Hydrogeological overview map of Lower Saxony 1: 200 000 — thickness of the upper aquifer complex

The map “Hydrogeological overview map of Lower Saxony 1: 200 000 — thickness of the upper aquifer complex” illustrates the large-scale distribution and thickness (in meters) of the upper supraregionally important aquifer complex. Depending on the information density, the information on the thickness is summarised more or less strongly. In this map representation, aquifers are classified as all sands (up to the fine sand area) and gravel whose silt or clay content is less than 5 %. For example, due to the layer description, a very weakly sloppy fine sand is still referred to as a groundwater conductor, while a weakly sloppy fine sand is described as low water conductive. In the loose rock regions of Lower Saxony, two superordinate aquifer complexes are distinguished. The upper aquifer complex consists of sands and gravel of the Pleistocene, as well as sands of the Pliocene and the Uppermiocene. The lower aquifer complex consists of permeable sediments of the sub- to middle-miocene, the so-called lignite sands. The two aquifer complexes are separated by the groundwater inhibitor Oberer Glimmerton, which consists of sloppy-tone sediments of the middle to upper miocene. In the areas where the Upper Glimmerton is missing as a separating intermediate layer (groundwater inhibitor), only one aquifer complex is usually formed — in large-scale terms. This case occurs both in the area of deep cut gutters, as well as in the area of highly elevated salt sticks. In the eastern part of Lower Saxony, the Upper Glimmerton has been demolished extensively. In the map, only one aquifer complex is presented in these areas and is referred to as the upper aquifer complex, although in these areas it is also attributed to the permeable sediments of lignite sands, which otherwise form the lower aquifer complex. The base of the upper aquifer complex is therefore either the upper micaton or, in the absence of it, sub-miocene to oligocene clay and mud. On the map, two areas are distinguished in the color scale: 1. Areas in which the aquifer complex is divided, i.e. the Upper Glimmerton is widespread and separates an upper floor from a lower floor. 2. Areas where the aquifer complex is unstructured because either the separation layer micaton is missing or a lower submiocene aquifer is not formed. It is possible that regionally other low-permeable sediments, such as quaternary basin entones, can assume the function of separating intermediate layers, which then cause a spatially limited division of the aquifer complex into two or more aquifers. On the basis of the available data, however, too little statements can be made about the area-like spread of low permeable quarterly sediments, since they do not have a constant appearance over larger areas like the micaton, but can also be formed very differently over short distances in their facies. Therefore, they cannot be taken into account in this overview map, although they are often of great importance for regional groundwater hydraulics. The depth of the base of the upper aquifer complex is shown in a separate map.本数据集涵盖的地图为《下萨克森州1:200 000水文地质概图——上部含水层复合体（aquifer complex）厚度》，该图展示了超区域重要的上部含水层复合体的大范围分布特征与厚度（单位：米）。根据信息密度差异，厚度相关信息会进行不同程度的汇总简化。 在该地图的图例分类中，含水层被划分为所有砂类（细砂级及以上）以及粉粒或黏土含量低于5%的砾石。例如，依据地层描述，极弱黏塑性细砂仍被划归为导水层（groundwater conductor），而弱黏塑性细砂则被归类为弱导水层。 在下萨克森州的松散岩石分布区，可区分出两类上层含水层复合体。上部含水层复合体由更新世（Pleistocene）砂与砾石、上新世（Pliocene）砂以及晚中新世（Uppermiocene）砂组成；下部含水层复合体则由中新世（Miocene）中下部的渗透性沉积物构成，即所谓的褐煤砂（lignite sands）。两类含水层复合体被作为隔水层（groundwater inhibitor）的上灰泥层（Oberer Glimmerton）分隔，该层由中新世中上部的黏塑性沉积物组成。 当上灰泥层作为分隔中间层缺失时，大范围区域内通常仅存在单一含水层复合体。这种情况既出现在深切沟谷区域，也见于高凸起的盐丘区域。在下萨克森州东部区域，上灰泥层已被大范围剥蚀，因此该类区域的地图仅展示单一含水层复合体，并将其标注为上部含水层复合体——尽管在该区域，这些沉积物同时也属于原本构成下部含水层复合体的褐煤砂渗透性沉积物。因此，上部含水层复合体的基底要么为上灰泥层，若缺失该层则为中新世亚阶至渐新世（oligocene）的黏土与泥质沉积物。 本次地图的色标区分两类区域：1. 含水层复合体存在分层的区域，即上灰泥层广泛分布，将上部含水层与下部含水层分隔开的区域；2. 含水层复合体无分层结构的区域，要么是分隔层上灰泥层缺失，要么是未形成下部中新世亚阶含水层的区域。 局部区域可能存在其他低渗透性沉积物（如第四纪（quaternary）盆地相沉积物（quaternary basin entones）），起到分隔中间层的作用，进而使含水层复合体在空间上被分割为两个或多个含水层。但基于现有数据，难以对低渗透性第四纪沉积物的区域分布做出可靠判断：这类沉积物无法像上灰泥层那样在大范围区域内保持稳定的产出特征，其岩相在短距离内即可发生显著变化。因此，尽管这类沉积物往往对区域地下水水力学具有重要意义，本概图并未将其纳入考量。上部含水层复合体的基底深度将在独立配套地图中予以展示。