Early Eocene Age Research Articles

Alveolina-dominated assemblages in the early Eocene carbonates of Jaintia Hills, NE India: Biostratigraphic and palaeoenvironmental implications

Larger benthic foraminifera (LBF) are significant proxies in biostratigraphy and also act as excellent indicators of shallow-marine carbonate environments in fossil series. The Palaeogene LBF recorded from Meghalaya, NE India (eastern part of the relic eastern Tethys/Neo-Tethys) have high potential for dating shallow-marine sediments and documenting the multiple episodes of carbonate sedimentation that have contributed to the development of the Sylhet Limestone Group. Early Eocene witnessed the proliferation of LBF species worldwide, the phenomenon better known as the Larger Foraminiferal Turnover (LFT). Genera like Alveolina, Nummulites and Orbitolites with broad species complexes thrived as the dominant LBF amidst numerous other taxa on the verge of extinction or only surviving as stable forms. The current study emphasizes on the biostratigraphic and palaeoenvironmental account of the early Eocene Umlatdoh Limestone successions outcropping in the Jaintia Hills of Meghalaya, primarily based on the recorded species of Alveolina and other larger benthic foraminifera. Five species of Alveolina — A. oblonga, A. schwageri, A. cf. ruetimeyeri, A. aff. haymanensis and A. aff. varians are recorded in the evaluated sections that indicate an early Eocene age corresponding to the Shallow Benthic Zone 10. Major carbonate facies types in the present assessment include oolitic-smaller benthic foraminiferal -green algal grainstone–packstone, smaller miliolid-Alveolina grainstone, green algal-benthic foraminiferal grainstone, larger porcellaneous (Alveolina) grainstone-packstone, Alveolina-nummulitid grainstone-rudstone, and nummulitid grainstone-rudstone, which indicate a shallow marine, high-energy depositional environment ranging from shoal-sandy bars to a distal inner ramp setting.

Depositional model and sequence stratigraphy of the Paleocene-Lower Eocene succession in the Farafra Oasis, Western Desert, Egypt

This work is to reconstruct a depositional model and establish a sequence stratigraphic framework for the exposed Paleocene-Lower Eocene succession in the Farafra Oasis, Western Desert, Egypt. This has been performed by an integration of the microfacies analysis with aid of the nannofossils and P/B foraminiferal ratio in the studied rocks. The identified microfacies and their related palaeoenvironments suggest a deposition in a carbonate shelf (inner, middle and outer shelf) environment. The Paleocene deposits (Dakhla, Tarawan and lower part of Esna formations) were laid down in a mid-to outer-shelf setting, whereas the deposits of Early Eocene age (Farafra Formation and upper part of Esna Formation) were deposited in an inner shelf setting. An integration of the resultant microfacies, nannofossils and P/B foramineferal ratio in the studied four stratigraphic sections led to record five 3rd order depositional sequences (SQs) separated by six sequence boundaries (SBs). Each sequence consists of transgressive (TST) and highstand (HST) systems tracts. The TST consists of a retrogradational package of facies (planktonic foraminiferal wackstones/packstones, as well as shales and marls rich in planktonic foraminifera) ended by marine flooding surface (MFS). The HST is made up of aggradational package of facies (nummulitic bioclastic packstone, algal alveoline packstone, alveoline-miliolid packstone and shale with a relatively low P/B foraminiferal ratio) topped by sequence boundary (SB). The sequence boundaries are distinguished by lithologic and paleontologic criteria. The recognized lithologic criteria comprise calcretes, iron-stained surface, extensive bioturbation and erosional irregular surfaces. The paleontologic criteria are evidenced by the time gaps (hiatus). The maximum flooding surfaces are recognized where there are a relatively high P/B foraminiferal ratio in the studied facies. The integrated results suggest that sedimentation regime of the studied Paleocene-Lower Eocene rocks was mainly controlled by tectonic activities and subsequent sea-level changes that were a result of a reactivation of the Syrian Arc System during Early Paleogene time.

