Wyniki wyszukiwania - BazTech

1

Middle to Late Jurassic carbonate-biosiliceous sedimentation and palaeoenvironment in the Tethyan Fatricum Domain, Krížna Nappe, Tatra Mts, Western Carpathians

Jach Renata, Reháková Daniela

Annales Societatis Geologorum Poloniae

|

2019

|

Vol. 89, No. 1

1--46

EN

The Jurassic of the Alpine-Mediterranean Tethys was characterized by the formation of several interconnected basins, which underwent gradual deepening and oceanization. Sedimentation in each basin was influenced by a specific set of interrelated factors, such as tectonic activity, seawater circulation, climate, chemistry and trophic state of seawater as well as evolutionary changes of the marine biota. This paper deals with the Fatricum Domain (Central Carpathians, Poland and Slovakia), which in the Jurassic was a pull-apart basin on a thinned continental crust. The sedimentation history of this domain during the Bajocian-Tithonian and its governing factors have been revealed. Facies analysis of the Bajocian-Oxfordian deposits evidences considerable relief of the basin-floor topography. Deposits in the Western Tatra Mts represent sedimentation on a submarine intrabasinal high, whereas the coeval deposits of the eastern part of the Tatra Mts accumulated in a deeper basin. The basin succession began with Bajocian bioturbated “spotted” limestones and siliciclastic mudstones (Fleckenmergel facies). These were succeeded by uppermost Bajocian - middle Bathonian grey nodular limestones, affected by synsedimentary gravitational bulk creep. The coeval deposits of the intrabasinal high are represented by well-washed Bositra-crinoidal limestones with condensed horizons. Uniform radiolarite sedimentation commenced in the late Bathonian and persisted until the early late Kimmeridgian. The basal ribbon radiolarites (upper Bathonian - lower Oxfordian), which consist of alternating chert beds and shale partings, are a record of seawater eutrophication, a related crisis in carbonate production and the rise of the CCD, which collectively resulted in biosiliceous sedimentation. The overlying calcareous radiolarites (middle Oxfordian - lowermost upper Kimmeridgian) marked a gradual return to carbonate sedimentation. The return of conditions that were favourable for carbonate sedimentation took place in the late Kimmeridgian, when the red nodular limestones were deposited. They are partly replaced by basinal platy limestones (uppermost Kimmeridgian - Tithonian) in the Western Tatra Mts. This lateral variation in facies reflects a change in the sedimentary conditions governed by a bathymetric reversal of the seafloor configuration, attributed to a further stage in the pull-apart transcurrent tectonics of the Fatricum Domain.

2

Review of existing systems of jaspers nomenclature and classification in Poland and worldwide

Powolny T., Dumańska-Słowik M.

Gospodarka Surowcami Mineralnymi

|

2017

|

T. 33, z. 2

43--52

EN

Nowadays, the term “jasper” is variably defined in petrology and gemology. The unification of the nomenclature and the classification of jaspers seems to be an essential challenge for petrologists worldwide. This misnomer is very commonly used among sellers or collectors of various gemstones. Therefore, a huge diversity in the mineralogical composition, geological settings and genesis of particular “spotted stones” is reported. In this paper the term “jasper” is proposed for all “spotted stones” which have technical properties that make them useful for jewelry and in the production of small stone accessories. Nevertheless, the introduction and approval of the term “true jasper” for rocks of hydrothermal-metasomatic origin and metamorphosed volcanogenic-sedimentary products to petrologic nomenclature is recommended. Different types of jaspers and related rocks have various economic significance. Jaspers or jasper-like rocks are decorative gemstones applied in jewelry, whereas others may be used as refractory materials or feldspar raw materials. In contrast, the petrographic research of jasperoids is useful during prospecting new ore deposits.

PL

Tematem artykułu jest problematyka nazewnictwa i klasyfikacji jaspisów oraz skał im pokrewnych w Polsce i na świecie. Termin jaspis jest obecnie różnie definiowany przez badaczy zajmujących się gemmologią i petrologią. Zróżnicowanie aktualnych poglądów dotyczących wspomnianych typów skał niesie ze sobą poważne konsekwencje. Termin jaspis cechuje się stosunkowo dużą popularnością wśród osób zajmujących się dystrybucją i sprzedażą kamieni ozdobnych. Jego stosowanie często okazuje się mylące dla potencjalnych nabywców „cętkowanych kamieni”. Z tego względu istotne wydaje się wprowadzenie do nomenklatury gemmologicznej i petrologicznej terminu jaspis prawdziwy (ang. true jasper). W artykule przedstawiono przegląd jaspisów występujących w Polsce oraz ich klasyfikację w świetle definicji podawanych przez różnych autorów. Uwzględniono w nim także ekonomiczne aspekty wykorzystania różnych rodzajów jaspisów. Większość tego typu skał ma zastosowanie w jubilerstwie, kamieniarstwie i produkcji drobnej galanterii kamiennej. Podobne do jaspisów pod względem mineralogicznym skały o charakterze jasperoidów mogą z kolei stanowić cenny wskaźnik przy poszukiwaniu złóż epitermalnych metali, takich jak np. złoto.

3

Integrated stratigraphy (radiolarians and calcareous nannofossils) of the Middle to Upper Jurassic Alpine radiolarites (Lombardian Basin, Italy):constraints to a genetic interpretation

Chiari M., Cobianchi M., Picotti V.

Volumina Jurassica

|

2006

|

Vol. 4, no. 1

152-153

EN

New biostratigraphic data obtained by integrating radiolarian and calcareous nannofossil stratigraphy document a depositional history for the Middle to Upper Jurassic radiolarites of the Southern Alps characterized by strong fluctuations in the sedimentation rates, associated with shifts from turbiditic to hemipelagic sedimentary processes. The radiolarites were studied in four sections located in different settings of the Lombardian Basin, a rifted basin of the northern Adriatic Plate, where this interval is known as Selcifero Lombardo Formation. The latter consists of two members, the Radiolarite and the Rosso ad Aptici, respectively, and passes, gradually, upwards to the Maiolica Formation. The sections studied were sampled in detail to obtain data on their lithology (using facies and microfacies analyses and calcimetry) and their nanno- and microfossils content (especially radiolarians, and calpionellids). An almost complete record of radiolarians was detected throughout the Selcifero Lombardo Formation, so that the Radiolarian Zonation (UAZones) for the Middle to Upper Jurassic interval, partially integrated with calcareous nannofossils and calpionellid biostratigraphic data, was successfully applied. Accordingly, the Radiolarite unit correlates with the Lower Bathonian (UAZ. 5) to the Kimmeridgian (UAZ. 11) interval, and the Rosso ad Aptici member displays an age spanning from Kimmeridgian to the base of Upper Tithonian (from the UAZ. 10-11 to nannofossil NJK zone). The base of the Maiolica Formation is assigned to Upper Tithonian, in agreement with the previous authors. We interpret the radiolarites as pelagic sediments relatively enriched in radiolarian during a long time span of basin starvation, due to the near absence of periplatform exportation. Because the very low sedimentation rates equally imply low radiolarian productivity, it is not necessary to claim for high water fertility during Middle to Late Jurassic, even if this latter condition likely played a role in development of the carbonate platforms.