Neogene Marine Research Articles

Century of Laskarev's landmark contribution to Paratethys Science

Laskarev?s seminal contribution to the recognition and elucidation of the Paratethys Sea within geological discourse stands as one of the pivotal milestones in our understanding of Neogene European paleogeography. Although the Neogene marine deposits of central and southeastern Europe were known before him, he greatly facilitated discourse and communication about them by giving them a paleogeographical name. By officially introducing the term Paratethys and meticulously delineating its geographic extent and history, Laskarev unveiled profound insights into past climates, environments, and biotic evolution across Central and Eastern Europe. His work provided a solid foundation for subsequent investigations of the Paratethys region. Moreover, beyond its scientific intrigue, the Paratethys Sea holds considerable economic importance due to its rich geo logical endowment. This reservoir of resources includes hydrocarbon reserves, mineral deposits, and a burgeoning potential for geotourism. While substantial strides have been made in unraveling its mysteries, the Paratethys Sea still beckons further exploration, promising untapped realms of knowledge and economic opportunity.

Miocene Stromboid Gastropods (Superfamily Stromboidea Rafinesque, 1815) from the Dwarka Basin, Western India and their Paleobiogeographic Implications

Abstract Stromboid gastropods (Superfamily Stromboidea) are one of the most diverse groups of gastropods present in the Neogene marine successions of western India. In the present endeavor, we report eight stromboid species, of which four are described as new, from the early-middle Miocene marine successions of the Dwarka Basin, western India. The species are Conomurex indica n. sp., Persististrombus deperditus, Persististrombus sp., Dilatilabrum mahalonobisi n. sp., Tibia indica, Terebellum obtusum, Hemithersitea kanerus n. sp. and Hemithersitea nadharus n. sp. Paleobiogeographic distribution of most of the stromboid genera reported here reveals a unidirectional migration from the Tethys Region towards the Indo-Pacific Region during the Paleogene and Neogene. Conomurex originated in the western India and further radiated to the eastern Indian-Western Pacific localities with the onset of the Neogene. Persististrombus and Tibia show widespread distribution in the Mediterranean and gradually radiated towards the eastern Africa-western India localities during the Paleogene. However, from the middle Miocene onwards, these two genera further migrated towards the eastern Indian-Western Pacific localities and became more diverse. The remaining two genera, i.e., Dilatilabrum and Hemithersitea originated in the Mediterranean and later migrated to take refuge in western India during the late Paleogene, and ultimately succumbed to extinction during the middle Miocene.

Geochemistry of thermal springs and associated gases along the Strymon River Valley (Bulgaria and Greece)

This paper presents and discusses the water and gas geochemistry of a large number of thermal springs occurring along the N-S trending Strymon Valley, from its source, near Sofia (Bulgaria), to the Aegean Sea (Greece). In Bulgaria springs have markedly alkaline pH, relatively low Total Dissolved Solids and prevalent Na-HCO3 to Na-Cl(SO4) in composition while the associated gas phase is mostly N2-dominated. When moving to the Greek sector, the thermal springs, Ca(Mg)-HCO3 to Na-HCO3, become less alkaline and more saline whereas the associated gas phase is CO2-dominated. The abrupt geochemical change in the Greek sector is caused by a variation in the thickness and nature of the sediments filling the Strymon Valley, the latter being characterized by a relevant amount of Neogene marine material. Such changes occur south of an important E-W lineament named Middle Mesta, south of which marble formations extensively crop out and are likely occurring below the sedimentary succession. The presence of these carbonate sequences embedded in the Neogene sediments is explaining the CO2-rich gases associated to the Greek springs. Water isotopes indicate a meteoric origin for the studied waters. From a geothermometric point of view, solute (previous studies) and gas (this work) geothermometers suggest that no high enthalpy systems occur in the Bulgaria and northern sector of Greece with estimated temperatures <120 °C. Consequently, these thermal springs can be regarded as tectonically-derived along the many fault systems that border the Strymon Valley. The convective circuits are thus originated from rainfall in the crystalline massifs that border the valley, i.e. the Serbo-Macedonian to the west and the Rhodope to the east.

New evidence for the antiquity of Desmostylus (Desmostylia) from the Skooner Gulch Formation of California.