Composite materials based on zeolite stilbite from Faroe Islands for the removal of fluoride from drinking water

Abstract In this work, three samples of the zeolite stilbite from the Faroe Islands have been used to prepare zeolite/hydroxyapatite composite materials that have been tested for the removal of fluoride present as geogenic contaminant in underground water. The Faroe Islands are an archipelago in the North Atlantic that have volcanic origins of Paleocene and early Eocene age. Early reports on the presence of zeolites in the Faroe Islands indicate abundance of chabazite, analcite, mesolite, heulandites, and stilbite, with heulandite and stilbite dominant in the northern and northwestern part of the islands. Further investigations of the Faroese Geological Survey yielded zeolitic phases in Vestmanna, Streymoy, Morkranes, and Eysturoy, as well as in the sea tunnel that connects the island of Eysturoy with the island of Borðoy. Three stilbite samples coming from these locations have been used with the aim of producing composite materials for fluoride removal. For this purpose, the samples were exposed to a phosphate solution at room temperature for selected periods of time, in such a way that a hydroxyapatite layer develops on the surface of the zeolite crystals. The resulting composites consist of approximately 93% zeolite and 7% nano-hydroxyapatite, which is the active phase for fluoride removal. Excess fluoride (above 1.5 mg/L according to WHO) in drinking waters provokes dental or skeletal fluorosis, an endemic health problem in more than 25 countries. The defluoridation studies in our work are performed using real waters from Spain with initial [F–] of 7.1 mg/L. The capacity of the Faroe Islands stilbite-based adsorbent reaches 0.3 mg F–/g, showing similar behavior regardless of the stilbite sample used. The impact of the particle size of stilbite in the final defluoridation capacity is remarkable. An increase in the particle size leads to a dramatic decrease in the surface area, affecting the growth of the nano–hydroxyapatite on the zeolite surface and hindering, as a result, its capacity to remove fluoride. Interestingly, electron microscopy and X–ray powder diffraction results clearly show that nano–hydroxyapatite grow on the zeolite surface with a preferential orientation that maximizes the exposure of the (001) face containing the active sites for defluoridation, thus explaining the high F-removal efficiency of these materials.

Palynofloral diversity and palaeoenvironments of early Eocene Akri lignite succession, Kutch Basin, western India

This study presents palynological analysis of lignite-bearing succession of Akri lignite mine, Kutch, Gujarat, and discussed the implications of the recovered palynomorphs for age, palaeovegetation and palaeoenvironments. A diverse palynological assemblage consisting of algal and fungal remains, pteridophytic spores, angiosperm pollen and dinoflagellate cysts has been recorded. The lower part of the succession (samples 1–5) is dominated by marine dinoflagellate cysts along with palm pollen belonging to family Arecaceae. The upper part of the succession (samples 6–8, 11) is dominated by terrestrial palynomorphs attributed to megathermal families (Bombacaceae, Ctenolophonaceae, Dipterocarpaceae, Meliaceae) followed by mangrove and back-mangrove elements. An early Ypresian age is inferred for the Akri lignite deposit, whereas a middle Ypresian–early Lutetian age is assigned to the post-lignite succession based on the age-diagnostic dinoflagellate cysts and spore-pollen assemblage. Furthermore, based on the distribution of marine and terrestrial palynomorphs, two palynological assemblages (A and B) have been recognised that are apparently controlled by changing depositional environment. The overall palynological assemblage points to a dense tropical rainforest that thrived in the vicinity of the depositional basin under high precipitation regime of warm and humid climate. The peat accumulation took place in a near-shore coastal swamp which was interrupted by fluctuating marine influences, followed by increased siliciclastic influx in a low-salinity coastal swamp dominated by mangroves. Moreover, the palynological comparison suggests that widespread lignite-bearing successions in the western Indian region are in part coeval and belong to the early Eocene (Ypresian) age.

Fossil Wood of Subfamily Detarioideae (family Fabaceae) from the Paleogene of the Indian Subcontinent: Origin and Palaeo-dispersal Pathways

Abstract A new fossil wood of Hopeoxylon i.e. H. umarsarensis sp. nov. showing close resemblance with the modern wood of Sindora/Copaifera of the subfamily Detarioideae (family Fabaceae) is described from the Umarsar lignite mine of Kutch basin, Gujarat that belongs to the Naredi Formation of the early Eocene age. Detarioideae is one of the reinstated subfamilies of the Fabaceae with diversity much higher in tropical Africa than in South America or Asia. The relics of this subfamily are known from the Paleocene onwards from various horizons of America, Africa, Europe, India and Southeast Asia. This is the oldest fossil record of the genus Sindora/Copaifera which contributes towards the understanding of the origin and palaeo-dispersal pathways of this early-diverging subfamily within the early branching Fabaceae.

