Latest Smithian Ammonoids in northern Utah

Corroborating the existence of a UAZ6 (Unitary Association Zone, a means of biostratigraphic correlation).  See the paper linked below.  Characterized by the ammonoid Psudosageceras augustum (Brayard & Bucher, 2008) in association with Xenoceltites subevolutus Spath 1930. Found in rocks previously assigned to the Induan (lower Lower Triassic) Dinwoody Fm., now assigned to the Olenekian (upper Lower Triassic, top of Smithian) Thaynes Group.

Pseudosageceras augustum left and Xenoceltites subevolutus right

Xenoceltites subevolutus left and Pseudosageceras augustum right

In press, Article in GEOBIOS

Available online 18 June 2021

Abstract

The late Smithian extinction represents a major event within the Early Triassic. This event generally corresponds to a succession of two and possibly three successively less diverse, cosmopolitan ammonoid assemblages, which when present, provide a robust biostratigraphic framework and precise correlations at different spatial scales. In the western USA basin, known occurrences of latest Smithian taxa are rare and until now, have only been documented from northeastern Nevada. Based on these restricted basinal occurrences, a regional zone representing the latest Smithian was postulated but not corroborated, as representative taxa had not yet been reported from outside Nevada. Here we document two new ammonoid assemblages from distant localities in northern Utah, overlying the late Smithian Anasibirites beds and characterized by the unambiguous co-occurrence of Xenoceltites subevolutus and Pseudosageceras augustum. The existence of a latest Smithian zone in the western USA basin is therefore validated, facilitating the identification of the Smithian/Spathian boundary and intra-basin correlation. This zone also correlates with the latest Smithian zone recognized from southern Tethyan basins. Additionally, these new data support other observed occurrences of Xenoceltites subevolutus throughout most of the late Smithian.

Some Prionitids Lumped

With a few very narrowly defined species, The Prionitidae is a family of very closely related ammonoids.  However most collections, especially from the western US, always contained "Prionitid" or "Prionitid indet.", Prionitids with bullae or ribs, maybe nodes or tubercles, that just didn't fit with any of the other described genera or species.  With new collections from the Smithian (Early Triassic) Sinbad Formation around the Utah/Arizona border, we were able to synonymize all these with ammonoids described in 1929 by Asa Mathews.  By priority, Gurleyites smithi Mathews 1929 replaces Arctoprionites resseri (Mathews 1929).  With a very wide range of intraspecific variation, the new taxon will fit just about anything that doesn't fit in one of the other defined taxa.

See our new paper here.

New middle and late Smithian ammonoid faunas from the Utah/Arizona border: New evidence for calibrating Early Triassic transgressive-regressive trends and paleobiogeographical signals in the western USA basin

 

 

Ammonoid Family Reunions (revised Feb. 11, 2021)

Two family reunions occurred in the distant past, the Prionitids and the Cardioceratids, this is a short review of those events.  The thing that draws attention to these two reunions is that members of the two families gathered in abundance and almost to the mutual exclusion of other families.  Both are recorded in rocks representing a relatively short time-span, a single biozone, the smallest standard unit used in biostratigraphy, representing a few hundred thousand years more or less.

PRIONITIDAE Hyatt, 1900:

Prionitids

About 251mya the Family Prionitidae met in what is now the western USA.  This event took place all over the world (? Tethys and northern Panthalassa), but for this report I will stick to the event and those attending in the western US.  This Family started with the Genus Meekoceras in the Early Smithian and culminated with the family reunion in the Late Smithian with at least 6 species in 4 genera with a few in open nomenclature.

·         Anasibirites Mojsisovics, 1896                     2 species

·         Hemiprionites Spath, 1929                            2 species

·         Wasatchites Mathews, 1929                          1 species

·         Gurleyites Mathews, 1929                            1 species

With a few Xenoceltitids and Hedenstroemiids.  (See Brayard et al. 2013, Jattiot et al. 2017, Mathews 1929, Smith 1932, for composition of the fauna and Jattiot et al. 2015 for a revision of Anasibirites, Brayard et al. 2020 for a revision of Gurleyites) Recorded in the Thaynes Group, UAZ₅ of Jattiot et al. 2017

Prionitid localities (from Brayard et al 2013)

CARDIOCERATINAE Siemiradzki, 1891:

Cardioceratids

About 162mya the Subfamily Cardioceratinae gathered in the Sundance Sea that covered much of Montana and Wyoming along with parts of Utah, Colorado, Idaho, and South Dakota.  This reunion started with Quenstedtoceras and Pavloviceras coming in from the north in Montana, and closed with 18 species in 4 genera and 3 subgenera. 

