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1

Klimat i oceanografia przełomu jury i kredy zachodniej Tetydy

Lodowski Damian Gerard

Przegląd Geologiczny

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2023

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Vol. 71. nr 10

514--522

EN

The key aspect for evaluation of potential effects of ongoing environmental changes is identification of their controlson one hand, and understanding of their mutual relations on other. In this context, the best source of information about medium and long term coThe key aspect for evaluation of potential effects of ongoing environmental changes is identification of their controlson one hand, and understanding of their mutual relations on other. In this context, the best source of information about medium and long term consequences of various environmental processes is the geologic record. Numerous different-scale palaeoenvironmental events took place during the Jurassic/Cretaceous transition; amongst them, the best documented so far are: long term marine regression during the Tithonian-early Berriasian, climate aridization during the late Tithonian-early Berriasian, and tectonic activity in western parts of the Neo Tethys Ocean during the late Berriasian-Valanginian. This study, which is based on the Ph Ddissertation of Damian Gerard Lodowski, attempts to reconstruct the latest Jurassic-earliest Cretaceous paleoenvironment and its evolution in the area of the Western Tethys, with special attention paid to cause-and-effect relationships between climate changes, tectonic activity and oceanographic conditions (perturbations in marine circulation and bioproductivity). Here are presented the basic results of high-resolution geochemical investigations performed in the Transdanubian Range (Hárskút and Lókút, Hungary), High-Tatric (Giewont, Poland) and Lower Sub-Tatric (Pośrednie III, Poland) series, Pieniny Klippen Belt (Brodno and Snežnica, Slovakia; Velykyi Kamianets, Ukraine) and Western Balkan (Barlya, Bulgaria) sections. The sections were correlated and compared in terms ofpaleoredox conditions (authigenic U), accumulation of micronutrient-type element (Zn) and climate changes (chemical index of alteration, CIA), providinga consistent scenario of the Tithonian-Berriasian palaeoenvironment evolution in various western Tethyan basins. Amongst the first-order trends and events, characteristic of studied sections are the two intervals recording an oxygen deficient at the seafloor: 1) the upper Tithonian-lowermost Berriasian (OD I); and 2) at the lower/upper Berriasian transition (OD II). Noteworthy, this phenomena cooccurred with elevated accumulations of nutrient-type elements (i. e. enrichment factor of Zn). Besides, collected data document the late Tithonian-early Berriasian trend of climate aridization, as well as the late Berriasian humidification. Such record is explained by a model, in which decreasing intensity of atmospheric circulation during the late Tithonian-early Berriasian was directly connected with climate cooling and aridization. This process resulted in lesser efficiency of up- and/or downwelling currents, which induced sea water stratification, seafloor hypoxia and perturbations in the nutrient-shuttle process during the OD I. On the other hand, the OD II interval may correspond to tectonic reactivation in the Neo Tethyan Collision Belt. This process might have led to physical cutoff of Alpine Tethys basins from the Neo Tethyan circulation (both atmospheric and oceanic), driving the limited stratification in the former, and limiting the effect of gradual humidification of global climate (i.e. due to increasing strength of monsoons and monsoonal upwellings). nsequences of various environmental processes is the geologic record. Numerous different-scale palaeoenvironmental events took place during the Jurassic/Cretaceous transition; amongst them, the best documented so far are: long term marine regression during the Tithonian-early Berriasian, climate aridization during the late Tithonian-early Berriasian, and tectonic activity in western parts of the Neo Tethys Ocean during the late Berriasian-Valanginian. This study, which is based on the Ph Ddissertation of Damian Gerard Lodowski, attempts to reconstruct the latest Jurassic-earliest Cretaceous paleoenvironment and its evolution in the area of the Western Tethys, with special attention paid to cause-and-effect relationships between climate changes, tectonic activity and oceanographic conditions (perturbations in marine circulation and bioproductivity). Here are presented the basic results of high-resolution geochemical investigations performed in the Transdanubian Range (Hárskút and Lókút, Hungary), High-Tatric (Giewont, Poland) and Lower Sub-Tatric (Pośrednie III, Poland) series, Pieniny Klippen Belt (Brodno and Snežnica, Slovakia; Velykyi Kamianets, Ukraine) and Western Balkan (Barlya, Bulgaria) sections. The sections were correlated and compared in terms ofpaleoredox conditions (authigenic U), accumulation of micronutrient-type element (Zn) and climate changes (chemical index of alteration, CIA), providinga consistent scenario of the Tithonian-Berriasian palaeoenvironment evolution in various western Tethyan basins. Amongst the first-order trends and events, characteristic of studied sections are the two intervals recording an oxygen deficient at the seafloor: 1) the upper Tithonian-lowermost Berriasian (OD I); and 2) at the lower/upper Berriasian transition (OD II). Noteworthy, this phenomena cooccurred with elevated accumulations of nutrient-type elements (i. e. enrichment factor of Zn). Besides, collected data document the late Tithonian-early Berriasian trend of climate aridization, as well as the late Berriasian humidification. Such record is explained by a model, in which decreasing intensity of atmospheric circulation during the late Tithonian-early Berriasian was directly connected with climate cooling and aridization. This process resulted in lesser efficiency of up- and/or downwelling currents, which induced sea water stratification, seafloor hypoxia and perturbations in the nutrient-shuttle process during the OD I. On the other hand, the OD II interval may correspond to tectonic reactivation in the Neo Tethyan Collision Belt. This process might have led to physical cutoff of Alpine Tethys basins from the Neo Tethyan circulation (both atmospheric and oceanic), driving the limited stratification in the former, and limiting the effect of gradual humidification of global climate (i.e. due to increasing strength of monsoons and monsoonal upwellings).

2

Unraveling the collisional history of the Western Carpathians through deep geophysical sounding

Soni Tanishka, Schiffer Chrystian, Mazur Stanisław

Geotourism / Geoturystyka

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2023

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nr 1-2 (72-73)

65--66

EN

The ALpine-CArpathian-PAnnonian (ALCAPA) block is one of the terranes involved in the Alpine-Tethys suture along with the North European Plate. In the Western Carpathians, this suture is supposed to be represented by the Pieniny Klippen Belt (PKB) which is a few kilometres wide and about 600 km long unit between the Outer Western Carpathians (OWC) and Central Western Carpathians (CWC) (Plašienka et al., 1997; Schmid et al., 2008). Unlike the Neotethian suture in the Western Carpathians, the PKB does not show the typical characteristics of a suture. The PKB is a sub-vertical unit with mainly shallow marine limestone and flysch deposits in a conspicuous “blockin-matrix” structure (Plašienka et al., 1997). The presence of “exotic” sediments in the PKB and the southernmost units of the OWC along with their shallow marine deposition environment led to the theory proposing the presence of a continental sliver called the Czorsztyn Ridge in the Alpine Tethys, dividing it into two oceanic/marine basins: the Magura Ocean to the north and the Vahic Ocean to the south (Plašienka, 2018). This controversial continental fragment possibly forming the basement for PKB successions, and its structural relationship with the adjoining OWC and CWC units, make it the main target of this project. The objective is to find evidence of the presence of this continental block, the Czorsztyn Ridge, which may have subducted along with the Vahic oceanic lithosphere underneath the CWC (Schmid et al., 2008). A passive seismic experiment will provide insight into the deep lithospheric structure across the PKP, testing the presence of a tectonic suture along with relaminated remnants of the Czorsztyn Ridge, and potential remnants of subducted or underthrusted lithosphere. Eighteen broadband stations have been deployed in a ~N-S transect (Fig. 1a) under the umbrella of the AdriaArray initiative, cutting across the PKB and Neotethian Meliata suture to the south. The data obtained during up to three years will complement 10 other permanent and temporary broadband stations, forming an approximate 370 km long profile and will be used to perform receiver function analysis and build structural and velocity models of the lithosphere (i.e., Schiffer, 2014; Schiffer et al., 2023) beneath the Western Carpathians. The horizontal extent of the imaging is shown in Figure 1b.

