Late middle Miocene caviomorph rodents from Tarapoto, Peruvian Amazonia

Miocene deposits of South America have yielded several species-rich assemblages of caviomorph rodents. They are mostly situated at high and mid- latitudes of the continent, except for the exceptional Honda Group of La Venta, Colombia, the faunal composition of which allowed to describe the late middle Miocene Laventan South American Land Mammal Age (SALMA). In this paper, we describe a new caviomorph assemblage from TAR-31 locality, recently discovered near Tarapoto in Peruvian Amazonia (San Martín Department). Based on mammalian biostratigraphy, this single-phased locality is unambiguously considered to fall within the Laventan SALMA. TAR-31 yielded rodent species found in La Venta, such as the octodontoid Ricardomys longidens Walton, 1990 (nom. nud.), the chinchilloids Microscleromys paradoxalis Walton, 1990 (nom. nud.) and M. cribriphilus Walton, 1990 (nom. nud.), or closely-related taxa. Given these strong taxonomic affinities, we further seize the opportunity to review the rodent dental material from La Venta described in the Ph.D. volume of Walton in 1990 but referred to as nomina nuda. Here we validate the recognition of these former taxa and provide their formal description. TAR-31 documents nine distinct rodent species documenting the four extant superfamilies of Caviomorpha, including a new erethizontoid: Nuyuyomys chinqaska gen. et sp. nov. These fossils document the most diverse caviomorph fauna for the middle Miocene interval of Peruvian Amazonia to date. This rodent discovery from Peru extends the geographical ranges of Ricardomys longidens, Microscleromys paradoxalis, and M. cribriphilus, 1,100 km to the south. Only one postcranial element of rodent was unearthed in TAR-31 (astragalus). This tiny tarsal bone most likely documents one of the two species of Microscleromys and its morphology indicates terrestrial generalist adaptations for this minute chinchilloid.

Preliminary Study of Geology, Alteration and Ore Mineralisation at East Motoling Area, South Minahasa District, North Sulawesi, Indonesia

The East Motoling area is one of the prospect areas in the Minahasa region of North Sulawesi, which has indications of low sulfidation epithermal-type mineralization. The research was conducted as a preliminary study to determine the characteristics of geological conditions, alteration, and ore mineralization in the epithermal system. The research method is divided into two main parts, such as fieldwork including surface geological mapping (lithology, stratigraphy, geomorphology, structural geology, alteration and mineralization) and laboratory analysis methods including petrographic analysis. The stratigraphy of the study area consists of altered volcaniclastic breccia, altered lapilli tuff, altered tuff, limestone, welded lapilli tuff, and andesitic breccia. Volcaniclastic breccia, altered lapilli tuff, and altered tuff, member of the Volcanic Rock Formation which is Late – Middle Miocene age, are the host rock for ore mineralization and hydrotermal alteration process. There are 3 types of alterations that have developed, namely argillic (illite + quartz ± kaolinite), sericitic (sericite + illite ± chlorite), and propylitic (chlorite + epidote ± illite). The dextral slip fault with NW – SE trend present as a main control structure to formation of extention fracture/vein. The epithermal veins are relatively north-northeast – south-southwest, north-northwest – south-southeast, and northwest – southeast. The textures of the veins divided into 7 main groups, namely that is bladed-quartz, breccia, calcedony, colloform, comb, mold, and massive quartz. Ore mineralization is forms in the veins as pyrite and banded sulfide. Apart from that, the disseminated pyrite also limitedly found around the veins.

New late Oligocene rodent faunas from the Pannonian basin

The rodent associations from the late Oligocene deposits of Ugljevik and Paragovo in the Pannonian basin are described. Pannoniamys paragovensis, a new genus and species of Spalacidae, is defined. The published data from a third late Oligocene locality in the area (Banovići) is included in the discussion of the changes in community structure through the time-interval studied. Although the composition of the rodent faunas studied differs, the dominating cricetid genus in all three associations is Deperetomys, a genus that appears in western Europe during the late middle Miocene. While the late Oligocene rodent record of central and southwestern Europe is characterised by endemic development, the regime in the Balkans seems to have been one of multiple immigrations and replacements. The late Oligocene age of the rodent fauna from Ugljevik estimated at about 26 Ma, provides a minimum age for the start of rifting in the Pannonian basin, some 6 Ma earlier than previously documented.

