Final answer:
The western and eastern zero lines on a geologic map may indicate transitional areas between erosion and deposition. Determination of the source and direction of clastic sediment transport requires analysis of lithofacies and isopach lines. Specific data from the geologic map is necessary to make definitive interpretations.
Step-by-step explanation:
The concept of western and eastern zero lines pertains to the geologic provinces and sedimentary processes. Typically, a zero line refers to a theoretical line where no net sedimentation occurs, and it is identified based on underlying geologic structures and sedimentary patterns. For instance, an erosional zero line would indicate an area of net erosion, while a depositional zero line would indicate an area of net deposition. As such, the western and eastern zero lines on a geologic map may represent the transition between these two processes depending on the context provided by the map and accompanying information such as isopach lines, which indicate sediment thickness, and lithofacies, which describe rock types and depositional environments.
To determine the source of clastic sediment and the direction of sediment transport, one must analyze the arrangement and patterns of lithofacies and isopach lines. Clastic sediments transported from a source area will display a fining upward sequence and the isopach lines will typically thin away from the source. Moreover, if the sediments are found to dip towards a particular direction, this can indicate the direction of both past sediment transport and tectonic forces.
Without specific figures and data, it is not possible to confidently affirm the erosional or depositional nature of the zero lines or to identify the precise location and direction of sediment transport. However, the principles outlined here are used by geologists to interpret such maps and understand the geologic history of a region.