Autor: Rakociński, M. - Katalog OPAC zbiorów

Skocz do pozycji: 1.

Tytuł:: The youngest Devonian record of "Housean pits" in ammonoids
Autorzy:: Rakociński, M.
Powiązania:: https://bibliotekanauki.pl/articles/2059005.pdf
Data publikacji:: 2012
Wydawca:: Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:: ammonoids
parasite
pearl formation
"Housean pits"
Polska
Upper Devonian
Opis:: An unusual occurrence of parasitic "Housean pits" in internal mould of ammonoid specimen referred to as Felisporadoceras cf. subvaricatum (Sobolew) from Middle Famennian of Poland are described. Hitherto the youngest representatives of goniatites showing a pitting on the internal moulds were known from the Middle Devonian (lower Givetian), thus, most probably the presented material constitutes the youngest world record of this phenomenon.
Źródło:: Geological Quarterly; 2012, 56, 2; 387-390
1641-7291
Pojawia się w:: Geological Quarterly
Dostawca treści:: Biblioteka Nauki

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Tytuł:: Anomalous Upper Devonian mercury enrichments : comparison of Inductively Coupled Plasma – Mass Spectrometry (ICP-MS) and Atomic Absorption Spectrometry (AAS) analytical data
Autorzy:: Racki, G.
Rakociński, M.
Marynowski, L.
Powiązania:: https://bibliotekanauki.pl/articles/2060451.pdf
Data publikacji:: 2018
Wydawca:: Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:: Mercury anomalies
analytical methods
geochemistry
Frasnian-Famennian boundary
Devonian-Carboniferous boundary
volcanism
Opis:: Mercury geochemistry is emerging recently as a hot topic in chemostratigraphical and facies research, owing to the diagnostic character of Hg enrichments as a proxy of volcanic activity (crucial in the context of assumed causal links between volcanic cataclysms and mass extinctions). Thus, as a prerequisite to such far-reaching interpretations, reliable analytical determinations of Hg concentrations are necessary. In conventionally performed analyses in sedimentary geochemistry, Inductively Coupled Plasma – Mass Spectrometry (ICP-MS) is usually applied, as an analytical standard for trace elements, including Hg. However, with a detection limit (DL) of 10 ppb, such measured values have been questioned as a conclusive geochemical indicator of Hg anomalies, and, instead, far more accurate techniques, such as Atomic Absorption Spectrometry (AAS; DL = 0.2 ppb), are requested. As a preliminary test of this view, we present comparative analysis of 91 samples from three sections encompassing the key Frasnian-Famennian and Famennian-Tournaisian boundary intervals in Morocco (Lahmida), Germany (Kahlleite) and Uzbekistan (Novchomok), for which Hg concentrations were determined by both methods in the same samples. Despite some differences, especially at low Hg concentrations, both analytical methods reveal the same 12 extraordinarily enriched samples in excess of 1 ppm (with one exception, the determination error is <20%), as well as similar overall chemostratigraphic patterns characterized by a few prominent Hg spikes, with a top value of 5.8 ppm. The Hg concentrations determined by ICP-MS and AAS are significantly correlated, as high as r = 0.98 (Novchomok), even if the first method reveals a general tendency toward slightly heightened values (by ~15 to 30% for medians). Therefore, ICP-MS results can conclusively be used in mercury chemostratigraphy in order to recognize extraordinary volcanic (or other) signals, at least in the Devonian geological record. False Hg anomalies were not generated by these conventional ICP-MS determinations.
Źródło:: Geological Quarterly; 2018, 62, 3; 487--495
1641-7291
Pojawia się w:: Geological Quarterly
Dostawca treści:: Biblioteka Nauki

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