Wyniki wyszukiwania - BazTech

1

Interconnected chambered trace fossils, Pliocene lower Tipam Formation, Tripura, India

Rajkumar Hemanta S., Šimo Vladimir

Annales Societatis Geologorum Poloniae

|

2020

|

Vol. 90, No. 3

261--270

EN

A new kind of trace fossil characterized by filled ellipsoidal chambers interconnected by a boxwork of burrows, shafts and tunnels, in different horizontal planes, is observed in the medium-grained fluvial sandstone of the Pliocene Lower Tipam Formation in the Amarpur area of Tripura in northeast India. The chambers have variable dimensions with lengths of 3-16 cm, widths of 3-10 cm and heights of 2-6 cm. Diameters of the connecting tunnels and shafts are 0.8-0.9 cm on average. The traces are considered to be nest systems of social insects. The discovery is noteworthy as far as the geology of Tripura state is concerned, as such chambered traces have not previously been reported from the Indian sub-continent. Morphology of the studied specimens point toward a new ichnospecies, Vondrichnus amarpurensis isp. nov. of the ichnofamily Krausichnidae.

2

Probable root structures and associated trace fossils from the Lower Pleistocene calcarenites of Favignana Island, southern Italy : dilemmas of interpretation

Uchman A., Ślączka A., Renda P.

Geological Quarterly

|

2012

|

Vol. 56, No. 4

745–-756

EN

Two types of large, branched structures from the Lower Pleistocene (Calabrian) high-energy calcarenites of Favignana Island are described: Faviradixus robustus gen. et sp. nov. and Egadiradixus rectibrachiatus gen. et sp. nov. They may be interpreted as root structures of large plants, trees and trees or shrubs, respectively. The former taxon co-occurs with the marine animal trace fossils Ophiomorpha nodosa, Ophiomorpha isp., Thalassinoides isp. and Beaconites isp. The interpretation as root structures although tentative is probable and can be related to short emergence episodes for the formation of E. rectibrachiatus or to longer emergence, responsible for the discontinuity at the base of the overlying Tyrrhenian deposits, for F. robustus. Calcified root mats of smaller plants associated with the Tyrrhenian or younger emergence surfaces are common.

3

Mykolaiv Sands in Opole Minor and beyond : sedimentary features and biotic content of Middle Miocene (Badenian) sand shoals of Western Ukraine

Wysocka A., Radwański A., Górka M.

Geological Quarterly

|

2012

|

Vol. 56, No 3

475--492

EN

The Mykolaiv Sands are a huge lithosome of Middle Miocene (Badenian) age, accommodated within the Fore-Carpathian Basin in the Western Ukraine. Typically developed in the area of Opole Minor, it spreads across adjacent regions of Opole to cover an area of about 1300 km2. The varied sedimentary structures and ubiquitous burrows, indicate their development as a stack of sand shoals or related bodies, up to a few tens of metres thick, some of which temporarily reached sea level. Amidst the shoals, storm scours intermittently formed channel-like infills, some with residual lags at the base. The reversed density stratification and/or an increasing gravity gradient involved mass movements, some of which may have been triggered by seismic shocks focused at the shore or the adjacent hinterland of Podolia and Volhynia. Special attention is paid to the diverse fossils, all taphonomically filtered (aragonite shells and chitinous carapaces being lost), but which locally are mass-aggregated. They typify particular sand sets/bodies, to form allochthonous assemblages, some members of which (the cirripedes Scalpellum and Creusia, the shark Hemipristis, the ray Myliobatis) are newly recognized in the Ukrainian part of the Fore-Carpathian Basin. The others enrich considerably the faunal content of the Middle Miocene (Badenian) Paratethyan basins, either in terms of taxonomic diversity, or the eco-taphonomy of selected taxa (the starfish Astropecten, diverse echinoids). The whole faunal content of the Mykolaiv Sands may owe its profuse development to the global Middle Miocene Climatic Optimum of early Badenian age.

