Distribution, sediment magnetism and geochemistry of the Saksunarvatn (10 180 ± 60 cal. yr BP) tephra in marine, lake, and terrestrial sediments, northwest Iceland

2002 ◽  
Vol 17 (8) ◽  
pp. 731-745 ◽  
Author(s):  
John T. Andrews ◽  
Aslaug Geirsdóttir ◽  
Jórunn Hardardóttir ◽  
Sarah Principato ◽  
Karl Grönvold ◽  
...  
Keyword(s):  
Terrestrial Sediments ◽  
Sediment Magnetism

Formations of Late Neogene and Pleistocene terrestrial sediments in the region of Mórágy Hill (Hungary)

2005 ◽  
Vol 48 (3) ◽  
pp. 317-337 ◽  
Author(s):  
László Koloszár ◽  
István Marsi
Keyword(s):  
Late Neogene ◽  
Terrestrial Sediments

USING SEDIMENT MAGNETISM TO ASSESS ANTHROPOGENIC IMPACTS TO NORTHEAST OHIO STREAMS

2018 ◽  
Author(s):  
John A. Peck ◽  
◽  
Gabrielle A. Gromofsky ◽  
Mary Lee King ◽  
Kristofer Mann ◽  
...  
Keyword(s):  
Anthropogenic Impacts ◽  
Sediment Magnetism

scholarly journals Topset-to-forest rollover trajectories as reliable predictors of sediment-volume partitioning into deep-lake areas

2021 ◽  
Author(s):  
Xian-Zheng Zhao ◽  
Cheng-Lin Gong ◽  
Li-Hong Zhou ◽  
Dong-Wei Li ◽  
Xiu-Gang Pu ◽  
...  
Keyword(s):  
Bohai Bay ◽  
Deep Lake ◽  
Bohai Bay Basin ◽  
Widespread Occurrence ◽  
Sediment Volume ◽  
Terrestrial Sediments ◽  
Qikou Sag ◽  
Sand Budget ◽  
Stacking Patterns

AbstractTopset-to-forest rollover trajectories and their relation to sediment- and sand-budget partitioning into deep-lake areas are far from being well understood, as compared with their marine counterparts of shelf edges. Two quantitatively distinctive topset-to-forest rollover trajectories and clinothem-stacking patterns were recognized in the Oligocene Qikou Sag of the Bohai Bay Basin and are quantified in terms of trajectory angles (Tse), topset thickness (Tt), forest thickness (Tf), bottomset thickness (Tb), and clinothem-set relief (Rc). Rising topset-to-forest trajectories have positive Tse of 0.15°–0.51° (averaging 0.35°). Ranges in Tt, Tf, Tb, and Rc of their associated progradational and aggradational clinothem sets are, respectively, 32.4–58.7 m (averaging 42.7 m), 76.9–176.2 m (averaging 148.3 m), 0 m, and 167.8–320.8 m (averaging 272.9 m). Falling topset-to-forest rollover trajectories, in contrast, have negative Tse of − 0.12° to − 0.02° (averaging − 0.06°). Ranges in Tt, Tf, Tb, and Rc of their associated progradational and downstepping clinothem sets are, respectively, 0 m, 266.0–395.7 m (averaging 333.4 m), 441.1–542.5 m (averaging 464.1), and 874.9–922.6 m (averaging 892.5 m). These two topset-to-forest rollover trajectories and clinothem-stacking patterns are closely linked to two distinctive patterns of sediment- and sand-volume partitioning into deep-lake areas, which are quantified in terms of Tt, Tb, and differential sediment aggradation of topset segments and forest-to-bottomset compartments (As/Ad). Rising topset-to-forest rollover trajectories and associated progradational and aggradational clinothem sets are characterized by aggradational topsets (reported as Tt of 32.4–58.7 m), a lack of time-equivalent bottomsets, and As/Ad of 0.22–0.87 (averaging 0.33), and are fronted by mud-dominated depositional deposits, with sporadic occurrence of thinner and regionally localized forest sands. They are, therefore, inefficient at delivering terrestrial sediments or sands into deep-lake settings. Falling topset-to-forest rollover trajectories and associated progradational and downstepping clinothem sets, in contrast, are characterized by toplap, erosional terminations but aggradational bottomsets (reported as Tb of 266.0–473.4 m), and As/Ad of 0, and are fronted by sand-rich depositional deposits, with widespread occurrence of thicker and regionally extensive time-equivalent deep-lake bottomset sands. They are, thus, efficient at delivering terrestrial sediments or sands into deep-lake settings. Topset-to-forest rollover trajectories and associated clinothem-stacking patterns are thus reliable predictors of sediment- and sand-volume partitioning into deep-lake areas, assisting greatly in developing a more dynamic stratigraphy.