Impacts of fault-sill interactions on sill emplacement in the Vøring Basin, Norwegian North Sea

Pre-existing faults may facilitate subsurface magma transport and sill trangression in sedimentary basins. Although widely recognized, interaction between faults and intrusion networks in sedimentary basins remains poorly imaged by seismic reflection data. To understand how sills interact with pre-existing faults in sedimentary basins, we use high-resolution 3-D seismic reflection data from the Naglfar Dome, Vøring Basin to examine the seismic expression of sills, interpret fault geometries and displacement patterns, and characterize sill-fault interactions. The sills are expressed as tuned reflection packages, meaning they are below ∼<50 ± 5 m thick, with saucer-shaped, transgressive, and strata-concordant morphologies that range in area from 6 km2 to 180 km2. The interconnected sills form a sill-complex, which was emplaced during the Eocene and cross-cuts three main stratigraphic intervals (i.e. the Nise, Tang, and Brygge Formations). Faults are of Early Paleocene to Early Eocene age, tectonic in origin and dominated by normal faults that are up to 28 km long. Fault and sill interactions define a spectrum, which we sub-divide into five categories (i.e. Type 1a, 1b, 2, 3 and 4); the two main end-member fault-sill relationships documented here are (a) sills stepping up stratigraphy short distances via faults and (b) those with inclined limbs intruded along fault planes. Whilst interactions between the faults and the sills are common, quantitative displacement analysis reveals fault displacement did not influence where sills exploited faults. In the study, the intricate interaction of fault and magmatic sills and its broader implications to structural compartmentalization and outcrop-scale studies in many magma-rich continental margins are demonstrated.

Ypresian Nummulites and their stratigraphic significance from El-Guss Abu Said plateau, Farafra Oasis, Western Desert, Egypt

El-Guss Abu Said plateau lies on the western scarp of Farafra Oasis. The studied succession consists of Esna Formation (shale) at the base, which is overlain by well-bedded alveoline marl (Nusf Formation) with occasional limestone ledges rich in nummulitic fauna. This unit ends with varved-like thin beds of marl and limestone before it is truncated by limestone unit of the Farafra Formation (limestone). Esna Formation is deep shelf facies as it is rich in planktonic foraminifera that assign it to Early Eocene in age. The first occurrence of nummulitic fauna was recorded in the lower part of Nusf Formation. Two species of Nummulites were identified; Nummulites solitarius de la Harpe 1883 and Nummulites fraasi de la Harpe 1883. These two species date this unit to Early Eocene time (Ypresian) that ranges from SBZ5 to SBZ6 of the standard Serra-Kiel et al., 1998, shallow benthic zonal scheme. The shift from deep shelf facies of Esna Formation to the carbonate platform facies of Nusf and Farafra Formations could point to a tectonic uplift that occurred in Early Eocene time.

New species from the Sabrina Flora: an early Paleogene pollen and spore assemblage from the Sabrina Coast, East Antarctica

Palynological analyses of 13 samples from two sediment cores retrieved from the Sabrina Coast, East Antarctica provide rare information regarding the paleovegetation within the Aurora Basin, which today is covered by the East Antarctic Ice Sheet. The assemblages, hereafter referred to as the Sabrina Flora, are dominated by angiosperms, with complexes of Gambierina (G.) rudata and G. edwardsii representing 38–66% of the assemblage and an abundant and diverse Proteaceae component. The Sabrina Flora also includes Battenipollis sectilis, Forcipites sp. and Nothofagidites (N.) spp. (mostly belonging to the N. cf. rocaensis-cf. flemingii complex), along with a few fern spores, including Laevigatosporites ovatus, a moderate presence of conifers, and previously undescribed angiosperm morphospecies. Two of these, Battenipollis sabrinae sp. nov. and being Gambierina askiniae sp. nov., are described herein. A majority of the assemblage is interpreted as deposited contemporaneously with sedimentation, including Gambierina spp., which is traditionally assigned a Cretaceous–earliest Eocene age range. However, our age diagnosis for the Sabrina Flora, based on key morphospecies, indicates that sediment was most likely deposited between the latest Paleocene to early–middle Eocene, and that Gambierina rudata and G. edwardsii extended longer than previously proposed.