3

Tracing palaeocurrents from the Arctic Realm into the Tethys Ocean: the use of glendonite as an indicator for cold bottom water masses

Merkel Anna, Munnecke Alex

Geotourism / Geoturystyka

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2023

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nr 1-2 (72-73)

49--49

EN

Today, the global conveyor belt of ocean currents is controlled by the configuration of continents and the climate. Conversely, ocean currents influence water and air temperatures as well as the amount of rainfall on a regional to local scale. In addition, they govern species distribution patterns, sedimentation patterns and the dispersal of nutrients in both oceans and epeiric seas. Therefore, the reconstruction of palaeocurrents is crucial for the understanding of ancient environments and the past climate. An important driver for the global ocean circulation is the formation of deep water. However, deep-water production is difficult to estimate, and its circulation is difficult to reconstruct, not only today but especially in the geological record. Palaeocurrent reconstructions are often based on the temporal and spatial distribution of marine species. In this presentation, a new approach is proposed which uses the occurrence of glendonites as a proxy for cool bottom currents. Glendonites are pseudomorphs after the hydrous carbonate mineral ikaite (CaCO3·6H2O) which only forms in environments characterised by near-freezing temperatures. Throughout the Phanerozoic, glendonites can be found in successions which were deposited in high latitudes. However, examples of glendonite occurrences in mid-latitudinal sections are also reported. One of these examples are upper Pliensbachian (Lower Jurassic) glendonites from a shallow-marine succession in South Germany which was located in the European epicontinental sea – an area, where it was technically too warm to form the precursor mineral ikaite. Based on petrographical and sedimentological investigations as well as stable isotope analyses it is concluded that a low temperature was the main factor for ikaite formation in the studied section. To explain the low water temperatures, a model for a thermohaline circulation in the European epicontinental sea is proposed. The cool climate in the late Pliensbachian initiated the growth of sea ice in high latitudes, leading to the formation of cold and saline bottom waters analogous to the modern formation of North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW). The cold bottom current flowed southward from the Arctic Realm through the Viking Corridor into the European Epicontinental Sea, thereby causing a massive cooling of the deeper parts of the epeiric sea, which led to the formation of ikaite in temperate areas. After passing the shelf, the bottom current entered the Western Tethys, probably forming a deep water mass. The proposed model can help to explain mid-latitudinal glendonite occurrences not only in the Pliensbachian, but also in other areas and time slices which are characterised by cooling. Moreover, it enables the use of the pseudomorph as a tracer for cold bottom currents which can be a helpful tool for the reconstruction of global ocean current patterns.

4

The evidence of Palaeotropics and the Gondwana-derived terrane: an alternative scenario of the Palaeotethys divide in SE Asia

Udchachon Mongkol, Burrett Clive, Thassanapak Hathaithip

Geotourism / Geoturystyka

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2023

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nr 1-2 (72-73)

73--74

EN

Along the Northern part of the West Thailand Region (NWTR), a long-lasting belt of radiolarian cherts, separates Pennsylvanian to Permian palaeotropical limestones of the Inthanon Zone to the east from Permian limestones in the west containing a temperate marine fauna in the Roadian and a biogeographically distinctive fusulinid fauna in the Wordian. Highly abundant but low diversity of Kungurian radiolarians in silicified shales as well as temperate faunas in limestones from the south and the west of Thailand, respectively support constrains in the temperate environment during the period of deglaciation in peri-Gondawana. The well-known underlying diamictite and overlying temperate sediments with the succeeding fully tropical limestone sequences support a gradational palaeoclimate transition. Devonian faunas found in condensed sequences of the NWTR were deposited in a deep platform or ramp environment. A lack of basalts in the NWTR does not suggest oceanic environments for any Palaeozoic sequence within the NWTR and a paucity of basalts in the northwestern part of the Inthanon Zone also does not provide good evidence of an oceanic realm. Indeed, ‘continental margin’ Carboniferous sandstones appear to underlie the palaeotropical limestones and their plant fossils and their benthonic faunas do not suggest oceanic conditions in the northwestern Inthanon Zone. We, therefore, suggest that an autochthonous or para-autochthonous Inthanon Zone origin for these Carboniferous sandstones is more likely than deposition within a subducting Palaeotethyan Ocean. A strong contrast between the ‘temperate’ Permian limestones of the NWTR and the tropical limestones of the Inthanon Zone further emphasises the Mae Yuam/Mae Sariang Fault Zone (MYMS FZ) as a reactivated oceanic boundary between Gondwana and ‘Cathaysia’ and is supported by the oceanic lithosphere origin of the detrital Cr spinels in the Triassic foreland basin siliciclastics of the NWTR. The limestones of the Inthanon Zone range from Visean to Permian and possibly Triassic and were deposited in shallow, tropical seas for over 90 million years. This longevity is either not possible or highly unlikely for shallow marine carbonates on volcanic seamounts supported on subducting (and therefore cooling and sinking) ocean crust (Huppert et al., 2020) but is possible on isolated carbonate platforms on continental crust separated by narrow basins with limited volcanism. Carboniferous sandstones and Devonian-Permian radiolarian cherts from the Inthanon Zone are continental marginal and are neither pelagic nor oceanic and are interpreted as deposited in extensional, deeper basins between the isolated carbonate platforms. We suggest an alternative hypothesis to the overthrust/ allochthon model where the NWTR is the eastern platform margin of the Sibumasu Terrane from the Devonian through to the Triassic and separated from the Inthanon Terrane by an ocean in the position of the MYMS FZ. It is suggested that Inthanon rifted from Gondwana in the Early Devonian and the NWTR, as part of the Sibumasu Terrane, rifted off in the early Permian. As the Inthanon Terrane ribbon continent drifted northwards the continental crust thinned and extended and small rift basins allowed basalts to be extruded associated with deep-water, continental margin, hemipelagic, non-hydrothermal radiolarian oozes. Isolated carbonate platforms were established on Carboniferous sandstone bases and were separated by deep-water but non-pelagic extensional basins. Turbidites originating on the carbonate highs supplied carbonates clasts containing Devonian through Permian conodonts, to the adjacent basins (Udchachon et al., 2018). We provisionally suggest that the Sukhothai Terrane rifted with Inthanon with its older siliciclastic successions of the Siluro-Devonian (?) Khao Kieo Formation and the unconformably overlying Carboniferous (Dan Lan Hoi Group) (Bunopas, 1982; Ueno & Charoentitirat, 2011) supplying siliciclastic and volcaniclastic debris to the Inthanon Zone. This hypothesis is broadly in accord with Dew et al.’s (2018) ‘explanation A’ for the crustal geochemistry of the northern Thailand terranes. In the early Permian (Kungurian) Sibumasu was probably in cool to temperate seas but by the middle Permian, the NWTR had rifted from Gondwana and was in the southern hemisphere tropics (13° ±2° S, Zhao et al., 2020). Terrane collision occurred during the Triassic (Ishida et al., 2006; Mitchell et al., 2012; Cai et al., 2017; Hara et al., 2021) with the establishment of a thrust front along the Mae Sariang Thrust Zone and the deposition of the mainly siliciclastic Mae Sariang Group on the NWTR within a foreland basin.

5

The Banda Arcs and Carpathia/Pannonia: new insights on the Tethys Twins

Milsom John

Geotourism / Geoturystyka

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2023

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nr 1-2 (72-73)

50--51

EN

The Outer Banda and Carpathian arcs, of eastern Indonesia and Europe respectively, are examples of the highly arcuate fold-and thrust belts enclosing extensional basins that have been named oroclines. Both regions have experienced large scale extension within what is, overall, a compressive regime created by the convergence of major continental blocks and, despite major differences stemming from the quasi-oceanic setting of the one and intracontinental the setting of the other, there are reasons to suppose that comparative studies may produce insights into the evolution of both areas (Milsom, 2000). Processes in the Banda region are in some respects more open to direct examination, because extension is more recent, deep seismic activity is more widespread and basement structures are not concealed beneath thick sediment cover. To a considerable extent these advantages have compensated for the disadvantages of poor access and a relatively sparse database. The final two decades of the Twentieth Century saw rapid advances in understanding the area in terms of both geology and geophysics. In the first decade of the 20th century the techniques of seismic tomography began to be applied (Hall & Spakman, 2003) and confirmed the earlier interpretation, based on hypocentre locations, of the presence of a single, scoop-shaped, slab underlying the Banda Sea (Milsom, 2001). Intensive field and laboratory studies of Seram, the largest island in the northern part of the Outer Arc, then identified exposures of rocks metamorphosed at ultra-high temperature in the vicinity of the crust-mantle boundary, which led to the abandonment of the earlier interpretations of the associated ultramafic rocks as ophiolitic (Pownall et al., 2013). The extreme extension that brought these rocks to the surface also affected the subducted lithosphere that underlies the Banda Sea, and is one of the many pointers to the importance of asthenospheric flows in creating the present situation. While similar in many respects, the Carpathia-Pannonia area shows an orocline at a much later stage in its evolution, with some evidence concealed by later overprinting and some processes that would have been important in earlier stages now no longer occurring. On the other hand, some other aspects of orocline formation are likely to be better displayed there than in the Banda region. The now increasingly well determined history of the destruction of the Western Tethys and the development of the Alps-Carpathian-Dinarides orogen (e.g. Handy et al., 2015) offers strong support for theories involving mantle flow as a key factor in orocline formation.