scholarly journals A nanocrystalline monoclinic CaCO3precursor of metastable aragonite

2018 ◽  
Vol 4 (12) ◽  
pp. eaau6178 ◽  
Author(s):  
Péter Németh ◽  
Enrico Mugnaioli ◽  
Mauro Gemmi ◽  
György Czuppon ◽  
Attila Demény ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Structure Determination ◽  
Diffuse Scattering ◽  
Diffraction Tomography ◽  
Synthetic Material ◽  
Near Surface ◽  
Surface Conditions ◽  
Terrestrial Sediments ◽  
Living Organisms ◽  
New Phase

Despite its thermodynamical metastability at near-surface conditions, aragonite is widespread in marine and terrestrial sediments. It abundantly forms in living organisms, and its abiotic formation is favored in waters of a Mg2+/Ca2+ratio > 1.5. Here, we provide crystallographic evidence of a nanocrystalline CaCO3polymorph, which precipitates before aragonite in a cave. The new phase, which we term monoclinic aragonite (mAra), is crystallographically related to ordinary, orthorhombic aragonite. Electron diffraction tomography combined with structure determination demonstrates that mAra has a layered aragonite structure, in which some carbonates can be replaced by hydroxyls and up to 10 atomic % of Mg can be incorporated. The diagnostic electron diffraction features of mAra are diffuse scattering and satellite reflections along aragonite {110}. Similar features have previously been reported—although unrecognized—from biogenic aragonite formed in stromatolites, mollusks, and cyanobacteria as well as from synthetic material. We propose that mAra is a widespread crystalline CaCO3that plays a hitherto unrecognized key role in metastable aragonite formation.

scholarly journals The Geochronology and Stratigraphic Evolution of Neogene Sedimentary Rocks in Jackson Hole, Wyoming

1984 ◽  
Vol 8 ◽  
pp. 33-37
Author(s):  
Douglas Burbank
Keyword(s):  
Fission Track ◽  
Sedimentary Rocks ◽  
Magnetic Polarity ◽  
Unique Sequence ◽  
Fluvial Sediments ◽  
Fission Track Dating ◽  
Hole Area ◽  
Terrestrial Sediments ◽  
Jackson Hole ◽  
Stratigraphic Evolution

The Miocene sediments of the Jackson Hole area constitute a unique sequence of terrestrial sediments. While much of the surrounding terrain was undergoing denudation during the Miocene, over 4000 m of volcaniclastic, lacustrine, and fluvial sediments accumulated in the vicinity of Jackson Hole. Recently completed paleontological and palynological studies have served to delineate complex biostratigraphic and climatic histories. The present research project has several goals. Chronologies are being developed for the Miocene sediments through the use of magnetic-polarity stratigraphies and fission-track dating. Sedimentation histories are being studied by combining lithologic data with chronologic information.

scholarly journals The Iso2k Database: A global compilation of paleo-δ<sup>18</sup>O and δ<sup>2</sup>H records to aid understanding of Common Era climate

2020 ◽  
Author(s):  
Bronwen L. Konecky ◽  
Nicholas P. McKay ◽  
Olga V. Churakova (Sidorova) ◽  
Laia Comas-Bru ◽  
Emilie P. Dassié ◽  
...  
Keyword(s):  
Large Scale ◽  
Climate Model ◽  
Global Environmental Change ◽  
Global Scale ◽  
Proxy Records ◽  
Global Environmental ◽  
Past 2000 Years ◽  
Wide Range ◽  
Terrestrial Sediments ◽  
Common Era