Diversity of gobioid fishes in the late middle Miocene of northern Moldova, Eastern Paratethys – part I: an extinct clade of Lesueurigobius look-alikes

Studies of otoliths suggest that Gobioidei, which are among the most species-rich groups of modern-day vertebrates, were prominent elements of late middle Miocene (early Sarmatian sensu lato) fish faunas in Europe and Western Asia. However, few complete skeletons have come to light. Here, we report an assemblage of six marine gobiid species, based on skeletons preserved with otoliths in situ, from the lower Volhynian (lower Sarmatian s.l.) of Karpov Yar, Naslavcea, northern Moldova (Eastern Paratethys). Previously only one of these species had been reported from the Central Paratethys, based on its otoliths alone. Five new species representing four new genera are described: †Katyagobius prikryli gen. et sp. nov., Pseudolesueurigobius manfredi gen. et sp. nov., †Sarmatigobius compactus gen. et sp. nov., †Yarigobius decoratus gen. et sp. nov., and †Y. naslavcensis gen. et sp. nov. All six species share the following set of characters, suggesting that they represent a monophyletic clade: 27–29 vertebrae (of which 10 are abdominal); spines of first dorsal fin distally filamentous; second dorsal fin with spine and 14–16 soft rays; anal fin with spine and 13–15 soft rays; caudal fin longish-to-lanceolate; otoliths (sagittae) with rounded, trapezoid-to-squarish shape. Their skeletal features suggest that they are closely related to Lesueurigobius Whitley, 1950, but the otoliths preserved in situ do not support such a classification. The new fossils most likely represent a stem lineage of the European Aphia lineage, and indicate that the diversity of gobiid lineages 12 million years ago differed clearly from that observed today.

Migration of deformation, subsidence, and basin formation in the SW Pannonian Basin (central Europe) and the change to contractional deformation

<p>The Pannonian Basin is a continental extensional basin system with various depocentres within the Alpine–Carpathian–Dinaridic orogenic belt. Along the western basin margin, exhumation along the Rechnitz, Pohorje, Kozjak, and Baján detachments resulted in cooling of diverse crustal segments of the Alpine nappe stack (Koralpe-Wölz and Penninic nappes); the process is constrained by variable thermochronological data between ~25–23 to ~15 Ma. Rapid subsidence in supradetachment sub-basins indicates the onset of sedimentation in the late Early Miocene (Ottnangian? or Karpatian, from ~19 or 17.2 Ma). In addition to extensional structures, strike-slip faults mostly accommodated differential extension between domains marked by large low-angle normal faults. Branches of the Mid-Hungarian Shear Zone (MHZ) also played the role of transfer faults, although shear-zones perpendicular to extension also occurred locally.</p><p>During this period, the distal margin of the large tilted block in the hanging wall of the detachment system, the pre-Miocene rocks of the Transdanubian Range (TR) experienced surface exposure, karstification, and terrestrial sedimentation. The situation changed after ~15–14.5 Ma when faulting, subsidence, and basin formation shifted north-eastward. Migration of normal faulting resulted in fault-controlled basin subsidence within the TR which lasted until ~8 Ma.</p><p>3D thermo-mechanical lithospheric and basin-scale numerical models predict similar spatial migration of the depocenters from the orogenic margin towards the basin center. The reason for this migration is found in the interaction of deep Earth and surface processes. A lithospheric and smaller crustal-scale weak zones inherited from a preceding orogenic structure localize initial deformation, while their redistribution controls asymmetric extension accompanied by the upraising of the asthenopshere and flexure of the lithosphere. Models suggest ~4–5 Myr delay of the onset of sedimentation after the onset of crustal extension and ~150–200 km of shift in depocenters during ~12 Myr. These modeling results agree well with our robust structural and chronological data on basin migration.</p><p>Simultaneously with or shortly after depocenter migration, the southern part of the former rift system, mostly near the MHZ, underwent ~N–S shortening; the basin fill was folded and the boundary normal faults were inverted. The style of deformation changed from pure contraction to transpression. The Baján detachment could be slightly folded, although its synformal shape could also be considered a detachment corrugation. Deformation was dated to ~15–14 Ma (middle Badenian) in certain sub-basins while in other sub-basins deformation seems to be continuous throughout the late Middle Miocene from ~15 Ma to ~11.6 Ma.</p><p>Another contractional pulse occurred in the earliest Late Miocene, between ~11.6 and ~9.7 Ma while the western part of the TR was still affected by extensional faulting and subsidence. All these contractional deformations can be linked to the much larger fold-and-thrust belt that extends from the Southern and Julian Alps through the Sava folds region in Slovenia. Contraction is still active, as indicated by recent earthquakes in Croatia.</p><p>Mol Ltd. largely supported the research. The research is supported by the scientific grant NKFI OTKA 134873 and the Slovenian Research Agency (research core funding No. P1-0195).</p>

