Lower Permian brachiopods from Oman: their potential as climatic proxies
Lower Permian brachiopods from Oman: their potential as climatic proxies
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DOI：
10.1017/s1755691008075634
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发表时间：
2008-01-01
影响因子：
1.2
通讯作者：
Jadoul, F.
中科院分区：
文献类型：
--
作者：
Angiolini, L.;Darbyshire, D. P. F.;Jadoul, F.
阿曼内陆豪什盆地的下二叠统(Al Khlata组至Saiwan组/下Gharif段)记录了从冰川作用、通过Haushi海的海洋沉积到亚热带沙漠的气候变化。为了研究好石海的古气候演化，我们在塞湾组类型剖面内逐层采集了8个物种31个腕足类贝壳的0、C和Sr同位素。我们通过扫描电子显微镜的超微结构、阴极发光和地球化学来评估成岩作用，并拒绝了15个不符合特定保存标准的贝壳。螺旋虫和螺旋虫比正节和产物更好地保存了纤维次生层，因此更适合于同位素分析。Delta O-18值为-3.7%至-3.1ppm。塞湾组底部腕足类的化石可能与冰川融水有关。在此之上，O-18三角洲的增加可能表明冈瓦那其他地方的冰聚集，或者更有可能是豪什海是新特提斯洋的一个蒸发海湾。德尔塔C-13的变化很小，在公布的数据范围内：其重值的趋势与日益干旱和营养不良的情况一致。与基于少量数据点外推的SakmarianLoWESS海水曲线相比，Saiwan锶同位素特征的放射性成因较差。在受限制的豪氏盆地蒸发情景中，锶同位素组成的变化可能反映了河流成分。
The Lower Permian of the Haushi basin, Interior Oman (Al Khlata Formation to Saiwan Formation/lower Gharif member) records climate change from glaciation, through marine sedimentation in the Haushi sea, to subtropical desert. To investigate the palaeoclimatic evolution of the Haushi Sea we used 0, C, and Sr isotopes from 31 brachiopod shells of eight species collected bed by bed within the type-section of the Saiwan Formation. We assessed diagenesis by scanning electron microscopy of ultrastructure, cathodoluminescence, and geochemistry, and rejected fifteen shells not meeting specific preservation criteria. Spiriferids and spiriferinids show better preservation of the fibrous secondary layer than do orthotetids and productids and are therefore more suitable for isotopic analysis. delta O-18 of - 3.7 to - 3.1 parts per thousand. from brachiopods at the base of the Saiwan Formation are probably related to glacial meltwater. Above this, an increase in delta O-18 may indicate ice accumulation elsewhere in Gondwana or more probably that the Haushi sea was an evaporating embayment of the Neotethys Ocean. delta C-13 varies little and is within the range of published data: its trend towards heavier values is consistent with increasing aridity and oligotrophy. Saiwan Sr isotope signatures are less radiogenic than those of the Sakmarian LOWESS seawater Curve, which is based on extrapolation between few data points. In the scenario of evaporation in a restricted Haushi basin, the variation in Sr isotope composition may reflect a fluvial component.