Abstract. Reconstructions of global hydroclimate during the Common Era (CE; the past ~ 2000 years) are important for providing context for current and future global environmental change. Stable isotope ratios in water are quantitative indicators of hydroclimate on regional to global scales, and these signals are encoded in a wide range of natural geologic archives. Here we present the Iso2k database, a global compilation of previously published datasets from a variety of natural archives that record the stable oxygen (δ18O) or hydrogen (δ2H) isotopic composition of environmental waters, which reflect hydroclimate changes over the CE. The Iso2k database contains 756 isotope records from the terrestrial and marine realms, including: glacier and ground ice (205); speleothems (68); corals, sclerosponges, and mollusks (145); wood (81); lake sediments and other terrestrial sediments (e.g., loess) (158); and marine sediments (99). Individual datasets have temporal resolutions ranging from sub-annual to centennial, and include chronological data where available. A fundamental feature of the database is its comprehensive metadata, which will assist both experts and non-experts in the interpretation of each record and in data synthesis. Key metadata fields have standardized vocabularies to facilitate comparisons across diverse archives and with climate model simulated fields. This is the first global-scale collection of water isotope proxy records from multiple types of geological and biological archives. It is suitable for evaluating hydroclimate processes through time and space using large-scale synthesis, model-data intercomparison and (paleo)data assimilation. The Iso2k database is available for download at: https://doi.org/10.6084/m9.figshare.11553162 (McKay and Konecky, 2020).

Screening of Antibiotic-Producing Actinomycetes from Marine, Brackish and Terrestrial Sediments of Samal Island, Philippines

2008 ◽  
Vol 4 (3) ◽  
Author(s):  
Marilen M Parugao ◽  
Ebner Bon G Maceda ◽  
Maria Angelica F Villano
Keyword(s):  
Terrestrial Sediments

Quaternary Climatic Changes and Landscape Evolution

2005 ◽  
Author(s):  
Jürgen Ehlers
Keyword(s):  
Climatic Change ◽  
Large Scale ◽  
Western Europe ◽  
Ice Sheets ◽  
Climatic Changes ◽  
Mountain Glaciers ◽  
Marine Deposits ◽  
The North ◽  
Terrestrial Sediments ◽  
International Geological Congress

The last 2–3 Ma have witnessed climatic changes of a scale unknown to the preceding 300 Ma. In the cold periods vegetation was reduced to a steppe, giving rise to large-scale aeolian deposition of sand and loess and river sands and gravels. In the warm stages, flora and fauna recolonized the region. Parts of Europe were repeatedly covered by mountain glaciers or continental ice sheets which brought along huge amounts of unweathered rock debris from their source areas. The ice sheets dammed rivers and redirected drainage towards the North Sea. They created a new, glacial landscape. This chapter presents an outline of the climatic history, and in particular the glacial processes involved in shaping the landscapes of western Europe. By convention, geologists generally tend to draw stratigraphical boundaries in marine deposits because they are more likely to represent continuous sedimentation and relatively consistent environments in comparison to terrestrial sediments. However, marine deposits from the period in question are relatively rarely exposed at the surface. According to a conclusion of the International Geological Congress 1948 the Tertiary/Quaternary boundary was defined as the base of the marine deposits of the Calabrian in southern Italy. In the Calabrian sediments fossils are found that reflect a very distinct climatic cooling (amongst others the foraminifer Hyalinea baltica). This climatic change roughly coincides with a reversal of the earth’s magnetic field; it is situated at the upper boundary of what is called the Olduvai Event. Consequently, it is relatively easy to identify; its age is today estimated at 1.77 Ma (Shackleton et al. 1990). However, in contrast to the older parts of the earth’s history, the significant changes within the Quaternary are not changes in faunal composition but changes in climate. For reasons of long-term climatic evolution the base of the Calabrian is not a very suitable global boundary. Its adoption excludes some of the major glaciations from the Quaternary. Therefore, in major parts of Europe another Tertiary/Quaternary boundary is in use, based on the stratigraphy of the Lower Rhine area (e.g. Zagwijn 1989). Here the most significant climatic change is already recorded as far back as the Gauss/Matuyama magnetic reversal (some 2.6 Ma ago).

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