenellus clarki, Olenellus sp.3, Bristolia harringtoni (middle part), Bristolia bristolensis (upper half).

Species: Arcuolenellus arcuatus (lowest part), Arcuolenellus aff. megafrontatis (lower half), Mesonacis cylindricus (not the highest part), Olenellus nevadensis, Olenellus clarki (not lowest part), Mesonacis fremonti (upper half), Olenellus sp.3 (upper part).

Related Research Articles

<i>Olenellus</i> Extinct genus of trilobites

Olenellus is an extinct genus of redlichiid trilobites, with species of average size. It lived during the Botomian and Toyonian stages (Olenellus-zone), 522 to 510 million years ago, in what is currently North-America, part of the palaeocontinent Laurentia.

Laudonia is an extinct genus of trilobites that lived during the early part of the Botomian stage, which lasted from approximately 524 to 518.5 million years ago. This faunal stage was part of the Cambrian Period. There are currently two named species assigned to it.

<i>Mummaspis</i>

Mummaspis is an extinct genus from a well-known class of fossil marine arthropods, the trilobites, with five known species. It lived during the early part of the Botomian stage, which lasted from approximately 524 to 518.5 million years ago. This faunal stage was part of the Cambrian Period.

Elliptocephala is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived from the later part of the Tommotian to the upper Botomian. Elliptocephala can easily be confused with Ellipsocephalus, a trilobite genus of the Ptychopariida order.

<span class="mw-page-title-main">Wheeler Shale</span> Geologic formation in Utah notable for trilobite fossils

The Wheeler Shale is a Cambrian (c. 507 Ma) fossil locality world-famous for prolific agnostid and Elrathia kingii trilobite remains and represents a Konzentrat-Lagerstätte. Varied soft bodied organisms are locally preserved, a fauna and preservation style normally associated with the more famous Burgess Shale. As such, the Wheeler Shale also represents a Konservat-Lagerstätten.

<span class="mw-page-title-main">House Range</span> Mountain range in Millard County, Utah, USA

The House Range is a north-south trending mountain range in Millard County, of west-central Utah. The House Range was named in 1859 by James H. Simpson. It was named by Simpson because "...of its well-defined stratification and the resemblance of portions of its outline to domes, minarets, houses, and other structures."

<i>Mesonacis</i>

Mesonacis is an extinct genus of trilobite that lived during the Botomian, found in North-America, and the United Kingdom. Some of the species now regarded part of Mesonacis, have previously been assigned to Angustolenellus or Olenellus (Angustolenellus). Angustolenellus is now regarded a junior synonym of Mesonacis.

<span class="mw-page-title-main">Marjum Formation</span>

The Marjum Formation is a Cambrian geological formation that overlies the Wheeler Shale in the House Range, Utah. It is named after its type locality, Marjum Pass, and was defined in 1908. The formation is known for its occasional preservation of soft-bodied tissue, and is slightly younger than the Burgess Shale, falling in the Ptychagnostus praecurrens trilobite zone.

<i>Peachella</i>

Peachella is an extinct genus of trilobites, fossil marine arthropods, with species of average size. It lived during the Toyonian stage, 516 to 513 million years ago, in what is today the southwestern United States. It can easily be distinguished from other trilobites by its club-like genal spines.

<i>Eopeachella</i>

Eopeachella is an extinct genus of trilobites, fossil marine arthropods, with species of probably small size, entire, articulate specimens have not yet been found. It lived during the Toyonian stage, in what is today the South-Western United States. Eopeachella angustispina is the only known species in this genus.

<i>Biceratopsinae</i>

The Biceratopsinae is an extinct subfamily of redlichiid trilobites within the family Biceratopsidae, with species of small to average size. Species belonging to this subfamily lived during the Toyonian stage, 516-513 million years ago, in the former continent of Laurentia, including what are today the South-Western United States and Canada.

<i>Biceratops</i>

Biceratops is an extinct genus of olenelloid redlichiid trilobites, of average size, with the largest specimen 8 centimetres or 3.1 inches long, not including the huge pleural spines of the 3rd segment of the thorax. It lived during the Toyonian stage, in what is today the South-Western United States. Biceratops can easily be distinguished from other members of Biceratopsidae by the absence of genal spines, in combination with effaced features of the raised axial area of the head shield, that is bordering the two horn-like projections that carry the eyes. Biceratops nevadensis is the only known species in this genus.

Mesolenellus is an extinct genus of trilobites that lived during the lower Cambrian (Botomian), found in Greenland and Spitsbergen.

<i>Bristoliinae</i>

The Bristoliinae is an extinct subfamily of trilobites, fossil marine arthropods, with species of small to average size. Species belonging to this subfamily lived during the Botomian and Toyonian stage (Olenellus-zone), 522-513 million years ago, in the former continent of Laurentia, including what are today Mexico, the Appalachian Mountains and the south-western United States, and Canada.

Lochmanolenellus is an extinct genus of trilobites, fossil marine arthropods, with one small species, L. mexicana. It lived during the Botomian stage (Olenellus-zone), 522–513 million years ago, in the South-West of the former continent of Laurentia, in what are today Mexico, and the South-Western United States.

