Radiocarbon analysis of halophilic microbial lipids from an Australian salt lake

Assigning accurate dates to hypersaline sediments opens important terrestrial records of local and regional paleoecologies and paleoclimatology. However, as of yet no conventional method of dating hypersaline systems has been widely adopted. Biomarker, mineralogical, and radiocarbon analyses of sediments and organic extracts from a shallow (13 cm) core from a hypersaline playa, Lake Tyrrell, southeastern Australia, produce a coherent age-depth curve beginning with modern microbial mats and extending to ~ 7500 cal yr BP. These analyses are furthermore used to identify and constrain the timing of the most recent change in hydrological regime at Lake Tyrrell, a shift from a clay deposit to the precipitation of evaporitic sands occurring at some time between ~ 4500 and 7000 yr. These analyses show the potential for widespread dating of hypersaline systems integrating the biomarker approach, reinforce the value of the radiocarbon content of biomarkers in understanding the flow of carbon in modern ecologies, and validate the temporal dimension of data provided by biomarkers when dating late Quaternary sediments.

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The Genome Sequence ofMethanohalophilus mahiiSLPTReveals Differences in the Energy Metabolism among Members of theMethanosarcinaceaeInhabiting Freshwater and Saline Environments

Archaea ◽

10.1155/2010/690737 ◽

2010 ◽

Vol 2010 ◽

pp. 1-16 ◽

Cited By ~ 25

Author(s):

Stefan Spring ◽

Carmen Scheuner ◽

Alla Lapidus ◽

Susan Lucas ◽

Tijana Glavina Del Rio ◽

...

Keyword(s):

Energy Metabolism ◽

Genome Sequence ◽

Salt Lake ◽

Methanogenic Archaea ◽

Distinct Species ◽

Freshwater Species ◽

Protein Coding ◽

Hypersaline Sediments ◽

Methanohalophilus Mahii ◽

Halophilic Species

Methanohalophilus mahiiis the type species of the genusMethanohalophilus, which currently comprises three distinct species with validly published names.Mhp. mahiirepresents moderately halophilic methanogenic archaea with a strictly methylotrophic metabolism. The type strain SLPTwas isolated from hypersaline sediments collected from the southern arm of Great Salt Lake, Utah. Here we describe the features of this organism, together with the complete genome sequence and annotation. The 2,012,424 bp genome is a single replicon with 2032 protein-coding and 63 RNA genes and part of theGenomic Encyclopedia of Bacteria and Archaeaproject. A comparison of the reconstructed energy metabolism in the halophilic speciesMhp. mahiiwith other representatives of theMethanosarcinaceaereveals some interesting differences to freshwater species.

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A chronology for Late Quaternary weathering in the Murray Basin, southeastern Australia: evidence from230Th/U dating of secondary uranium phosphates in the Lake Boga and Wycheproof granites, Victoria

Australian Journal of Earth Sciences ◽

10.1080/08120099.2011.594090 ◽

2011 ◽

Vol 58 (7) ◽

pp. 835-845 ◽

Cited By ~ 6

Author(s):

W. D. Birch ◽

S. J. Mills ◽

R. Maas ◽

J. C. Hellstrom

Keyword(s):

Late Quaternary ◽

Southeastern Australia ◽

Murray Basin ◽

Uranium Phosphates

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Botryoidal and Spherulitic Aragonite in Carbonates Associated with Microbial Mats: Precipitation or Diagenetic Replacement Product?

Frontiers in Earth Science ◽

10.3389/feart.2021.698952 ◽

2021 ◽

Vol 9 ◽

Author(s):

Yuzhu Ge ◽

Giovanna Della Porta ◽

Chelsea L. Pederson ◽

Stephen W. Lokier ◽

René Hoffmann ◽

...

Keyword(s):

Extracellular Polymeric Substances ◽

Microbial Mats ◽

Salt Lake ◽

Pore Space ◽

Depositional Environments ◽

Formation Mechanisms ◽

Microbial Biofilms ◽

Marine Carbonate ◽

Fluid Properties ◽

Underlying Mechanisms

Similar carbonate fabrics may result from different pathways of precipitation and diagenetic replacement. Distinguishing the underlying mechanisms leading to a given carbonate fabric is relevant, both in terms of an environmental and diagenetic interpretation. Prominent among carbonate fabrics are aragonite botryoids and spherulites, typically interpreted as direct seawater precipitates and used as proxies for fluid properties and depositional environments. This study investigated μm to mm-scale Holocene botryoidal and spherulitic aragonite from marine and non-marine carbonate settings associated with microbial mats, and reports two distinct formation mechanisms: 1) early diagenetic replacement, and 2) primary precipitation via nanocrystal aggregation. In the intertidal microbial mats of Khawr Qantur (Abu Dhabi), botryoidal and spherulitic aragonite are replacement products of heavily micritized bioclasts. To form the botryoidal and spherulitic aragonite, skeletal rods and needles, resulting from disintegration of micritized bioclasts, recrystallize into nanocrystals during early marine diagenesis. These nanocrystals then grow into fibrous crystals, forming botryoidal and spherulitic aragonite. In the lacustrine microbial bioherms of the hypersaline Great Salt Lake (United States) and in the hydrothermal travertines of Bagni San Filippo (Italy), botryoidal and spherulitic aragonite evolve from nanocrystals via precipitation. The nanocrystals are closely associated with extracellular polymeric substances in microbial biofilms and aggregate to form fibrous crystals of botryoidal and spherulitic aragonite. The studied fabrics form a portion of the bulk sediment and show differences in terms of their formation processes and petrological features compared to the often larger (few mm to over 1 m) botryoidal and spherulitic aragonite described from open-marine reefal cavities. Features shown here may represent modern analogues for ancient examples of carbonate depositional environments associated with microbialites. The implication of this research is that botryoidal and spherulitic aragonite associated with microbial mats are relevant in paleoenvironmental interpretations, but must be combined with a detailed evaluation of their formation process. Care must be taken as the term “botryoidal and spherulitic aragonite” may in fact include, from the viewpoint of their nucleation and formation mechanism, similar fabrics originated from different pathways. At present, it seems unclear to which degree the μm to mm-scale botryoids and spherulites described here are comparable to their cm-to dm-size counterparts precipitated as cements in the open pore space of reefal environments. However, it is clear that the investigation of ancient botryoidal and spherulitic aragonite must consider the possibility of an early diagenetic replacement origin of these precipitates.

