Fissure Infillings Research Articles

Systematics and paleobiogeography of Sardolagus obscurus n. gen. n. sp. (Leporidae, Lagomorpha) from the early Pleistocene of Sardinia

AbstractThe extreme rareness of Sardinian fossil sites older than Middle and Late Pleistocene makes the Monte Tuttavista karst complex (E Sardinia, Italy) very important. Remarkable lagomorph material, recovered from several fissure infillings of Monte Tuttavista referable to the Capo Figari/Orosei 1 and Orosei 2 faunal sub-complexes (early Pleistocene, ~2.1/1.9–1.1 Ma), allowed us to describe a new endemic insular leporid, Sardolagus obscurus n. gen. n. sp. The new taxon is characterized by a peculiar combination of an advanced p3 (Lepus-type) and a primitive P2 lacking deep flexa. The origin of such discrepancy, unprecedented among continental and insular endemic European leporids, is unclear. It could be the result of: (1) an independent evolution of p3 from an ancestor bearing the primitive P2/p3 (e.g., Alilepus, Hypolagus), or (2) a selective reversal morphocline from an Oryctolagus/Lepus-like leporine. The lack of data about the phylogenetic origin of the new taxon makes any inference about its possible arrival to Sardinia problematic. Crossing the European leporid records and evidence of migrations to Sardinia, we hypothesize three possible ages in which the ancestor of Sardolagus obscurus could have arrived in Sardinia, restricted to the late Miocene–early/late Pliocene (~8–3.6 Ma). The phylogenetic relationship between Sardolagus obscurus n. gen. n. sp. and the oldest Sardinian leporid, recorded from Capo Mannu D1 and dated at the early/late Pliocene boundary (~3.6 Ma), is unclear at present, however it is quite likely that they pertain to the same lineage.UUID: http://zoobank.org/ca8e0023-7c9d-4b00-a294-d166c37c5c71

Carbon, oxygen, and sulfur isotope compositions and model of the Silurian rock formation in northwestern Belarus

The paper describes the results of study of the Silurian clayey–carbonate rocks ranging from the Telychian Stage (Llandovery) to the Gorstian Stage (Ludlow) recovered by the Borehole Davtyuny 3k in northwestern Belarus. Rocks of the Sheinwoodian Stage demonstrate a positive excursion of δ13C with amplitude of 4.7‰, marking the Ireviken biotic event recorded in the global chemostratigraphic curve. Values of δ18O for the carbonate material in the studied section (25.5–29.2‰ SMOW) are close to those for Silurian rocks from the Baltic region, Scandinavia, Ukraine, Poland, and Canada. The whole section contains postsedimentary gypsum as nodules and the infilling of fissures and fenestrae. Values of δ34S in gypsum (21.3–26.7‰ CDT) are close to those for the Silurian rocks on the Phanerozoic isotope plot. The formation of gypsum was related to a partial development of the supralittoral environment over the sublittoral and littoral clayey–carbonate substrate. The seawater accumulated in lowlands of the supralittoral plain after storms was intensely concentrated during arid conditions and accumulated in the clayey–carbonate sediment. The subsequent underground evaporation promoted the formation of gypsum as nodules in the unlithified sediments and the infilling of fissures and fenestrae in the lithified rocks.

Seismites in the Dasheng Group: New evidence of strong tectonic and earthquake activities of the Tanlu Fault Zone