<i>Bristolia</i>

Bristolia is an extinct genus of trilobite, fossil marine arthropods, with eight or more small to average size species. It is common in and limited to the Lower Cambrian shelf deposits across the southwestern US, which constitutes part of the former paleocontinent of Laurentia.

<i>Fritzolenellus</i>

Fritzolenellus is an extinct genus from a well-known class of fossil marine arthropods, the trilobites, with three known species. It lived during the early part of the Botomian stage, which lasted from approximately 524 to 518.5 million years ago. This faunal stage was part of the Cambrian Period. Fritzolenellus occurred in parts of the paleocontinent Laurentia in what are now Northwestern Canada, Northwestern Scotland, and North-Greenland.

<i>Emigrantia</i>

Emigrantia is an extinct genus of trilobites, fossil marine arthropods, of small to average size. It lived during the Toyonian stage, in what is today the South-Western United States. Emigrantia can easily be distinguished from other trilobites by the sturdy but not inflated genal spines, that are attached at midlength of the cephalon, in combination with effaced features of the raised axial area of the head shield.

Bolbolenellus is an extinct genus of trilobites, fossil marine arthropods, with five species attributed to it currently. It can be easily distinguished from all other trilobites by the combination of the absence of dorsal sutures in the head shield like all Olenellina, and a distinctly bulbous frontal lobe (L4) of the raised axial area in the head called glabella. The species lived at the end of the Lower Cambrian.

References

  1. ↑ Palmer, A.R. (1998). "A proposed nomenclature for stages and series for the Cambrian of Laurentia". Canadian Journal of Earth Sciences. 35 (4): 323–328. Bibcode:1998CaJES..35..323P. doi:10.1139/cjes-35-4-323. ISSN   1480-3313.
  2. ↑ Sundberg, F. A. (2005). "The Topazan Stage, a New Laurentian Stage (Lincolnian Series_ "Middle" Cambrian)". Journal of Paleontology. Paleontological Society. 79 (1): 63–71. doi:10.1666/0022-3360(2005)079<0063:TTSANL>2.0.CO;2. JSTOR   4094961. S2CID   130681546.
  3. ↑ Sundberg, F. A.; McCollum, L. B. (2000). "Ptychopariid Trilobites of the Lower-Middle Cambrian Boundary Interval, Pioche Shale, Southeastern Nevada". Journal of Paleontology. Paleontological Society. 74 (4): 604–630. doi:10.1666/0022-3360(2000)074<0604:PTOTLM>2.0.CO;2. JSTOR   1306942. S2CID   130102939.
  4. ↑ https://engineering.purdue.edu/Stratigraphy/references/Drumian0.pdf [ bare URL PDF ]
  5. ↑ Robison, R. A. (1964). "Upper Middle Cambrian Stratigraphy of Western Utah". Geological Society of America Bulletin. 75 (10): 995–1010. Bibcode:1964GSAB...75..995R. doi:10.1130/0016-7606(1964)75[995:UMCSOW]2.0.CO;2. ISSN   0016-7606.
  6. 1 2 This is just younger than the Bathyuriscus-Elrathina zone, or at least just younger than the Stephen Formation. See
  7. ↑ Robison, R. A.; Wiley, E. O. (1995). "A New Arthropod, Meristosoma: More Fallout from the Cambrian Explosion". Journal of Paleontology. 69 (3): 447–459. Bibcode:1995JPal...69..447R. doi:10.1017/s0022336000034855. JSTOR   1306320. S2CID   133177339.
  8. ↑ Stoyanow, A. (1958). "Sonoraspis and Albertella in the Inyo Mountains, California". Geological Society of America Bulletin. 69 (3): 347–352. Bibcode:1958GSAB...69..347S. doi:10.1130/0016-7606(1958)69[347:SAAITI]2.0.CO;2. ISSN   0016-7606.
  9. ↑ Stitt, J. H.; Rucker, J. D.; Diane Boyer, N.; Hart, W. D. (1994). "New Elvinia Zone (Upper Cambrian) Trilobites from New Localities in the Collier Shale, Ouachita Mountains, Arkansas". Journal of Paleontology. 68 (3): 518–523. Bibcode:1994JPal...68..518S. doi:10.1017/s0022336000025890. JSTOR   1306200. S2CID   133418468.
  10. 1 2 Landing, E.; Westrop, S.R.; Adrain, J.M. (19 September 2011). "The Lawsonian Stage - the Eoconodontus notchpeakensis FAD and HERB carbon isotope excursion define a globally correlatable terminal Cambrian stage". Bulletin of Geosciences: 621–640. doi: 10.3140/bull.geosci.1251 .
  11. ↑ Webster, Mark (2011). "Trilobite Biostratigraphy and Sequence Stratigraphy of the Upper Dyeran (traditional Laurentian "Lower Cambrian) in the southern Great Basis, USA". Museum of Northern Arizona Bulletin. 67.
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