Desmostylus is an extinct marine mammal genus that belongs to Desmostylia, a clade of extinct herbivorous mammals. While desmostylian remains are widely reported from Paleogene and Neogene marine strata of the North Pacific Rim, occurrences of the genus Desmostylus are almost entirely limited to middle Miocene strata, with only a few early Miocene records from Japan. Here we report a Desmostylus tooth from the earliest Miocene (Aquitanian) Skooner Gulch Formation in northern California, USA. This specimen exhibits cuspules around the crown, a primitive trait of the subfamily Desmostylidae, as seen in more basal branching desmostylid taxa such as Cornwallius and Ounalashkastylus, but with a high tooth crown and thickened enamel. The specimen is also diagnostically different from all other desmostylid genera, such as Cornwallius, and Ounalashklastylus. The Aquitanian age of the Skooner Gulch Formation implies that the distinctive tooth morphology of Desmostylus has persisted, largely unchanged, for more than 15 million years and that desmostylids possibly originated in western North America.

Evolutionary norm-breaking and extinction in the marine tropics

Evolutionary innovations, defined as character states that transcend clade norms, are often studied in an exclusively phylogenetic context, but their distribution in time and space indicates that geography also influences the evolution of new ecological, morphological, and physiological traits. In an analysis of 99 fossillzable, norm-breaking innovations in tropical marine Neogene molluscan clades that arose uniquely in either (but not in both) the Indo-West Pacific (IWP) or Atlantic-East Pacific (AEP) realms, I show that there are far more innovations in the IWP (79%) than those in the AEP (21%). Most of the innovations are interpretable as defensive or competitive adaptations or as indicators of extreme habitat specialization. Although the innovations arose in taxonomically rich biotas, only 9% are associated with subclades comprising 10 or more species each, indicating that they contributed little to overall taxonomic richness. Compilations of extant species in 30 pantropical molluscan clades show that the IWP accounts for 71% of tropical shallow-water species, implying that the per-species incidence of norm-breaking innovations is higher there than in the AEP. Only 5% of innovations became extinct in the IWP as compared with 38% in the AEP, mirroring a similar difference in the magnitudes of Late Miocene and later taxonomic extinction in the two realms. These data imply that large-scale disruption strongly limits norm-breaking innovation. Opportunities for adaptive innovation are therefore likely to be few in today's heavily overexploited and disturbed biosphere.

Miocene-Holocene paleoenvironmental changes in the Tinto River estuary (SW Spain) evidenced by sedimentology, geochemistry and fauna

This paper investigates the paleoenvironmental evolution of a long core extracted in a small cove located in the Tinto-Odiel estuary (SW Spain). The inferred reconstruction is supported by sedimentological, geochemical, paleontological data and dating. Seven phases have been identified, with the transit from Late Neogene marine environments to a subrecent freshwater pond and a final anthropic filling. On the basis of these data, this area was flooded during the maximum of the MIS-1 transgression (6.5-5.2 cal. kyr BP), with the temporary presence of a subtidal channel with phanerogam meadows. During this evolution, three geochemical peaks have been detected, which correspond to 1) the first evidence of mining activities (~4.5 cal. kyr BP), 2) an interval of intensive mining (1850-1960) and 3) an industrial period (1966-1985), affected by the dumping of highly polluting waste into this estuary.

Strontium isotope stratigraphy of late Cenozoic fossiliferous marine deposits in North Borneo (Brunei, and Sarawak, Malaysia)

• Sr-isotope stratigraphy of fossiliferous marine deposits in northern Borneo. • Burdigalian to Tortanian ages revealed for thirteen fossil-rich shallow marine deposits. • Origin of reworked specimens could be traced by the obtained SIS ages. • Trace element and stable isotope chemistry of the well-preserved shells can be linked to habitat-conditions. • Altered and recrystallized specimens helped tracing diagenetic pathways. Neogene marine deposits of North Borneo are locally very rich in fossils that provide glimpses into the past biodiversity. However, dating these onshore sediments with biostratigraphy is often hampered by the lack and/or the poor preservation state of index fossils. Therefore, the fossiliferous sites were targeted with strontium isotope stratigraphy (SIS) to obtain higher precision relative dating. Well-preserved macrofossils were screened using a multidisciplinary approach, and 87 Sr/ 86 Sr ratios of the most pristine remains were used to date the embedding sediments. Most of the measured ages fall in the expected chronostratigraphic framework established by large scale studies for the region. The oldest, Burdigalian (early Miocene) ages were measured for the Sibuti Formation in Sarawak (17.71 ± 0.2My and 16.7 ± 0.2My) followed by a Serravallian (middle Miocene) age within the Belait Fm in Brunei (12.1 + 1.4/-1.2My). Eight localities from the younger units, the Miri and Seria formations in Brunei, gave a range in age from 10.5 ± 1 to 7.0 + 0.9/-0.5My (Tortonian-Messinian). Reworked fossil assemblages from Tutong beach were also investigated and the SIS ages of Late Miocene support an origin from the younger part of the Seria Fm. One locality, in Lumapas where limestone crops out in Brunei, gave an unexpected younger age (Tortonian, late Miocene, 10.6 ± 1My) compared to estimates projected for its assumed stratigraphic position in the lower Belait Formation (late Burdigalian). These challenging data require more research, yet if the young age is accepted, the stratigraphic situation of the limestone needs further revision.

