Valeri Sachanski | Bulgarian Academy of Sciences (original) (raw)
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Review of the Bulgarian Geological Society
Paleozoic (Silurian and Devonian) cherts from Western Bulgaria occur in three tectonic units: Svo... more Paleozoic (Silurian and Devonian) cherts from Western Bulgaria occur in three tectonic units: Svoge, Lyubash-Golo Bardo and Morava. The SiO2 content in these rocks varies from 76.06% to 96.02%. The silica source and depositional settings of the cherts have been interpreted based on the received geochemical major element data. The calculated Si/(Si+Fe+Al+Ca) ratio and Al–Fe–Mn diagram plotting at non-hydrothermal field suggest that most of silica in the cherts is biogenic or both biogenic and terrigenous in origin. On the other hand, all studied siliceous samples plot into the field of the continental margin sediment environments on the Fe2O3/TiO2 vs. Al2O3/(Al2O3+Fe2O3) diagram. The calculated MnO/TiO2 ratio also indicates deposition in continental shelf or slope environments.
Paleozoic of Northern Gondwana and Its Petroleum Potential A Field Workshop, Sep 9, 2012
Geologica Balcanica, Nov 1, 2017
Proceedings of the Bulgarian Academy of Sciences, 2022
Two sandstone samples from the upper and lower part of the Ordovician succession of Svoge Unit we... more Two sandstone samples from the upper and lower part of the Ordovician succession of Svoge Unit were analyzed in order to determine their detrital zircon U–Pb age spectra using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). One sample was collected from the Hirnantian siliciclastic glaciomarine deposits of the Sirman Formation. The other sample is amiddle Darriwilian sandstone from the lower half of the Grohoten Formation. Additionally, micropetrographic studies were performed. They are composed predominantly of detrital monocrystalline quartz grains with uniform or rarely undulose extinction and only sporadically presented feldspar grains, muscovite flakes and single rock fragments. The heavy mineral assemblages are also characterized mostly by detrital zircon. As suggested from previous studies of the Hirnantian glaciomarine deposits of Sirman Formation, the provenance of siliciclastic material was most probably associated with sedimentary recycling of mat...
Unit, the Lyubash Monocline and the Morava Unit. The West Bal kan and Lyubash units con sist of s... more Unit, the Lyubash Monocline and the Morava Unit. The West Bal kan and Lyubash units con sist of siliciclastic de pos its: black grap to lit ic shales, banded pale shales and black siltstones. The Lud low, Pridoli, Lochkovian, Pragian and Emsian were rec og nized on the ba sis of graptolite and tentaculite fau nas. In the Morava Unit, the Lud low black shales are pro gres sively re placed by clayey lime stones and nod u-lar and micritic lime stones in the Pridoli and Early De vo nian. Newly ob tained cono donts show the pres ence of the siluricus, eosteinhornensis, woschmidti, postwoschmidti, delta-pesavis, sulcatus, dehiscens and gronbergi zones. Petrographic study of the Morava Unit shows an in creas ing car bon ate con tent and shallowing con di tions up wards. The biostratigraphical cor re la tion and fa cies in-ter pre ta tion re veal the co eval ex is tence of two dif fer ent depositional en vi ron ments within the same shelf ba sin as well as a grad ual shift in prox i mal di ...
Review of the Bulgarian Geological Society, 2020
The Late Devonian (372–359 million AD) is a time of prolonged climate instability with catastroph... more The Late Devonian (372–359 million AD) is a time of prolonged climate instability with catastrophic disturbances to global marine ecosystems at the Frasnian–Famennian (F/F) and Devonian–Carboniferous (D/C) boundaries. Global atmospheric CO2 content and climate change in the middle Paleozoic, especially in the Late Devonian, coincide with major events of extinction of organism groups. Anoxic intervals were documented within the Kellwasser event near the Frasnian/Famennian boundary (F/F), the Annulata event in Famennian and the Hangenberg event near the Famennian/Tournaisian boundary (D/C).
