An official website of the United States government
Abstract The upper Ediacaran stratigraphic record hosts fossil assemblages of Earth’s earliest communities of complex, macroscopic, multicellular life. Tubular fossils are a common and diverse, though frequently undercharacterized, component of many of these assemblages. Gaojiashania cyclus is an enigmatic tubular fossil and candidate index fossil found in upper Ediacaran strata globally and is best known from the Gaojiashan Lagerstätte of South China. Here we describe a recently discovered assemblage of Gaojiashania fossils from the Ediacaran Dunfee Member of the Deep Spring Formation of Nevada, USA. Both body and trace fossil affinities have been proposed for Gaojiashania; we present morphological and biostratinomic evidence for a body fossil affinity for the Dunfee specimens. Additionally, previous studies have highlighted that Ediacaran tubular fossils are characterized by a wide range of preservational modes, including association with pyrite, apatite, or clay minerals and preservation as carbonaceous compressions. Petrographic, SEM, and EDS data indicate that the Dunfee Gaojiashania specimens are preserved as ‘Ediacara-style’ external, internal and composite molds, in siltstone and sandstone with a clay mineral-rich matrix of both aluminosilicates and non-aluminous Mg- and Fe-rich silicate minerals that we interpret as authigenic clays. Authigenic clay-mediated fossilization of unmineralized tissues, including moldic preservation in heterolithic siliciclastic strata, as indicated by the Dunfee Gaojiashania, may be linked to the prevalence of both silica-rich and ferruginous seawater conditions prior to both the radiation of silica-biomineralizing organisms and the rise of ocean and atmospheric oxygen to modern levels. In this light, clay authigenesis may have played a critical role in facilitating multiple modes of Ediacaran and Cambrian exceptional fossilization, thus shaping the stratigraphic distribution of a range of Ediacara macrofossil taxa.
more »
« less
This content will become publicly available on May 20, 2026
RIBBON-LIKE COMPRESSION FOSSILS FROM THE LATE EDIACARAN ESMERALDA MEMBER OF THE DEEP SPRING FORMATION AT MOUNT DUNFEE, NEVADA, USA
Abstract We describe > 200 ribbon-like macroscopic fossils from terminal Ediacaran strata at Mount Dunfee, Nevada, USA ∼ 115 m below the local placement of the Ediacaran–Cambrian boundary. They are preserved as casts and molds, composed of Fe-oxides and Fe-rich aluminosilicates in an aluminosilicate clay matrix. Measurements of 50 of the specimens provide a fossil size range of 0.22–0.74 mm-wide and 0.1–75.0 mm-long. Some specimens evidence original flexibility and appear to be fragmented, consistent with soft body preservation. They are therefore interpreted as body fossils, rather than trace fossils. Given this interpretation, we suggest that the fossils’ size range and ribbon-like morphologies are consistent with them being members of the problematicum Vendotaenia, which have not been previously reported from Ediacaran strata within the southern Great Basin. The phylogenetic affinity of vendotaenids is unresolved, but they are commonly interpreted as a form of eukaryotic macroalgae. This report firmly establishes vendotaenids in Ediacaran strata on Laurentia, broadening their known paleogeographic range during the end-Ediacaran Period. Additionally, the morphology of the fossils described here supports the notion that, although vendotaenids are reported from many Ediacaran paleocontinents globally, there was low macroalgal diversity at the end of the Ediacaran Period.
