Paleomagnetism of the Carboniferous-Permian Patquía Formation, Paganzo basin, Argentina: implications for the apparent polar wander path for South America and Gondwana during the Late Palaeozoic
Paleomagnetism of the Carboniferous-Permian Patquía Formation, Paganzo basin, Argentina: implications for the apparent polar wander path for South America and Gondwana during the Late Palaeozoic
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阿根廷帕甘佐盆地石炭纪-二叠纪帕基亚地层的古地磁：对晚古生代南美洲和冈瓦纳大陆明显的极地漂移路径的影响
DOI：
10.1344/105.000001578
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发表时间：
2010
期刊：
影响因子：
1.5
通讯作者：
C. Limarino
中科院分区：
文献类型：
--
作者：
S. Geuna;L. Escosteguy;C. Limarino
本文研究了阿根廷帕甘佐盆地（Paganzo Basin，Argentina）乌芒山脉（Sierra de Umango）蓬塔德尔维恩托（Punta del Viento）和一些已报道的地点的石炭-二叠纪Patquia组红层的磁性。而所有网站的特点是由赤铁矿作为主要的磁性载体和反极性的剩磁，我们发现了一个模式的变化，磁性能沿着集成列Patquia形成。下段（晚石炭世）表现出更高的自然和饱和等温剩磁强度（NRM和SIRM，分别）比二叠纪上段。NRM强度从Patquia组下段到上段的下降可能与赤铁矿颜料的数量和/或粒度变化有关，这可能反映了环境和/或沉积背景的变化。至于NRM的方向值，两个剖面的古地磁极报告明显不同。下段提供了一个与晚石炭世冈瓦纳古陆极点一致的极点位置，而上段的极点则偏离了早二叠世的位置。我们无法确定上段磁极是由于290 Ma的初次磁化还是由于~260-270 Ma的再磁化;即便如此，获得的古磁极还是稳健的，表明在晚石炭世下部沉积之后，该区域在~ 30 o逆时针旋转中出现了快速明显的极移，并且与圣拉斐尔造山期相一致。
The magnetic properties of the Carboniferous-Permian red beds of the Patquia Formation at Punta del Viento, Sierra de Umango and some previously reported localities, all in the Paganzo Basin (Argentina), have been studied. Whereas all sites are characterized by hematite as the main magnetic carrier and a reversed-polarity magnetic remanence, we found a pattern of variation in magnetic properties along the integrated column for Patquia Formation. The Lower Member (Late Carboniferous) showed higher intensity of natural and saturation isothermal remanent magnetisation (NRM and SIRM, respectively) than the Permian Upper Member. The fall in NRM intensity from the Lower to Upper Member of the Patquia Formation may be related to a change in quantity and/ or grain-size of the hematite pigment, which may reflect the change in environmental and/or depositional setting. As for directional values of NRM, paleomagnetic poles reported for both sections are clearly different. The lower section provided a pole position coincident with Late Carboniferous poles for Gondwana, while the upper section poles are departed from the Early Permian position. We cannot decide whether the Upper Member pole is due to a primary magnetisation at 290 Ma or to a remagnetisation at ~260-270 Ma; even so, the obtained paleomagnetic pole is robust and indicates a rapid apparent polar wander in a ~30o counter clockwise rotation of the region, after deposition of the Late Carboniferous lower section, and in coincidence with the San Rafael Orogenic Phase.