黑马 U-Pb 约会 雪球地球 融水事件
Liam Courtney-Davies1, Rebecca M Flowers1, Christine S Siddoway2
1Department of Geological Sciences, University of Colorado Boulder, Boulder, CO 80309.
概括
科罗拉多州的塔瓦卡维砂岩注射矿揭示了冰时期冰时期的罕见陆地记录. 这项研究提供了在融水事件期间潜冰层沙子注入的证据,支持全球冰盖理论.
科学领域:
- 地质地质地质地质地质地
- 古气候学 古气候学
- 沉积物学的沉积物学
背景情况:
- 雪球地球假设假设在冷纪 (720-635万年前) 期间存在全球冰盖.
- 以前的冷期冰川的证据主要是在海洋环境中发现的,这限制了对陆地冰川过程的理解.
- 需要一种罕见的陆地记录才能充分理解低度冰川事件.
研究的目的:
- 调查科罗拉多州的Tavakaiv (Tava) 砂岩注射岩和山脊,作为冷纪冰期的陆地记录.
- 分析塔瓦矿床的地质特征和地质年代学,以了解冰下过程.
- 提供关于在冰下环境中沙子注入和流化机制的见解.
主要方法:
- 详细地质地图绘制和分析注射石,山脊和化学气候变化的晶状岩石.
- 在 hematite U-Pb 地质年代学上的 hematite-quartz 静脉,以确定沙子注射事件的日期.
- 与现代类似物进行比较,例如南极洲的罗斯海峡,用于冰下流体动力学.
主要成果:
- 塔瓦沉积物表现出流体化和变形的特征,表明存在冰下环境.
- 沙子注入事件的年代约为690-660万年前,使用U-Pb地质年代学.
- 早期注射与裂变和地热加热的基底融化有关,而晚期注射与斯图尔特期 (约661万年前) 的脱冰相对应.
结论:
- 塔瓦砂岩注射岩提供了对低度冰川的关键陆地证据.
- 冰川负荷,流体过压和融水事件导致了沙子注入和变形在冰川下.
- 深层化学气候变化早于冷时代的沙子注入,这表明冰川侵蚀有限,与雪球地球条件一致.
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