Final Breakup Research Articles

The Matzitzi Formation in southern Mexico: A record of Pangea final assembly or breakup initiation along inherited suture belts?

AbstractThe breakup of Pangea fundamentally shaped modern continents and controlled the climatic distribution and biodiversity on Earth. Although our knowledge on the processes that control the assembly and breakup of supercontinents has significantly improved, the timing of supercontinent assembly and breakup initiation remains in some cases controversial. According to the available data, the assembly of Pangea was completed in middle Permian time, resulting in the formation of major orogenic belts and transform faults like the N–S‐trending, dextral, Caltepec fault in Mexico. Pangea breakup initiation is bracketed to early Middle Triassic time. In this work, we present new sedimentological, structural and U‐Pb geochronological data from a fluvial unit, the Matzitzi Formation of southern Mexico, the age and tectonic setting of which have remained an enigma for the past century. Our data document that the Matzitzi Formation is the stratigraphic record of a late Permian, anastomosing fluvial system that flowed in a—NNE‐trending extensional trough developed on top of the Caltepense belt, a transpressive belt formed along the Caltepec fault. We propose and discuss three possible scenarios for the tectonic setting of the Matzitzi Formation. In the first scenario, the unit is the stratigraphic record of the Caltepec fault late activity, which caused local NW–SE extension along the western margin of Pangea during its final assembly. In the second scenario, the Matzitzi Formation was deposited in an extensional basin formed by slab rollback along the western equatorial Pangea margin. In the third scenario, the extensional basin of the Matzitzi Formation was formed in the framework of the Pangea breakup. In this case, our data would suggest that Pangea breakup initiation must be dated back to late Permian time, which is ca. 15 m.y. older than the Middle Triassic age documented by the previous work. Considering that evidence of Permian extension has also been reported along the Appalachian belt, we suggest that the Matzitzi Formation was deposited during regional‐scale extension of western equatorial Pangea; therefore, we preliminarily support the third scenario. The distribution of Permian extension along suture belts developed during Pangea assembly highlights the fundamental role played by pre‐existent zones of weakness in the breakup of a supercontinent.

Geochemistry and Sr–Nd isotopic studies of Paleoproterozoic ( c. 2.3 Ga) meta-lamprophyre from the Rapuru area, Nellore Schist Belt, southern India: implications for back-arc basin magmatism and its relevance to the Columbia supercontinent assembly

Abstract This study reports on two lamprophyre dykes from the Rapuru area along the margin of the Eastern Dharwar Craton (EDC) and the Nellore Schist Belt (NSB). The Rapuru lamprophyre (RL) dykes are situated along the southern extension of the Prakassam Alkaline Province (PAP). The RL dykes are deformed, yet still preserve a porphyritic–panidiomorphic texture, with mica phenocrysts, and amphibole and feldspars in the groundmass. Geochemically, the RL dykes have a low Mg# (0.28–0.37), and Ni (30–60 ppm) and Cr (119–228 ppm) concentrations that indicate their evolved nature, such as for other reported lamprophyres from the PAP and EDC. This is further supported by Sr–Nd isotopic ratios that show an affinity towards a mid-ocean ridge basalt (MORB)–ocean island basalt (OIB)-like signature and a juvenile magmatic nature. The RL seems to have been affected by two major influences, namely, the primary source region, which is geochemically juvenile similar to the compositional field of enriched-MORB, and the continental lithosphere. Such magmas are known to have formed in a back-arc-basin environment. The initial 87 Sr/ 86 Sr ratio ( c. 0.7012–0.7045) and initial ε Nd ratios (3.13–7.93) are in line with back-arc basin basalts recorded in other parts of the world. The field observations and bulk-rock Sr–Nd radiogenic isotope values in the present study support the Paleoproterozoic nature of the RL. This concurrence of juvenile radiogenic isotopes and fluid-related trace element compositions apparently suggest dehydration of a subducted-slab-triggered metasomatism of the overlying mantle wedge in a subduction-related geodynamic setting. Such intrusive lamprophyre rocks of older ages are limited in India as well as other parts of the world. The 2.1 and 1.8 Ga rocks are widely considered to represent the initial accretion and final break-up of an erstwhile Columbia supercontinent assembly. We argue that the RL were formed in the Paleoproterozoic during the waxing stages of the Columbia supercontinent assembly in a back-arc basin environment, most probably due to the low degree of partial melting of the asthenosphere–lithospheric interaction caused by the introduction of an influx of subduction components into the arc–back-arc basin system.