Late Neogene chronostratigraphy and integrated paleoecological trends in the southwestern Caribbean Sea

Palynology of the Neogene marine stratigraphic sequences in tropical latitudes is poorly studied Most studies focus on lower to middle Miocene deposits in the Caribbean, emphasizing the biostratigraphic value of dinoflagellate cysts. The palynological and calcareous nannofossil analysis of 50 samples from DSDP Hole 502A and their integration with the paleomagnetic and planktonic foraminifera data reveal a detailed and reliable chronostratigraphic framework, and the interpretation of the paleobathymetric and paleoenvironmental evolution of the sequence. Fossil content in a continuous late Tortonian to late Gelasian (~7.56-1.80 Ma) sequence of deep-marine sediments serves to calibrate ages of dinoflagellate cysts, and comparison with high latitude records reveals synchronous (Operculodinium janduchenei, Selenopemphix dionaeacysta, Barssidinium taxandrianum, and Lejeunecysta interrupta) and asynchronous events (Quadrina? condita) with biostratigraphic potential for the southwestern Caribbean Sea. Our results highlight the importance of analyzing continental palynomorphs in deep-marine deposits to increase the temporal resolution of future palynostratigraphic schemes. Micropaleontogical data indicate a lower bathyal–abyssal environment and four paleoceanographic settings defined by changes in surface water productivity. These intervals fluctuate from mesotrophic-oligotrophic (~7.56–6.31 Ma) to eutrophic (~6.18–4.98 Ma), oligotrophic (~4.74–3.41 Ma), and mesotrophic surface water conditions (~3.26–1.80 Ma). Changes in trophic conditions are strongly related to the paleoceanographic reorganization associated with the constriction and complete closure of the Central American Seaway, seasonal upwelling episodes, and the input of terrigenous organic matter probably transported from southern Central America and northern South America by turbidity currents.

Multi-proxy evidence of Caribbean-sourced marine incursions in the Neogene of Western Amazonia, Brazil

The timing of continental-scale marine flooding events in Western Amazonia during the Neogene is still an unsolved question. Despite broad proxy-based evidence of such events, the pathways and duration of late Miocene marine incursions remain controversial. We provide coupled calcareous and organic microfossil and geochemical data from six onshore cores from Neogene sequences of the Solimões Basin, Brazil. Our records support minor marine influence in the early Miocene (23.0, 21.1, 18.6, and 16.3 Ma), middle Miocene (14.9, 13.7, and 12.9 Ma) and early Pliocene (4.7, 4.2–4.1, and 3.8 Ma), and conspicuous marine incursions in the late Miocene (11.1–8.8 Ma) suggested by the consistent presence of salinity-indicative microfossils and geochemical data. Our findings challenge the view of major marine incursions in the early and middle Miocene in the studied area. We propose for the first time a new late Miocene incursion (LMI) event as the main marine flooding event in Western Amazonia during the Neogene. These onshore records are compared with three offshore cores from the Atlantic and Pacific Oceans. The similarity between microfossil assemblages of the Solimões Basin and the Caribbean Sea, and evidence of increased runoff from the Orinoco river drainage system, strongly suggest the Caribbean Sea as the primary source area of the marine incursions, supporting a Venezuelan seaway. We further show for the first time the potential linkage between Neogene marine incursions (mainly the LMI) into the Solimões Basin and major disturbances in the global carbon cycle.