More than 80 layers of seismites were recognized from the Early Cretaceous Dasheng Group in the Mazhan and Tancheng graben basins in the Tanlu Fault Zone, eastern China. The responsible seismic events took place about 110–100 Ma in the Early Cretaceous. The fault zone was affected at the time by strong tectonics, due to tension-related stretching and scattered squeezing by strike-slip faults. These tectonic activities induced a series of strong earthquakes with Richter magnitudes (M) of 5–8.5. The earthquakes affected saturated or semi-consolidated flood and lake sediments, and produced intra-layer deformations by several processes, including liquefaction, thixotropy, drop, faulting, cracking, filling and folding, which resulted in the formation of various soft-sediment deformation structures, such as dikes and veins of liquefied sand, liquefied breccias, liquefied homogeneous layers, load structures, flame structures, ball-and-pillow structures, boudinage, diapirs, fissure infillings, a giant conglomerate wedge, and syn-sedimentary faults. The seismites are new evidence of tectonic and seismic activities in the Tanlu Fault Zone during the Early Cretaceous; the series of strong seismic events that can be deduced from them must be considered as a response to the destruction of the North China Craton.

Dinoflagellate cysts from neptunian dykes in the Middle Jurassic of Poland — A stratigraphical approach

Dinoflagellate cysts are of use in determining the age of allochthonous sediments within host rocks. Due to the high durability of the cyst walls they are able to persist in difficult environmental and synsedimentary conditions. This case study focuses on palynological analysis of neptunian dykes cutting through Middle Jurassic clays with siderite concretions exposed in three sites in Central Poland. Within the fissures, intense mixing of palynodebris from the host rock with the infilling sediments took place. Palynological analysis of the internal sediments from the fissure infillings revealed well-preserved mixed assemblages of Middle and Late Jurassic taxa enabling the age of the process to be constrained. The analysis of the infillings of neptunian dykes is of particular importance as sometimes this provides the only proof of eroded sediments, and the fissure systems are usually evidence of regional extensional tectonic activities.

Evolutionary history of the African soricid Myosorex (Insectivora, Mammalia) out of Africa

ABSTRACT The species Myosorex meini Jammot, 1977 was a nomen nudum because it was named in an unpublished dissertation. The species is here revised using the new material found in the Late Pliocene fissure infillings of Almenara-Casablanca 1 and 4 (province of Castelló, East of Spain) and from the Tollo de Chiclana localities 1B, 3, 10, and 10B in the Guadix Basin (province of Granada, Southeastern Spain). A new diagnosis is given with some differential characters to identify the species within the family. The species definitively belongs to the genus Myosorex. A definitive new allocation for the genus into the subfamily Crocidosoricinae is proposed as an alternative to the classical assignment to the Crocidurinae. This is justified by available data coming from different fields of research, such as genetics, reproductive biology, morphology, and paleontology. Within the Crocidosoricinae, the tribe Myosoricini Kretzoi, 1965 is resurrected, and two other ones, the Crocidosoricini and the Oligosoricini, are redefined. From the paleobiogeographical point of view, the occurrence of the African genus Myosorex constitutes a new striking evidence of the faunal exchange between Eurasia and Africa that took place during the Messinian Salinity Crisis.

THE ENDEMIC CANID CYNOTHERIUM (MAMMALIA, CARNIVORA) FROM THE PLEISTOCENE DEPOSITS OF MONTE TUTTAVISTA (NUORO, EASTERN SARDINIA)

This paper presents the main results related to the analysis of fossils of the endemic Sardinian canid Cynotherium , discovered during the past years within the rich fossiliferous karst deposits in the Monte Tuttavista area (Eastern Sardinia, Nuoro). The analysis indicates that the remains from various fissure infillings differ in size and dental characters, which are suggestive of evolutionary phases under endemic conditions. The chronological sequencing of fissures obtained based on the evolutionary stage of the fossil canid is consistent with that emerging from the analysis of the whole mammal assemblages occurring in the same fissures. The possible evolutionary relationships of the Sardinian canid to the Plio-Pleistocene mainland species are also considered; a derivation from a population of late Canis arnensis (or Canis mosbachensis ) population is supported.