The onset of seafloor spreading at the northeastern continent-ocean boundary of the South China Sea

The transition from continental to oceanic crust and the initial formation of typical oceanic crust at passive rifted margin are still poorly understood. In this study, deep crustal structures in the transitional domain of the northeastern South China Sea (SCS) margin are investigated and studied according to newly-acquired high-resolution reflection seismic data and gravity modeling. Three strong reflectors (R1, R2 and R3) are imaged in the narrow transitional domain. About 1 s in the two-way travel time (TWTT) beneath the top basement, R1 shows a similar morphology to the top basement, and quite likely represents a partial serpentinization interface. The presence of R1 suggests a tectonically dominated extensional stage prior to the final lithospheric rupture of the SCS. R2 is from magmatic intrusions or plutons (sills or dikes) from decompression melting. R3 is observed at ~2.5–2.2 s TWTT beneath the top basement but shoals seawards. R3 likely resulted from magmatic relicts in the paleo-melt transfer channels and/or from frozen molten materials in a shear zone of the lithospheric and asthenospheric mantle. The occurrence of R3 indicates the onset of a robust seafloor spreading system. The gradual seaward increase in magmatic activity highlights that, towards the final lithospheric breakup, tectonic extension was overtaken by magmatism. Increased magmatism and partial serpentinization formed a narrow hybrid transitional crust. Nevertheless, the breakup was not an instantaneous event. The last-stage transient magmatism occurred in a very narrow zone and does not rule out that the margin was predominantly amagmatic during the rifting and breakup. Based on reflection seismic and gravity modeling, we propose that the onset of typical seafloor spreading occurred at about 30 Ma around the study area, and the continent-ocean boundary (COB) should be located further seawards in the northeastern SCS margin.

Forced subduction initiation within the Neotethys: An example from the mid-Cretaceous Wuntho-Popa arc in Myanmar

Abstract Despite decades of research, the mechanisms and processes of subduction initiation remain obscure, including the tectonic settings where subduction initiation begins and how magmatism responds. The Cretaceous Mawgyi Volcanics represent the earliest volcanic succession in the Wuntho-Popa arc of western Myanmar. This volcanic unit consists of an exceptionally diverse range of contemporaneously magmatic compositions which are spatially juxtaposed. Our new geochemical data show that the Mawgyi Volcanics comprise massive mid-oceanic ridge basalt (MORB)-like lavas and dikes, and subordinate island arc tholeiite and calc-alkaline lavas. The Mawgyi MORB-like rocks exhibit flat rare earth elements (REEs) patterns and are depleted in REEs, high field strength elements (except for Th) and TiO2 concentrations relative to those of MORBs, resembling the Izu-Bonin-Mariana protoarc basalts. Our geochronological results indicate that the Mawgyi Volcanics formed between 105 and 93 Ma, coincident with formation of many Neotethyan supra-subduction zone ophiolites and intraoceanic arcs along orogenic strike in the eastern Mediterranean, Middle East, Pakistan, and Southeast Asia. Combined with its near-equatorial paleo-latitudes constrained by previous paleomagnetic data, the Wuntho-Popa arc is interpreted as a segment of the north-dipping trans-Neotethyan subduction system during the mid-Cretaceous. Importantly, our restoration with available data provides new evidence supporting the hypothesis of a mid-Cretaceous initiation of this >8000-km-long subduction system formed by inversion of the ∼E-W–trending Neotethyan oceanic spreading ridges, and that this was contemporaneous with the final breakup of Gondwana and an abrupt global plate reorganization.