·             Cardioceras Neumayr & Uhlig, 1881         

o   Scarburgiceras Buckman, 1924    6 species

o   Cardioceras Buckman, 1923         1 species

o   Goliathiceras Buckman, 1919       2 species

·             Scoticardioceras Buckman, 1925                     2 species

·            Vertebriceras Buckman, 1920                          4 species

·            Cawtoniceras Buckman, 1923                         3 species

With rare Perisphinctids.  (see Imlay 1982, and Reeside 1919 for composition of the fauna, and Howarth 2017 for a revision of the Stephanoceratoidea)  This reunion is recorded in the cordatum Zone of the Swift Formation of Montana, the Sundance Formation of Wyoming, Montana, and South Dakota, and the Stump Formation of Utah, Idaho, and Colorado. 

Cardioceratid localities (from Imlay 1982)

Localities for the reunions in the western US are shown, but the events were probably global.

References:

Brayard, A., Bylund, K. G., Jenks, J., Stephen, D. A., Olivier, N., Escarguel, G., Fara, E. & Vennin, E., 2013, Smithian ammonoid faunas from Utah: implications for Early Triassic biostratigraphy, correlations and basinal paleogeography. Swiss Journal of Paleontology 132:141-219

Brayard, A., Olivier, N., Vennin, E., Jenks, J., Bylund, K., Stephen, D., McShinsky, D., Goudemand, N., Fara, E., Escarguel, G., 2020. New middle and late Smithian ammonoid faunas from the Utah/Arizona border: new evidence for calibrating Early Triassic transgressive-regressive trends and paleobiogeographical signals in the western USA basin. Global and Planetary Change 192

Howarth, Michael K., 2017, Part L, Revised, Volume 3B, Chapter 6: Systematic descriptions of the Stephanoceratoidea and Spiroceratoidea. Treatise Online 84:1–101, 66 fig.

Imlay, R. W., 1982, Jurassic (Oxfordian and Late Callovian) Ammonites from the Western Interior Region of the United States, U.S.G.S. Professional Paper 1232, 44 p., 26 pls.

Jattiot, R., Bucher, H., Brayard, A., Monnet, C., Jenks, J. F. & Hautmann, M., 2015, Revision of the genus Anasibirites Mojsisovics (Ammonoidea): an iconic and cosmopolitan taxon of the late Smithian (Early Triassic) extinction. Papers in Palaeontology 2 (1):155 –188.

Jattiot, R., Bucher, H., Brayard, A., Brosse, M., Jenks, J.F., Bylund, K.G., 2017, Smithian ammonoid faunas from northeastern Nevada: implications for Early Triassic biostratigraphy and correlation within the western USA basin. Palaeontographica A (Paleozoology, Stratigraphy), doi: 10.1127/pala/2017/0070.

Mathews, Asa A. L., 1929, The Lower Triassic Cephalopod Fauna of the Fort Douglas Area, Utah, Walker Museum Memoirs Vol.1 No.1 University of Chicago Press, 46 p., 11 pls.

Reeside, J. B., Jr., 1919, Some American Jurassic Ammonites of the Genera Quenstedticeras, Cardioceras and Amoeboceras, Family Cardioceratidae, U.S.G.S. Professional Paper 118, 64 p., 24 pls.

Smith, J. P., 1932, Lower Triassic Ammonoids of North America, U.S.G.S. Professional Paper 167,199 p., 81 pls. 

Fish near the Early Triassic Equator!

Romano, C., Jenks, J., Jattiot, R., Scheyer, T., Bylund, K., & Bucher, H. 2017. Marine Early Triassic Actinopterygii from Elko County (Nevada, USA): Implications for the Smithian equatorial vertebrate eclipse. Journal of Paleontology, 1-22. doi:10.1017/jpa.2017.36

Abstract

The Early Triassic vertebrate record from low paleolatitudes is spotty, which led to the notion of an ‘equatorial vertebrate eclipse’ during the Smithian. Here we present articulated ray-finned fishes (Actinopterygii), collected from the marine Lower Triassic Thaynes Group at three new localities in Elko County (Nevada, USA), which were deposited within the equatorial zone. From the Smithian of the Winecup Ranch, we describe two partial skulls of the predatory actinopterygian Birgeria (Birgeriidae), attributed to B. americana new species and Birgeria sp. Birgeria americana n. sp. is distinguished from other species by a less reduced operculogular series. With an estimated total length of 1.72–1.85m, it is among the largest birgeriids. We confirm that Birgeria encompasses species with either two or three rows of teeth on the maxilla and dentary, and suggest that species with three well-developed rows are restricted to the Early Triassic. From the latest Smithian of Palomino Ridge, we present a three-dimensional, partial skull of the longirostrine predator Saurichthys (Saurichthyidae). This and other occurrences indicate that saurichthyids were common in the western USA basin. From the early late Spathian of Crittenden Springs, we describe a posterior body portion (Actinopterygii indet.). This find is important given the paucity of Spathian osteichthyan sites. We provide a summary of Early Triassic vertebrate occurrences in the United States, concluding that vertebrate fossils remain largely unstudied. The presence of predatory vertebrates in subequatorial latitudes during the Smithian confirms that Early Triassic trophic chains were not shortened and contradicts the ‘equatorial vertebrate eclipse’.

