Condensed ammonoid beds of the Hallstatt facies (Anisian-Ladinian) are widespread around the Ancient Theatre of Epidaurus,in the locality Theokafta of the Argolis Peninsula (eastern Peloponnesus).The Hallstatt Formati...Condensed ammonoid beds of the Hallstatt facies (Anisian-Ladinian) are widespread around the Ancient Theatre of Epidaurus,in the locality Theokafta of the Argolis Peninsula (eastern Peloponnesus).The Hallstatt Formation in Argolis appears,generally,in the form of lensoid bodies of variable sizes,inclination and direction and is always found overlying a formation consisting of keratophyric tuffs.In fact,the contact of the keratophyric tuffs with the overlying limestones,specifically evidenced by an in situ brecciated zone,is stratigraphic and constitutes the base of the Hallstatt Limestones.The contact of the Hallstatt Limestones with the overlying radiolarites is stratigraphic as well.Lithofacies and biostratigraphic research has focused on the lowermost horizons of the Hallstatt Limestones of Anisian age (average thickness about 1.30 m),where a dense sampling has been performed,followed by detailed facies analysis.The lowermost horizons of the Hallstatt Limestones of Theokafta represent typical hiatus beds/concretions sensu Wetzel and Allia (2000),characterized by discontinuous sedimentation and erosion.They consist of red ammonoid-bearing hemipelagic limestones with calcium carbonate nodules floating in an enriched Fe-oxides matrix with dispersed lensoid/prismatic calcium carbonate crystals.This part of the section is characterized by condensed sedimentation,due to significant lowering of the rate of sedimentation and includes omission surfaces,firmgrounds and hardgrounds along certain horizons.Nine lithostratigraphic units have been distinguished in the lowermost horizons of the Hallstatt Limestones,including radiolarian packstones,volcaniclastic facies,packstones/floatstones with ammonoids and lag deposits.Tselepidis (2007) defined nine distinct ammonoid biozones from the Anisian to Ladinian,documenting deposition of the Hallstatt facies during a low depositional rate over nearly 5 million years (using the timescale of Gradstein et al.,2004).The biozones:Japonites/Paracrochordiceras,Hollandites,Procladiscites展开更多
基于行星会合指数运动学方程,推演出太阳质心到太阳系质心距离变化的计算公式,并利用该公式重建太阳质心相对于太阳系质心的距离变化时间序列,作为太阳轨道运动的替代性指标,使用聚合经验模态分解(Ensemble empirical mode decompositio...基于行星会合指数运动学方程,推演出太阳质心到太阳系质心距离变化的计算公式,并利用该公式重建太阳质心相对于太阳系质心的距离变化时间序列,作为太阳轨道运动的替代性指标,使用聚合经验模态分解(Ensemble empirical mode decomposition,EEMD)方法分析0~25.0 ka BP太阳质心到太阳系质心的距离与Δ^14C时间序列。结果显示:两者均存在蕴含~2300 a周期(Hall⁃statt cycle)的IMF分量;互相关分析证实两者蕴含的Hallstatt周期分量间具有相关性,0~13.9 ka BP与13.9~25.0 ka BP年代相关系数分别可达0.52、0.44,并且太阳质心到太阳系质心距离的变化超前于太阳活动指标Δ^(14)C的变化。表明太阳质心远离太阳系质心时,大气^(14)C含量增加,对应于太阳活动较弱的时期;太阳质心靠近太阳系质心时,大气^(14)C含量减小,对应于太阳活动较强的时期。这一认识对于进一步探究太阳活动Hallstatt周期的成因机制提供了新的依据和思路。展开更多
文摘Condensed ammonoid beds of the Hallstatt facies (Anisian-Ladinian) are widespread around the Ancient Theatre of Epidaurus,in the locality Theokafta of the Argolis Peninsula (eastern Peloponnesus).The Hallstatt Formation in Argolis appears,generally,in the form of lensoid bodies of variable sizes,inclination and direction and is always found overlying a formation consisting of keratophyric tuffs.In fact,the contact of the keratophyric tuffs with the overlying limestones,specifically evidenced by an in situ brecciated zone,is stratigraphic and constitutes the base of the Hallstatt Limestones.The contact of the Hallstatt Limestones with the overlying radiolarites is stratigraphic as well.Lithofacies and biostratigraphic research has focused on the lowermost horizons of the Hallstatt Limestones of Anisian age (average thickness about 1.30 m),where a dense sampling has been performed,followed by detailed facies analysis.The lowermost horizons of the Hallstatt Limestones of Theokafta represent typical hiatus beds/concretions sensu Wetzel and Allia (2000),characterized by discontinuous sedimentation and erosion.They consist of red ammonoid-bearing hemipelagic limestones with calcium carbonate nodules floating in an enriched Fe-oxides matrix with dispersed lensoid/prismatic calcium carbonate crystals.This part of the section is characterized by condensed sedimentation,due to significant lowering of the rate of sedimentation and includes omission surfaces,firmgrounds and hardgrounds along certain horizons.Nine lithostratigraphic units have been distinguished in the lowermost horizons of the Hallstatt Limestones,including radiolarian packstones,volcaniclastic facies,packstones/floatstones with ammonoids and lag deposits.Tselepidis (2007) defined nine distinct ammonoid biozones from the Anisian to Ladinian,documenting deposition of the Hallstatt facies during a low depositional rate over nearly 5 million years (using the timescale of Gradstein et al.,2004).The biozones:Japonites/Paracrochordiceras,Hollandites,Procladiscites
文摘基于行星会合指数运动学方程,推演出太阳质心到太阳系质心距离变化的计算公式,并利用该公式重建太阳质心相对于太阳系质心的距离变化时间序列,作为太阳轨道运动的替代性指标,使用聚合经验模态分解(Ensemble empirical mode decomposition,EEMD)方法分析0~25.0 ka BP太阳质心到太阳系质心的距离与Δ^14C时间序列。结果显示:两者均存在蕴含~2300 a周期(Hall⁃statt cycle)的IMF分量;互相关分析证实两者蕴含的Hallstatt周期分量间具有相关性,0~13.9 ka BP与13.9~25.0 ka BP年代相关系数分别可达0.52、0.44,并且太阳质心到太阳系质心距离的变化超前于太阳活动指标Δ^(14)C的变化。表明太阳质心远离太阳系质心时,大气^(14)C含量增加,对应于太阳活动较弱的时期;太阳质心靠近太阳系质心时,大气^(14)C含量减小,对应于太阳活动较强的时期。这一认识对于进一步探究太阳活动Hallstatt周期的成因机制提供了新的依据和思路。