Paleogeography and biogeography of the Gondwanan final breakup and its terrestrial vertebrates: New insights from southern South America and the “double Noah's Ark” Antarctic Peninsula

The Mesozoic plate tectonic and paleogeographic history of the final break up of West Gondwana had a profound effect on the distribution of terrestrial vertebrates in South America. As the supercontinent fragmented into a series of large landmasses (South America, Antarctica, Australia, New Zealand, the Indian subcontinent, and Madagascar), particularly during the Late Jurassic and Cretaceous, its terrestrial vertebrates became progressively isolated, evolving into unique faunal assemblages. The episodic nature of South American mammalian Cenozoic faunas became apparent in its modern formulation after George Gaylord Simpson's seminal works on this topic. Two aspects add complexity to this generally accepted scheme: first, the fact that South America is not (and was not) a biogeographic unit, as the Neotropical Region does not include its southernmost tip (the Andean Region, including Patagonia and the southern Andes). Second, and intimately linked with the first one, that South America was not an island continent during the Late Cretaceous and the beginning of the Cenozoic, being its southernmost portion closely linked with West Antarctica up to the late Paleocene at least. Here we stress on this second aspect; we summarize a series of recent, detailed paleogeographical analyses of the continental breakup between Patagonia (including the Magallanes Region) and the Antarctic Peninsula crustal block, beginning with the opening of the Atlantic Ocean in the Early Cretaceous and running up to the Early Paleogene with the expansion of the Scotia Basin. In second place, we comment on the implications of these distinct paleogeographic and paleobiogeographic scenarios (before and after their geographic and faunistic isolation) for the evolution of South American terrestrial mammalian faunas. Summarizing, (1) we recognize a West Weddellian terrestrial biogeographic unit with the assemblage of the southern part of South America (Patagonia and the Magallanes Region) and the Antarctic Peninsula (and probably Thurston Island) crustal block of West Antarctica, spanning from the Late Cretaceous (Campanian) through the Early Paleogene (Paleocene); (2) we suggest that the Antarctic Peninsula acted as a double "Noah's Ark” regarding, first, the probable migration of some non-therian lineages into southern South America; later, the migration of metatherians to Australasia.

Magma-assisted fragmentation of Pangea: Continental breakup initiation and propagation

Pre-magmatic continental extension often precedes the major magmatic expulsion of large igneous provinces (LIPs). However, the cause-and-effect relationship between pre-magmatic rifting and the extrusion of large amount of magma is controversial. It remains unclear whether magmatism arises as a consequence of passive rifting or whether it is related to active upwelling of the mantle. In addition, the relationship between the pre-magmatic stages and the final breakup, with the onset of conjugate passive margins, is ambiguous. In this study, we compiled available data from six LIPs (Central Atlantic, Karoo, Parana-Etendeka, Deccan, North Atlantic, and Afar igneous provinces) that successively occurred during the fragmentation of Pangea and found that pre-magmatic rift trends may show a high obliquity or even be orthogonal with respect to the future passive margins. We conclude that syn-magmatic rifts should not be directly correlated, both structurally and dynamically, to the ancient pre-magmatic rift phase. Furthermore, following the breakup of a supercontinent, seafloor spreading usually initiates within volcanic passive margins (VPMs) and then propagates away to create non-volcanic passive margins (NVPMs) as a consequence of the consumption and cooling of a sub-lithospheric positive thermal anomaly. Major transform faults often exist between VPMs and NVPMs, acting as a mechanical barrier to mantle melting and magmatism transportation.

Tectono - Magmatic and stratigraphic evolution of final rifting and breakup: Evidence from the tip of the southwestern propagator in the south China sea

In this study, we explore the tectono-sedimentary and magma evolution of final rifting and continental breakup along the SW conjugate margins of the South China Sea (SCS). Based on new seismic observations, we define and map three rift domains, referred to as “box-shaped”, “wedging” and “proto-oceanic”. Each of these domains is characterized by: (1) the shape and thickness of the crust; (2) the specific architecture of the syn-rift mega-sequence that includes three system tracts each one including syn- and post-rift packages; and (3) different deformation styles.Results are synthetized in two Wheeler diagrams that provide a complete description of the tectono-magmatic and stratigraphic evolution of final rifting and breakup within two neighboring segments of the SW-SCS. We conclude that: 1) localization of deformation occurs simultaneous and perpendicular to the migration of magma-emplacement in front of a propagating spreading system, 2) the arrival of magma controls continental breakup, and 3) the final rifting stage and breakup are diachronous. The relationships between extension, sedimentation and magmatic processes observed in the SW-SCS differ significantly from the classical models derived from the N-Atlantic or the Alpine Tethys. Main differences include the way the crust is thinning/necking, the sharp transition to breakup and the style of magma emplacement linked to crustal breakup.

