在古比奥 (意大利) 的白-第三纪边界跨越1000万年来的形状
W Alvarez1, F Asaro, A Montanari
1Department of Geology and Geophysics, University of California, Berkeley 94720, USA.
概括
在白-第三纪 (KT) 边界的异常显示了复杂的细结构,不完全由单独的冲击解释. 这种详细的分析完善了我们对KT事件和大规模灭绝的理解.
科学领域:
- 地质化学 地质化学
- 古生物学的古生物学
- 行星科学 行星科学
背景情况:
- 在白-第三纪 (KT) 边界的异常表明外星撞击事件与大规模灭绝相吻合.
- 之前在意大利古比奥 (Gubbio) 进行的基于有限样本的研究,导致对这种异常的解释.
- 关于在KT边界的形状和起源的确切形状和起源仍然存在争议.
研究的目的:
- 为了对Gubbio KT边界的异常进行更详细的调查.
- 为了澄清分布的细结构和潜在原因.
- 改进对KT事件及其相关大规模灭绝的理解.
主要方法:
- 一个57米厚的地质序列的分析,跨越1000万年.
- 利用改进的中子激活分析 (NAA) 技术进行精确的度测量.
- 在KT边界层检查了的分布.
主要成果:
- 确认了一个单一的,明显的异常,恰好在KT边界.
- 异常呈现出复杂的细结构,特别是在侧面的"尾巴"中.
- 的度峰值 (3000 ppt) 位于1厘米的粘土层中,其尾部在背景 (12-13 ppt) 上方为20-80 ppt.
结论:
- 在Gubbio KT边界的详细的形状具有复杂的细结构.
- 诸如再加工,扩散,生物化 (挖掘) 和米兰科维奇周期性等因素可能有助于异常的细结构.
- 这种细结构的确切起源需要进一步调查,完善冲击事件模型.
相关概念视频
Spanning Openings in Brick Walls
In brick wall construction, supporting structures are crucial for openings like windows and doors to maintain the integrity and support the weight of the wall above. These supports include lintels, corbels, and arches, each serving specific structural purposes.
Lintels are primary supports used to span openings and can be crafted from materials such as reinforced concrete, steel-reinforced brick masonry, or simple steel angles. These are straightforward to install and are typically concealed...
Lintels are primary supports used to span openings and can be crafted from materials such as reinforced concrete, steel-reinforced brick masonry, or simple steel angles. These are straightforward to install and are typically concealed...
The Buckingham Pi Theorem
The Buckingham Pi theorem provides a structured method to simplify fluid dynamics problems by reducing complex systems of variables to dimensionless terms.
Design Example: Marking Boundaries of a Site Using a Compass
Marking site boundaries using a compass is a precise surveying technique that ensures the accuracy of boundary delineation. The process begins by using provided site details, including the bearings and lengths of each boundary line. The initial step involves calculating latitudes and departures for all sides of the site. This computation verifies that the traverse is free of errors, ensuring a closed and accurate boundary.The process starts at a known point, such as Point A, which is often...
Indeterminate Products
Indeterminate forms also arise in the evaluation of limits involving products, particularly when one factor approaches zero while the other tends to positive or negative infinity. This situation, commonly described as a zero-times-infinity form, does not have an immediately interpretable outcome. Depending on how the factors behave relative to one another, the limit of such a product may be zero, infinite, or a finite nonzero value.Product Limits and Algebraic RewritingTo analyze limits of this...
Extended Versions of Green’s Theorem
Green’s Theorem connects the circulation of a vector field around a closed curve with the behavior of the field across the region enclosed by that curve. It provides a way to replace a line integral around a boundary with a double integral over the interior region, making it especially useful in plane geometry, fluid flow, and vector calculus.Although Green’s Theorem is often introduced using simple regions without gaps, it can also be applied to regions made from several simple parts. This...
Divergence Theorem in 3D Space
In vector calculus, flux measures the total flow of a vector field through a surface. For a closed surface in three-dimensional space, this means measuring how much of the field passes outward through every point on the boundary. Directly calculating this flux can be difficult when the surface has a complicated or irregular shape. The Divergence Theorem provides a powerful alternative by relating surface flux to behavior inside the enclosed region.The Divergence Theorem states that the outward...