Review of the Bulgarian Geological Society, 2021
Geochemical studies of different Paleozoic intervals composed of bedded cherts, revealed in the w... more Geochemical studies of different Paleozoic intervals composed of bedded cherts, revealed in the western parts of the Srednogorie and Morava-Rhodope zones are presented: Saltar Fm; the lower and middle part of Katina Fm; the lowest part of Parchar Fm, and Tumba Fm. To determine whether the different bedded cherts intervals are hydrothermally affected, triangular diagrams of the A-F-Mn ratio were used. The low content of Fe compared to Al gives grounds to claim that the Pre-Varisian Paleozoic bedded cherts in Bulgaria are not associated with endogenous processes.
Review of the Bulgarian Geological Society, 2021
Two sandstone samples from the upper and lower parts of the Ordovician succession of the Svoge Un... more Two sandstone samples from the upper and lower parts of the Ordovician succession of the Svoge Unit were analyzed in order to determine their detrital zircon U-Pb age spectra using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Multi-dimensional scaling statistical technique allowed a reliable objective identification of the potential source areas in North Africa and paleogeographic reconstructions were made. Both samples indicate a close proximity to the Trans-Saharan Belt provenance, which is the most probable source of the detrital component.
DESCRIPTION Upper Silurian and Lower Devonian shelf deposits in West Bulgaria are exposed in thre... more DESCRIPTION Upper Silurian and Lower Devonian shelf deposits in West Bulgaria are exposed in three main Alpine tectonic units: the West Balkan Unit, the Lyubash Monocline and the Morava Unit. The West Balkan and Lyubash units consist of siliciclastic deposits: black graptolitic shales, banded pale shales and black siltstones. The Ludlow, Pridoli, Lochkovian, Pragian and Emsian were recognized on the basis of graptolite and tentaculite faunas. In the Morava Unit, the Ludlow black shales are progressively re placed by clayey limestones and nodular and micritic limestones in the Pridoli and Early Devonian. Newly obtained conodonts show the presence of the siluricus, eosteinhornensis, woschmidti, postwoschmidti, delta-pesavis, sulcatus, dehiscens and gronbergi zones. Petrographic study of the Morava Unit shows an in creasing carbonate content and shallowing conditions upwards. The biostratigraphical correlation and fa cies interpretation reveal the coeval existence of two different depo...
Review of the Bulgarian Geological Society
Paleozoic (Silurian and Devonian) cherts from Western Bulgaria occur in three tectonic units: Svo... more Paleozoic (Silurian and Devonian) cherts from Western Bulgaria occur in three tectonic units: Svoge, Lyubash-Golo Bardo and Morava. The SiO2 content in these rocks varies from 76.06% to 96.02%. The silica source and depositional settings of the cherts have been interpreted based on the received geochemical major element data. The calculated Si/(Si+Fe+Al+Ca) ratio and Al–Fe–Mn diagram plotting at non-hydrothermal field suggest that most of silica in the cherts is biogenic or both biogenic and terrigenous in origin. On the other hand, all studied siliceous samples plot into the field of the continental margin sediment environments on the Fe2O3/TiO2 vs. Al2O3/(Al2O3+Fe2O3) diagram. The calculated MnO/TiO2 ratio also indicates deposition in continental shelf or slope environments.
Paleozoic of Northern Gondwana and Its Petroleum Potential A Field Workshop, Sep 9, 2012
Geologica Balcanica, Nov 1, 2017
Proceedings of the Bulgarian Academy of Sciences, 2022
Two sandstone samples from the upper and lower part of the Ordovician succession of Svoge Unit we... more Two sandstone samples from the upper and lower part of the Ordovician succession of Svoge Unit were analyzed in order to determine their detrital zircon U–Pb age spectra using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). One sample was collected from the Hirnantian siliciclastic glaciomarine deposits of the Sirman Formation. The other sample is amiddle Darriwilian sandstone from the lower half of the Grohoten Formation. Additionally, micropetrographic studies were performed. They are composed predominantly of detrital monocrystalline quartz grains with uniform or rarely undulose extinction and only sporadically presented feldspar grains, muscovite flakes and single rock fragments. The heavy mineral assemblages are also characterized mostly by detrital zircon. As suggested from previous studies of the Hirnantian glaciomarine deposits of Sirman Formation, the provenance of siliciclastic material was most probably associated with sedimentary recycling of mat...