A tectonic model for the Transcontinental Arch: Progressive migration of a Laurentian drainage divide during the Neoproterozoic–Cambrian Sauk Transgression

AbstractA widespread provenance shift recorded by passive margin strata of western Laurentia, from predominant Stenian (1.2–1.0 Ga) detrital zircon age components to their absence, occurred during the Neoproterozoic–Cambrian Sauk transgression and is commonly used as a ca. 540 Ma chronostratigraphic marker throughout the west/south‐western United States. However, in Neoproterozoic–Cambrian strata of this region, we identify a probable shift from distal to more proximal Stenian‐age zircon sources before a diachronous loss of Stenian detrital zircon age components. We suggest these provenance patterns reflect progressive subsidence of the passive margins surrounding Laurentia and concomitant relative uplift of the Transcontinental Arch, a broad and segmented northeast–southwest trending topographic high across the Laurentian midcontinent possibly due to lithospheric flexure. The Transcontinental Arch segments align with transverse rift structures of the Neoproterozoic–Cambrian Iapetan margin and the Mesoproterozoic Midcontinent Rift, perhaps reflecting rejuvenation of midcontinent lithospheric weaknesses during the Sauk transgression and final Rodinia breakup.

Investigating the Porcupine Atlantic margin, offshore Ireland, through integration of new seismic reflection and gravity data

While the offshore Irish Atlantic margin and related rift basins have been intensively studied for several decades, the Porcupine Bank, straddling between the well-studied Porcupine and Rockall basins, is a poorly understood region due to lacking sufficient geophysical data coverage. In this study, ten newly acquired long-offset multichannel seismic profiles extending across the western Porcupine Bank margin, combined with potential field data, are used to investigate the crustal architecture, tectonic history, and rift-related magmatism along the margin. Significant margin-parallel and margin-perpendicular structural variations are observed and these are used to map the crustal architecture in terms of rifted margin domains. In the transitional zone between continental and oceanic crust, both peridotite ridges with shallow reflective basement and exhumed serpentinized mantle with deeper and smoother basement are interpreted, similar to the conjugate Iberian and Newfoundland margins, as well as further south at the Goban Spur margin. In addition to inferred variations in extension rate during poly-phased rifting episodes, the reactivation of pre-existing inherited Caledonian and Variscan structural fabrics are proposed to have influenced the variable geometries and distributions of the crustal domains along the Porcupine Atlantic margin. Northwestward increasing volcanism and related reflectivity patterns support the transition from magma-poor rifting in the southeast to magma-rich rifting in the northwest. Rigid plate reconstructions of the Irish Atlantic and the Newfoundland margins, particularly involving the Flemish Cap, back to the Early Campanian period, show asymmetric rifting and final continental breakup migrating toward the Porcupine Bank region. This asymmetry is possibly due to oblique extension between the two margins, and/or oblique deformation on the Porcupine Bank side due to its rotation during the opening of the Porcupine Basin.

Late Mesoproterozoic low-P/T–type metamorphism in the North Wulan terrane: Implications for the assembly of Rodinia

AbstractRegional metamorphism provides critical constraints for unravelling lithosphere evolution and geodynamic settings, especially in an orogenic system. Recently, there has been a debate on the Rodinia-forming Tarimian orogeny within the Greater Tarim block in NW China. The North Wulan terrane, involved in the Paleozoic Qilian orogen, was once part of the Greater Tarim block. This investigation of petrography, whole-rock and mineral geochemistry, phase equilibrium modeling, and in situ monazite U-Pb dating of garnetite, pelitic gneiss, and quartz schist samples from the Statherian–Calymmian unit of the North Wulan terrane provides new constraints on the evolutionary history of the Greater Tarim block at the end of the Mesoproterozoic during the assembly of Rodinia. The studied samples yielded three monazite U-Pb age groups of ca. 1.32 Ga, 1.1 Ga, and 0.45 Ga that are interpreted to be metamorphic in origin. The tectonic significance of the early ca. 1.32 Ga metamorphism is uncertain and may indicate an extensional setting associated with the final breakup of Columbia. The ca. 1.1 Ga low-pressure, high-temperature (low-P/T)–type granulite-facies metamorphism is well preserved and characterized by a clockwise P-T path with a minimum estimation of ∼840–900 °C and ∼7–11 kbar for peak metamorphism, followed by postpeak decompression and cooling. A tectonothermal disturbance occurred at ca. 0.45 Ga, but with limited influence on the preexisting mineral compositions of the studied samples. The characteristics of the metamorphism indicate an arc–back-arc environment with ongoing subduction of oceanic lithosphere at ca. 1.1 Ga. Combined with previous studies, we suggest that the Greater Tarim block probably experienced a prolonged subduction-to-collision process at ca. 1.1–0.9 Ga during the assembly of Rodinia, with a position between western Laurentia and India–East Antarctica.

