(LAC-93) Geologic map of the Mare Humorum region of the moon

The surface of the moon is heterogeneous. Surface materials are classed on the basis of telescopic observations into units each having a limited range of physical properties such as topography, visible under low-illumination and albedo, the reflectivity under full-Moon illumination. Such units are considered analogous to the rock-stratigraphic formations of terrestrial geology. By application of the principles of superposition and intersection, these rock units are arranged in order of relative age and grouped into time stratigraphic units. Following terrestrial contention, the major time-stratigraphic units are designated systems, and their subdivisions, series; corresponding to these units are periods and epochs of time, respectively (Shoemaker, 1962;Shoemaker and Hackman, 1962). The type localities of most of the systems and series recognized to date are in the vicinity of Mare Imbrium. Correlation of many of the rock stratigraphic units of the Mare Humorum region with the rock stratigraphic units of the Mare Imbrium region is still uncertain.

月球表面具有非均质性。基于望远镜观测结果，月面物质可被划分为多个单元，每个单元均具备有限范围的物理属性，例如低光照条件下可观测的地形特征，以及反照率（albedo，即满月光照下的反射率）。此类单元被认为与地球地质学中的岩石地层组具有类比性。通过运用叠置原理与截切原理，可将这些岩石单元按相对年代顺序进行排序，并划分为时间地层单元。遵循地球地质学的通用惯例，主要的时间地层单元被命名为“系”，其亚级细分单元则为“统”；与之相对应的地质年代单位分别为“纪”与“世”（Shoemaker, 1962;Shoemaker and Hackman, 1962）。截至目前，绝大多数已确定的系与统的模式产地均位于雨海（Mare Imbrium）周边区域。洪堡海（Mare Humorum）区域的诸多岩石地层单元与雨海区域岩石地层单元之间的地层对比关系，目前仍不明确。