Unit, the Lyubash Monocline and the Morava Unit. The West Bal kan and Lyubash units con sist of s... more Unit, the Lyubash Monocline and the Morava Unit. The West Bal kan and Lyubash units con sist of siliciclastic de pos its: black grap to lit ic shales, banded pale shales and black siltstones. The Lud low, Pridoli, Lochkovian, Pragian and Emsian were rec og nized on the ba sis of graptolite and tentaculite fau nas. In the Morava Unit, the Lud low black shales are pro gres sively re placed by clayey lime stones and nod u-lar and micritic lime stones in the Pridoli and Early De vo nian. Newly ob tained cono donts show the pres ence of the siluricus, eosteinhornensis, woschmidti, postwoschmidti, delta-pesavis, sulcatus, dehiscens and gronbergi zones. Petrographic study of the Morava Unit shows an in creas ing car bon ate con tent and shallowing con di tions up wards. The biostratigraphical cor re la tion and fa cies in-ter pre ta tion re veal the co eval ex is tence of two dif fer ent depositional en vi ron ments within the same shelf ba sin as well as a grad ual shift in prox i mal di ...
Review of the Bulgarian Geological Society, 2020
The Late Devonian (372–359 million AD) is a time of prolonged climate instability with catastroph... more The Late Devonian (372–359 million AD) is a time of prolonged climate instability with catastrophic disturbances to global marine ecosystems at the Frasnian–Famennian (F/F) and Devonian–Carboniferous (D/C) boundaries. Global atmospheric CO2 content and climate change in the middle Paleozoic, especially in the Late Devonian, coincide with major events of extinction of organism groups. Anoxic intervals were documented within the Kellwasser event near the Frasnian/Famennian boundary (F/F), the Annulata event in Famennian and the Hangenberg event near the Famennian/Tournaisian boundary (D/C).
Review of the Bulgarian Geological Society, 2021
Geochemical studies of different Paleozoic intervals composed of bedded cherts, revealed in the w... more Geochemical studies of different Paleozoic intervals composed of bedded cherts, revealed in the western parts of the Srednogorie and Morava-Rhodope zones are presented: Saltar Fm; the lower and middle part of Katina Fm; the lowest part of Parchar Fm, and Tumba Fm. To determine whether the different bedded cherts intervals are hydrothermally affected, triangular diagrams of the A-F-Mn ratio were used. The low content of Fe compared to Al gives grounds to claim that the Pre-Varisian Paleozoic bedded cherts in Bulgaria are not associated with endogenous processes.
Review of the Bulgarian Geological Society, 2021
Two sandstone samples from the upper and lower parts of the Ordovician succession of the Svoge Un... more Two sandstone samples from the upper and lower parts of the Ordovician succession of the Svoge Unit were analyzed in order to determine their detrital zircon U-Pb age spectra using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Multi-dimensional scaling statistical technique allowed a reliable objective identification of the potential source areas in North Africa and paleogeographic reconstructions were made. Both samples indicate a close proximity to the Trans-Saharan Belt provenance, which is the most probable source of the detrital component.
DESCRIPTION Upper Silurian and Lower Devonian shelf deposits in West Bulgaria are exposed in thre... more DESCRIPTION Upper Silurian and Lower Devonian shelf deposits in West Bulgaria are exposed in three main Alpine tectonic units: the West Balkan Unit, the Lyubash Monocline and the Morava Unit. The West Balkan and Lyubash units consist of siliciclastic deposits: black graptolitic shales, banded pale shales and black siltstones. The Ludlow, Pridoli, Lochkovian, Pragian and Emsian were recognized on the basis of graptolite and tentaculite faunas. In the Morava Unit, the Ludlow black shales are progressively re placed by clayey limestones and nodular and micritic limestones in the Pridoli and Early Devonian. Newly obtained conodonts show the presence of the siluricus, eosteinhornensis, woschmidti, postwoschmidti, delta-pesavis, sulcatus, dehiscens and gronbergi zones. Petrographic study of the Morava Unit shows an in creasing carbonate content and shallowing conditions upwards. The biostratigraphical correlation and fa cies interpretation reveal the coeval existence of two different depo...