Provenance of Upper Jurassic–Lower Cretaceous strata in the Mentelle Basin, southwestern Australia, reveals a trans-Gondwanan fluvial pathway

Australia, and East Gondwana more broadly, host extensive Paleozoic–Mesozoic sedimentary basins with thick siliciclastic sequences. These sediments were for the greater part transported by large-scale fluvial systems; however, the spatial and temporal patterns of sediment dispersal remain poorly understood. We investigate the provenance of rift strata in the Mentelle Basin, Western Australia, which were deposited during the Late Jurassic–Early Cretaceous breakup of India from Australia-Antarctica. Monazite U–Pb and zircon U–Pb–Hf isotopic signatures suggest that the Upper Jurassic–Lower Cretaceous syn-rift sediments were supplied predominately by a transcontinental river system draining sediments from interior regions of East Antarctica to the northern Gondwanan passive margin. This fluvial system was focused within the developing rift between India and Australia-Antarctica. Provenance of the transgressive marine post-breakup strata reflects a transition to a proximal sediment source and marks the end of the transcontinental fluvial system after the final breakup of India from Australia-Antarctica in the Valanginian (~136 Ma). Statistical comparison of detrital zircon spectra of Mentelle Basin syn-rift strata with other Australian Paleozoic–Mesozoic rift strata located along our proposed transport route suggests that the transcontinental fluvial pathway was active since the Late Paleozoic. We infer that this fluvial system was one of the principal modes of siliciclastic sediment delivery to rift and passive margin basins of western Australia.

Precursor extension to final Neo-Tethys break-up: flooding events and their significance for the correlation of shallow-water and deep-marine organisms (Anisian, Eastern Alps, Austria)

The Anisian depositional history in the Western Tethys realm provides the possibility to study the stepwise opening of the Neo-Tethys, and is well preserved in the sedimentary record of the Northern Calcareous Alps. Whereas the depositional characteristic in the Early (to early Middle) Anisian is characterized by shallow-water carbonates, formed in a semi-restricted environment, the situation changed in the Middle Anisian. A rapid increase of subsidence resulted in an abrupt deepening event with deposition of deeper-water limestones, in some cases even with chert nodules, sometimes with resedimented shallow-water debris intercalated in radiolaria-filament wackestones, or with clayey or marly intercalations. This abrupt deepening, termed the Annaberg Event, is followed by a shallow-water carbonate evolution. The deeper-water limestones can be dated by conodonts and shallow-water organisms like calcareous algae or foraminifera from the resedimented intercalations as Late Bithynian to Early Pelsonian. In contrast to the Early Anisian microbial carbonates, formed under semi-restricted conditions, the Middle Anisian (Pelsonian) shallow-water carbonates were formed under fully marine influence and a diverse fauna and flora was, therefore, able to counterbalance the rapid subsidence by increasing carbonate production. During Middle Anisian times, the newly tectonically created accommodation space became rapidly filled by shallow-water carbonates. At the end of the Middle Anisian (Late Pelsonian), the final break-up of the Neo-Tethys led to a rapid decrease of carbonate production and widespread deposition of deep-marine and condensed limestones. This drowning event (Reifling Event) was accompanied by the formation of a horst-and-graben morphology, dated by conodonts and ammonoids as late Middle Anisian from overlying condensed limestones. In contrast to the well-known drowning event in the late Middle Anisian, precursor events to the final oceanic break-up of the Neo-Tethys have not yet been described, but play an important role in the reconstruction of the opening history of the Neo-Tethys. This knowledge gap is filled by the analysis of exactly datable sedimentary successions in the central Northern Calcareous Alps.