more »
« less
- PAR ID:
- 10611856
- Publisher / Repository:
- Society for Sedimentary Geology
- Date Published:
- Journal Name:
- Palaios
- Volume:
- 40
- Issue:
- 5
- ISSN:
- 0883-1351
- Page Range / eLocation ID:
- 131 to 140
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract The terminal Ediacaran Period is signaled worldwide by the first appearance of skeletonizing tubular metazoan fossils, e.g.,CloudinaGerms, 1972 andSinotubulitesChen, Chen, and Qian, 1981. Although recent efforts have focused on evaluating the taxic composition and preservation of such assemblages from the southwestern United States, comparable forms reported in the 1980s from Mexico remain to be re-examined. Here, we reassess the latest Ediacaran skeletal materials from the La Ciénega Formation of the Caborca region in Sonora, Mexico, using a combination of analytical methods: optical microscopy of extracted fossils, thin-section petrography, scanning electron microscopy and energy dispersive X-ray spectroscopy, and X-ray tomographic microscopy. From our examination, we conclude that the La Ciénega hosts a polytaxic assemblage of latest Ediacaran tubular organisms that have been preserved through two taphonomic pathways: coarse silicification and calcareous recrystallization preserving finer details. Further, these fossils show signs that their shells might not have been inflexible or completely mineralized in vivo, and that they might also record tentatively interpreted predation traces in the form of drill holes or puncture marks. This work, along with ongoing efforts around the world, helps to provide a framework for biostratigraphic correlation and possible subdivision of the Ediacaran Period, and further shapes our view of metazoan evolution and ecology in the interval directly preceding the Cambrian explosion.more » « less
-
The Ediacaran−Cambrian boundary strata in the Great Basin of the southwestern United States record biological, geochemical, and tectonic change during the transformative interval of Earth history in which metazoans diversified. Here, we integrate new and compiled chemostratigraphic, paleontological, sedimentological, and stratigraphic data sets from the Death Valley region, the White-Inyo Ranges, and Esmeralda County in Nevada and California and evaluate these data within a regional geologic framework. A large negative carbon isotope (δ13C) excursion—also known as the Basal Cambrian Excursion, or BACE—is regionally reproducible, despite lateral changes in sedimentary facies and dolomitization across ∼250 km, consistent with a primary marine origin for this perturbation. Across the southern Great Basin, Ediacaran body fossils are preserved in a variety of taphonomic modes, including cast and mold preservation, two-dimensional compressional preservation, two-dimensional and three-dimensional pyritization, and calcification. The stratigraphic framework of these occurrences is used to consider the relationships among taphonomic modes for fossil preservation and paleoenvironmental settings within this basin. In this region, Ediacaran-type fossils occur below the nadir of the BACE, while Cambrian-type trace fossils occur above. Sedimentological features that include giant ooids, stromatolites, and textured organic surfaces are widespread and abundant within the interval that records biotic turnover and coincide with basaltic volcanism and the BACE. We hypothesize that the prevalence of these sedimentological features, the BACE, and the disappearance of some Ediacaran clades were caused by environmental perturbation at the Ediacaran-Cambrian boundary.more » « less
-
Fossils represented as Cloudina? were reported in the Antarctic Taylor Formation by Yochelson and Stump in 1977. Their assessment presented thin sections of specimens derived from an oolitic limestone breccia. Notably, one thin section contained a single presumed trilobite fragment, leading the authors to attribute the materials to the early Cambrian. The remaining fossil materials were characterized as tubes of varying preservational quality, likely overprinted by recrystallization. The structure of tubular fossils, as viewed in thin section, appeared bilayerd, showing a thicker outer layer surrounding a thinner, darker, inner layer, enveloping the innermost lumen or cavity of the tube. While one specimen was reported to have two layers, it lacked other identifying features, such as the characteristic nested structure typical of Cloudina. The authors acknowledged the dissimilarity of their specimens to those reported from Namibia by G.J.B. Germs but noted similarities to Cloudina borrelloi from the San Juan Province, Argentina described by Yochelson and Herrera in 1974. This led the authors to cautiously identify their Antarctic specimens as Cloudina?, though subsequent reports expressed skepticism about placing the Argentinian materials within the Cloudina genus, suggesting a more plausible association with Salterella or Acuticloudina. Based on this single report, Ediacaran paleontologists have often, but tenuously, expanded the geographic distribution of Cloudina to include Antarctica. As the International Commission on Stratigraphy’s Ediacaran Subcommission has defined the use of Ediacaran tubicolus organisms, including all plausible designations of Cloudina, as the leading index fossil group for placement of the terminal Ediacaran stage, this long-overdue reexamination is both timely and important for gaining a clearer picture of the cosmopolitan nature of this genus. Our initial analysis shows that these tubicolus taxa are single-walled, non-nested, and smooth-walled, gently tapering, conical tubes. Herein, we aim to aim to reevaluate the taxonomy of these fossils using modern microanalysis and high-resolution photography to shed light on their potential phylogeny and evaluate their role in the broader context of late Ediacaran to early Cambrian tubular fossils.more » « less
-
Abstract Fossils are rare in Cambrian strata of the Uinta Mountains of northeastern Utah, and are important because they can help integrate our understanding of laterally adjacent but discontiguous rock units, e. g., the Tintic Quartzite of Utah and the Lodore Formation of Utah-Colorado. New body fossils from strata previously mapped as Tintic or Cambrian Undifferentiated, but here interpreted as the Ophir Formation, include indeterminate hyoliths and hyolithids, brachiopods including a linguloid, and the trilobitesTrachycheilusResser, 1945 andElrathiellaPoulsen, 1927. The last two assign these strata to theEhmaniellaBiozone (uppermost Wuliuan Stage; Miaolingian Series) or traditional Laurentian middle Cambrian. These data, together with fossil occurrences elsewhere in Utah, require that the Tintic Quartzite was deposited prior to and/or during the early Wuliuan, and suggest that the unit could be correlative to much of the Lodore Formation of Utah and Colorado.more » « less