Early Triassic Moenkopi/Thaynes - Ammonoid Biostratigraphy, Correlation and Paleogeography

Smithian ammonoid faunas from Utah: implications for Early Triassic biostratigraphy, correlation and basinal paleogeography

Arnaud Brayard, Kevin G. Bylund, James F. Jenks, Daniel A. Stephen, Nicolas Olivier, Gilles Escarguel, Emmanuel Fara, Emmanuelle Vennin, Swiss Journal of Palaeontology, 2013, 132:141-219

Abstract

Intensive sampling of the lower portion of the Thaynes and Moenkopi Groups (Lower Triassic) at separate localities within the Confusion Range, Pahvant Range, Mineral Mountains, Star Range, Kanarraville, Cedar City, Torrey and San Rafael Swell areas (mainly central and southern Utah, USA) leads to the recognition of a new key regional Smithian ammonoid succession. The new biostratigraphical sequence, which is more precise than the long-recognized Meekoceras gracilitatis and Anasibirites kingianus Zones, comprises twelve subdivisions, thus resulting in a sequence with much higher resolution that can be correlated not only with other western USA sites, but also with major worldwide localities as well. Middle and late Smithian faunas contain many taxa with wide geographic distribution, thus enabling long-distance correlation with faunal successions from other regions (e.g., British Columbia, Canadian Arctic, South China, Spiti and Oman). New assemblages from the lowermost beds are the least diversified and poorest preserved; they represent the earliest early/middle Smithian ammonoid faunas reported from the western North American basin. They highlight (a) the sudden Smithian advancement of the marine transgression within this epicontinental sea, (b) that this event is diachronous, and (c) that the paleotopography of the basin most likely was highly irregular. The newly obtained ammonoid succession also allows us to date and follow the transgression from the northern and central part of the basin to the southwesternmost and southeasternmost parts, which were reached during the late Smithian (Anasibirites kingianus beds). In addition, we briefly discuss the now-limited previous regional biozonation in the light of these new results. One new genus (Minersvillites) and nine new species (Kashmirites utahensis, Kashmirites confusionensis, Kashmirites stepheni, ?Xiaoqiaoceras americanum, Minersvillites farai, Inyoites beaverensis, Meekoceras olivieri, Meekoceras millardense, Vercherites undulatus) are also described.


The ammonoids are mostly all the old Early Triassic ones described by C.A.White from collections made by the early geologic surveys of the american west, and by J.P.Smith in the early part of the last century.  A more precise and revised biostratigraphy is proposed.  Below is one of the newly described ammonoids, this one from the Minersville area, one of the earliest Smithian ammonoids found in the western USA.

Vercherites undulatus Brayard Bylund and Jenks 2013

The rocks we have been working in represent the Permian and Early Triassic transition beds, usually some Permian limestones followed by an erosive surface, conglomerate, then a transgressive sequence with marginal marine redbeds, inner shelf, outer shelf and basinal deposits following.

Moenkopi and Thaynes Groups as exposed near Minersville

Permian rocks at the bottom, then the red Black Dragon Formation, and capped with the Sinbad Formation.  As exposed just west of Capitol Reef National Park.

     As you can see, some very wonderful country to explore and work in.  More papers are in the works covering the paleontology and geology of these rocks, I'm really looking forward to the adventure.

PRIONITE-MARE

The Family PRIONITIDAE is a nightmare of taxonomy.  The amount of intraspecific variation, or even intrageneric variation is overwhelming.  Most generic assignments are based on the shape, size, amount, and/or lack of ribs, bullae, nodes, whether they cross the venter or stop short, whether the nodes are mid flank or start near the umbilicus, whether the inner whorls or the outer whorls are smooth.  A lot of specific and generic assignments are arbitrary, a slightly arched venter instead of a flat venter is cause for different generic assignment of forms that basically look exactly alike. 