The Newly Discovered Neoproterozoic Aillikite Occurrence in Vinoren (Southern Norway): Age, Geodynamic Position and Mineralogical Evidence of Diamond-Bearing Mantle Source

During the period 750–600 Ma ago, prior to the final break-up of the supercontinent Rodinia, the crust of both the North American Craton and Baltica was intruded by significant amounts of rift-related magmas originating from the mantle. In the Proterozoic crust of Southern Norway, the 580 Ma old Fen carbonatite-ultramafic complex is a representative of this type of rocks. In this paper, we report the occurrence of an ultramafic lamprophyre dyke which possibly is linked to the Fen complex, although 40Ar/39Ar data from phenocrystic phlogopite from the dyke gave an age of 686 ± 9 Ma. The lamprophyre dyke was recently discovered in one of the Kongsberg silver mines at Vinoren, Norway. Whole rock geochemistry, geochronological and mineralogical data from the ultramafic lamprophyre dyke are presented aiming to elucidate its origin and possible geodynamic setting. From the whole-rock composition of the Vinoren dyke, the rock could be recognized as transitional between carbonatite and kimberlite-II (orangeite). From its diagnostic mineralogy, the rock is classified as aillikite. The compositions and xenocrystic nature of several of the major and accessory minerals from the Vinoren aillikite are characteristic for diamondiferous rocks (kimberlites/lamproites/UML): Phlogopite with kinoshitalite-rich rims, chromite-spinel-ulvöspinel series, Mg- and Mn-rich ilmenites, rutile and lucasite-(Ce). We suggest that the aillikite melt formed during partial melting of a MARID (mica-amphibole-rutile-ilmenite-diopside)-like source under CO2 fluxing. The pre-rifting geodynamic setting of the Vinoren aillikite before the Rodinia supercontinent breakup suggests a relatively thick SCLM (Subcontinental Lithospheric Mantle) during this stage and might indicate a diamond-bearing source for the parental melt. This is in contrast to the about 100 Ma younger Fen complex, which were derived from a thin SCLM.

Initial separation of the South Qinling Terrane from the Yangtze Block during the Ediacaran: Insights from sequence correlation and zircon Hf isotope of tuff

The seldom investigated Ediacaran strata in the South Qinling Orogen contain precious sedimentary records that can provide critical insights into the tectonic evolution of the South China Block during the late Neoproterozoic. Here, we present U-Pb dating and Hf isotopic analyses on zircons obtained from a tuff layer of the Heyu section in the South Qinling Orogen. U- Pb dating of zircons gave concordia ages of 633.4 ± 3.1 Ma and 631.4 ± 3.9 Ma (by LA-ICP-MS and SHRIMP, respectively), which are in good agreement with published dates of Ediacaran Cap carbonate from the Yangtze Platform and other regions worldwide. Among the zircons group dated by LA-ICP-MS, 28 grains had markedly positive εHf (t) values ranging from 7.8 to 14.4 with a weighted mean of 11.3 ± 0.8, implying that they were derived from depleted mantle. The zircon εHf (t) values were very similar to those of contemporaneous mafic-ultramafic intrusion swarms and A-type granites in the South Qinling Orogen, suggesting an intimate provenance affinity to Yaolinghe Group volcanic rocks. This indicates that the South Qinling Terrane was dominated by an intra-plate rift setting during the late Neoproterozoic. The Ediacaran succession in the Heyu section is comparable to that in the Yangtze Platform, comprising an initially deepening- and then shallowing-upward sequence in the lower part, and a shallowing-upward sequence in the upper part. The South Qinling Terrane and Yangtze Platform had similar shallow-water environments during the early Ediacaran but evolved in different directions during the late Ediacaran with a relative stability in the Yangtze Platform and a deep-water basin environment in the South Qinling Terrane. It is proposed that the South Qinling Terrane experienced intense extension during the Ediacaran, likely in response to the final breakup of the Rodinia supercontinent or slab pull induced by subduction during the assembly of Gondwana.

