排序方式： 共有5条查询结果，搜索用时 15 毫秒
1
1.
Micro-organisms producing microbially induced sedimentary structures, particularly epibenthic cyanobacteria, are not facies-dependent and could flourish in any environment if appropriate ecological conditions were provided. Hence, the changes in environmental parameters are the controlling factors on ecological tolerance of the producers. This study on the lower Cambrian successions of the Lalun Formation in Central Iran shows that paralic environments reacted differently to changes in parameters such as river and tide energy, palaeo-topography, the rate of sediment supply and fluctuations in sea-level, even though all were characterized by sandy substrates suitable for the development of microbially induced sedimentary structures. Therefore, the abundance and preservation of microbially induced sedimentary structures varied in the different paralic environments. From a sequence stratigraphic viewpoint, this study demonstrates that erosional discontinuities lacked the conditions required for the substrate stabilization by microbial communities. The distribution, size and type of microbially induced sedimentary structures within high frequency cycles generally follow the trends of changes in vertical facies stacking patterns. Within systems tracts, the pattern, morphological diversity and size of microbially induced sedimentary structures are not dependent on the type of systems tract, but on the type of depositional system developed such as delta, incised valley, coastal plain, estuaries and shoreline to shelf systems. Generally, estuarine and peritidal carbonates record an increase in the development of mat colonization during the transgressive systems tract, owing to decreased sedimentation rate as well as extended shallow water habitats. In contrast, the existence of microbially induced sedimentary structures depends on the pattern of shoreline shift in depositional systems developed during the highstand systems tract, such as open coast tidal flat and delta environments. If a shoreline regression was continuous (depositional trend and stacking pattern are a set of high frequency cycles), a greater increase in the aggradational component than the progradational component would cause intensified destructive processes hindering the development of microbial communities. 相似文献
2.
Ezzadin N. Baban Aram N. Tawfiq Kakarash I. M. Gardi 《Arabian Journal of Geosciences》2014,7(9):3575-3588
The present study seeks to interpret seismic reflection data for an area measuring approximately about 1,450 km2 within the Erbil plain in the Kurdistan Region of Iraq to produce subsurface geological pictures. Thirteen seismic lines were identified by the Iraqi Oil Exploration Company using dynamite sources and then processed; then, a seismic line, BH-15, of around 432.5 km total length was used in this study. Three horizons (reflectors) were selected and identified by tying them directly to Demir Dagh well no. 1, these are H1, a reflector that represents the near top of the Lower Fars Formation; H2, a reflector that represents the top of the Pila Spi Formation; and H3, a reflector that represents the top of the Shiranish Formation. The qualities of the reflectors range between fair and good. All the isochrone and depth maps and 3D view pictures of the reflectors show the same main subsurface structural features trending in a NW–SE direction, namely, Erbil trough, Sherawa trough, and the southeastern plunge of the Demir Dagh anticline. Ninety-five normal and reverse-type faults trending in a NW–SE direction were detected. Also, the maps show that the reflectors tend to increase in dipping and deepening towards the southeastern and eastern parts. 相似文献
3.
Vanessa R. Levesque Aram J. K. Calhoun Kathleen P. Bell Teresa R. Johnson 《社会与自然资源》2017,30(2):245-260
Given the complexity and multiplicity of goals in natural resource governance, it is not surprising that policy debates are often characterized by contention and competition. Yet at times adversaries join together to collaborate to find creative solutions not easily achieved in polarizing forums. We employed qualitative interviews and a quantitative network analysis to investigate a collaborative network that formed to develop a resolution to a challenging natural resource management problem, the conservation of vernal pools. We found that power had become distributed among members, trust had formed across core interests, and social learning had resulted in shared understanding and joint solutions. Furthermore, institutions such as who and when new members joined, norms of inclusion and openness, and the use of small working groups helped create the observed patterns of power, trust, and learning. 相似文献
4.
Aram BAYET-GOLL Paul M. MYROW Guillermo F. ACE?OLAZA Reza MOUSSAVI-HARAMI Asadollah MAHBOUBI 《《地质学报》英文版》2016,90(5):1572-1597
The Lower Ordovician Shirgesht Formation in central Iran is composed of siliciclastic and carbonate rocks deposited in diverse coastal and marine shelfal environments (tidal flat, lagoon, shoreface, offshore-shelf and carbonate ramp). Five facies associations contain diverse ichnofossil assemblages that show distinct proximal to distal trends formed in a wide range of physical-chemical conditions. The ethological groups of trace fossils in the Shirgesht Formation reflect a gradient of depositional stress conditions across a wave-influenced shoreline and shelf. Deposits of wave-influenced environments make up a significant component of the geological record of shallow marine settings, and the ability to determine paleoenvironments in detail in such successions is critical for reconstruction of depositional histories and sequence-stratigraphic interpretation.The Cruziana ichnofacies of the study shows highly diverse suites that record the establishment of a benthic community under stable conditions and a long-term colonization window. The Skolithos ichnofacies recognized is a low diversity opportunistic ichnocommunity suite that resulted from colonization after tempestite deposition in a stressed environment. The strata record an onshore to offshore replacement of the Cruziana ichnofacies (with abundant feeding traces of deposit-feeders) by the Skolithos ichnofacies (dominated by suspension-feeders and predators). A transitional zone between the two ichnofacies coincides with the offshore-transition/distal lower-surface deposits. The distribution of ichnofacies, the diversity and range of ethological characteristics reflected by the ichnogenera, and the wide range of wave-dominated coastal facies demonstrate the potential to use individual trace fossils and ichnofacies for significantly refined palaeoenvironmental analysis of wave-dominated coastal settings, particularly in Ordovician successions. 相似文献
5.
Bayet-Goll Aram Esfahani Fariba Shirezadeh Daraei Mehdi Monaco Paolo Sharafi Mahmoud Mohammadi Amir Akbari 《International Journal of Earth Sciences》2018,107(6):2233-2263
International Journal of Earth Sciences - The Tournaisian–Visean carbonate successions of the Esfahan–Sirjan Basin (ESB) from Sanandaj–Sirjan Zone, Iran, have been used to... 相似文献
1