Tozer, 1994, in his monograph of Canadian Triassic Ammonoids, discussed the differences between Population Taxonomy and Typological Taxonomy and admitted that his classification, especially of the Prionitidae, was arbitrary, and to use a strictly typological taxonomy would mean almost every specimen was a seperate species.  He also talked about using the typological method just to show what the taxon looked like.

To see a Prionitid, it is easily assigned to the Prionitidae, and the beds containing it are easily assigned to the Late Smithian, and usually to the biozone and/or beds known for the Prionitidae.  Is it really necessary to split them into a bunch of different species or genera?  I suppose I could live with a few nominal species divided amongst a few genera for the time being, at least until the family is revised and a more natural classification determined.  Still, what a Prionite-mare.

For references see THIS old post, along with an old rant of the same topic. ;)

SR2 Anasibirites Bed

Like at all other localities, about as thick as the hammer. The lower beds at this locality are a lot less fossiliferous than at any other, they have also been baked by the nearby igneous intrusions, so I don't think they are worth collecting in detail.

A closeup. All the small circular spots are drippings from the Pinyon tree above

Cephalopods - Present and Past

Cephalopods - Present and Past:



Stephen, D.A., Bylund, K.G., Bybee, P.J. and Ream, W.J.: Ammonoid beds in the Lower Triassic Thaynes Formation of western Utah, USA, p. 243-252

In the 20 years since I located the Triassic fossil bearing beds in the Confusion Range of western Utah, I have only co-authored papers on sponges and gastropods. Now, a paper on the Ammonoids. The first of many I hope.

MC Anasibirites Beds

Permian on the left, Black Dragon (Moenkopi red beds on left), Thaynes and then more redbeds on right
(possibly Chinle conglomerate capping hills on right)

?Hemiprionites, Anasibirites and Wasatchites

Anasibirites beds (gray) in center, about 20-25cm thick, with small "body chamber beds" (15cm thick) below,
with high angle fault. Beds with Inyoites and Guodunites below, Thick 50-60cm brown bed.

Cool folding in basal beds of Thaynes Group.

Early Triassic Anasibirites Beds

The Anasibirites Beds in the Confusion Range (above) comprise approximately 30 cm of limestone packed with cephalopod shells. On a recent two week trip collecting fossils from a few new outcrops and a couple of classic ones, I noticed how similar they all are.

From the Cephalopod Gulch locality, near Salt Lake City, where Mathews first described the Anasibirites fauna in the Western US (above). Another approximately 30 cm bed packed with the same fossils.

Smiths Phalen Ranch locality near Currie Nevada (above), another ~30 cm of limestone containing Anasibirites and Wasatchites.

A new locality (to me) in south west central Utah, where beds containing the Anasibirites fauna also occur. This locality needs a little more collecting to verify the thickness and content of the beds, but they seem to be much the same as the others.

Localities to the east, like the Pahvant Range, San Rafael Swell and near Cedar City have the Anasibirites fauna though not as abundant as those to the north and west. Other localities like Crittenden Springs, Nevada, where Anasibirites and other Prionitids occur in lenses above the Meekoceras beds and a locality in Southeastern Idaho (Jim Jenks pers. com.), add to the data.

All these beds record a short time interval right after an extinction event near the end of the Smithian Stage of the Early Triassic.

Sinbad Member Southern San Rafael Swell

Hondoo Arch. Limestone of the Jurassic Carmel Formation holding it up above the Navajo Sandstone, Kayenta and Wingate cliffs below, Varicolored Chinle below, and the upper part of the Moenkopi at the base.

Yellowish Sinbad Limestone on the other side of a fault, the gray fossiliferous base seen below the upper dolomitic beds.

It is hard to separate in this view, the Sinbad is in the middle, between red beds.

Gray beds on both side of the canyon

Sinbad Member near it's Type locality

Sinbad Formation of the Thaynes Group capping mesa, Black Dragon Formation of the Moenkopi Group just below (oil bleached in this area of the San Rafael Swell) and the ?Coconino/BlackBox Dolomite in foreground. One of the many waterpockets visible in the wash.

A tadpole in one of the waterpockets, probably a Spadefoot toad

The northern exposure of the Sinbad. Butte in background made up of Wingate Sandstone and the Chinle Formation.

One of the very poorly preserved ammonoids found in the Sinbad.