A story told by calcareous nannofossils—the timing and course of an Eocene meteorite impact in central Jordan

A circular structure, 5.5 km in diameter, in central eastern Jordan has been interpreted as a large meteorite impact structure. The age of the Waqf As Suwwan impact is poorly constrained. By examining calcareous nannofossils from the sediments exposed in this structure, an age model of the timing of the event has been obtained. A total of 81 smear slides from two cores (BH-1, BH-2) penetrating the sediments of the central structure were prepared in order to obtain a biostratigraphic age for the post-impact sediments. The calcareous nannofossils assign sediments below the breccias of the core BH-1 an age of late Campanian to late Maastrichtian and a mixture of late Maastrichtian to early Eocene ages in the breccia horizon, while core BH-2 is of early Maastrichtian to late Maastrichtian age. The upper part of the sediments, removed in from adjacent area, consists of breccia components. The presences of calcareous nannofossil marker assemblages suggest that these components were derived from two different sources: a Cretaceous and a Paleocene-Early Eocene one. The deposition of the breccia resulted from gravitational collapse of water-saturated sediments in two stages; the earlier of these was more intensive than the latter. The stratigraphic framework and the presence of reworked Cretaceous and Paleocene calcareous nannofossils within Paleogene nannofossil Zone NP12/NP13 suggests an early Eocene age for the impact. The upper part of the Cretaceous sediments was thermally altered by the impact causing partial or complete dissolution of the calcareous nannofossils. This caused overgrowth for the more resistant species, while others were dissolved.

Benthic Foraminifera and Geochemistry Across the Paleocene–eocene Thermal Maximum Interval in Jordan

AbstractThis study presents benthic foraminiferal data from two sedimentary successions across the Paleocene–Eocene Thermal Maximum (PETM) from Jordan. Calcareous nannofossil biozones NP9a, NP9b, and NP10 of latest Paleocene and earliest Eocene age were encountered in proximal (core OS–01) and distal (core OS–28) sites. Lithologically, the investigated sequence consists of marls, shales, and limestones attributed to the Muwaqqar Chalk-Marl Formation and the Um Rijam Chert Limestone Formation. The δ13Corg curve records the typical carbon isotope excursion (CIE) and shows four distinctive intervals (pre-CIE, CIE-“core”, CIE-“recovery”, post-CIE) over the entire PETM interval in both cores.In the pre-CIE interval, the more proximal site (OS–01) shows high abundances of Neoeponides duwi co-occurring with an outer neritic Midway-type fauna. The fauna indicates meso- to eutrophic conditions in a middle- to outer-neritic setting. The more distal site (OS–28) is characterized by outer-neritic to upper-bathyal taxa (e.g., Cibicides pseudoacutus, Gavelinella beccariiformis, Nuttallides truempyi) suggesting well-ventilated, oligo- to mesotrophic seafloor conditions.The earliest Eocene corresponds to the CIE-“core” interval and is marked by a negative δ13Corg signal, high TOC, low CaCO3 contents, and near absence of benthic foraminifera. Oxygen deficiency in bottom waters with increased organic flux is the most likely scenario to explain the elevated organic content at the seafloor.The subsequent CIE-“recovery” interval of early Eocene age is marked by a restoration of oxygenated seafloor conditions. The proximal site is characterized by a relatively elevated TOC content and high abundance of Lenticulina spp., Valvulineria scrobiculata and common Anomalinoides zitteli, suggesting moderate oxygen conditions and mesotrophic bottom waters. The distal site is characterized by low TOC content and the presence of Lenticulina spp., Valvulineria scrobiculata, Anomalinoides zitteli and Oridorsalis plummerae, indicating a normalization of the organic flux and moderate oxygen concentrations near the seafloor.The post-CIE interval is marked by low TOC content in both cores. Benthic foraminifera include abundant Anomalinoides zitteli and common Lenticulina spp., Valvulineria scrobiculata, Oridorsalis plummerae, Cibicidoides rigidus, Cibicidoides pharaonis, and Anomalinoides praeacutus in the proximal setting. Mesotrophic conditions and a better ventilation of bottom waters are suggested for this interval. Lenticulina spp., Valvulineria scrobiculata, and Oridorsalis plummerae are also associated with the post-CIE interval in the distal site, suggesting similar mesotrophic conditions with renewed oxygenation in bottom waters.