Spatial Analysis of the Possible First Serbian Conurbation

After the breakup of the former Republic of Yugoslavia, the number of inhabitants in newly formed state of Serbia has been in constant decrease. On the other hand, the number of urban areas has been growing. One of the main goals of former Socialist Federal Republic of Yugoslavia was the development of all the areas, including the rural ones. In the ‘60s and the ‘70s, the land with special purpose was supposed to be of the utmost importance. Urban regions were to be better connected and enlarged. The main reason for it was the distribution of economic activities as well as the process of deagrarization which had already been in progress. In 1966, the first spatial plan of a special-purpose area, being the outset of an idea in a Socialist country, was in fact the proposition of the first Yugoslav conurbation. The long forgotten project was about to be reinforced in 1996, when thirty years later the country was in a transitional period, heading towards market capitalization. After the final breakup of Yuoslavia, there was a growing need for preservation of the urban areas and large trade centers, along with the necessity of better communication among municipalities. The ambitious project in question called “Morava city”, has never been brought to life. The main purpose of this manuscript is to answer the question of the actual necessity of this potential conurbation by means of GIS methodology, qualitative and quantitative techniques, and demographic and sociological factors. Accordingly, by means of spatial analysis, the communist project is placed into post-communist environment. Finally, the manuscript focuses on the relationship between rural and urban areas, traffic connectivity, geographical position, and most importantly on the sustainability and profitability of the first Serbian conurbation.

Revisiting the Australian‐Antarctic Ocean‐Continent Transition Zone Using Petrological and Geophysical Characterization of Exhumed Subcontinental Mantle

AbstractThe final lithospheric breakup of the Australian‐Antarctic rift system remains controversial due to sparse geological constraints on the nature of the basement along the ocean‐continent transition (OCT) zones. We present new interpretations of multichannel seismic reflection transects and new petrological data of dredged mantle rocks along the East Antarctic margin (Seamount B, offshore Terre Adélie). By combining both data sets, we show that a 50–100 km wide domain of cold and fertile subcontinental mantle was exhumed along the magma‐poor Antarctic margin. This study represents only the second locality, along with the Iberia‐Newfoundland margins, where the importance of exhumed mantle domains along OCTs can be clearly identified. The dredged peridotites preserve characteristics similar to mantle xenoliths found in syn‐ to post‐rift volcanism at the eastern end of the Australian margin (Victoria and Tasmania), indicating the exhumation of fertile subcontinental mantle during rifting between Australia and Antarctica. Seamount B represents the initial stages of exhumation of cold subcontinental lithosphere along an OCT during rifting. This thick mantle domain was likely affected by melt impregnation at high pressure (8 kbar), leading to the formation of plagioclase‐pyroxenites. The combination of continental rifted blocks, a wide domain of volcanic‐poor subcontinental mantle and (ultra‐) slow spreading is analogous to OCTs from the Jurassic Western Tethys and Iberia‐Newfoundland rifted margins. Additionally, evidence of melt stagnation at high pressure suggests that magmatism along the Australian‐Antarctic rifted margins was sufficient to form magnetic anomalies that can be used as isochrons despite their formation in lithosphere other than mature, steady‐state ocean crust.

Numerical modeling of failed rifts in the northern South China Sea margin: Implications for continental rifting and breakup

Failed rifts record important information of continental extension and breakup process in the northern South China Sea (SCS) margin. The Tainan Southern Depression and the Baiyun Sag to the east are characterized with lower-crust high-velocity anomalies (LCHVA), and intracrust detachment faults, whereas the Xisha Trough to the west develops on a larger scale with crust-cutting normal faults and absence of LCHVA. These contrasts indicate different rifting processes between the northeastern and northwestern SCS. 2D numerical modeling is performed to understand the formation mechanism of these failed rifts. Two types of mechanisms are proposed: I) syn-rift competitive type and II) rift migration type with a half extension rate of 2 cm/yr and 1.5 cm/yr, respectively. In type I, two rifts develop initially on the shoulders of the weak zone, but they compete with each other during extension. One rift becomes dominant to furnish the final breakup, whereas the other one is abandoned. The crust structure of this type fits the observations in the Baiyun Sag and the Tainan Southern Depression. However, in type II, only one rift develops at the beginning. The initial rifting center will migrate and the final continental breakup will occur at a place far from the initial rifting location. In this type, normal faults cut through whole crust and wide extensional margins will form, such as observed in the Xisha Trough. Our results suggest that the depth-dependent extension of the SCS is strongly heterogeneous, resulting primarily from varying extensional rates.