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Dramatic reduction in size of the lowland Macquarie River in response to Late Quaternary climate-driven hydrologic change

Quaternary Research ◽

10.1017/qua.2018.48 ◽

2018 ◽

Vol 90 (2) ◽

pp. 360-379 ◽

Cited By ~ 5

Author(s):

Paul P. Hesse ◽

Rory Williams ◽

Timothy J. Ralph ◽

Zacchary T. Larkin ◽

Kirstie A. Fryirs ◽

...

Keyword(s):

River Discharge ◽

Late Quaternary ◽

Optically Stimulated Luminescence ◽

Fluvial System ◽

Sediment Delivery ◽

Lowland Rivers ◽

Southeastern Australia ◽

Quaternary Climate ◽

Hydrologic Change ◽

Single Grain

AbstractPalaeochannels of lowland rivers provide a means of investigating the sensitivity of river response to climate-driven hydrologic change. About 80 palaeochannels of the lower Macquarie River of southeastern Australia record the evolution of this distributive fluvial system. Six Macquarie palaeochannels were dated by single-grain optically stimulated luminescence. The largest of the palaeochannels (Quombothoo, median age 54 ka) was on average 284 m wide, 12 times wider than the modern river (24 m) and with 21 times greater meander wavelength. Palaeo-discharge then declined, resulting in a younger, narrower, group of palaeochannels, Bibbijibbery (125 m wide, 34 ka), Billybingbone (92 m, 20 ka), Milmiland (112 m, 22 ka), and Mundadoo (86 m, 5.6 ka). Yet these channels were still much larger than the modern river and were continuous downstream to the confluence with the Barwon-Darling River. At 5.5 ka, a further decrease in river discharge led to the formation of the narrow modern river, the ecologically important Macquarie Marshes, and Marra Creek palaeochannel (31 m, 2.1 ka) and diminished sediment delivery to the Barwon-Darling River as palaeo-discharge fell further. The hydrologic changes suggest precipitation was a driving forcing on catchment discharge in addition to a temperature-driven runoff response.

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Seismotectonics of the 1987–1988 Lakeside, Utah, Earthquakes

Seismological Research Letters ◽

10.1785/gssrl.64.3-4.225 ◽

1993 ◽

Vol 64 (3-4) ◽

pp. 225-238

Author(s):

James C. Pechmann ◽

Walter J. Arabasz ◽

Ethan D. Brown

Keyword(s):

Focal Mechanism ◽

Salt Lake ◽

Epicentral Distance ◽

Late Quaternary ◽

Great Salt Lake ◽

Epicentral Area ◽

Lake Center ◽

The Right ◽

Foreshock Activity ◽

Pumping Activity

Abstract From September 1987 through March 1988, an earthquake sequence which induded shocks of ML 4.8 and 4.7 on September 25 and October 26, respectively, and a total of 8 moderate-sized events of ML ≥ 3.8, occurred in NW Utah beneath a desert basin west of the Great Salt Lake (center of activity: 41° 12.0′ N, 113° 10.5′ W). Wood-Anderson seismograms indicate nearly identical magnitudes for the two largest earthquakes but a factor of two to five larger seismic moment for the first. Significant aspects of the 1987–1988 sequence induded: foreshock activity, proximity (epicentral distance, Δ, of 7 to 12 km) to a major pumping facility completed in early 1987 to lower the level of the Great Salt Lake, an unambiguous strike-slip focal mechanism for the ML 4.8 mainshock, and the lack of a clear association with late Quaternary surface faults. Despite constraints on accessibility to the epicentral area, the stations of the regional seismic network (Δ ≥ 60 km) were supplemented with local stations—initially four portable seismographs and later up to four telemetered stations (2 ≤ Δ ≤ 27 km) that operated continuously from October 7, 1987, through March 1988. Well-located aftershock foci form a 6-by-6-km zone between 6 and 12 km depth which is steeply dipping and trends SSE, parallel to the right-lateral nodal plane of the mainshock focal mechanism. Despite coincidental timing and proximity of the earthquakes to major pumping activity at the surface, the case for induced seismicity related to the pumping is weak.

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