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Wyszukujesz frazę "Tanner, L." wg kryterium: Wszystkie pola


Wyświetlanie 1-4 z 4
Tytuł:
Tetrapod trace fossils from lowermost Jurassic strata of the Moenave Formation, northern Arizona, USA
Autorzy:
Tanner, L.
Lucas, S.
Powiązania:
https://bibliotekanauki.pl/articles/2061343.pdf
Data publikacji:
2008
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
burrows
tetrapod
cynodont
tritylodontid
rhizolith
Moenave
Lower Jurassic
Opis:
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.
Źródło:
Volumina Jurassica; 2008, 6, 1; 133-141
1896-7876
1731-3708
Pojawia się w:
Volumina Jurassica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Whitmore Point Member of the Moenave Formation: Early Jurassic Dryland Lakes on the Colorado Plateau, Southwestern USA
Autorzy:
Tanner, L.
Lucas, S.
Powiązania:
https://bibliotekanauki.pl/articles/2061348.pdf
Data publikacji:
2008
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
Utah
Arizona
Hettangian
Moenave Formation
meromictic
dryland
perennia
ephemeral
lacustrine
Opis:
The Lower Jurassic Whitmore Point Member of the Moenave Formation in Arizona-Utah, USA, comprises fish- and coprolite-bearing shales, siltstones, sandstones, and minor limestones. These facies were deposited in ephemeral and perennial lakes subject to episodic desiccation and incursions of coarse clastics during floods. Meromictic conditions developed during perennial episodes, probably due to salinity stratification, which enhanced preservation of organic matter in gray to black shales. These lakes formed on the floodout of a north-northwest oriented (relative to modern geography) system of mainly ephemeral streams on a broad and open floodplain. The Whitmore Point Member both overlies and interfingers laterally with alluvial red-bed facies of the Dinosaur Canyon Member of the Moenave Formation. The vertical transition from alluvial to lacustrine sedimentation recorded by the Dinosaur Canyon and Whitmore Point members of the Moenave Formation most probably resulted from a eustatically-controlled rise in base level during the Early Jurassic (Hettangian). The Dinosaur Canyon Member also interfingers laterally with eolian dune deposits of the Wingate Sandstone, which was deposited by winds that reworked coastal plain sediments to the north of the study area. Thus, on this part of the Colorado Plateau, fluvial, lacustrine and eolian sedimentary facies were deposited contemporaneously in laterally adjacent paleoenvironments.
Źródło:
Volumina Jurassica; 2008, 6, 1; 11-21
1896-7876
1731-3708
Pojawia się w:
Volumina Jurassica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetostratigraphy and paleopoles of the Kayenta Formation and the Tenney Canyon Tongue
Autorzy:
Steiner, M.
Tanner, L.
Powiązania:
https://bibliotekanauki.pl/articles/2077334.pdf
Data publikacji:
2014
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
Pliensbachian magnetostratigraphy
Kayenta Formation
paleopole
J-1 cusp
North America
formacja Kayenta
szpic J-1
Ameryka Północna
Opis:
The Kayenta Formation is the third in a series of stratigraphic units making up the Glen Canyon Group that were sampled along US Hwy 89 in southern Utah. The Kayenta is dominantly reversed polarity with a number of very short normal polarity intervals. Above the Kayenta and interbedded in the Navajo Sandstone is the Tenney Canyon Tongue of the Kayenta Formation. The lower half of the Tenney Canyon Tongue was also sampled and is dominantly normal polarity with three short reversed polarity intervals. The dominantly reversed magnetostratigraphy of the Kayenta appears to match that of Early Pliensbachian polarity interval “e-Pli R.” The dominance of normal polarity of the Tenney Canyon Tongue suggests that the Tenney Canyon may have been deposited in the upper half of the Pliensbachian polarity interval “ePli-N.” The suggested polarity matches indicate that the Kayenta and Tenney Canyon Tongue strata are 187–190 Ma in age. The paleopoles of the two units are statistically identical. The combined data of the Kayenta-Springdale-Whitmore Point show that the J-1 cusp terminated before the deposition of the Kayenta Formation. The North American continent/pole returned to its Late Triassic position during/after Springdale time, apparently along the same path used to reach the apex of the J-1 cusp.
Źródło:
Volumina Jurassica; 2014, 12, 2; 31--38
1896-7876
1731-3708
Pojawia się w:
Volumina Jurassica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Pedogenic and lacustrine features of the Brushy Basin Member of the Upper Jurassic Morrison Formation in western Colorado: Reassessing the paleoclimatic interpretations
Autorzy:
Tanner, L.
Galli, K.
Lucas, S.
Powiązania:
https://bibliotekanauki.pl/articles/2077335.pdf
Data publikacji:
2014
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
aridisol
inceptisol
calcrete
palustrine
lacustrine
pedogenesis
pedogeneza
jeziorny
bagienny
Opis:
Study of the pedogenic features of the Upper Jurassic Morrison Formation in western Colorado, USA, shows a clear difference in the types of paleosols between the strata of the lower and upper Brushy Basin Member. Lower Brushy Basin paleosols are mostly calcareous Aridisols with Stage I through Stage III calcrete Bk horizons, abundant root traces, occasional vertic features, but only rarely with ochric epipedons. Upper Brushy Basin paleosols are mainly thicker and commonly display ochric epipedons and well-developed Bt and Bw horizons. We assign these paleosols to the order Inceptisol. Limestones occur in the Brushy Basin Member and include both uniformly micritic limestones and limestones with strongly brecciated textures. The former contain sparse body fossils and charophyte debris, while the latter are characterized by clotted-peloidal fabrics with circumgranular cracking and silica replacement. We interpret these limestones as the deposits of carbonate in small water bodies on a low-gradient flood plain, with the textures resulting from pedogenic reworking of the carbonate sediment. We find no evidence for the presence of extensive lacustrine or wetlands (Lake T’oo’dichi’) deposits in the study area. The paleoclimate suggested by all of these features is strongly seasonal, but subject to variations on orbital (precessional and higher) timescales causing intervals of semi-aridity during weaker monsoons, to alternate with sub-humid periods during stronger monsoons. The apparent long-term change in climate during Brushy Basin deposition potentially resulted from northward drift of North America.
Źródło:
Volumina Jurassica; 2014, 12, 2; 115--130
1896-7876
1731-3708
Pojawia się w:
Volumina Jurassica
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-4 z 4

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