J 2009

Early Middle Frasnian platform reef strata in the Moravian Karst interpreted as recording the atmospheric dust changes: the key to understanding perturbations in the punctata conodont zone

HLADIL, Jindřich, Leona KOPTÍKOVÁ, Arnošt GALLE, Václav SEDLÁČEK, Petr PRUNER et. al.

Basic information

Original name

Early Middle Frasnian platform reef strata in the Moravian Karst interpreted as recording the atmospheric dust changes: the key to understanding perturbations in the punctata conodont zone

Name in Czech

Ranné středněfrasnské útesové platformní sedimenty Moravského krasu interpretované jako záznam změn atmosférického prachu: klíč k pochopení výkyvů v konodontové zóně punctata

Authors

HLADIL, Jindřich (203 Czech Republic, guarantor), Leona KOPTÍKOVÁ (203 Czech Republic), Arnošt GALLE (203 Czech Republic), Václav SEDLÁČEK (203 Czech Republic), Petr PRUNER (203 Czech Republic), Petr SCHNABL (203 Czech Republic), Anna LANGROVÁ (203 Czech Republic), Ondřej BÁBEK (203 Czech Republic, belonging to the institution), Jaroslav FRÁŇA (203 Czech Republic), Jana HLADÍKOVÁ (203 Czech Republic), Jiří OTAVA (203 Czech Republic) and Milan GERŠL (203 Czech Republic)

Edition

Bulletin of Geosciences, Praha, Czech Geological Survey, 2009, 1214-1119

Other information

Language

English

Type of outcome

Článek v odborném periodiku

Field of Study

10500 1.5. Earth and related environmental sciences

Country of publisher

Czech Republic

Confidentiality degree

není předmětem státního či obchodního tajemství

Impact factor

Impact factor: 0.983

RIV identification code

RIV/00216224:14310/09:00051203

Organization unit

Faculty of Science

UT WoS

000264709300009

Keywords (in Czech)

minerální prach, útes, sedimentace částic, sedimentární rytmy, stromatactis, klimatické podmínky, magnetická susceptibility, gamaspektrometrie, geochemie, výkyvy střední punctata, impaktní událost Alamo, svrchní devon, brunovistulický terán, Morava, Česká republika

Keywords in English

mineral dust; platform reef; sedimentation of particulates; sedimentary rhythms; stromatactis; climate conditions; magnetic susceptibility; gamma-ray spectrometry; geochemistry; mid-punctata Zone perturbations; Alamo impact event

Tags

Tags

International impact, Reviewed
Změněno: 12/4/2012 14:22, Iva Klímová

Abstract

V originále

Development of new stratigraphic techniques has led to better understanding of the compositional variability and quantity of dust-related impurity components in pure marine limestones, with a considerable impact on stratigraphic resolution and explanation of causality. The early Middle Frasnian (E-MF, punctata Zone) stratigraphic interval was selected for this study in order to assess the contribution of atmospheric dust and to distinguish between the robust climatically driven anomalies and the potential distant effect of the Alamo impact. The location of the study in the Moravian Karst area has two advantages: there are no mixed carbonate-siliciclastic sediments, only the pure limestone of a platform reef complex, and the authors have access to voluminous survey and drilling reports. The methodology employed for undertaking the most recent research was based on succession and combination of the following steps: biostratigraphy and facies analysis, magnetic susceptibility (MS), gamma-ray spectrometry (GRS), instrumental neutron activation analysis (INAA), and finally, separation and assessment of rare non-carbonate particles. The natural atmospheric dust burden, deposition, and embedding in pure carbonate traps were, most likely, threefold higher during the Frasnian in the Upper Devonian in comparison with Quaternary platform reef counterparts. Variation of 10-100 ka averages is medium in terms of the Frasnian ranges of MS-GRS values, and the base and top of the E-MF interval are manifested by robust elevations of these values. Forced anomalies in MS, GRS and geochemical signals that defy the normal sequence of rhythms were found: two anomalies disturb the broad middle part of the E-MF interval and one is superimposed on the upper part of the punctata-hassi zones strata. The most significant disturbance was found near the mid-punctata Zone level. In spite of the relatively low magnitude, it shows features that are usually related to major environmental crises which occured in the Devonian, such as the Chotec, Kacak or Kellwasser events. These include a large depression in MS and dust-particle concentration values coupled with a period of sea level lowstand and calm atmospheric conditions (stage A), and an abrupt shift to high MS that has a comb-like pattern that gradually fades upward, developed together with a forced flooding surface, increased detritism, and stormy conditions (stage B). It is a reverse of the normal cyclicity in pure limestone when the high impurity corresponds to lowstands. A very small amount of particulate material of an exotic nature was found at the A-B stage interface and assessed: it contained iron-rich silicate microspherules and drops, devitrified glasses, tiny mineral/rock clasts of hyperbasite compositions, as well as pellets and clumps of glasses and phlogopites. The silt-sized particles show ablated and striated surfaces, flow deformation of devitrified glasses, and layered onion-like structures. Iron-rich lamellae with meshwork crystal patterns occur among decrepitated crystalline mineral phases. This material is tentatively attributed to some vigorous ejection of deep Earth layers, or speculatively, to some previously undescribed olivine-phyric to basaltic and Ni-, Cr-depleted siderolite material of meteoritic origin.

In Czech

viz. anglický abstrakt