Numerical Modeling of Instability and Breakup of Elliptical Liquid Jets

Numerical simulations are performed to provide an in-depth insight into the effect of instabilities on liquid jets discharging from elliptical orifices. The axis-switching phenomenon and breakup are simulated and characterized under the effect of disturbances imposed at the nozzle exit. The simulations are based on the volume of fluid approach and an adaptive meshing. A range of orifice aspect ratios from 1 to 4 at the Rayleigh breakup regime is considered. The evolution of the jet cross section and axis switching under the influence of disturbances is compared with that of nonperturbed elliptical jets. It is found that the axis-switching repetition and breakup length exponentially decrease with the initial amplitude of disturbances. For a fixed amplitude, the optimum wavenumber responsible for minimum breakup length is observed to be dependent on ellipticity of the orifice. Moreover, it is found that the form of final breakup leads to elimination of the satellite droplets at the optimum wavenumbers, while the droplet size decreases and becomes more uniform.

Dating the origin and diversification of Pan-Chelidae (Testudines, Pleurodira) under multiple molecular clock approaches

Pan-Chelidae (Testudines, Pleurodira) is a group of side-necked turtles with a currently disjointed distribution in South America and Australasia and characterized by two morphotypes: the long-necked and the short-necked chelids. Both geographic groups include both morphotypes, but different phylogenetic signals are obtained from morphological and molecular data, suggesting the monophyly of the long-necked chelids or the independent evolution of this trait in both groups. In this paper, we addressed this conflict by compiling and editing available molecular and morphological data for Pan-Chelidae, and performing phylogenetic and dating analyses over the individual and the combined datasets. Our total-evidence phylogenetic analysis recovered the clade Chelidae as monophyletic and as sister group of a clade of South American extinct chelids; furthermore Chelidae retained inside the classical molecular structure with the addition of extinct taxa in both the Australasian and the South American clades. Our dating results suggest a Middle Jurassic origin for the total clade Pan-Chelidae, an Early Cretaceous origin for Chelidae, a Late Cretaceous basal diversification of both geographic clades with the emergence of long-necked lineages, and an Eocene diversification at genera level, with the emergence of some species before the final breakup of Southern Gondwana and the remaining species after this event.

Cambrian-Eocene pre-rift, pulsed rift, passive margin and emplacement processes along the northern margin of the Southern Neotethys: Evidence from the Antalya Complex in the Alanya Window (S Turkey)

Sedimentary rocks in the Alanya Window document pulsed Permian-Triassic rifting in a proximal basin setting, adjacent to the Tauride continental unit (Geyik Dağ). Late Cambrian-Early Ordovician clastic sediments accumulated along the north margin of Gondwana on a variable shallow-marine shelf. Above an unconformity related to rift-shoulder uplift, Late Permian facies document shallow-marine to evaporitic environments during regional tectonic subsidence (first main rift pulse). Above a second unconformity (both extension and sea-level controlled), Early Triassic carbonates and mudrocks accumulated on an unstable, gently subsiding shelf. Mudrocks, sandstones and lithoclastic debris-flows, derived from the underlying succession, accumulated during the Middle Triassic (Anisian-early Ladinian), implying strong tectonic subsidence and flank uplift (second main rift pulse). Radiolarian mudstones accumulated during late Middle Triassic-early Late Triassic in a well-oxidised, organically productive, but relatively quiescent, deep-water basin above the carbonate compensation depth (CCD). Thick (100s m) lithoclastic sandstone turbidites (commonly plant-rich) and localised debris-flows accumulated during the Late Triassic (Carnian), together with detached blocks of underlying lithologies (third main rift pulse), combined with regional uplift. Alkaline basaltic sills were intruded locally. Final continental break-up to create the Southern Neotethys took place regionally during the Late Triassic (Carnian). Latest Triassic-Late Cretaceous deposition records passive margin subsidence. Variable low-grade metamorphism and two-stage tectonic emplacement (southwards(?) then northwards) took place during latest Cretaceous and Eocene, respectively. The tectonic-sedimentary development of the Antalya Complex provides insights into rift/continental break-up processes that differ from the recently well-documented Alpine-North Atlantic region.