Low-latitude vegetation and climate dynamics at the Paleocene-Eocene transition – A study based on multiple proxies from the Jathang section in northeastern India

We present a multi-proxy study of an upper Paleocene-lower Eocene succession from the paleo-equatorial region. The study is carried out on a coal-bearing, shallow-marine succession exposed at Jathang, east Khasi hills, Meghalaya, northeastern India. The succession was deposited in a low-energy, coastal marsh-bay complex. Dinoflagellate cyst biostratigraphy yields a late Paleocene to early Eocene age for the section. The deposits of the lower part of the succession represent a transgressive systems tract (TST) defined by seven parasequences, each starting with bay sediments deposited during transgression, followed by a shallowing-upward bay fill-marsh deposit. In the vertical succession, each parasequence acquires an increasingly marine character, culminating in a maximum flooding surface at the Paleocene-Eocene boundary. It is followed by four shallowing upward parasequences deposited in a highstand systems tract (HST). Enhanced chemical weathering and high terrestrial supply are testified by raised SiO2 and Al2O3 contents and high percentages of terrestrial palynomorphs. The pollen flora recovered from the Jathang section was used for quantitative paleoclimate and vegetation reconstructions. The Coexistence Approach was applied based on Nearest Living Relatives (NLRs) of sixty fossil species recorded at different stratigraphic levels. Seven climate variables were determined for the fossil assemblages, and, as a measure of the seasonality of climate, the number of dry months was estimated. Our study shows that during the Paleocene there existed warm, seasonally dry tropical climate conditions with mean annual temperature at ca. 24–26 °C and mean annual precipitation at ca. 700–1800 mm, and with a dry season of 5–6 months. Particularly warm and wet, perhumid climate conditions with 26–27 °C and 2200–3200 mm mean annual precipitation with a dry period of 2–3 months were reconstructed for the latest Paleocene-earliest Eocene interval. The study shows a distinct vegetational turnover from palm-dominated, seasonally dry tropical forest during the Paleocene to highly diversified dicotyledonous megathermal rainforest during the latest Paleocene-early Eocene. The present study demonstrates that the reduced duration of the dry period during the latest Paleocene-earliest Eocene, due to a more active hydrological cycle, played a major role in determining the climate and shaping the vegetation cover in the paleo-equatorial region. There is evidence from our data that seasonality of rainfall is the determining factor for the tropical forest vegetation pattern of the equatorial region rather than mean annual rainfall condition. As the main trigger for the observed step-wise changes of the hydrology along the studied succession, the fast northward movement of the Indian Plate is inferred.

A new fossil wood from the highly diverse early Eocene equatorial forest of Gujarat (western India)

During the early Eocene (∼55–52Ma), when the Indian subcontinent relished equatorial climatic conditions, lignite was deposited along its north western margin. Lignite mines of northwestern India have proved to be an outstanding resource for palaeoenvironmental information. The Vastan lignite mine of the early Eocene age situated near Surat district (Gujarat) is one of the well-dated and fossiliferous lignite mines in western India. A fossil wood, retrieved from this mine, is systematically described and shows a strong resemblance to the modern genus Chisocheton of the family Meliaceae. Plant fossils are the best source to reconstruct the palaeoenvironment of any region, and here a luxurious, highly diverse tropical evergreen forest is interpreted in and around the fossil locality in contrast to the tropical thorn forest of the present day. This early Eocene highly diverse equatorial forest, once covered a significant portion of the Indian subcontinent, is now restricted in fringes known as Western Ghats in south India attesting to changes in climate.

