MORPHOLOGY AND PRESERVATION OF GAOJIASHANIA, AN ENIGMATIC TUBULAR FOSSIL FROM THE UPPER EDIACARAN DUNFEE MEMBER, DEEP SPRING FORMATION, NEVADA, USA DOI

A Rivas,

Paul M. Myrow, Emily F. Smith

и другие.

Palaios, Год журнала: 2024, Номер 39(12), С. 444 - 461

Опубликована: Дек. 19, 2024

Abstract The upper Ediacaran stratigraphic record hosts fossil assemblages of Earth’s earliest communities complex, macroscopic, multicellular life. Tubular fossils are a common and diverse, though frequently undercharacterized, component many these assemblages. Gaojiashania cyclus is an enigmatic tubular candidate index found in strata globally best known from the Gaojiashan Lagerstätte South China. Here we describe recently discovered assemblage Dunfee Member Deep Spring Formation Nevada, USA. Both body trace affinities have been proposed for Gaojiashania; present morphological biostratinomic evidence affinity specimens. Additionally, previous studies highlighted that characterized by wide range preservational modes, including association with pyrite, apatite, or clay minerals preservation as carbonaceous compressions. Petrographic, SEM, EDS data indicate specimens preserved ‘Ediacara-style’ external, internal composite molds, siltstone sandstone mineral-rich matrix both aluminosilicates non-aluminous Mg- Fe-rich silicate interpret authigenic clays. Authigenic clay-mediated fossilization unmineralized tissues, moldic heterolithic siliciclastic strata, indicated Gaojiashania, may be linked to prevalence silica-rich ferruginous seawater conditions prior radiation silica-biomineralizing organisms rise ocean atmospheric oxygen modern levels. In this light, authigenesis played critical role facilitating multiple modes Cambrian exceptional fossilization, thus shaping distribution Ediacara macrofossil taxa.

Язык: Английский

Particulate Cadmium Accumulation in the Mesopelagic Ocean DOI Creative Commons
Allison Laubach, Jong‐Mi Lee, Matthias Sieber

и другие.

Global Biogeochemical Cycles, Год журнала: 2025, Номер 39(1)

Опубликована: Янв. 1, 2025

Abstract Observations of dissolved cadmium (dCd) and phosphate (PO 4 ) suggest an unexplained loss dCd to the particulate phase in tropical oxyclines. Here, we compile existing observations Cd phosphorus (P), present new data from US GEOTRACES GP15 Pacific Meridional Transect examine this phenomenon a perspective. We use simple algorithm reproduce station depth profiles P via regeneration possible subsurface accumulation. Our examination reveals decoupling driven by variable partitioning between two pools with differing labilities. Further, identify evidence for accumulation at 31 stations. Subsurface occurs most consistently mesopelagic but can be found all examined ocean basins. This is not well‐correlated oxygen or sulfide concentration. Instead, observe that regions where concentration relatively high compared zinc (dZn) speculate it result enhanced biological uptake response micronutrient balance.

Язык: Английский

Процитировано

1
GEOTRACES: Ironing Out the Details of the Oceanic Iron Sources? DOI Creative Commons
Tim M. Conway, Rob Middag, Reiner Schlitzer

и другие.

Oceanography, Год журнала: 2024, Номер 37(2)

Опубликована: Янв. 1, 2024

Dissolved iron (dFe) is an essential micronutrient for phytoplankton, with vanishingly low oceanic dissolved concentrations (pico- to nanomoles per kg) known limit growth—and thus influence primary productivity and carbon cycling—over much of the surface ocean. However, because considerable challenges associated contamination-free sample collection accurate analysis such dFe concentrations, first reliable measurements came only in 1980s. Further, by 2003, despite several decades research, there were ~25 full-depth profiles worldwide, dust considered be main source. Since 2008, facilitated extensive field campaign rigorous intercalibration international GEOTRACES program, has been “explosion” availability data, hundreds now available. Concurrently, a paradigm shift view marine Fe cycle where multiple sources contribute, some forms can transported great distances through intermediate deep Here, we showcase datasets across different ocean basins, synthesize our current multi-source cycle, spotlight sediments as important source, look future directions constraining boundary exchange.