Roberts Rift, Canyonlands, Utah, A Natural Hydraulic Fracture Caused by Comet or Asteroid Impact

AbstractThe impact that created Upheaval crater in Canyonlands National Park, Utah, is invoked here as the source for energy that simultaneously caused Roberts rift. However, no temporal linkage has been proven between the impact and rifting events.Roberts rift lies between 22 and 32 km northeast of the Upheaval impact crater on a subradial trend. The fissure contains clasts that were carried as much as 1,000 m upward from Paleozoic sources into the Mesozoic section.A plausible model for both the rifting and clast movement involves incremental loading of overpressured fluid compartments in the Pennsylvanian Paradox section and attendant hydraulic fracturing of the overlying confining strata during the impact event. The clasts were proppants entrained in upward moving fluids that originated from overpressured aquifers in the Pennsylvanian section or materials eroded from the fissure walls.Alteration halos and mineralization along the fissure reveal that there was upward leakage of reducing fluids from the overpressured zones following opening of the fissure. The fissure infillings became cemented with time, thus reducing fissure permeabilities to negligible.

Vertebrate fissure faunas with special reference to Bristol Channel Mesozoic faunas

Abstract Throughout the Mesozoic and Cenozoic, tectonically activated joint fissures and karstic cave systems have acted as reservoirs for terrestrial vertebrate remains. They yield concentrations of microfaunal elements rarely if ever preserved in other situations. In the 1850s, Charles Moore realized their potential and exploited them to discover the earliest known mammals in late Triassic fissure infillings in the Carboniferous Limestone of Somerset. The history of that discovery and its associated problems of interpretation are recorded. His work greatly influenced succeeding generations of palaeontologists and, as techniques developed, fossil fissure discoveries have made a major impact on our understanding of vertebrate evolution.

Vertebrate fissure faunas with special reference to Bristol Channel Mesozoic faunas

Throughout the Mesozoic and Cenozoic, tectonically activated joint fissures and karstic cave systems have acted as reservoirs for terrestrial vertebrate remains. They yield concentrations of microfaunal elements rarely if ever preserved in other situations. In the 1850s, Charles Moore realized their potential and exploited them to discover the earliest known mammals in late Triassic fissure infillings in the Carboniferous Limestone of Somerset. The history of that discovery and its associated problems of interpretation are recorded. His work greatly influenced succeeding generations of palaeontologists and, as techniques developed, fossil fissure discoveries have made a major impact on our understanding of vertebrate evolution.

The Allophaiomys complex in Southern Europe

The representation of Allophaiomys in Southern Europe has increased considerably thanks to the intensive samplings carried out in recent years in the Guadix-Baza basin and other sites in Spain (Casablanca and Cueva Victoria fissure infillings). In addition to the type-species, Microtus (Allophaiomys) pliocaenicus, these finds have provided information on two additional species: M. (Allophaiomys) chalinei Alcalde, Agusti & Villalta and M. (Allophaiomys) vandermeuleni n. sp. (type-locality: Barranco de los Conejos in the Guadix-Baza basin, Southern Spain). The latter species differs from other Allophaiomys representatives by its large size and its very deep LRA-3 (lingual reentrant angle 3), which contrasts with the primitive shape of the anteroconid complex. The evolutionary relationships of the different Allophaiomys species are analyzed by two different approaches. First, the phenetic view of the early evolution of Microtus in Europe is based exclusively on the A, B and C parameters commonly used in the systematics of this genus. A second phylogenetic approach is attempted also taking into account other morphological characters. As a consequence of the results shown by the mostly parsimonious cladogram, the subdivision of the Allophaiomys stock into two assemblages, the first one dealing with the “European” Pitymys (or Terricola, according to Brunet-Lecomte, 1988) and a second one dealing with the Chionomys group, is proposed. Moreover, this divergence can be traced back to the very early Pleistocene, instead of the middle Pleistocene age usually accepted for this splitting process. Thus, M. (A.) vandermeuleni shares a common ancestor with the Chionomys group, while M. (A.) chalinei is situated close to the origin of M. (A.) nutiensis. On the other hand, M. (A.) burgondiae is proposed as the sisterspecies of M (Allophaiomys) jordanicus ( Haas) (not Arvicola). Therefore, a middle Pleistocene age is proposed for the site of Ubeidiya.

