Journal of Earth System Science ( IF 1.3 ) Pub Date : 2020-10-28 , DOI: 10.1007/s12040-020-01476-z M Venkateshwarlu
Abstract
Magnetostratigraphy or magnetic polarity stratigraphy (MPS) is constructed with paleomagnetic parameters for the Campanian–Maastrichtian (Upper Cretaceous) onshore sediment sequences of the Cauvery Basin, southern India. Twenty-nine sedimentary outcrops in the vicinity of Ariyalur district of Tamil Nadu, India were studied using AF (5–150 mT) and thermal demagnetization (100–700°C). The observed remanence carrier is attributed to hematite through rock magnetic experiments. The virtual geomagnetic pole (VGP) latitudes were computed using the acquired characteristic remanent magnetization (ChRM) directions. The mean ChRM produce Dm= 338, Im= –38, (α95=23.91°, k = 15.73, N=60). The mean VGP is estimated at 51.33°N, 292.71°E deriving a paleolatitude of 21.3°S. The constructed magnetic polarity stratigraphy (MPS) is correlated with the standard geomagnetic polarity time scale (GPTS). The composite MPS of these sequences comprises of 12 magnetozones (6 normal and 6 reversed events) that are corroborated with Chron C33n to Chron C30n of the GPTS. The derived paleolatitude position from the present study places Indian subcontinent at little shallow southern latitudes indicating moderately higher drift velocities during Upper Cretaceous.
Research Highlights
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Magnetic polarity stratigraphy (MPS) is constructed with paleomagnetic parameters for the Campanian–Maastrichtian (Upper Cretaceous) onshore sediment sequences of the Cauvery Basin, southern India.
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The mean direction results in the declination at 338° and inclination at –38° (α95= 23.91) and the pole position at 51°N, 293°E with a paleolatitude of 21.3°S.
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The MPS of Ariyalur Group sequences of Cauvery Basin recorded 12 magnetozones (6 normal and 6 reversed events) and correlated with GPTS of LaBrecque et al. (1977) from Chron C33n to Chron C30n.
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The paleolatitude position highlights the higher velocities of the drift of the Indian subcontinent during Upper Cretaceous period.
中文翻译：
印度南部Cauvery盆地沉积物的新古地磁极和地层
摘要
利用印度南部Cauvery盆地的Campanian-Maastrichtian（上白垩统）陆上沉积序列的古地磁参数构造了磁地层学或磁极地层学（MPS）。使用自动对焦（5-150 mT）和热消磁（100-700°C）研究了印度泰米尔纳德邦Ariyalur地区附近的29个沉积露头。通过岩石磁性实验，观察到的剩磁载体归因于赤铁矿。使用获取的特征剩磁（ChRM）方向计算虚拟地磁纬度（VGP）纬度。平均CHRM产生DM = 338，林= -38，（α 95 = 23.91°，ķ = 15.73，Ñ= 60）。平均VGP估计为51.33°N，292.71°E，古纬度为21.3°S。构造的磁极地层学（MPS）与标准地磁极性时标（GPTS）相关。这些序列的复合MPS包含12个磁区（6个正常事件和6个反向事件），它们与GPTS的Chron C33n至Chron C30n确证了。从本研究得出的古纬度位置将印度次大陆置于南部浅水区的一点浅处，表明在上白垩纪期间漂移速度适度较高。
研究重点
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利用印度南部Cauvery盆地的Campanian-Maastrichtian（上白垩统）陆上沉积序列的古地磁参数构造了磁极地层学（MPS）。
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平均方向导致在赤纬338°及倾斜可以在-38°（α 95 = 23.91），并在51°N，293°E杆位21.3一个古纬度°S。
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Cauvery盆地Ariyalur群序列的MPS记录了12个磁区（6个正常事件和6个反向事件），并与LaBrecque等人的GPTS相关。（1977）从Chron C33n到Chron C30n。
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古纬度位置突显了上白垩纪印度次大陆的较高漂移速度。
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