6

Temporal and spatial heterogeneity of the Ailaoshan–Song Ma–Song Chay ophiolitic mélange, and its significance on the evolution of Paleo-Tethys

Lin Wei, Liu Fei, Wang Ying, Meng Lingtong, Faure Michel, Chu Yang, Nguyen Vuong Van, Wu Qinying, We Wei, Thu Hoai Luong Thi, Vu Tich Van

Geotourism / Geoturystyka

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2023

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nr 1-2 (72-73)

42--43

EN

The ophiolite is the direct evidence to restore the oceanic evolution, and it is used to identify the convergence boundary of the plates. Compared with ophiolite, ophiolitic mélange, especially its matrix, contains more information about the evolution of ocean. The evolution of eastern Paleo-Tethys, between the South China and Indochina blocks, recorded the whole process of rifting from Gondwana and their northward migration and convergence. To understand the tectonic implications from matrix of ophiolitic mélange, the Mesozoic Paleo-Tethys Ailaoshan–Song Ma–Song Chay suture zone located in the North Vietnam–Southeast Yunnan region acts as an ideal study area. Based on the structural geology, we reviewed previous zircon U-Pb dating and Lu-Hf isotopic analyses on the detrital zircon from the Ailaoshan–Song Ma–Song Chay ophiolitic mélange. Accordingly, we subdivide the matrix of these ophiolitic mélange into four parts (M1, M2, M3, and M4; Fig. 1). M1 is mainly located in the middle segment of the Ailaoshan–Song Ma belt. It shows age peaks of 440 Ma and 960 Ma with εHf(t) values of −19.6 ~ +10.3. M2 is mainly located in the NW segment of the Ailaoshan–Song Ma belt, showing a dominant age peak of ~260 Ma. Particularly, it has εHf(t) values of −28.9 ~ +8.1. M3 is mainly located in the SE segment of the Ailaoshan–Song Ma belt, showing the peaks at ~250 Ma, 440 Ma, and 960 Ma with εHf(t) values of −21.9 ~ +10.1. M4 is mainly located in the Song Chay belt, showing the peaks at ~310 Ma, 470 Ma, 610 Ma, 770 Ma, and 965 Ma with εHf(t) values of −28.2 ~ +10.8. The geochronological data of the detrital zircon from the matrix of the Ailaoshan– Song Ma–Song Chay ophiolitic mélange zone, documents a temporal heterogeneity between the M1, M2, M3, and M4 units, which formed at 310–270 Ma, 265–250 Ma, 245–240 Ma, and 310–255 Ma, respectively. The different components and provenances of each unit reflect a strike-parallel heterogeneity (Fig. 1). The M1 unit was mainly sourced from the Paleozoic sedimentary rocks of the Indochina Block (IB). The main provenance for the M2 unit is Emeishan Large Igneous Province (ELIP). The magmatic arc developed in the IB provided the materials for the M3 unit, and the detrital materials of the M4 were mainly sourced from the South China Block (SCB) (Fig. 1). The Cenozoic strike-slip deformation led to an inverted geometry of the M1, M2, and M3 units, accounting for a strike-perpendicular heterogeneity straight to the strike of the orogenic belt. The temporal, strike-parallel, and strike-perpendicular heterogeneity help us to decipher the tempo-spatial evolution of the Paleo-Tethys. The M1, M2, M3, and M4 units contain information from different evolutionary stages, likely recording the comprehensive history of the ancient oceanic basin. Importantly, our results demonstrate that both the active continental margin of the IB and the passive continental margin of the SCB acted as provenance sources that supplied significant amount of detrital material in the ophiolitic mélange matrix, indicating that the Paleo-Tethys Ocean was a “narrow” or “limited” ocean rather than the archipelagic ocean proposed before.

7

Tectono-sedimentary evolution of the junction area between the Western and Eastern Carpathian nappe systems (Ukrainian Carpathians)

Hnylko Oleh

Geotourism / Geoturystyka

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2023

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nr 1-2 (72-73)

25--26

EN

The Carpathians contain the remains of the Western Tethys, the main of which are: continental/microcontinental fragments (Alkapa and Tisza-Dacia terranes) of the Tethys Ocean, now located in the Central (Inner) Carpathians, and (palaeo)accretionary prisms, building mainly the Outer Carpathians. The Ukrainian Carpathians occupy the junction where the Western Carpathian and Eastern Carpathian nappe systems converged. In the presented work, author try to reconstruct the tectono-sedimentary evolution of the Eastern and Western Carpathian nappe systems in the junction area on the basis of own and published geomapping works, stratigraphic, sedimentological and structural research using existing restorations (see van Hinsbergen et al., 2020 and references therein). The Central Western Carpathian nappes (part of the Alcapa Terrane) are not exposed in Ukraine and probably buried under Neogene Transcarpathian Depression. The Central Eastern Carpathian nappes (part of the Tisza-Dacia Terraine) are represented in Ukraine by the Marmarosh thick-skinned basement nappes, that were formed in the Early Cretaceous time and overlapped by the latest Early Cretaceous–Paleogene post-nappe sedimentary cover. Between the Central Eastern and Central Western Carpathian nappe systems, the Pieniny Klippen Belt suture zone and Monastyrets Nappe filled with Paleogene flysch are developed. The structure of the junction between the Outer Eastern and Outer Western Carpathian nappe systems is more complicated. In Ukraine, the Outer Carpathians are made up of a several stacked nappes filled with Cretaceous–Neogene, mainly flysch sediments uprooted from their original substratum. In the Eastern Carpathian segment of Tethys at the Late Jurassic and/or Early Cretaceous, Ceahlau-Severin ocean (called Fore-Marmarosh one in Ukraine) was opened between the Dacia continental block (part of the Tisza-Dacia Terrane) and the Eurasian continent (van Hinsbergen et al., 2020 and references therein), that suggested by rift oceanic and continental basalts occurring under the Cretaceous flysch of the Outer Eastern Carpathian. Sinking of the Dacia (micro)continent into a subduction zone existed in the Neotethys ocean and inclined to the west (van Hinsbergen et al., 2020), could have caused the east-directed thrusting of the thick-skinned Marmarosh Nappes towards the CeahlauSeverin ocean. Ahead the Marmarosh nappe pile, the Eastern Carpathian Internal flysch thin-skinned nappes such as the Kamyanyi Potik, Rahiv, Burkut, Krasnoshora, Svydovets and Chornohora ones were formed. Coarsening upward and regular younging of the stratigraphic successions from inner to outer nappes suggest their attribution to the accretionary wedge growed in the Early Cretaceous–Paleogene time due to the subduction of the Outer Carpathian flysch basin basement under the Marmarosh pile. In the Western Carpathian segment, the Pieniny Klippen Belt accretionary wedge began to rise in the Late Cretaceous due to subduction of the Penninic oceanic domain under the Central Western Carpathians (part of the Alcapa Terrane) accompanied by detaching and grouping together originally very distant lithofacies (Plašienka, 2018 and references therein). The Western Carpathian Internal flysch nappes such as the Magura and Dukla units were attached to the Fore-Alcapa prism during the Middle Eocene–Oligocene, accordantly to outward shifting and uplifting of the trench-like Magura and Krosno lithofacies during this time. Closuring of the Monastyrets “between-terrainian” flysch basin at the late Eocene suggests the collision of the Alcapa and Tisza–Dacia terranes at the turn the Eocene and Oligocene. As a result, the Fore-Alcapa and Fore-Tisza-Dacia wedges were incorporated within an amalgamated internal wedge system that limited from the SW the Outer Carpathian basin. This unificated Menilite–Krosno basin was gradually uplifted and its deposits were subsequently thrusted as the external Silesian, Skyba and Boryslav-Pokyttya nappes onto the Miocene Carpathian Foredeep. Sedimentological and structural data suggest northeastward shift/migration of the wedge front–trench/foredeep– forebulge during Carpathian evolution. In addition, the junction of the Eastern and Western Carpathian accretionary wedges is complicated by strike-sleep movements.

8

Stratigraphy of the Jajarkot nappe: finding the rocks of the Tethys province

Lamsal Sunil, Paudyal Kabi Raj

Geotourism / Geoturystyka

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2023

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nr 1-2 (72-73)

41--41

EN

There are several thrust sheets in the Lesser Himalayan region of Nepal. The Jajarkot nappe is one of them. It is located immediately west of the Kahun Klippe and east of the Karnali Nappe. There is no unified stratigraphy established for this thrust sheet. In the present research, an attempt was made to establish the stratigraphy of the Jajarkot nappe to fulfill the research gap. Previously described by Fuchs & Frank (1970) and Sharma (1980), the Jajarkot nappe in western Nepal have two distinctive crystalline lithological units: the Chaurjhari Formation and Thabang Formation. The previous unit consists of garnet-grade schist, and quartzites, with intrusions of basic rocks and granites, while the later unit consists of grey to brown crystalline limestones with biotite-quartz-schists. An unconformity is observed above the Thabang Formation. The younger geological unit above the unconformity is mapped as the Jaljala Formation, which is composed of finegrained calcareous sandstone and calcareous siltstone with minor proportions of limestones and grey-green slates. At present work, a preliminary geological study was carried out to work on the stratigraphy of the Jajarkot nappe in the Jaljala areas at 1:25,000 scales. Fossils of crinoids are found in the rock unit of the Jaljala Formation. These fossils are considered the index fossils of the Silurian. In this case, the Jaljala Formation would be equivalent to the rocks of the Tethyan affinity, and further study is under progress. The concept that the thrust sheets are moved from north to south in the Himalayas will be evidenced by these findings. An attempt is made to correlate the presently found fossils with the crinoids of the Phulchauki Group of the Kathmandu nappe and with the root zone of the Tethys succession.