4

Miocene burrows of the Ghost Crab Ocypode and their environmental significance (Mykolaiv Sands, Fore-Carpathian Basin, Ukraine)

Radwański A., Wysocka A., Górka M.

Acta Geologica Polonica

|

2012

|

Vol. 62, no. 2

217-229

EN

The huge lithosome of the Middle Miocene (Early Badenian) Mykolaiv Sands, developed at the external margin of the Fore-Carpathian Basin in western Ukraine, is recognized to represent a shallowing-up sequence. Special attention is paid to burrows of the Ghost Crab Ocypode which are pantropical in present-day littoral habitats. In the Stratyn section, burrows of this type become a crucial tool in the interpretation of basin bathymetry, which starts from distal offshore depths, through the foreshore, to the backshore where the Ocypode burrows record a temporary break in sedimentation. Lithification of the sand layers and the Ocypode burrows subsequently progressed in beachrock mode. The Stratyn section demonstrates that the development of submerged shoals and/or emergent parts, throughout the huge mass of the Mykolaiv Sands, is probably responsible for their great variation in thickness in western Ukraine, which has long proved difficult to explain.

5

Ichnocoenoses in the Oligocene to Miocene foredeep basins (Northern Apennines, central Italy) and their relation to turbidite deposition

Monaco P., Checconi A., Milighetti M.

Acta Geologica Polonica

|

2010

|

Vol. 60, no. 1

53-70

EN

Analysis of trace fossil abundance and diversity in the Oligocene to Miocene foredeep and piggyback basins of the Tuscan-Romagna-Umbrian Apennines allows us to recognize five ichnocoenoses. The deposits reflect sedimentary environments from slope to basin plain, whose sedimentation was directly controlled by synsedimentary tectonics: attached fan lobes and channels, lobe- and channel-fringes, overbank-fringes of intrabasinal highs, distal detached lobes of basin plain and slope-proximal interfans. The graphoglyptid: non-graphoglyptid ratio has been considered as the chief factor in the study of ichnologic material from Falterona-Cervarola-Trasimeno, Marnosoarenacea and Marne di Vicchio-Verghereto stratigraphic units. The study shows that there is an increase in ichnodiversity and ichnodensity of graphoglyptids, which are typical mainly in detached lobes of basin plain and overbank-levee deposits whose background ichnofauna also shows better preservation.

6

Integrated stratigraphical study of the candidate Oxfordian Global Stratotype Section and Point (GSSP) at Redcliff Point, Weymouth, Dorset, UK

Page K., Melendez G., Hart M., Price G., Wright J., Bown P., Bello J.

Volumina Jurassica

|

2009

|

Vol. 7, no. 1

101-111

EN

Ham Cliff near Redcliff Point, Weymouth, Dorset (SW England) exposes one of Europe's most complete Callovian-Oxfordian boundary sequences and has consequently been identified as a potential candidate GSSP for the base of the Oxfordian Stage. The boundary sequence lies within the thick mudrock facies of the Oxford Clay Formation and is abundantly fossiliferous, cardioceratid ammonites in particular being conspicuous. By convention, the stage boundary is drawn at the first occurrence of the genus Cardioceras here represented by C. redcliffense Page, Melendez and Wright at the base of the Scarburgense Subchronozone of the Mariae Chronozone. Associated Perisphinctoidea (including Peltoceras, Alligaticeras and Euaspidoceras) provide additional biostratigraphical information. Other macrofossil groups show less discernible changes, although frequent belemnites (Hibolithes) provide new highresolution carbon and strontium isotope data which are consistent with global curves and continuous sedimentation across the boundary interval. Magnetostratigraphic information is also available. Foraminiferal assemblages are dominated by epistominids but include a flood of early planktonic forms, including ?Globuligerina oxfordiana (Grigelis) immediately above the boundary. Well-preserved nannofloras are dominated by Watznaueria with conspicuous Zeugrhabdotus, podorhabdids and Stephanolithion indicating the NJ14 Biozone. Ostracoda and holothurian spicules are also recorded. These results are synthesised to provide a multidisciplinary, integrated review of the suitability of Redcliff Point for the definition of an Oxfordian GSSP. Correlations with the French candidate site in Haute-Provence are discussed and proposals made for formally establishing a GSSP for the base of the Oxfordian Stage in Europe.