Impact crater versus bioherm on the Nullarbor Plain, Australia

<p>The Nullarbor Plain is ~200,000 km<sup>2</sup> large planar karst surface in southern Australia, composed of middle Cenozoic shallow-water limestones of Eucla Group. The youngest formation, covering the top of the plain, is middle Miocene extremely fossiliferous sub-tropical Nullarbor Limestone. In the late Middle Miocene the area was uplifted and exposed to terrestrial denudation and erosion since. Although the plain is in general considered extremely flat, the present geomorphological features indicate a relatively complex geomorphology formed by a combination of tectonic deformation, fluvial and aeolian activity and karst denudation. Due to the absence of orogenesis and only minor influence of post-Miocene sediment deposition, the geomorphology of the Nullarbor preserved footprints of Earth processes through a long, middle Miocene-to-present, time span.</p><p>The presence of dry climate and consequent lack of vegetation also aided for numerous meteorite findings, but no visible impact deformations have been recorded. The latter, in combination with capability of the plain to inherit/imprint old geomorphological features, and accessibility of recently built 0.4 arc sec TanDEM-X-DEM by the German Aerospace Centre, motivated the search of a possible meteorite craters with spatial analysis of the plain. The analysis of DEM images revealed a single geomorphological feature with circular uplifted rim (diameter: 1200 m – 1300 m; height: 7 m in relation to outer elevation; width: 200 – 450 m), central uplift (diameter: 500 m; height: 10 m in relation to outer elevation), and a circular trough in between (2 – 3 m higher than outer elevation). Its morphology differs from other geomorphological features observable on the Nullarbor Plain, and represents a unique phenomenon, which cannot be explained as a part of tectonic, volcanic, fluvial, karst or aeolian processes.</p><p>This feature is therefore a candidate for a possible relict of a meteorite crater, which occurrence is supported by topographical characteristics including uniqueness of the shape compared to other features on the plain. On the other hand, geological characteristics of the exposed rock within the “crater” lack any of the general diagnostic evidence for impact events (e.g., shocked quartz, brecciation), but rather indicate presence of boundstones with frame-builders preserved in in-situ position and thus suggesting the preservation of a bioherm. The occurrences of bioherms, however, are seldom individual (unlike impact craters) and more likely occur in clusters. The question remaining for this conference discussion is whether dissolutional imprinting of an impact crater could denude any of the characteristic impact structures whilst preserving the shape, or are we looking at a single bioherm preserved as a primary marine depositional feature?</p><p>ACKNOWLEDGEMENT: We acknowledge the financial support of Slovenian Research Agency (P6-0101; I0-0031; N1-0162), the Australian Speleological Federation Karst Conservation Fund and TerraSAR-X / TanDEM-X (DEM_GEOL2288).</p>

Miocene structural inversion of the Adjara-Trialeti back-arc basin as a far-field effect of the Arabia-Eurasia collision