Concurrence of folding and remagnetization events in the Monterrey Salient (NE Mexico)

Carbonate formations from many locations reveal magnetizations that are secondary. Attaching a numerical age to these remagnetizations would provide information on orogenic processes. To contribute to the effort of assigning an age to remagnetization events, Lower Cretaceous formations from the Monterrey Salient in northeast Mexico were sampled. Individual fold tests reveal eight site-pair synfolding remagnetizations (set A) of Eocene age. The remanence is a chemical remanent magnetization (CRM) carried by magnetite. The magnetization of set B is possibly due to an early carbonate alteration that produced a remanence significantly older than folding. A complexity of set B is that the site pairs reveal k-versus-unfolding percentage diagrams with maximum unfolding peaks at 100 to 125%. An explanation of multiple deformation phases with an earlier horizontal folding phase around a non-plunging horizontal axis and a later vertical axis rotation is suggested for the past 100% peaks of the B sites. The latter deformation, rotation about a vertical axes, is revealed by a declination-strike test in set A sites and site means of the full collection that deviate counterclockwise from the reference declination. By combining synfolding results with published 40Ar/39Ar illite ages of folding (Fitz-Diaz et al., 2016), remagnetization ages in set A sites of 48–52Ma are obtained. The magnetization in set B sites is likely older, though not well constrained. Interestingly, prior results from the central Sierra Madre Oriental, to the south, show two remagnetization events, Late Cretaceous and Early Eocene in age, in a succession from W to E (Nemkin et al., 2015). The age of folding and remagnetization acquisition in set A sites along the Monterrey Salient are concurrent with the frontal, remagnetized folds in the central Sierra Madre Oriental. Thus, the timing of major remagnetization in the Monterrey Salient occurred in the Eocene.

BIOSTRATIGRAPHY OF EARLY EOCENE MARGALA HILL LIMESTONE IN THE MUZAFFARABAD AREA (KASHMIR BASIN, AZAD JAMMU AND KASHMIR)

The Early Eocene Margalla Hill Limestone is well exposed in core of Hazara Kashmir Syntaxis. A section at Battlian is measured and sampled for paleontological studies, where its lower contact with Patala Formation and upper contact with Chorgali Formation is transitional and conformable. The total observed thickness is 73 meters and 60 samples were collected from bottom to top at different levels, 50 thin sections were studied. 19 species of larger forams including age diagnostic Nummulites mamillatus, Nummulites atacicus, Assilina spinosa, Assilina laminosa, Assilina granulosa, Assilina exponens, Textularia sp., Miliolid sp., Alveoloina pasticillata, Alveolina elliptica, Alveolina ovulum, Quinqueloculina, Discocyclina peruviana, Rotalia trochidiformis, Ranikothalia sindensis, Skeasaria ornata Nodosaria sp., Lockhartia tipper and Dasycladacean algae were also observed. In conclusions, presence of benthic foraminifera indicated that Margala Hill Limestone was deposited in Neotethys warm and shallow marine in the Battlian area Muzaffarabad, whereas early Eocene age is assigned on the basis of benthic foraminifera observed. .

Provenance of the Cretaceous–Eocene Rajang Group submarine fan, Sarawak, Malaysia from light and heavy mineral assemblages and U-Pb zircon geochronology

The Rajang Group sediments in central Borneo form a very thick deep-water sequence which was deposited in one of the world's largest ancient submarine fans. In Sarawak, the Lupar and Belaga Formations form the Rajang Group, characterised by turbidites and large debris flows, deposited in an interval of at least 30Ma between the Late Cretaceous (Maastrichtian) and late Middle Eocene. Borneo is one of the few places in SE Asia where sediments of this age are preserved. Heavy mineral assemblages and detrital zircon U-Pb dating permit the Rajang Group to be divided into three units. The Schwaner Mountains area in SW Borneo, and West Borneo and the Malay Tin Belt were the main source regions and the contribution from these source areas varied with time. Unit 1, of Late Cretaceous to Early Eocene age, is characterised by zircon-tourmaline-dominated heavy mineral assemblages derived from both source areas. Unit 2, of Early to Middle Eocene age, has zircon-dominated heavy mineral assemblages, abundant Cretaceous zircons and few Precambrian zircons derived primarily from the Schwaner Mountains. Unit 3, of Middle Eocene age, has zircon-tourmaline-dominated heavy mineral assemblages derived from both sources and reworked sedimentary rocks. There was limited contemporaneous magmatism during deposition of the Rajang Group inconsistent with a subduction arc setting. We suggest the Rajang Group was deposited north of the shelf edge formed by the Lupar Line which was a significant strike-slip fault.