Язык: Английский

Процитировано

5
Elevated Marine Dissolved Silica Levels Explain a Wide Range of Ediacaran–Cambrian Ediacara‐Style Fossil Deposits DOI
Lidya G. Tarhan, Ashleigh v.S. Hood, Mary L. Droser

и другие.

Geobiology, Год журнала: 2025, Номер 23(2)

Опубликована: Март 1, 2025

The processes responsible for the fossilization of Ediacara Biota-Earth's earliest fossil record communities complex, multicellular organisms-have long been debated. On basis both geologic and experimental investigations, recent studies have proposed that early diagenetic silica cementation may pivotal to moldic preservation in sandstone ("Ediacara-style preservation") assemblages from eponymous Member South Australia. However, extent which can explain other instances Ediacara-style units recording disparate depositional environments, paleogeographies, ages has not previously constrained. Herein, we present new paleontological, petrographic, geochemical data a range assemblages, encompassing variety Ediacaran Cambrian macroorganism morphologies, ecologies, taxonomic affinities, as well sedimentary records organic substrates macrofaunal interactions they record. These indicate formation cements was widespread phenomenon sandy seafloor environments likely played role these exceptional assemblages. Moreover, persistence linked authigenic into strata provides evidence end-Ediacaran disappearance Biota due evolutionary rather than taphonomic phenomena.

Язык: Английский

Процитировано

0
Introduction to the special issue on twenty years of GEOTRACES: An international study of the marine biogeochemical cycles of trace elements and isotopes DOI Creative Commons
Tim M. Conway, Jessica N. Fitzsimmons, Rob Middag

и другие.

Oceanography, Год журнала: 2024, Номер 37(2)

Опубликована: Янв. 1, 2024

This special issue of Oceanography celebrates the transformational findings international GEOTRACES program in chemical oceanography, 20 years after drafting Science Plan 2004 (GEOTRACES Planning Group, 2006). With section cruise phase ending soon, and a planned pivot toward smaller-​scale process studies, this is an opportune time to look back at achievements during last two decades highlight some advances our understanding processes that determine oceanic distributions trace elements isotopes (TEIs).

Язык: Английский

Процитировано

0
MORPHOLOGY AND PRESERVATION OF GAOJIASHANIA, AN ENIGMATIC TUBULAR FOSSIL FROM THE UPPER EDIACARAN DUNFEE MEMBER, DEEP SPRING FORMATION, NEVADA, USA DOI

A Rivas,

Paul M. Myrow, Emily F. Smith

и другие.

Palaios, Год журнала: 2024, Номер 39(12), С. 444 - 461

Опубликована: Дек. 19, 2024

Abstract The upper Ediacaran stratigraphic record hosts fossil assemblages of Earth’s earliest communities complex, macroscopic, multicellular life. Tubular fossils are a common and diverse, though frequently undercharacterized, component many these assemblages. Gaojiashania cyclus is an enigmatic tubular candidate index found in strata globally best known from the Gaojiashan Lagerstätte South China. Here we describe recently discovered assemblage Dunfee Member Deep Spring Formation Nevada, USA. Both body trace affinities have been proposed for Gaojiashania; present morphological biostratinomic evidence affinity specimens. Additionally, previous studies highlighted that characterized by wide range preservational modes, including association with pyrite, apatite, or clay minerals preservation as carbonaceous compressions. Petrographic, SEM, EDS data indicate specimens preserved ‘Ediacara-style’ external, internal composite molds, siltstone sandstone mineral-rich matrix both aluminosilicates non-aluminous Mg- Fe-rich silicate interpret authigenic clays. Authigenic clay-mediated fossilization unmineralized tissues, moldic heterolithic siliciclastic strata, indicated Gaojiashania, may be linked to prevalence silica-rich ferruginous seawater conditions prior radiation silica-biomineralizing organisms rise ocean atmospheric oxygen modern levels. In this light, authigenesis played critical role facilitating multiple modes Cambrian exceptional fossilization, thus shaping distribution Ediacara macrofossil taxa.

Язык: Английский

Процитировано

0