<p>Young back-arc rift basins, because of the not yet dissipated extensional thermal signature, can be easily inverted following changes in the geodynamic regime and/or far-field stress transmission. Structural inversion of such basins mainly develops through reactivation of normal faults, particularly if the latter are favourably oriented with respect to the direction of stress transfer. The Adjara-Trialeti fold-and-thrust belt of SW Georgia is an example of this mechanism, resulting from the structural inversion of a continental back-arc rift basin developed on the upper plate of the northern Neotethys slab in Paleogene times, behind the Pontides-Lesser Caucasus magmatic arc. New low-temperature thermochronological data [apatite fission-track (AFT) and (U-Th)/He (AHe) analyses] were obtained from a number of samples, collected across the Adjara-Trialeti belt from the former sedimentary fill of the basin and from syn-rift plutons. AFT central ages range between 46 and 15 Ma, while AHe ages cluster mainly between 10 and 3 Ma. Thermal modelling, integrating AFT and AHe data with independent geological constraints (e.g. depositional/intrusion age, other geochronological data, thermal maturity indicators and stratigraphic relationships), clearly indicates that the Adjara-Trialeti back-arc basin was inverted starting from the late Middle Miocene, at 14-10 Ma. This result is corroborated by many independent geological evidences, found for example in the adjacent Rioni, Kartli and Kura foreland basins and in the eastern Black Sea offshore, which all suggest a Middle-Late Miocene phase of deformation linked with the Adjara-Trialeti FTB building. Adjara-Trialeti structural inversion can be associated with the widespread Middle-to-Late Miocene phase of shortening and exhumation that is recognised from the eastern Pontides to the Lesser Caucasus, the Talysh and the Alborz ranges. This tectonic phase can in turn be interpreted as a far-field effect of the Arabia-Eurasia collision, developed along the Bitlis suture hundreds of kilometres to the south.</p>

Late middle Miocene Konan flora from northern Hokkaido, Japan

Plant macrofossils from the upper middle Miocene Konan Tuffaceous Sandstone and Mudstone Member of the Bifuka Formation, known as the Konan flora, northwest of Shibetsu City, Hokkaido, Japan, were taxonomically revised. A total of 31 taxa were recognized, which were assigned to 14 families and 19 genera, including a new fossil species, Salix palaeofutura sp. nov. The Konan flora includes three taxa of evergreen conifers, one perennial monocot herb and 27 deciduous dicots. The most abundant and common species were Fagus palaeojaponica, Acer subcarpinifolium, Acer protojaponicum, Picea sp. A and Cercidiphyllum crenatum, in addition to a number of species of the Betulaceae and Salicaceae. From the absence of evergreen angiosperms as well as the common occurrence of Fagus palaeojaponica, Picea, Acer and Betulaceae species, this flora was comparable to that seen in the modern Mixed Northern Hardwood Forest of East Asia, which is distributed in northernmost Honshu and extends toward lowland Hokkaido. On the basis of floral features, mode of occurrence, and the lithology of plant-bearing beds, the Konan flora was deemed to represent mountain to riverside vegetation with humid and cool temperate climatic conditions. In contrast to the early to late Miocene floras in Japan, the Konan flora belongs to the late Miocene–Pliocene Mitoku-type flora, with a few relict species from the early Miocene. The Konan flora represents one of the earliest occurrences of this type of flora, suggesting that floral modernization was initiated much earlier in areas with humid and cool temperate climate than previously thought.

Bojongmanik Formation Sedimentation Mechanism in the Middle to Late Miocene (N9-N17) in the Rangkasbitung Basin

The Rangkasbitung Basin, is a part of Banten Depression which was formed by a normal fault, and then fi lled by marine deposits. This research carried out to understand the sedimentation process of Middle Miocene Bojongmanik deposits, the age, paleoenvironment and lithology (sediment sequence). In this research, 55 samples were taken from the study area, approximately 595 km2. Measurement of the stratigraphic section is carried out to determine the correlation both vertically and horizontally. The residue of dissolving peroxide method was carried out during the samples preparation. Then genus and species of planktonic and benthonic foraminifera were identifi ed and determined. The foraminifera analysis guide has been used to determine the age and depositional environment. The sequences of Bojongmanik Formation were deposited in Middle to Upper Miocene (N9 to N17). Based on the planktonic foraminifera distribution, the succession of each sequence can be correlated. During Middle Miocene (N9 - N12), the lowest part of Bojongmanik Formation is deposited at 100m-200m and 100m-80m depth, while in the other site, the correlated sequence is recorded that deposited at 80m-20m depth (outer to edge of inner neritic facies). In late Middle Miocene (N13 - N14), the regression process was happened. Almost the succession was deposited on land, while in deep site, a less part of sediments was formed as land facies but the most of it deposited as marine facies. In Upper Miocene (N 15 - N 17), the sedimentation continued in the transitional to edge neritic in back mangrove to mangrove environmental setting (upper to lower delta plain), and in other sites the sediment is no longer formed. Based on distribution of benthonic foraminifera there are observed the biofacies changes laterally. In bathymetric of depositional environment maps it can be depicted two higher paleoenvironmental sites (Cigudeg and Muncang highs) and two lower sites (Leuwiliang and Jasinga basins).