7

Tetrapod trace fossils from lowermost Jurassic strata of the Moenave Formation, northern Arizona, USA

Tanner L., Lucas S.

Volumina Jurassica

|

2008

|

Vol. 6, no. 1

133-141

EN

At Moenkopi Wash along the Ward Terrace escarpment of northern Arizona strata of the upper Dinosaur Canyon Member of the Moenave Formation contain sedimentary structures we interpret as casts of tetrapod burrows. Sandstone casts and in situ burrows occur concentrated in two horizons that extend several hundred meters along the Ward Terrace escarpment. The structures, hosted in beds of eolian sandstone, form interconnecting networks of burrows that branch at right angles. Individual burrow casts have sub-circular cross sections and consist of nearvertical tunnels and horizontal to low-angle galleries that connect to larger chambers. Most burrow casts measure 5 to 15 cm in diameter, are filled by sandstone of similar grain size as the host rock, and have walls that are unlined and lack external ornamentation. Bedding plane exposure of the lower horizon reveals that the density of burrows exceeds 30 vertical tunnels per square meter. One exposure in the upper horizon reveals burrows concentrated in a mound-like structure with 1 m of relief. Rhizoliths, distinguished from burrows by their typical smaller diameters, calcareous infilling, and downward branching, co-occur with these burrows in the upper horizon. The fossil burrows in the Moenave Formation appear to have been constructed by a fossorial tetrapod with social behavior similar to the modern Mediterranean blind mole-rat. Although no skeletal remains are associated with the burrows, the fossil record suggests that the most likely producers of the Moenave burrows were tritylodontid cynodonts.

8

Mass aggregation of Middle Miocene spine-coated echinoids Echinocardium and their integrated eco-taphonomy

Radwański A., Wysocka A.

Acta Geologica Polonica

|

2001

|

Vol. 51, nr 4

295-316

EN

A unique "Fossillagerstatte" of spatangoid echinoids of the genus Echinocardium from the Middle Miocene (Badenian) sandy deposits of the Fore-Carpathian Depression, as exposed at Gleboviti (=Chlebowice) in the Ukraine, is characterised by a mass occurrence of tests often preserving their entire spine canopy, apparently unaffected by taphonomic filtering. These echinoids represent a new species, Echinocardium leopolitanum sp.nov., and are assumed to have had a similar mode of life as the extant, cosmopolitan species E. cordatum (PENNANT, 1777), i.e. relatively deep burrowing and confined to the sublittoral. Violent storms and/or storm-generated currents are held responsible for stirring up the sand and for bringing live specimens, of all ontogenetic stages, to the surface upon which followed deposition of a heavy-loaded sediment from which they could not escape. Thus, specimens are interpreted to have been buried alive, with all spines attached. Mass aggregation of tests occured either in patches laid down in vortical flutes on the current-swept seafloor, or within tabular scrolls of cross-bedded strata where they are locally imbricated. A functional analysis of the spines of Echinocardium leopolitanum sp.nov., and primarily of the large, triangular fan of plastron spines, suggests specimens to have been adapted to rapid burrowing throughout a weakly coherent and nutrient-poor sandy bottom. Ascribed to Echinocardium leopolitanum sp.nov. burrows, whose structure is comparable to, if not identical with, those of other Echinocardium species. The taxonomic potential of such burrows is discussed and it is suggested that names applied recently in ichnological analyses are in need of a modern revision.