Dominance of Miocene echinoderms in the equatorial Neogene marine platform of Brazil and their insights into the paleoenvironment

Echinoderms are one of the most important invertebrates in the early to middle Miocene heterozoan carbonate deposits of the Pirabas Formation of the northern Brazil. The well-preserved echinoid tests were useful for accurate identification, whereas the sediment filling the tests provide significant information regarding the rock matrix. The dominance of disarticulated ophiuroid, crinoid, and asteroid plates, and damage on the echinoderm test provides a basis for taphonomic processes to elucidate a paleoenvironmental interpretation based on the echinoderm assemblages. Nineteen echinoderm taxa (ten valid species and nine species in open nomenclature) were recorded based on well-preserved and/or fragmented tests and/or spines, including Abertellidae †Abertella pirabensis (Santos, 1958), Placatenellidae †Placatenella complanata (Brito, 1981), Clypeasteridae †Clypeaster lamegoi Santos, 1958, †Clypeaster paraensis Brito, 1979, and †Clypeaster paulinoi Santos, 1958, Cassidulidae †Anisopetalus oliveirai (Santos, 1958) and †Rhyncholampas candidoi Fernandes and Morais, 1994, Echinolampadidae †Echinolampas paraense Santos, 1958, Schizasteridae †Agassizia eugeniae Brito and Ramires, 1974 and Schizaster sp., Cidaridae Cidaris sp., †Phyllacanthus priscus Brito and Ramires, 1974, and Prionocidaris sp. The smaller echinoderm fragments were dominated by disarticulated plates of Gorgonocephalidae ophiuroids, Comatulidae crinoid Sievertsella sp., Goniasteridae asteroids, as well as spines and tests fragments of Cidaridae echinoids. The echinoderm assemblages suggest an inshore and shallow water paleoenvironment over a soft sandy carbonate bottom. MicroCT analyses of sediments filling echinoid tests exhibited a microfossil assemblage, including foraminifera, sponges, ahermatypic corals, bryozoans, and mollusks. Broken and disarticulated tests and plates in chaotic orientations suggest high-energy paleoenvironment. Evidence of test damage indicates complex predator-prey interactions. Overall, the microCT analyses of echinoid tests proved to be a high accuracy non-destructive, analytical approach for investigating fossil echinoderms and their paleoenvironment.

First Neogene record of Pelecanus (Aves: Pelecanidae) from México

The distal end of a humerus from a pelican was found in upper Miocene marine strata in the lower part of the Trinidad Formation near Rancho La Trinidad in Baja California Sur, México. This bone represents the first bird fossil from the Trinidad Formation and the first Neogene record of Pelecanus from México. Not only is this one of the very few fossils of the family Pelecanidae from Neogene strata in North America, but it is also the first record of a pelican from Neogene marine rocks in western North America.

The genus Sveltia (Gastropoda, Cancellariidae) in the Atlantic Pliocene of Iberia with a new species from the Cenozoic Mondego Basin of Portugal

AbstractThe cancellarid genus Sveltia Jousseaume, 1887, is widespread in western European and North African Neogene marine fossil assemblages. In Pliocene deposits it is commonly represented by Sveltia varicosa (Brocchi, 1814), which until recently was considered a widely distributed taxon in the Mediterranean Sea and adjacent Atlantic faunas. A recent review of the species from the Pliocene of Italy and Spain (Guadalquivir Basin), leading to the erection of S. confusa, prompted the reassessment of the Sveltia material from the Atlantic Pliocene of the Portuguese Mondego Basin and the subsequent description of Sveltia sofiae n. sp. Consequently, a mosaic of species has emerged from what was previously viewed as the broad Atlanto-Mediterranean range of the widespread and quite variable S. varicosa. From a biogeographic standpoint, it is now clear that S. varicosa was a Mediterranean species, occurring east of the Alboran Sea. Sveltia confusa had a mainly Atlantic distribution, from the French Pliocene Ligerian Gulf to the Gulf of Cadiz, at least, and straddling the Strait of Gibraltar into the Alboran Sea. Sveltia sofiae n. sp. was endemic to western Iberia, represented today only in the western Portuguese Mondego Basin. Sveltia is a thermophilic genus. Since early Pliocene times, because of northeastern Atlantic sea surface temperature decline, it underwent a southward range contraction, occurring today—in the eastern Atlantic—from Cape Blanc, Mauritania, south. This range reduction was coupled with the post mid-Piacenzian southward contraction of the Pliocene Mediterranean-West African tropical molluscan province and the consequent rise of the present-day Mediterranean-Moroccan subtropical province.UUID: http://zoobank.org/0cf3c73a-8d57-472e-87e4-f1ad065e5fb6.