9

Sequence stratigraphy of the Upper Cretaceous–Eocene Belqa Group of Jordan (southern Tethys margin)

Kalifi Amir, Ardila-Sanchez Maria, Messaoud Jihede Hay, Laila Wesam Abu, Buchem Frans van, Ibrahim Khalil, Powell John

Geotourism / Geoturystyka

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2023

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nr 1-2 (72-73)

32--32

EN

The Belqa Group of Jordan (Upper Cretaceous–Eocene) contains a remarkable succession of sedimentary lithofacies, including chalk, sandstone, chert, phosphorite, oyster mounds and organic-rich marls deposited along the passive southern margin of the Neo-Tethys Ocean. The Belqa Group is now outcropping in spectacular wadis where they can be studied in detail. The exceptional outcrops exposures provide unique opportunities for studying three-dimensional spatial facies variations. However, this 3D facies distribution requires robust time control and the combination of modern sequence stratigraphic concepts and high-resolution dating methods. We report the establishment of a regional sequence stratigraphic model that provides the temporal framework for further detailed sedimentological, palaeontological and geochemical studies. Preliminary results show a stratigraphic organization in four major depositional sequences (3rd order), which are broadly in agreement with the lithostratigraphic formations. The age dating is based on new nano-fossil analyses and C/O and Sr isotope stratigraphy. A subdivision into higher-frequency sequences (4th/5th order) significatively improves the resolution of the stratigraphic framework and our understanding of spatio-temporal distribution of the sedimentary facies. The four sequences are: 1) The B1 sequence (Upper Coniacian-Santonian), characterized by a transgressive phase of chalk-rich sedimentation (coccolithophore-dominated) and a regressive phase of a prograding siliciclastics with a distal transition to the first phosphorite-chert facies. 2) The B2 sequence (Lower Campanian) also starts with a transgressive chalk dominated facies and subsequently develops into a chert-dominated marl facies (radiolarian-dominated). The chert is locally associated with thin phosphates and coquinas, as well as organic-matter rich facies in proximal marine settings. 3) The B3 sequence (Upper Campanian) is also characterized by a transgressive chalk dominated facies. The regressive phase is constituted by dm- to m-thick phosphorite beds that were deposited coevally with giant oyster banks (decameter scale). 4) The B4 sequence (Maastrichtian-Paleocene) represents a dramatic facies change to organic-rich pelagic marls, and can probably be further subdivided. This sedimentary succession highlights both gradual and rapid changes in biogenic productivity and geochemistry. These changes are punctuated and partly driven by significant relative sea-level changes, and likely also larger scale palaeoceanographical processes that are the focus of future work.

10

Rifting and closure of two branches of the Tethys; from Neotethys to Alpine Tethys

Fodor Laszlo

Geotourism / Geoturystyka

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2023

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nr 1-2 (72-73)

19--20

EN

The western termination of the Neotethys is marked by a complex interaction of several small oceanic basins which were formed and closed progressively. The western end of the Neotethys was opened from Permian to Middle Triassic; spreading started from Anisian. The rifting was associated with acidic, sometimes basic magmatism; Permian intrusions are widespear in certain zones (Eastern Alps), and together with Middle Triassic volcanites, played a role in weakening of the extending continental lithosphere. The rifting process was interacting with evaporite tectonism in regions where Late Permian evaporites were formed potentially as a post-rift or intra-rift stage. Due to loading of the ovelying Early Triassic clastic-carbonate ramp sequence, and the still ongoing extensional deformation, and/ or gravitational sliding of shelf domains toward deepening extended continental margin, salt tectonics probably started in latest Early Triassic. The uprising salt walls strongly influenced shelf and eventually slope deposition; the minibasins between salt walls often hosted carbonate ramp or platform development while collapsing salt structures could turn to deep “intra-platform” basins. The salt tectonics controlled the continuing facies differentiation during the Late Triassic. The development of salt-cored normal faults are not characteristic for a typical post-rift passive margin, but due to their relation to underlying salt, facies differentiation was maintained. The earliest sign of rifting of the Alpine Tethys can be seen in the Late Triassic deep grabens (Southern Alps, southern Transdanubian Range). This is the reason that separation of salt-related deformation, and crustal extension is not evident in some zones. The closure of the Neotethys started with intra-oceanic subduction, probably with a double polarity, and the formation of a supra-subductional new oceanic lithosphere (the Vardar zone in some interpretations). The age of this process is somewhat controversial in different models. Isotopic ages of metamorphic sole of the Vardar ophiolites suggest 175–170 Ma while neutral to acidic differentiates in the eastern Vardar testify ongoing Late Jurassic oceanic magmatism (~155–155 Ma). A complex system of melange was formed under and in front of the emplacing upper plate Vardar ophiolite. While sub-ophiolitic melange with serpentinitic matrix formed below the overlying hot oceanic lithosphere, the sediment-hosted melange contains blocks from different zones of the passive margin and partly the overlying ophiolite. Stratigraphic ages indicate that this processes happend during the Middle and Late Jurassic. The obduction happened in latest Jurassic (Tithonian) indicated by reef limestone on top of ophiolites. This was followed by the imbrication of the underlying passive margine Adriatic continental lithospere during the entire Cretaceous and Cenozoic. Clastic foreland basins were formed within this lower plate supplied partly by the passive upper plate ophiolite. The Alpine Tethys went on intensive rifting which ended with break-up in late Middle or in the Late Jurassic on its southern Piemont-Ligurian branch. The onset of subduction is not exactly clear but could happen in the Late Cretaceous resulted in high-pressure metamorphism of the oceanic domains in the Eocene (Tauern window). The Transdanubian Range of Hungary was situated between the two oceanic domains during the whole Mesozoic. While this unit has not been buried and only deformed modestly, the sedimentary events reflect the complex evolution. Middle Triassic rifting resulted in disruption of Early Triassic mixed siliciclastic-carbonate ramp into platform and somewhat deeper grabens. Small-scale synsedimentary faults and neptunian dykes testify this phase. Away from the break-up zone, the area underwent important post-rift subsidence compensated by platform carbonate sedimentation through the Late Triassic. However, the trace of initial Late Triassic rifting is present in forms of synsedimentary faults in the western side, closer to the future Neotethys. Following the earliest Jurassic decline of platform biota, the ongoing Alpine rifting disintegrated the entire TR carbonate platform into shallower, sediment free ridges and somewhat deeper grabens. This rifting and subsidence resulted in deposition of pelagic red nodular limestone in the Aalenian-Bajocian. After cherty sedimentation in the Callovian–Oxfordian, very modest extension appeared in the latest Jurassic. Although this phase could be considered as the final extension of the Alpine Tethys rifting far to the west, it is more probable that in fact this is due to slight downbending of the TR below the distal ophiolite emplacement to the east. The Neotethyan influence prevaild in the eastern TR during the Early Cretaceous. A clastic foreland basin was supplied by ophiolite and supra-ophiolite detritus of the obducted Neotethyan Vardar unit. Structural cituation changed in the late Early Cretacoues, around 115 Ma (Albian). The entire TR underwent shortening. The unit, formerly the lower plate of the Neotethyan system, was emplaced, as the highest nappe, on to the other continental units of the Austroalpine system. Within the Eastern Alps, this was associated with intracontinental subduction initiated in zone of Permian magmatism having thermally weakened the lithosphere. The relationship of this subduction, and associated high to ultrahigh pressure metamorphism is not clear, but eventually could have connected to large-scale displacement of the Neotethyan subduction zone at its northernmost termination zone. The complete change of the TR, from lowermost position to upper plate, is the reflection of complex 3D geometry of overlapping oceanic domains and could happen in other Tethyan areas

11

Red algae grains from the Żurawnica Sandstone Member in the Sucha Beskidzka area (Magura Nappe, Polish Outer Carpathians) as the indicator of shallow water palaeoenvironment on the intrabasinal Tethyan ridge

Koczur Maria, Waśkowska Anna, Bassi Davide

Geotourism / Geoturystyka

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2023

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nr 1-2 (72-73)