δ18O and δ13C for limestones, calcite fissure infillings and calcite precipitates from Sweden

Abstract δ18O and δ13C for limestones, calcite fissure infillings and calcite precipitated on the present rock surface have been analysed. The calcite samples were collected from different geological environments in Sweden. Most results can be correlated to crystallization conditions or redistribution due to fluid activation in fissures.

The postcranial skeleton of the Lower Jurassic eosuchian Gephyrosaurus bridensis

The postcranial skeleton of the reptile Gephyrosaurus bridensis is described. The material was extracted from the Lower Jurassic fissure infillings of South Wales and comprises the broken and dissociated bones of many different individuals. The skeleton, like the skull, retains many primitive features which justify the inclusion of Gephyrosaurus within the Eosuchia. A comparison of the skeleton with that of other genera supports the conclusion that Gephyrosaurus represents a separate eosuchian lineage. The skeleton is that of a small, unspecialized terrestrial reptile which could move quickly in pursuit of prey.

Ore transport and deposition in the Red Sea geothermal system: a geochemical model

Thermodynamic calculation of distribution of dissolved aqueous species in the Red Sea geothermal brine provides a model of ore transport and deposition in good agreement with observed accumulations of base metal sulfides, anhydrite, and barite. The Red Sea brine is recirculated seawater that acquires high salinity by low-temperature interaction with Miocene evaporites and is subsequently heated to temperatures in excess of 200°C by interaction with recent rift zone intrusive rocks. At temperatures up to 250°C, NaSO − 4 and MgSO 0 4 are the dominant sulfur-bearing species. H 2S forms by inorganic sulfate reduction at the higher temperatures but is maintained at a uniform concentration of about 2 ppm by the strength of the sulfate complexes. Chloride complexes solubilize metals at the higher temperatures, and thus sulfide and metals are carried together into the Atlantis II Deep. Below 150°C, the brine becomes supersaturated with respect to chalcopyrite, sphalerite, galena, and iron monosulfide due to chloride-complex dissociation. Sulfide precipitation rates, based on the rate of brine influx, are in good agreement with measured sedimentation rates. Anhydrite precipitates as crystalline fissure infillings from high-temperature inflowing brine. Barite forms from partial oxidation of sulfides at the interface between the lower hot brine and the transitional brine layer.

Polyphase Limestone Dikes in the Oamaru Region, New Zealand

Numerous tabular bodies of sedimentary rock cut discordantly through bedded Oligocene volcaniclastic sediments along the coast at Oamaru, South Island, New Zealand. Most such dikes represent infilling of irregular fissures which opened spasmodically along the crests of submerged volcanogenic mounds. Infillings predominantly comprise biogenic debris in a wide variety of texture and composition. Dikes are multilayered, with layers either parallel to the walls or at various angles. Layers of different lithotypes, phases , reflect significant temporal differences between episodes of infilling. Layers of similar lithotypes, pulses , reflect relatively short temporal differences or fluctuations in the filling process during a single episode of infilling. Processes of infill range from gravitationally-induced cohesionless grain flow and viscous mudflow to hydrodynamic injections resulting from opening and closing of the fissures. Dike microfacies represent seafloor sediments from probable Lower Oligocene into Lower Miocene time. Some phases reflect transient deposits that are not present in the normal stratigraphic sequence of the coastal region. All fissures did not open at the same time or always follow the same routes, and a definitive regional sequence of phase emplacement cannot be determined.