Checklist of California Paleogene–Neogene marine Mollusca since Keen and Bentson (1944)

This checklist is a sequel to the one published by A. Myra Keen and Herdis Bentson in 1944 and is an alphabetical listing of California marine Paleogene–Neogene mollusk species or subspecies described and/or figured in the published literature spanning the interval of 1944 through 2020. The original data are given for each species and subspecies of bivalves, gastropods, chitons (polyplacophorans), scaphopods, and cephalopods. Where detected, formation names, ages, taxonomy, systematics, and specimen disposition were corrected. A total of 559 genera and 1,698 species/subspecies were tabulated, with the bivalves and gastropods being the most abundant taxa. Bivalve and gastropod diversity steadily built up during the Paleocene, nearly doubled during the Eocene warm time, declined greatly during the cool time of the Oligocene, rebounded to its highest peak in the Miocene and then declined slightly during the Pliocene. The other classes represented only minor faunal components. Chitons were only reported from the Pliocene, and cephalopods had their highest diversity during the Paleocene and Eocene. Bivalve genera having the highest diversity are: Glycymeris, Macoma, Mactromeris, Nuculana, and Tellina. Gastropod genera having the highest diversity are Cancellaria and Turritella. It is very likely that the Turritella species/subspecies complex has been significantly overnamed. The high point of research productivity of published reports on California Paleogene-Neogene mollusks was in 1990–1994, and a significant decline occurred in 1995–1996, following the closure of the Menlo Park USGS Paleontology and Stratigraphy facility. An overall decline in productivity has continued, with noticeable upticks in 2003 and in recent years.

Morphological–phylogenetic analysis of the late Cenozoic Chlamydini von Teppner (Bivalvia, Pectinidae) of southern South America

AbstractThe tribe Chlamydini was highly diversified in the marine Neogene of southern South America, reaching its maximum taxonomic diversity during the Miocene. However, the evolutionary relationships of South American taxa remain uncertain. This is the first phylogenetic analysis based on a large morphological matrix on Pectinidae, which focuses on South American taxa and species related to Chlamys s.s. The phylogenetic analysis is based on a matrix composed of 145 shell‐characters scored for 48 species, and multiple searches were conducted using equal and implied weighting. Two new monophyletic clades are defined, Multiplicata and Pauciplicata. The first includes Dietotenhosen, Ckaraosippur, Zygochlamys, Moirechlamys (South America), the North‐West Pacific Azumapecten, and the North‐East Pacific Chlamys hastata. Pauciplicata is represented by Chokekenia (Patagonia, Argentina), Laevichlamys (tropical Atlantic and Indo‐Pacific), Semipallium (Indo‐Pacific), Swiftopecten (South America and North Pacific), and Jorgechlamys + Reticulochlamys (Patagonia, Argentina). All of these genera are monophyletic except for the paraphyletic Jorgechlamys. The oldest documented occurrence of the tribe is Semipallium foulcheri from the lower Oligocene, a derived taxon that pushes the divergence time of basal genera to the Eocene–Oligocene boundary, generating ghost lineages in all clades, except Jorgechlamys + Reticulochlamys. Pauciplicata and Multiplicata diverge in the early history of the tribe, at the Eocene–Oligocene boundary. Future analyses are necessary to gain a better understanding of the taxonomic arrangement of this poorly understood tribe. Further insights into the relationships of its deepest nodes may well resolve many ghost lineages.

Diversity and biostratigraphy of the late Oligocene-late Miocene sand dollars (Echinoidea: Scutelliformes) of Argentina and Uruguay