GSA Rocky Mountain Section

AMMONOIDS OF THE LOWER TRIASSIC THAYNES GROUP IN THE PAHVANT RANGE, UTAH

EARLY TRIASSIC CONODONTS IN THE PAHVANT RANGE OF CENTRAL UTAH

Groups, Formations, Beds, Horizons and Zones

A little snippet (edited) from an email to Dan:

Lucas et al 2007 (on the Timpoweap) raised the Thaynes and Moenkopi Formations to Group status. If we dont accept Lucas et al, do we extend the Sinbad Member into the Confusion Range or extend the Thaynes Formation into the Pahvant Range. To me the rocks in the Pahvant Range, a few thin limestone beds in a fairly thick shale sequence, are more like the rocks in the Confusion Range than they are to the rocks in the San Rafael Swell (type Sinbad) where you get a fairly thin set of limestone beds with very little shale. Having hiked up to the Virgin in Dog Valley with Arnaud and Dawn, we noticed alot more thin limestone beds above the anasibirites beds, I didnt notice a clear contact to separate the Sinbad from the "Middle Red Formation" unless you just use the first set of red beds, the Virgin could probably be mapped. Ideally a new name for the rocks in Dog Valley and the Confusion range would make me happy, but that is beyond the scope of our abstract. So I was thinking of just calling them both the lower part of the Thaynes Group. Arnaud put Sinbad Formation on his strat sections for Dog Valley, and Thaynes Group for the DH sections. I think he used Sinbad Formation because the geologic map of the Richfield Quad and The Geology of Millard County both call it Sinbad* (or we discussed it in the field?). I really dont think it should be called Sinbad.

A formation is a mappable unit of rocks, a group is a set of similar formations, what separates one formation from another?

Jim asked me yesterday if I had heard of the Claraia Zone. I remembered seeing it somewhere like in Silberling & Tozer 1968, but Jim corrected me and read it as the Claraia Beds. It seems that Hintze used it in the Geologic History of Utah and/or The Geology of Millard County* (I will have to check on these). Is there a Claraia Zone? I also remember seeing Xxxxxx Horizon on a few papers. I think "Zone" is a formally defined unit, whereas Beds and Horizon are informal, can they be used interchangeably? Is an Horizon just a little thicker than a set of Beds?

*after reading the Geology of Millard County and the Richfield Map, It seems Hintze didn't refer to the Sinbad, he only calls it Moenkopi.

DH-4 Observations

I decided to drive out to the Disappointment Hills on Saturday morning. Very little snow on the south facing slopes in the House and Confusion Ranges, down quite low on the north slopes, the roads are in good shape and were actually dusty. No snow at the eastern outcrops except for a couple of drifts on some of the north slopes, I didnt get up to DH-1. The sun was shining and the temp. was about 45 most of the day, a great day.
-
Trying to see just which bed my old "Meekoceras" quarry is in. I found several Inyoites in float just below the quarry, they may be the widely umbilicate form common in bed 5 at DH-1. There is a very thin bed about 50cm below the quarry bed (maybe equiv. to bed 4). Below this bed is a gastropod shale, some fairly large, with body chamber molds of some acute ventered ammonoids though more like Inyoites than Aspenites (This is where the Aspenites figured in our recently accepted paper was found). This shale is also where the ?Meekoceras molds and large Arctocerid molds are found on the small knoll just north-west of the quarry. This would mean the thick bed at the base of that knoll is equiv. to bed 3, and the thin bed on the next knoll west would be bed 5. I need to map DH-4 with a little more detail.
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If the quarry was equiv to bed 9, the small bed below may be bed 8 and the gastropod shale would be the same as between bed 8 and bed 6 (bed 7 would be a thin bed in the middle of the shale). To find Owenites in the quarry bed or the bed below would possibly solve this question. The lack of small "Xenoceltites" like those at DH-1 at this interval (like the lavender bed) also puts doubt on this theory.
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The bedded bivalves found in the quarry level is not really like bed 9, so for now I am leaning toward an equivalence with bed 5

DH1 Annotated Outcrop Photo

Just because the beds show up so well through the snow.

In the Field

Dr. Hugo Bucher, Dr. Arnaud Brayard and Jim Jenks
out on the outcrop

Arnaud at DH-1 in the snow



Dawn getting ready to take vengence on a fossil

Xenoceltites

An update for this old post

Xenoceltites-Boreoceras-Wyomingites

I found an old photo of the specimen on display at the museum. Where did those constrictions come from? I am leaning more toward Xenoceltites now, as the sculpture, especially on the early whorls, is more like it than of Wyomingites. I could have swore all the whorls were smooth.

Presentation on line

If you go to the abstract, you can now download a pdf file of the presentation I gave at the GSA meeting in Las Vegas last month.

Abstract for Presentation 12-9

4.8 Mb presentation handout download.

GSA Las Vegas

Well, Wes found out he cant give the talk at the GSA meeting in Las Vegas. The honor falls to Me!

Paper No. 12-9 11:00AM-11:20AM, March 20, 2008

A first time for everything I guess.