نتایج جستجو برای: calcareous nannofossil
تعداد نتایج: 3540 فیلتر نتایج به سال:
Abstract. Late Miocene to Pliocene sediments from the NW Australian shelf, drilled by International Ocean Discovery Program (IODP) Expedition 356, provide unique records of paleoclimatic variations under warmer-than-present conditions. During period 6 3.5 Ma, area was dominated warm, tropical waters supplied an intensified, uninterrupted Indonesian throughflow and characterised prevailing humid...
Nowadays, primary productivity variations at the SW Iberian Margin (IbM) are primarily controlled by wind-driven upwelling. Thus, major changes in atmospheric circulation and wind regimes between Marine Isotope Stages (MIS) 12 9 could have driven substantial phytoplankton which remains poorly understood. We present a high-resolution calcareous nannofossil record from Shackleton Site Integrated ...
The mechanisms of early diagenetic quartz formation under low-temperature conditions are still poorly understood. In this study we investigated lithified cherts consisting of microcrystalline quartz recovered near the base of a 420 m thick Miocene-Holocene sequence of nannofossil and diatom ooze at a drill site in the Eastern Equatorial Pacific (Ocean Drilling Program Site 1226). Precipitation ...
Calcareous tempestite levels interbedded with Ammonitico Rosso and other related pelagic facies have been recognized. The previously described examples of calcareous tempestites in pelagic facies are scarce. The studied outcrops are Middle and Late Jurassic in age and correspond to ancient sediments in the Southern Iberian Continental Paleomargin. These outcrops are now included in a notably de...
The phylogenetic relationships of the Dinophyceae (Alveolata) are not sufficiently resolved at present. The Thoracosphaeraceae (Peridiniales) are the only group of the Alveolata that include members with calcareous coccoid stages; this trait is considered apomorphic. Although the coccoid stage apparently is not calcareous, Bysmatrum has been assigned to the Thoracosphaeraceae based on thecal mo...
Calcareous sediments are located in temperate and tropical areas near offshore hydrocarbon industries and petrochemical reserves such as the Persian Gulf of Iran. These sediments have complicated physical properties which make them completely different from silicate soils. Carbonate sediments are mainly formed by the skeletal remains of marine organisms. Therefore, a wide variety of engineering...
Based on morphological and molecular data, calcareous dinoflagellates (Thoracosphaeraceae, Peridiniales) are a monophyletic group comprising the three major clades Ensiculifera ⁄Pentapharsodinium, Thoracosphaera ⁄Pfiesteria, and Scrippsiella sensu lato. We used stratigraphically well-documented first occurrences of particular archeopyle types to constrain relaxed Bayesian molecular clocks appli...
Tropical coastal marine ecosystems including mangroves, seagrass beds and coral reef communities are undergoing intense degradation in response to natural and human disturbances, therefore, understanding the causes and mechanisms present challenges for scientist and managers. In order to protect our marine resources, determining the effects of nutrient loads on these coastal systems has become ...
There are large agricultural areas in the world where wheat yields are limited by low phosphorus (P) availability. Breeding for P uptake and P utilization efficiency may reduce this problem. This study was conducted to determine the contribution of P uptake and utilization efficiency to grain yield of selected spring wheat genotypes in different environments. Thirty-eight semidwarf spring bread...
Ocean acidification represents a pervasive environmental change that is predicted to affect a wide range of species1,2, yet our understanding of the emergent ecosystem impacts is very limited. Many studies report detrimental effects of acidification on single species in lab studies, especially those with calcareous shells or skeletons3–5. Observational studies using naturally acidified ecosyste...
نمودار تعداد نتایج جستجو در هر سال
با کلیک روی نمودار نتایج را به سال انتشار فیلتر کنید