35--35

EN

The Żurawnica Sandstone Member was deposited in the Paleocene on the northern slope of the Magura Basin in the western part of the Tethys. It is built of clastic material transported by gravitational currents from shallow parts of the Foremagura Ridge (Cieszkowski et al., 1999), which was an uplifted intrabasinal structure. At the top of the Żurawnica Hill (Beskid Makowski, location known as Kozie Skały) a well-exposed section crops out. It is a part of flysch succession of the Magura Nappe (Cieszkowski et al., 2006). In the lower part of the section thick-bedded sandstone with red algal grains occurs. Algal remnants were redeposited from the photic zone of the carbonate platform, which developed on the Foremagura Ridge. Their structure-taxonomic differentiation allows to reconstruct algal palaeoenvironment. The red algae are represented by Sporolithaceae, Melobesioideae, and Mastophoroideae genera. They correspond to three algal facies: debris, algal pavement facies, and Melobesioideae rhodolith pavement facies. Sand-sized red algal grains are the most numerous. They are fragmented and well rounded crustaceous algal thalli, typically with no traces of bioerosion. They represent algal debris facies, which was developed in high energy environment (Nebelsick et al., 2005). Red algae grains could be fragmented and rounded during turbidity transport, but considering the different degree of abrasion, especially in gravel fraction, it should be assumed that the rounding took place before the turbidity transportation. Two types of gravel grains are present: not rounded algal limestone clasts and rhodoliths. The non-rhodolith grains are built of encrusting (layered and foliose), warty, and lumpy algal crusts. Rhodoliths can be divided into two types: irregular and regular ones. Irregular rhodoliths are up to 3 cm in diameter. They contain large nuclei constituting grain skeleton. Both non-rhodolith grains and irregular rhodolits are polygeneric and contain numerous benthic organisms (bryozoans, encrusting foraminifera, and bivalves) between algal lamella, as well as constructional voids. They are bioeroded. They are elements of algal pavement facies for which the occurrence of the algal buildups with irregular rhodoliths in areas, where the energy of the environment is a bit higher is typical (Nebelsick et al., 2005, 2013; Bassi et al., 2017). The regular rhodoliths, up to 0.5 cm in size, contain small carboniferous nuclei. Typically, they are unigeneric (Sporolithaceae, Melobesioideae) and not contain other benthic organisms. Lack of constructional voids was observed in thick algal encrustation. Only encrusting growth form was observed. Regular rhodoliths are typically developed as a main part of Melobesioideae rhodoliths pavement facies, which is rather “deep” water facies of high energy environments (Adey, 1986; Bassi et al., 2017).

12

Reappraisal of the Changning-Menglian Belt as a Suture Zone for the Tethys in Western Yunnan, China: Late Paleozoic faunal and sedimentary evidence

Huang Hao, Zeng Jianbing, Jin Xiaochi

Geotourism / Geoturystyka

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2023

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nr 1-2 (72-73)

27--28

EN

The Changning-Menglian Belt in western Yunnan, China has long been considered a major Tethyan suture in SE Asia, based mainly on fragmented Paleozoic ophiolites, slices of Devonian-Triassic radiolarian cherts and possible seamount limestones of Permo-Carboniferous age (Fig. 1). However, some students also argued for a setting of passive continental margin for this belt and a cryptic suture further east representing the vanished Tethyan Ocean (Ridd, 2015). To evaluate this hypothesis, we have been studying late Paleozoic strata and fusulinids in this belt for years. We recently collected late Carboniferous to Middle Permian fusulinids from various sections in this belt, including ascendingly Triticites assemblage, Sphaeroschwagerina sphaerica assemblage, Eoparafusulina assemblage, Chalaroschwagerina solita assemblage and Neoschwagerina assemblage. Further comparison reveals that the fusulinid taxonomy in this belt still differs from that in S China. For instance, the Early Permian fusulinids in this belt generally lack Pseudoschwagerina, a typical Cathaysian element. Moreover, quantitative analysis (Rarefaction) confirms that the generic diversity in this belt remains lower than in S China. These results supports that a substantial portion of the Permo-Carboniferous limestones in this belt originated from seamounts located far from the northern Gondwana margin, meanwhile slightly south of the equatorial region, also considering the couplet of carbonates and underlying basalts (OIB type). Furthermore, petrographic and geochemical analyses of the Carboniferous siliciclastic Nanduan Formation demonstrate a mature continental provenance and two peaks of detrital zircon ages (ca. 950 Ma and ca. 550 Ma) (Zheng et al., 2019). Notably, these two peaks are also shared by metasedimentary rocks (e.g., the Ximeng and Lancang Groups) widespread in this belt as well as peri-Gondwana blocks. These data suggest that the Paleozoic siliciclastics covering this belt’s eastern and western parts were derived from the Gondwana margin. Therefore, significant siliciclastic inputs from the Gondwana margin over much of this belt contradict the implied vast Paleozoic ocean in this belt. In contrast, the siliciclastic Nanpihe Group (Devonian-early Carboniferous) in the central part demonstrates a detritus source from continental arcs and clusters of detrital zircon ages of ca. 435 Ma and ca. 950 Ma, which correlates well to Silurian magmatism in the Simao and S China blocks. In conclusion, we propose that the Changning-Menglian Belt was part of the passive continental margin on the eastern flank of the Baoshan-Shan Block during the late Paleozoic, while and tectonostratigraphic slices of seamount limestones, Nanpihe Formation or even ophiolites are allochthonous and were displaced to their present position during the Late Triassic closure of the Tethys.

13

Palaeogeographic perturbations in the key-area between the Alpine Tethys and the Neotethys Realms during the time of tectonic overturns: Jurassic of the Alpine-Dinaric transition zone

Rožič Boštjan

Geotourism / Geoturystyka

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2023

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nr 1-2 (72-73)

60--61

EN

The major Mesozoic palaeogeographic disintegration of the present-day transitional area between the Alps and the Dinarides (Slovenia) occurred due to the Middle Triassic rifting event related with the opening of the Neotethys Ocean. By the Norian, three major palaeogeographic units were formed: the Dinaric (Adriatic, Friuli) Carbonate Platform (DCP) in the south, intermediate, E-W extending Slovenian Basin (SB) and the Julian Carbonate Platform (JCP) in the north. The platforms were characterized by a Dachstein type platform, while the basin was filled with hemiplegic and resedimented limestones, most of which are now dolomitized. To the west, there was a shallow water “bridge” between the two platforms. After the Triassic-Jurassic Boundary crisis, the palaeogeographic setting was preserved, but the margins of the platforms turned into ooidal factories. During the Early Jurassic, SB was almost exclusively filled with ooid calciturbidites from the north, which can be explained by the wind/leeward position of the basin with respect to the particular platform. The first rifting phase of the opening Alpine Tethys, generally dated to the earliest Jurassic, is poorly expressed in this area. The main products are limestone breccias that occur in the western part of the SB. In contrast, the second rifting phase (dated to the Pliensbachian in Slovenia) completely disintegrated JCP. The margins subsided first and were characterized by open shelf conditions with crinoid meadows, while the inner parts of the JCP remained shallow-marine. In the SB, the initial subsidence can be seen in the altered composition of the calciturbidites. Namely, the ooid/peloid dominated resediments changed to crinoid/ lithoclast dominated. In the Toarcian, sedimentation ended on most of the JCP, with only sporadic marls occurring at the margins. At the same time, the sedimentary environment of the DCP also deepened and nodular or crinoid limestone was deposited. The SB is characterized by uniform clay-rich sediments that vary greatly in thickness, indicative of differential subsidence caused by the second rifting phase. In the Middle Jurassic, shallow-water sedimentation re-established on the DCP, the margin being characterized again by ooidal shoals, the sedimentation of the SB gradually changed to siliceous limestone, while the JCP and the “bridge” between the JCP and DCP are characterized by non-sedimentation. The last important Jurassic change occurred during the Bajocian-Bathonian stages. Condensed Ammonitico Rosso-type limestone began to be deposited on the “bridge” and the JCP, while sedimentation in the SB changed to pure radiolarite. In the past, this was interpreted as a result of thermal subsidence associated with oceanization of the Alpine Tethys. However, studies in the last decade suggest a more complex tectonic evolution. Because the area in question lies between the opening Alpine Tethys to the west and the concurrent onset of subduction of the Neotethys to the east, it has been subject to strong differential subsidence between the largescale DCP and all units north of it. The exact nature of the tectonic deformation is not yet clear, but a transtensional regime is most probable. These events resulted in the disintegration and collapse of the northern DCP margin, as evidenced by the sedimentation of limestone breccia megabeds along the entire SB southern margin. These megabeds not only indicate enhanced tectonics, but also provide important information about the pre-Middle Jurassic architecture of the DCP margin, which is no longer preserved. They consist of very diverse limestone lithoclasts and an ooid packstone matrix. Analysis of the clasts revealed that the Late Triassic DCP margin was characterized by Dachstein-type reefs and the Early Jurassic by ooid shoals. In the interior of SB, these strata merge into ooid calciturbidites interlayered between radiolarite and become completely wedged in the northern part of the basin. Corresponding gravity-flow deposits also sedimented on the subsided “bridge” between the DCP and the JCP, and even on the northern margin of the DCP itself. An important difference is the simpler composition of the resediments in this area. Namely, they consist entirely of Middle Jurassic platform margin and slope lithoclasts. This is explained by the less pronounced palaeotopography between the active platform and submerged “bridge”, which did not allow erosion of the older platform limestone (as observed in SB). The described collapse of the DCP margin caused it to retreat, and marginal reefs formed over the underlying inner platform limestones in the Late Jurassic. The emersion phase in the Kimmeridgian ended reef growth and the margin turned back into ooid rich shoals. At the same time, the SB was characterized by continuous radiolarite sedimentation and drowned JCP together with the “bridge” with the Ammonitico rosso facies, characterized by several stratigraphic gaps. Rare calciturbidites are interbedded in areas near the DCP (southern SB and a drowned “bridge”). At the end of Jurassic, all areas north of the DCP show uniform sedimentation of the Biancone Limestone Formation.