Introduction: Scutelliforms were diverse and widespread in shallow marine environments during Neogene times in South America. Nevertheless, they have almost never been used as biostratigraphic tools. Objective: To provide a refined stratigraphic frame useful for calibrating temporal dimensions of scutelliform diversity from Argentina and Uruguay and its correlation with the molluscan assemblages previously proposed. Methods: A detailed survey of their geographic and stratigraphic provenance was carried out. We revised both the bibliography and collections (institutional and from our own field work). Results: The group is represented by 14 species belonging to six genera, and four assemblages were identified. Numerical dates of the Neogene marine rocks obtained recently allowed their placement in a chronological scheme: “Iheringiella” sp. A is restricted to the late Oligocene, the genera Camachoaster and “Eoscutella” and the species Monophoraster telfordi to the early Miocene, Abertella gualichensis and Abertella miskellyi to the middle Miocene, and Monophoraster duboisi, Amplaster coloniensis and Amplaster ellipticus to the late Miocene. Non-lunulate scutelliforms are not restricted to the late Oligocene as previously supposed. The oldest occurrence of the genus Monophoraster corresponds to the early Miocene, and along with Iheringiella are long-living taxa that embrace the 25.3 Ma-18.1 Ma (Iheringiella patagonensis) and approximately 15 Ma-6.48 Ma (Monophoraster darwini) intervals. The presence of Iheringiella in the early Miocene of northeastern Patagonia is corroborated, reaching there its northernmost distribution. Monophoraster darwini has a temporal range from the late Miocene (where it was previously thought to be restricted) back to the middle Miocene, since this is the species yielded in the well-known and discussed “Monophoraster and Venericor Beds”. Conclusions: The Paleogene-Neogene scutelliforms of Argentina and Uruguay range from the late Oligocene to the late Miocene. There is a good correspondence among the numerical ages, molluscan biozones and scutelliform assemblages.

Marine diagenesis of ikaite: Implications from the isotopic and geochemical composition of glendonites and host concretions (Palaeogene–Neogene sediments, Sakhalin Island)

AbstractGlendonites represent pseudomorphs after calcium carbonate hexahydrate (ikaite) and can be used as indicators of past cold climates, because ikaite only naturally occurs in cold environments (&lt;7°C) in the modern. The results of a multi‐proxy study of 11 glendonite and host concretion samples from Palaeogene (Gennoishi Formation) and Neogene (Bora and Vengeri formations) sediments from Sakhalin Island, Russian Far East are reported here. Petrographic, cathodoluminescence, powder X‐ray diffraction and scanning electron microscope analyses reveal that glendonites are composed of several successive mineralogical phases: low‐magnesium ikaite‐derived calcite, high‐magnesium acicular cement (calcite and dolomite) and blocky calcite or authigenic quartz filling the remaining pore space. Host concretions comprise sandy limestones cemented by high‐magnesium calcite. The δ13C and δ18O values for host concretions and enclosed glendonites are very similar, with δ13C ranging from –20.3 to +1.9‰ Vienna Pee‐Dee Belemnite and δ18O ranging from –3.4 to +3.4‰ Vienna Pee‐Dee Belemnite. Such isotopic values suggest that seawater was the main source of oxygen, while dissolved inorganic carbon and decaying organic matter were the main carbon sources for ikaite growth, concretion and glendonite cementation. The 87Sr/86Sr values within the glendonites and host concretions are significantly lower compared with coeval Palaeogene–Neogene marine carbonates, suggesting an influence of continental runoff on their isotopic composition. Post Archean Australian Shale normalized rare earth element patterns display negative Ce anomalies and positive Eu anomalies, with a depletion in light rare earth elements or bulge in middle rare earth elements. Such spectra of rare earth elements indicate that ikaite growth and replacement occurred very close to the aerobic–anaerobic boundary, with pore waters derived from trapped seawater and/or ikaite dehydration. Since Mg/Ca ratios and alkalinity increase with depth below the sediment–water interface, subsequent mineral phases show enrichment in Mg, while the lack of diagenetic alteration by basinal fluids enabled preservation of the primary isotopic and geochemical characteristics of ikaite within the recrystallized pseudomorph.

Distinguishing reworked diatoms derived from Neogene marine strata in modern coastal assemblages for understanding taphonomic processes and reconstructing Holocene paleoenvironments in the Tokachi coastal area, Hokkaido, Japan

Identification of autochthonous, allochthonous, and reworked (derived fossil) taxa in diatom analyses is of fundamental importance for understanding how taphonomic processes affect diatom assemblages and for estimating paleoenvironments in coastal areas. To characterize modern and Neogene diatom assemblages, we surveyed the distributions of modern diatom assemblages and of Neogene fossil diatom assemblages in the Toberi River area, eastern Hokkaido, Japan. Then, on the basis of these results, we analyzed two cores collected near the Toberi River mouth and examined changes in the fossil diatom assemblages during the late Holocene. The results showed that not only allochthonous and extinct diatom taxa, but also extant taxa that have persisted over an extended geological time period, should be excluded when diatom assemblages are analyzed to reconstruct Holocene paleoenvironments in this area.

