Buried Quaternary valleys in the south-western Baltic Sea (BurVal-Baltic)

本项目致力于了解构造对潜谷演化的控制作用。隐伏河谷(冰下河道)是指从冰川地体切割成的前第四纪沉积记录中的深沟道形态特征。这些挖方和填方结构在最近的研究中一直是一个激烈的辩论问题，因为它们拥有大量的地下水供应，它们包含用于建筑的集合体，并且通常具有最完整的冰川地质过程和古气候条件的沉积记录。它们的形成一般归因于冰川覆盖时期冰川下的融水输送切割了下伏的地层。一些作者注意到了埋藏的山谷和下面的构造断层之间的空间相关性；然而，从来没有建立起主要的因果相关性。对于所建议的研究，我们拥有一个密集的剖面网格，包括来自波罗的海西南部的大约20.000公里的多通道和大约6.000公里的参数沉积物回声测深仪数据。这些数据首次能够通过解析详细的山谷和山谷充填几何以及下部后二叠纪层序中的断层和褶皱的数据，在盆地范围内研究埋藏山谷的演化。根据对一些剖面的初步解释，我们阐述了以下有待检验的工作假说：1)后二叠世序列被大量的近垂直断层解剖。2)垂直断层附近最大、分布最密集的第四纪与几公里宽、约10m高的背斜有关。3)在某些情况下，观察到的断层-背斜组合与流体垂直运移有关。4)断背斜演化促进并在空间上控制了埋藏峡谷的切割。(5)近垂直断层及其伴生背斜主要由冰载构造作用形成。我们将通过地震解释来探讨这些假设。假设1-4将通过系统绘制和量化埋藏山谷、垂直断层和背斜附近以及流体的地震指示器来验证。冰负荷引起的构造概念是基于之前发表的，但更多的是基于当地的研究。关于这一概念，这里提出的项目是在盆地范围内量化(冰荷引起的)现代构造及其对第四纪地质学意义的第一步，也是关键的一步。如果假设成立，由此产生的模型有可能影响所有暂时被冰覆盖的高纬度地区的第四纪研究。横穿后二叠纪地层的近垂直断层的预期丰度代表了可能的流体运移路径，这将对包括地下水循环模型在内的所有应用构成重要限制。

This project strives for understanding the tectonic control on Buried Valley evolution. Buried Valleys (subglacial channels) are defined as deep channel-form features incised into the pre-Quaternary sedimentary record from glaciated terrains. These cut and fill structures have been a matter of intense debate in recent studies as they hold significant supplies of groundwater, they contain aggregate for construction and typically have a most complete sedimentary record of glacial geological processes and paleo-climate conditions. Their formation is generally attributed to subglacial melt-water transport incising the underlying strata during periods of glacial coverage. Several authors noticed a spatial correlation between Buried Valleys and tectonic faults beneath; however, a principle causative correlation was never established. For the suggested study we hold a dense profile grid comprising ca. 20.000 km of multi-channel and ca. 6.000 km of parametric sediment echosounder data from the south-western Baltic. These data allow for the first time a study of Buried Valley evolution on a basin wide scale by means of data that resolve both the detailed valley and valley fill geometry as well as faults and folds within the Post-Permian succession beneath. According to a preliminary interpretation of some profiles we elaborated the following working hypotheses to be tested: 1) The Post-Permian succession has been dissected by abundant near vertical faults. 2) The largest and most densely spaced Quaternary near vertical faults are associated with few kilometers wide and some 10 m high anticlines. 3) In some instances the observed fault-anticline assemblages are associated with vertical fluid migration. 4) The fault-anticline evolution facilitated and thus spatially controlled the incision of Buried Valleys. 5) The near vertical faults and associated anticlines result mainly from ice-load induced tectonics. We will approach these hypotheses by seismic interpretation. Hypotheses 1-4 will be tested by systematic mapping and quantification of Buried Valleys, near vertical faults and anticlines as well as seismic indicators for fluids. The ice-load induced tectonic concept is based on previously published, but rather local studies. Regarding this concept the here proposed project is a first and crucial step to quantify (ice-load induced) recent tectonics and its meaning for Quaternary geology on a basin wide scale. If the hypotheses hold, the resulting models bear the potential to influence Quaternary research in all regions of high latitudes which were temporally ice-covered. The expected abundance of near vertical faults which cross-cut the post-Permian strata represent possible fluid migration paths, which would represent important constrains for all applications which include models about ground water circulation.