14

Palaeobiogeography of Late Bajocian–Tithonian ammonites of northeastern Iran

Majidifard Mahmoud Reza

Geotourism / Geoturystyka

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2023

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nr 1-2 (72-73)

46--46

EN

Jurassic rocks are widely distributed and superbly exposed in the Alborz Mts. (northern Iran) and Koppeh Dagh (northeastern Iran). The Lower Jurassic and large parts of the Middle Jurassicare characterized by a thick siliciclastic succession, whereas the Upper Bajocian to Tithonian rocks are predominantly carbonates, which represent a platform, slope and basin system. The Upper Bajocian-Tithonian ammonite faunas the NNE Iran are mostly of Submediterranean affinity, but elements of Subboreal, Mediterranean, and Ethiopian provinces are occasionally intermingled. Palaeobiogeographically the Late Bajocian to Bathonian ammonites belong to Submediterranean Province, as elsewhere in north and central Iran. This is supported by the occurrence of ammonites such as Garantiana and Morphoceras and some cosmopolitan taxa such as Cadomites and Oxycerites. In order to unravel the origin of the faunal elements and their migration routes, the relationship of the ammonite fauna of Iran to that of other regions was evaluated. On the whole, at the species level, the Toarcian to Early Bajocian ammonite faunas of northern and central Iran show a close relationship to that of northwestern Europe. A characteristic feature of this fauna is the scarcity of Phylloceratidae (accounting for less than 1% up to 3%) and the absence of Lytoceratidae. Remarkably, from Late Bathonian onward to Kimmeridgian, Phylloceratidae account for more than 50% of the ammonites fauna. Palaeogeographic reconstructions show the position of the Iranian plate (North and Central Iran) during the Middle Jurassic time at the southern margin of Eurasia at a palaeo-latitude of around 30° N which rather corresponds to European regions (Enay & Cariou, 1997). The open migration routes across pericontinental shelf seas along the northern Tethyan margin that were approximately parallel to palaeo-latitudes may explain the strong affinities of the Late Bajocian–Bathonian ammonites of northern and Central Iran to those of the Submediterranean Province. The Callovian ammonite fauna has a typical northwest Tethyan character, and belong to the Submediterranean faunal province (Seyed-Emami et al., 2013), and are largely dominated by Phylloceratidae ammonites. These pelagic taxa that preferred open oceanic conditions are accompanied consistently by Perisphinctidae, Reineckeiidae, Oppeliidae (Hecticoceratinae), Macrocephalitidae , Tulitidae, Aspidoceratidae (Parawedekindia, Peltoceras). On the other hand, this is supported by the occurrence of Submediterranean ammonites such as Macrocephalites, Pachyceras, and some cosmopolitan taxa such as Hecticoceras and Reineckeia. Some taxa from the Oxfordian- Kimmeridgian belong to the Western Tethys Province (Sequeirosia and Passendorferia) or Subboreal Province (Cardioceras). It is remarkable that, besides some cosmopolitan ammonites, there is no direct connection with faunas from southwestern Iran, western India and the southern Tethys. Finally, the Tithonian ammonite faunas of northeastern Iran are mostly of Submediterranean affinity (Seyed-Emami et al., 2013). However elements of the Mediterranean faunal provinces occasionally occur. In order to unravel the origin of the faunal elements and their migration routes, the relationship of the ammonite fauna of Iran to that of other regions need to be analysed in the future. Especially the appearance of several allegedly regionally restricted Ataxioceratidae such as Phanerostephanus, Nannostephanus, Nothostephans and the Oppeliidae as Oxylenticeras, which occur in Ethiopian Province (Page, 2008) is of great palaeobiogeographical interest.

15

Mid-oceanic seamount carbonates in Eastern Paleotethyan suture zones

Ueno Katsumi

Geotourism / Geoturystyka

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2023

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nr 1-2 (72-73)

75--76

EN

Mid-oceanic seamount-capping (atoll-type) carbonates make a popular stratigraphic entity in the geology of Japan since they are often seen as various-sized (but usually large and typically huge) exotic blocks within ancient (mostly Permian to early Cretaceous) accretionary complexes distributed in the Japanese Islands. These carbonates consist of very thick and pure (in the sense that it lacked input of continental detritus), usually massive and fossiliferous, shallow-marine limestone, and rest on oceanic-island basalts (OIB) of hot-spot origin, formed in the Panthalassa Ocean. Stratigraphically, they comprise a unique sedimentary succession that records long-term (sometimes over 80 myr.), continuous, shallow-marine environmental and biotic changes during late Paleozoic and early Mesozoic times of the oceanic sector with a stable tectonic setting, and can only be found within the accretionary orogen in the context of Ocean Plate Stratigraphy (OPS). Thus, the mid-oceanic seamount carbonate succession is a “surefire” geological item for the investigation of the ancient subduction zone and suture zone. On the basis of my research expertise working on these mid-oceanic carbonates in Japan over many years, especially in the Carboniferous–Permian Akiyoshi Limestone known as the most typical seamount-capping atoll-type carbonate body in the Panthalassa Ocean, I exported this, essentially “made-in-Japan” and “cultivated-in-Japan”, geological concept of “mid-oceanic seamount carbonates within the accretionary orogen” to Southeast Asian geology, for better understanding the general geotectonic subdivision and evolution of the relevant region, especially for clarifying the position of Paleotethyan suture zones and the geohistory of the Eastern Paleotethys Ocean. In today’s Southeast Asia, Paleotethyan mid-oceanic seamount carbonates are distributed in Northern Thailand and western Yunnan, SW China where Gondwana and Tethys meet together. Of these two regions, Northern Thailand is subdivided into three basic geotectonic domains; from east to west the Cathaysian Indochina Block, Sukhothai Zone (a Permian–Triassic island arc developed along the Indochina margin), and peri-Gondwanan Sibumasu Block. In the eastern part of Sibumasu, a geotectonically peculiar area called the Inthanon Zone can be identified on which Paleotethyan oceanic rocks including the Carboniferous–Permian Doi Chiang Dao Limestone of mid-oceanic seamount origin are widely distributed. This limestone succession, sometimes making kilometer-sized huge limestone blocks, is estimated to be 1000 m thick or more, and consists mostly of shallow-marine fossiliferous massive limestone without siliciclastic intercalation throughout. Basalts having intra-plate (oceanic volcanic island) geochemistry are observed at the base of the succession. Foraminifers, especially fusulines, are the fundamental fossil group for establishing its detailed chronostratigraphy, and they clarified that the limestone continuously accumulated from the Visean (middle Early Carboniferous) to the Changhsingian (latest Permian) over the time of 90 myr. In western Yunnan, the Changning–Menglian Belt is defined between the Lincang Massif (a Permian–Triassic island arc system formed along the easterly Simao Block with Cathaysian affinity) to the east and the peri-Gondwanan Baoshan Block to the west. The Changning–Menglian Belt, subdivided into the East, Central, and West zones, entirely has been regarded as a closed remnant (suture zone) of the Paleotethys Ocean, but actually it is only in the Central Zone where oceanic rocks are distributed. Paleotethyan mid-oceanic carbonates in this belt are called the Banka Limestone, which is over 1200 m in total thickness and generally massive and pure, being free from continental siliciclastic input for the entire succession spanning nearly 90 myr. Foraminiferal (mostly fusuline) biostratigraphy suggested continuous deposition ranging from the Visean to the Changhsingian without significant hiatus in the succession. Thus, the Banka Limestone in western Yunnan is exactly correlated in view of lithostratigraphy, chronostratigraphy, and tectonostratigraphy to the Doi Chiang Dao Limestone in Northern Thailand. In a broad geotectonic perspective, the Paleotethyan oceanic rocks including the Doi Chiang Dao Limestone, distributed in the Inthanon Zone are considered to form various-sized tectonic outliers upon autochthonous basement rocks of Sibumasu now, which consists of early Paleozoic– Triassic sedimentary, meta-sedimentary, and igneous intrusive rocks. Similarly, those distributed in the Central Zone of the Changning–Menglian Belt are structurally resting by almost flat-lying faults (thrusts) upon siliciclastic rocks of the West and/or East zones, which presumably represent passive-margin (continental slope) sediments of the westerly, Gondwanan Baoshan Block. These mid-oceanic rocks are interpreted to have been once incorporated within an accretionary prism formed by the subduction of the Paleotethyan oceanic lithosphere beneath the Permian–Triassic island arc system represented by the Lincang Massif–Sukhothai Zone. The resultant collision of the Cimmerian (peri-Gondwanan) Sibumasu–Baoshan Block to the Cathaysian Indochina–Simao Block, thus the closure of the Paleotethys Ocean in present-day Southeast Asia, at around Triassic–Jurassic boundary time emplaced rocks of the accretionary complexes (containing Paleotethyan oceanic rocks as exotic blocks) onto the marginal part of the Sibumasu–Baoshan Block as large thrust sheets (nappe).