A multidisciplinary study and palaeoenvironmental interpretation of middle Miocene Keles lignite (Harmancık Basin, NW Turkey), with emphasis on syngenetic zeolite formation

The Harmancık Basin, in the north-easternmost Miocene graben in western Anatolia, hosts a 12.6-m-thick coal seam located in the Keles coalfield, in which coals are being exploited by open-cast mining methods. Syngenetic clinoptilolite/heulandite-type zeolite formation in the upper part of coal seam and carbonaceous clayey diatomite as a roof rock have been identified for the first time, and the palaeoenviromental reconstruction of the coal seam was conducted using a multidisciplinary approach. The coal facies and palynological data show that vegetation and depositional changes took place during the middle Miocene, which resulted in vertical variations in elemental and mineralogical compositions. During the initial stages of mire development woody vegetation (e.g. pollen with affinity to Cupressaceae) prevailed, telmatic conditions were common, and preservation of organic matter was high due to anoxic conditions. Thus, relatively low-ash yield was observed in the lower and middle parts of the coal seam. Furthermore, the presence of kaolinite and smectite-type clay mineral aggregates in these parts of the coal seam suggests that alteration of synchronous volcanic inputs took place under weak acidic to neutral conditions. In contrast, limnotelmatic conditions prevailed during the late stages of peat-accumulation, and macrophytes coinciding with herbaceous peat-forming vegetation (e.g. Osmundaceae, Polypodiaceae, and Nymphaeaceae) were dominant. The elevated Gelification Index (GI) values in the uppermost parts of the coal seam could be related to development of alkaline conditions in the palaeomires, which also caused formation of syngenetic clinoptilolite/heulandite-type zeolite from the alkaline activations of synchronous volcanic inputs. Even though palynological data points to the prevalence of freshwater conditions during peat-accumulation, B enrichments along Sr/Ba ratio higher than 1.0 could point to possible marine influence; however, no Neogene marine deposits have been identified in the Harmacik Basin. Nevertheless, the SEM-EDX data show the presence of traceable Ba and Sr in clinoptilolite/heulandite grains, and Sr-bearing barite around feldspar grains in the studied samples from the upper parts of the coal seam. This implies K-feldspars and K-rich alkali-feldspars, derived from synchronous volcanic ash fall, altered under alkaline conditions. Moreover, alginite proportions increased towards the upper parts of the seam, while relatively high Hydrogen Index (HI) values were reached in the uppermost part of coal seam and carbonaceous clayey diatomite roof-rock sample. Furthermore, palynolgical data imply that vegetation changes towards the roof of the coal seam reflect the progressive development of more humid conditions and nutrient-rich surface waters, which favoured increased algal activity.

Ontogenetic growth pattern of the extinct megatooth shark Otodus megalodon—implications for its reproductive biology, development, and life expectancy

ABSTRACT The extinct megatooth shark, Otodus megalodon (Lamniformes: Otodontidae), is known primarily from its gigantic teeth in the late Neogene marine fossil record. It is known to reach at least 14.1‒15.3 m in length, but its reproductive biology and ontogenetic growth pattern have remained largely in the realm of speculation. Here, we examined incremental growth bands in fossil vertebrae of a 9.2-m-long individual O. megalodon, revealing that the shark was born large, 2 m in length, and died at age 46. This large size at birth is characteristic of lamniform sharks and is indicative of live-bearing reproduction along with embryos’ intrauterine cannibalism behaviour in the form of oophagy. The trajectory of the generated growth curve beyond the age of death and the maximum length (about 15 m) calibrated from the largest known teeth of O. megalodon suggest that the species had a lifespan of at least 88–100 years with an average growth rate of about 16 cm/yr at least for the first 46 years. As one of the largest carnivores that ever existed on Earth, deciphering such growth parameters of O. megalodon is critical to understand the role large carnivores play in the context of the evolution of marine ecosystems.

Freshwater lacustrine centric diatom fossils from the Neogene marine sediments in the Dewa Mountains, Akita Prefecture, Northeast Japan

Freshwater lacustrine centric diatom fossils from the Neogene marine sediments in the Dewa Mountains, Akita Prefecture, Northeast Japan