Pirin metamorphic and igneous evolution revisited in a geochronological frame based on U-Pb zircon studies

New isotopic data obtained from zircons by the U-Pb method during the last decade show the necessity of a revision of the tectonometamorphic and igneous evolution of the Pirin–Pangaion Unit of the Alpine Morava–Rhodope tectonic zone. The northern (Pirin) subunit of this unit consists of four areas built up of metamorphic rocks (amphibolite facies) of the Rhodopian supercomplex. These areas are separated by Late Alpine granite plutons of batholithic dimensions. The northernmost (Krupnik) area is built up of rocks of the Rupchos Group (complex) of varied composition and intense multiphase deformation and metamorphism. The oldest metamorphic phase is dated as Cadomian (528–517 Ma), and its products also suffered Hercynian superimposed amphibolite-facies metamorphism and anatexis. A septum of granitised metamorphics preserved between the Krupnik granite pluton (Triassic, ca 240 Ma) and the early Oligocene North Pirin (Kresna) pluton is characterised by Hercynian (330–300 Ma) anatexis. The principal metamorphism within the southern area around the early Oligocene South Pirin (Teshovo) granite pluton is dated both in the Bachkovo quartzo-feldspathic gneisses (named also Kriva-reka metagranites or orthogneisses) and in the Lukovitsa schists and paragneisses as Hercynian (ca 300–290 Ma). Therefore, the polymetamorphic evolution of the Pirin Subunit consists of a Cadomian phase and a strong Hercynian overprint followed by Triassic granitoids. We confirm the Thanetian–early Eocene age (58–55 Ma) of the Spanchevo granite, partially formed by in situ anatexis. Its intrusion was followed by a compression phase during the mid-Eocene thrusting of the Ograzhden Unit over the Pirin–Pangaion Unit, along the Strimon Thrust. The last magmatic phase (ca 34–31 Ma) was represented by a granitoid association formed during the latest Eocene–early Oligocene in extensional conditions and as a result of mixing of anatectic crust-derived magma with magma of mantle origin. It was part of a volcano-plutonic association related to the Macedonian–Rhodope magmatotectonic province. A high-temperature metamorphic overprint of the same age is recorded in the metamorphics as formation of andalusite in the metapelites, and skarns at the contacts of some of the granitoid bodies.

Lignite deposits of the Kutch Basin, western India: Carbon isotopic and palynological signatures of the early Eocene hyperthermal event ETM2

This study presents new results of combined palynological and stable carbon isotope (δ13C) investigations carried out in the well known lignite sequence at Panandhro, District Kutch, in the Gujarat state of western India. Dinoflagellate cysts and associated spore-pollen assemblage assign an early Eocene (Ypresian) age to the lignitic succession at Panandhro. Furthermore, a pronounced negative Carbon Isotope Excursion (CIE) of about 2.7‰, correlated to the Second Eocene Thermal Maximum (53.7Ma), a globally recognized hyperthermal event, was discovered in the middle part of the succession, consistent with the palynological constraints. This is the first record of an Eocene hyperthermal event (ETM2) from the Kutch Basin. Our data has regional implications for the age of the lignitic sequences across western India as it demonstrates that there is no significant age difference between the lignite deposits of the Kutch and Cambay basins. Our results also support a Lutetian age for the previously described vertebrate fossils, including whales, from the Panandhro mine section.