16

Mesozoic tectonostratigraphy of the Western Tethys Realm – a review

Gawlick Hans-Jürgen

Geotourism / Geoturystyka

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2023

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nr 1-2 (72-73)

21--22

EN

The Mesozoic sedimentary sequences in the Western Tethys Realm are incorporated in different mountain ranges, most of them located in the eastern Mediterranean area (Eastern and Southern Alps; Western, Eastern and Southern Carpathians; Dinarides, Albanides, Hellenides; units in the Pannonian realm: Pelso, Tisza), others are located to the west (e.g. the Apennine and the Betic Cordillera) These mountain ranges were formed since the Jurassic and experienced in parts polyphase mountain building processes and deformation, lasting until today. Therefore, the tectonostratigraphic evolution of the different Wilson cycles are in cases hard to assign to a specific cycle, because the evolution of the different Wilson cycles is overlapping. This resulted in contrasting palaeogeographic reconstructions and controversial regional tectonic interpretations. In general, two different Wilson cycles can be distinguished. The older Wilson cycle reflect the geodynamic history of the Neo-Tethys (Meliata-Hallstatt, Maliac, Vardar, Pindos/Mirdita/Dinaridic oceans in other nomenclature), and the formed orogen is part of the Tethysides with following evolution as documented in the sedimentary record of the wider Adria plate: – A Late Permian to Middle Anisian rift (graben) stadium with sedimentation of siliciclastics and carbonate ramp deposits in an epicontinental sea. – A Middle Anisian to Middle Jurassic passive margin evolution after the late Middle Anisian oceanic break-up: a) The complex Middle to Late Triassic shallow- to deep-water carbonate platform evolution from the inner shelf (platform facies) to the outer shelf (open-marine basinal facies), and b) the Early to Middle Jurassic pelagic platform evolution. – A Middle to Late Jurassic convergent tectonic regime triggered by ophiolite obduction (“active continental margin evolution”) with the interplay of thrusting, trench and trench-like basin formation, mass movements, and the onset and growth of carbonate platforms, followed by latest Jurassic to Early Cretaceous mountain uplift and unroofing. – Final closure of the remaining open part of the NeoTethys (= Vardar Ocean) in Late Cretaceous to Paleogene times. The younger Wilson cycle reflect the geodynamic history of the Alpine Atlantic (Ligurian, Piemont, Pennine, Vah, Alpine Tethys oceans in other nomenclature), and the formed orogen is part of the Alpides with following evolution as documented in the sedimentary record of the wider Adria plate: – An Early Jurassic (Hettangian to Toarcian) rift (graben) stadium with sedimentation of fully marine deposits in areas the rift cross-cut the older proximal Neo-Tethys shelf and siliciclastics and carbonate ramp deposits in areas the rift cross-cut continental domains. – A Middle Jurassic to Late Cretaceous passive margin evolution after the oceanic break-up since the Toarcian with formation of shallow-water platforms in latest Jurassic–earliest Cretaceous times in certain areas, but predominantly with deposition of hemipelagic sedimentary sequences. – ALate Cretaceous to Paleogene convergent tectonic regime triggered by subduction and subsequent continent (wider Adria) – continent collision (Europe), followed by Neogene mountain uplift and unroofing. In contrast to the fairly well understood Alpine Atlantic Wilson cycle a lot of open questions exist regarding the NeoTethys Wilson cycle. The main focus is therefore the time frame before the “Mid-Cretaceous” mountain building process with the rearrangement of tectonic units, i.e. the Mesozoic plate configuration in the Western Tethys Realm. Due to the fact that the “Mid-Cretaceous” and younger polyphase tectonic motions and block rotations draws a veil over the older Mesozoic plate configuration, several crucial and still topical questions remain, e.g.: 1) How many Triassic-Jurassic oceans existed in the Western Tethyan Realm. Show these oceanic domains different life cycles, i.e. is the opening and the closure of these oceanic domains contemporaneous or differ their age, and where are the suture zones? In general, two main types of contrasting interpretations/models remain: a) Multi-ocean reconstructions with several oceanic domains between continental blocks, and b) One-ocean reconstruction: an allochthonous model which interprets the ophiolites as overthrust ophiolitic nappe stack (or single ophiolite sheet) from the Neo-Tethys to the southeast to east. 2) Were the Southern Alps/Dinarides/Albanides/Hellenides, the Eastern Alps/Western Carpathians plus some Pannonian units (ALCAPA), some units in the Circum-Pannonian realm (e.g., Tisza Unit), and Pelagonia (including Drina-Ivanjica Unit) independent microplates between independent oceanic domains in Triassic-Jurassic times? Or have these units been scattered by polyphase younger tectonic movements modifying an united continental realm (north-western part of Pangaea) of the Triassic European shelf? The Early Jurassic Pangaea break-up resulted, e.g., in the opening of the Central Atlantic Ocean and its eastward continuation, the Alpine Atlantic.

17

Mafic and ultramafic associations of ophiolite (possible Tethyan ophiolite) in the Panlin-Pyaunggaung area, Mogok, Myanmar

Myint Tin Aung, Ko Mi Mi, Thin Aung Kyaw, Peng Touping

Geotourism / Geoturystyka

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2023

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nr 1-2 (72-73)

53--53

EN

The Panlin-Pyaunggaung area is situated within the Mogok Metamorphic Belt (MMB) in Myanmar. The MMB extends for over 1,000 km along the western part of ShanThai Terrene (also known as Sibumasu Terrene) from the Andaman Sea as a narrow linear belt, then sharply bends east-northeastward through the northern part of Mogok including Panlin-Pyaunggaung area toward the China-Myanmar border and finally further northward into the East Himalayan Syntaxis. It comprises a sequence of regionally high-grade metamorphic rocks, representing the amphibolite-granulite facies grade belt intruded by granitoid rocks of various ages. Metamorphic rock units exposed in the area are marbles, calc-silicates and gneisses. Igneous rocks are peridotite, dunite, serpentinite, gabbro, granite, leucogranite, syenite and pegmatite. The ultramafic rocks (Pyaunggaung peridotites) mainly occur in the northern part of Mogok and have been considered as tectonites. Ophiolite sequence which consists, from bottom to top, of upper mantle peridotites/dunites, layered ultramafic-mafic rocks, layered gabbros, and felsic dikes occurs in the area indicating the typical lower part of ophiolite suite. The present ultramafities are mainly dunite-peridotite (harzburgitic or dunitic composition). Magnetic susceptibility of ophiolites reflects the highest point (39.75 ∙ 10−3 SI units). It is found that the chromite spinel observed in ophiolites and it contains high Pm, Cr, Ni & V. These criteria suggested that ophiolites in the area were deep seated origin coming from the upper mantle source. Panlin-Pyaunggaung Ophiolites in the area fall within the field of the Alpine-type peridotite. High Ni–Low Al content corresponds to the suprasubduction zone (SSZ) ophiolites and might have a similar tectonic stetting of Tagaung-Myitkyina Ophiolite Belt in Myanmar.

18

Late Cretaceous palaeoenvironmental and tectonostratigraphic reconstructions on the Polish sector of Peri-Tethys

Kwietniak Anna, Łaba-Biel Anna, Urbaniec Andrzej, Filipowska-Jeziorek Kinga

Geotourism / Geoturystyka

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2023

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nr 1-2 (72-73)

39--40

EN

The study area is located in the central part of the Carpathian Foreland in Poland (Fig. 1), and the analysed interval includes mixed carbonate-clastic sediments of the Upper Cretaceous and the uppermost part of the profile of carbonate sediments of the Upper Jurassic. The sedimentation of the studied formations during the Late Jurassic and Cretaceous took place in the shelf zone of the northern, passive margin of the Tethys Ocean. The western Tethys, unlike its eastern margins, was not a single open ocean; rather, it covered many small plates, Cretaceous island arcs and microcontinents (Palcu & Krijgsman, 2023). The spatial range of the subbasins created between these islands was significantly limited, resulting in a large diversity of palaeoenvironments and the mixed carbonate-clastic sediments of a shallow sea. The entire Upper Jurassic to Cretaceous complex can be viewed as a carbonate platform that lasted almost until the end of the Late Cretaceous with an episode of Early Cretaceous erosion. The sedimentary cover formed at that time initially reached considerable thickness (presumably about 2,000 m). Dislocation and bathymetric differentiation within the carbonate platform initiated the development of a complex depositional environment. During the Late Cretaceous, the syndepositional activity of NW-SE dislocation sequences resulted in an extensive flexural deflection within the Upper Jurassic-Lower Cretaceous sedimentary complex and lowermost part of the Upper Cretaceous complex. The resulting accommodation space was filled with a complex of Upper Cretaceous carbonate formations within which there are intervals with a significant share of siliciclastic material. At the end of the Late Cretaceous as well as in the Paleocene, movements of the Laramie phase led to the re-uplift of the analysed part of the Carpathian Foreland. During this tectonic episode, the reactivation of an older fault system occurred, mainly in the NW-SE directions. The Upper Cretaceous formations deposited in the flexural depression underwent a partial inversion and intensive erosion process, lasting until the beginning of the Neogene, which contributed to the reduction of thicknesses or the removal of some of the Upper Cretaceous formations, especially in the areas, adjacent to the major dislocations. The material for analysis consisted of 3D seismic data and geological information from the wells. In the scope of the project, we approached linking 3D seismic image and well data to reconstruct, as detailed as possible, the palaeoenvironment of the studied segment of the Late Cretaceous basin based on the chronostratigraphic method. The analysis shows various palaeomorphological elements that can bring insight into the sedimentation environments (Fig. 2). The significant influence of tectonic processes on the depositional history of the sedimentary basin was also evidenced. The tectonostratigraphic interpretation divided the Late Cretaceous sediments into two different tectonic phases (Łaba-Biel et al., 2023). Analysis of a thick Miocene interval that overlies directly on the Mesozoic formations enabled to reason about the influence of the Alpine orogenesis on the study area that was manifested by the reactivation of major regional faults in the central part of the Carpathian Foreland. This phase is directly related to the stage of progressive closure of the Tethys Ocean due to the collision of tectonic plates.

