overlying

Overlying is the descriptive term for a relationship in which one feature lies on top of another. It functions as both a present participle of the verb overlie and as an adjective to characterize the higher in a vertical sequence. The concept is used in several fields to express a positional or temporal order, often with implications for age, deposition, or function.

In geology and stratigraphy, the overlying unit lies above the underlying unit and is typically younger according to the law of superposition. This relationship helps interpret depositional history and structural disturbance, and is described in maps and sections by noting the overlying bed, the contact between units, and any unconformities where deposition ceased before overlying occurred. Examples include sandstone overlying shale or a cap rock lying atop other formations.

In biology and medicine, overlying describes tissues or membranes that lie on top of another structure, such as mucosa overlying cartilage or skin overlying a lesion, indicating a superficial location relative to deeper tissues. In engineering and geotechnical contexts, overlying soils or sediments affect load transfer, groundwater flow, and stability, such as the cover on a foundation or underground structure.

Limitations include complications from tilting, erosion, or faulting, which can obscure simple vertical order. When used carefully, the term helps convey the arrangement and relative ages or functions of layered or layered-like features.