Palaeozoic tectonism, sedimentation and mineralization in West Tasmania

Abstract This paper deals with the palaeotectonic evolution, depositional environment and metallogenetic events in West Tasmania during the Palaeozoic, as revealed by a programme of mineral exploration jointly financed by Rio Tinto Australian Exploration Pty. Ltd. and by Electrolytic Zinc Company of Australasia Ltd. The area of investigation formed in Cambrian time firstly a basin of neritic sedimentation, marked by arenaceous and carbonate deposits; then evolved into a eugeosynclinal belt flanked to the west and east by two Precambrian geanticlines, and comprising a volcanic arc (Mt. Read Volcanic Arc) and a deep depositional furrow (Dundas Trough). The volcanic arc consisted of flows and hypabyssal bodies of acid and intermediate composition, associated with thick pyroclastic deposits — volcanic breccias, agglomerates, ignimbrites, tuffs, ash‐beds and tuffaceous slates. This succession (Mt. Read Volcanics) appears to exceed 8,000 ft. in thickness, and is regarded by the authors as the product of volcanism along meridionally directed and deep‐seated faulting. A Lower to Middle Cambrian age is assigned to these volcanics. They would have been uplifted and probably folded in Middle Cambrian time to form a source of supply to the Dundas Trough which developed along their western margin. The uplift and erosion period is marked by an unconformity between the volcanics and the synorogenic suite of the Dundas Trough. This suite (Dundas Group) of Middle to Upper Cambrian age, begins with argillites, black slates and cherty layers, followed by greywacke, subgreywacke, pebbly mudstones and conglomerate. It ends locally with a boulder conglomerate (Misery Conglomerate) which is probably of continental origin. The similarities between this succession and the classic flysch deposits of the geosynclinal sedimentary cycle is pointed out, and the origin of the Dundas Trough as a furrow of archipelagos is inferred. The Cambrian geosynclinal evolution did not, however, culminate with a mountain‐building phase. Instead, a system of rift valleys developed in Lower Ordovician time. The main graben thus formed extended, over 100 miles at least, along the present West Coast Range, where it is marked by a belt, 3–4 miles wide, of breccias (Jukes Breccia), overlain by conglomerates and sandstones (Owen Conglomerate)‐a typical red‐bed formation reaching 3,000 feet in thickness. This clastic suite represents terrestrial infillings of coalescing fan‐glomerates, scree and alluvial blankets, resting on and essentially confined to the Cambrian volcanic belt. It is thus manifest that the graben developed along this belt probably as a collapse structure in the old volcanic zone. The Lower Ordovician period of faulting and continental deposition was followed by the general transgression of the Upper Ordovician‐Silurian‐Lower Devonian sea, which covered large portions of Tasmania and much of the eastern mainland of Australia (Tasman Geosyncline). The folding of this Geosyncline in Devonian time disrupted the Cambro‐Ordovician structural elements and brought about new folding and faulting trends. Eroded during the Carboniferous, deeply buried beneath the Permo‐Triassic sedimentary mantle, re‐exposed by epeirogenic uplifts during the Tertiary and deeply dissected by the Quaternary cycles of erosion, the palaeotectonic elements of West Tasmania offer outstanding examples of superimposed deformations and old rift valley developments. The relations between palaeotectonics, igneous activity and metallogenetic phenomena are discussed. The main copper‐zinc‐lead deposits of West Tasmania, together with numerous mineral prospects, lie on the fault zone delimiting the Volcanic Arc‐Owen Graben zone to the west. They are probably related to the Cambrian effusive and hypabyssal porphyries, felsites and keratophyres. Other deposits, of less importance at present, are zonally arranged around granitic masses, where they often occur as narrow fissure infillings unquestionably related to the Devonian orogenic cycle.

Note on the Sandstone Injections of Eathie Haven, Cromarty

AbstractThe sandstone injections which penetrate the Kimmeridgian strata of Eathie are described, the presence of sill-like injections being particularly noted. It is considered that the occurrence of “sandstone-sills” at Eathie is of importance in ascertaining the mode of origin of the injections of the locality. It is further suggested that the sills support the hypothesis that the injections are the result of infilling of fissures from below by sand and water.