19

Larger Benthic Foraminifera from Paleocene–Eocene carbonates, Eastern Tethys, Meghalaya NE India – their comparison with Western Tethys and palaeobiogeographical significance

Tewari Vinod Chandra

Geotourism / Geoturystyka

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2023

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nr 1-2 (72-73)

71--72

EN

India–Asia plate collision and uplift of the Himalaya took place during Paleocene–Eocene time (50 Ma). The extension of western Tethys Sea from Europe to Asian eastern Tethyan region has been correlated by assemblages of Larger Benthic Foraminifera (LBF). Global correlation and paleobiogeography of the eastern Meghalayan and western Tethyan Sea is discussed on the basis of SBZ of Paleocene– Eocene foraminifera assemblages (Fig. 1). Paleocene–Eocene Lakadong Limestone and Umlatodoh Limestone were deposited in shallow marine carbonate ramp depositional environment in Shillong Plateau, Meghalaya, NE India. The sedimentation basin is part of the Eastern Tethys and LBF and calcareous algae is the major carbonate facies. Coral reefs are not developed in these carbonates in contrast with the western Tethys limestones in Adriatic Platform and western European –Alpine region (Tewari et al., 2007).The LBF and algal assemblage in both the limestones is consistent with other parts of Eastern Tethys in Eastern India and Tibet (Hottinger, 1971; Scheibner & Speijer, 2008, Tewari et al., 2010). The latest Paleocene (Biozone SBZ4) miscellanids and ranikothalids are replaced by Early Eocene alveolinids and nummulitids, which dominates LBF assemblages in the western Tethyan realm at the P-E boundary (Scheibner & Speijer, 2008), Thanetian (SBZ4 Biozone) is equivalent to Tethyan platform stage II (Scheibner & Speijer, 2008). In standard biozones Ilerdian (SBZ5-SBZ6), a general reorganization in LBF communities is recorded with a long life and low reproductive potential (Hottinger, 1971). However, in the Meghalayan LBF assemblages of the lowest Eocene (biozones SBZ5/6) are still dominated by Ranikothalia and Miscellanea, while new LBFs that first emerged within this time interval elsewhere (e.g. Assilina, Alveolina and Discocyclina) are less important and Nummulites are absent. Later, in the Early Eocene there was a gradual diversification of Discocyclina and Assilina species (Fig. 1), while Ranikothalia disappeared and Miscellanea became less important by the end of the SBZ5/6 biozones. Similar LBF assemblages have been recorded in other parts of east Tethys in western India and Tibet (Scheibner & Speijer 2008; Tewari et al., 2010 and references therein). Such LBF assemblages in east Tethys thus differ from west Tethys. Palaeobiogeographical barriers must have existed between India and Eurasia during early collision of Indian Plate with Eurasia Plate around 50 Ma (Tewari et al., 2010 and references therein). These barriers prevented migration of certain LBF species of Nummulites and Alveolina between these two palaeogeographic regions. LBF dominated facies in the other basins of Meghalaya like Umlatodoh Limestone are well developed in low latitude. However, mixed coral-algal reefs and LBF facies were sparse in low-mid latitude carbonate environments (Adriatic Platform of Italy-Slovenia, Oman, Egypt, Libya, NW Somalia; Tewari et al., 2007, 2010; Scheibner & Speijer, 2008 and references therin). In contrast to west Tethys, corals are absent in Eastern Tethys (calcareous algae is present in SBZ3 and SBZ4 Biozone, Fig. 1) in the Meghalaya and other low-latitude eastern Tethys (Scheibner & Speijer, 2008). Carbonate ramp (shallow tidal flat ) carbonate environments were dominated by LBFs from Early to Late Paleocene (SBZ4, SBZ5, biozones; Fig. 1). It is interpreted that the collision of the Indian and Asian plates must have generated this difference in palaeobiodiversity by creating barriers, which prevented migration of certain LBFs (Nummulites) from west to east. Later, in the Early Eocene (SBZ6, SBZ7-SBZ8 biozones), recorded from younger Umlatodoh Limestone in the upper part gradually replaced by LBF dominated facies in the east, with highly diversified LBF species of Nummulites, Discocyclina, Discocylina jauhrii etc.), indicating stable shallow marine environmental conditions. Stable carbon and oxygen isotope analyses from Paleocene–Eocene Lakadong Limestone and Umlatodoh Limestone strongly supports a shallow marine carbonate platform deposition in Eastern Shallow Tethys, Meghalaya, India (Tewari et al., 2010)

20

Jurassic and Cretaceous evolution of Tethys: Palaeoceanographic events

Yilmaz İsmail Ömer

Geotourism / Geoturystyka

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2023

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nr 1-2 (72-73)

81--81

EN

Jurassic and Cretaceous evolution of Tethys Ocean is characterized by extension of oceans basins, rifting, development of carbonate platforms and sea level fluctuations. Ocean basins and platform margins were sides of records of collaboration of oceanic, sea level and climate changes in different scales. Deposition of organic sediment increased on the margins of the ocean basins at certain time intervals due to changes in oceanic circulation and chemistry, productivity, climate and sea level. Oceanic Anoxic Events (OAE) stated to took place at aperiodic time intervals and generally associated with organic matter deposits and anoxic water columns. Records of oceanic anoxic event can also be associated by potential source rocks in Jurassic and Cretaceous along Tethys Ocean basins and can be tracked by stable isotope shifts, turnover of fossil groups, presence of black shales/organic rich mudstones, change in redox sensitive elements. Volcanic contribution in oceans is also considered as one of the collaborators of OAE generations. OAE records in Jurassic is seen in Toarcian interval and stated as Toarcian OAE. In Cretaceous, OAE records can be stated as Weissert, Faraoni, Selli (OAE1a), Noir, Fallot, Jacop, Kilian, Paquier (OAE1b), Leenhardt, Amadeus (OAE1c), Breistroffer (OAE1d), Bonarelli (OAE2), and OAE3. Generally, Cretaceous OAE are globally correlated or at least hemispherical. Some of them can be weakly correlated due to different duration and magnitude. Stratigraphic positions of OAE can also be used better marker levels in sequence stratigraphic interpretations. Therefore, positions of OAE are very important in terms of higher resolution for platform to basin correlations and even basin to basin. Cretaceous Oceanic Anoxic Events in eastern Tethys Ocean in Pontides and Taurides can be seen in Cretaceous successions (Mid-Barremian, Aptian, Albian, Cenomanian-Turonian) of Central Pontides (NW Turkey) and Central Taurides (S Turkey) (Yilmaz et al., 2004, 2010, 2012) as presence of black shales. The Mid-Barremian black shales (MBE) have been recorded within turbidite succession in deep marine setting in central Sakarya zone of Pontides following the drowning of the platform (Yilmaz et al., 2012). 2‰ shifts in carbon isotope curve is recorded in parallel with European basins, but with low TOC value. The Aptian black shales (OAE1a) are recorded in pelagic carbonate slope environments in central and north of Sakarya zone of Pontides and represented by a negative carbon isotope shift with 2‰, and TOC around 2% (Yilmaz et al., 2004; Hu et al., 2012). In Sakarya zone of Pontides, OAE2 is recorded in pelagic slope carbonates with carbon isotope curve more than 1‰ positive shift and >2% TOC. Another OAE2 was recorded in Antalya Nappes of Taurides without carbon isotope curve but TOC > 20% (Yurtsever et al., 2003, Bozcu et al., 2011). OAE1a equivalent in Tauride Carbonate platform can be interpreted as presence of dark colored thick stromatolite bearing platform carbonates transgressivley overlying the karstic sequence boundary. The OAE1a and OAE2 levels recorded in Turkey can easily be correlated with European examples and mainly controlled by sea level and tectonics in largescale and climate and oceanographic changes in small-scale. The most extensive distribution of the OAE records in Turkey belong to OAE1a and OAE2, and display potential for source rocks for hydrocarbon exploration.