Problems related to the taxonomic placement of incompletely preserved amber fossils: transfer of the Paleogene liverwort &amp;lt;i&amp;gt;Cylindrocolea dimorpha&amp;lt;/i&amp;gt; (Cephaloziellaceae) to the extant &amp;lt;i&amp;gt;Odontoschisma&amp;lt;/i&amp;gt; sect. &amp;lt;i&amp;gt;Iwatsukia&amp;lt;/i&amp;gt; (Cephaloziaceae)

Abstract. A revision of the Baltic and Bitterfeld amber fossils assigned to Cylindrocolea dimorpha (Cephaloziellaceae) has yielded evidence of the presence of multicellular, bifid underleaves, which have not previously been reported for this species and conflict with the current circumscription of the family. We transfer the fossil species to Odontoschisma (sect. Iwatsukia) and propose the new combination O. dimorpha of the Cephaloziaceae. Characteristics of the fossil include an overall small size of the plant, entire-margined, bifid leaves and underleaves, more or less equally thickened leaf cell walls, ventral branching that includes stoloniform branches with reduced leaves, and the lack of a stem hyalodermis and gemmae. Placement of the fossil in Cephaloziaceae profoundly affects divergence time estimates for liverworts based on DNA sequence variation with integrated information from the fossil record. Our reclassification concurs with hypotheses on the divergence times of Cephaloziaceae derived from DNA sequence data that provide evidence of a late Early Cretaceous to early Eocene age of the Odontoschisma crown group and an origin of O. sect. Iwatsukia in the Late Cretaceous to Oligocene.

Botryococcus from the early Eocene lignite mines of western India: inferences on morphology, taphonomy and palaeoenvironment

Botryococcus, an important member of the planktonic algae, occurs in freshwater pools, lakes and occasionally in brackish-water lagoons, with wide distribution in tropical and temperate climate zones throughout the world. It is recognised as an oil-producing alga that is found in rock records from the Precambrian onwards. Here, this alga was retrieved from two different lignite mines of Rajasthan and Gujarat (western India), of early Eocene age. Apart from discussing its structural details, alterations in structures and preservation biases, this alga was used to reconstruct the depositional environment of the region based on its morphological and taphonomical characteristics. The images under transmitted light, fluorescence and scanning electron microscopy display aggregates of the irregular colonies, spherical to oval in shape, with cups arranged in definite patterns. The taphonomic characteristics of a large number of these algae indicate their autochthonous origin and in situ burial conditions. The dissolution of their outer layers suggests early diagenetic processes and loss of integrity due to microbial activity in the later phases of their burial in these sediments. The environment in the early Eocene has been reconstructed on the basis of the present findings, along with earlier recorded palynofacies from the region.

Episodic slab rollback and back-arc extension in the Yunnan-Burma region: Insights from Cretaceous Nb-enriched and oceanic-island basalt–like mafic rocks

One highly debated topic related to the nature of the Cretaceous mantle and geodynamic processes in SE Asia is whether they were dominated by the Tethyan or Pacific Ocean subductions. The main reason for this puzzle is the lack of geochemical studies on mantle-derived mafic rocks in SE Asia. In this paper, we report Early Cretaceous Nb-enriched diabases (ca. 139 Ma) and Late Cretaceous Nb-enriched (ca. 68 Ma) and oceanic-island basalt (OIB)−like (ca. 73 Ma) amphibolites from the Ailaoshan tectonic zone in the Yunnan-Burma region. The ca. 139 Ma diabases and ca. 68 Ma amphibolites display similar geochemical features with typical Nb-enriched basalts, e.g., high Na 2 O, TiO 2 , and Nb (>7 ppm) contents, and high (Nb/Th) PM , (Nb/La) PM , and Nb/U ratios. Unlike adakite-associated Nb-enriched basalts, our Nb-enriched diabases and ampibolites were derived through mixing between OIB-like and arc-like mantle source components in the spinel stability field ( 2 and Nb (20.0−26.0 ppm) contents, and OIB-like rare earth element patterns and trace-element spidergrams. The OIB-like rocks were generated by a low degree of partial melting of garnet-facies peridotite (>80 km). In combination with previous Cretaceous to early Eocene age data from granitoids, three significant magmatic flare-ups are identified at 140−115 Ma, 75−64 Ma, and 55−50 Ma, with two magmatic gaps at 115−75 Ma and 64−55 Ma. Given the distances of the studied area from the Pacific and Neotethyan trenches (2400−5000 km and 320 km, respectively), these Cretaceous igneous rocks more likely formed in a Neotethyan subduction-related tectonic setting, rather than a Pacific Ocean−related setting. We propose a tectonic model involving episodic flat slab subduction, slab rollback, and intracontinental back-arc extension for Neotethyan subduction in the Yunnan-Burma region.