In the ideal case, the geologist will discover a single rock unit with a unique collection of easily observed attributes called a marker horizon that can be found at widely spaced localities.Any feature, including colour variations, textures, fossil content, mineralogy, or any unusual combinations of these can be used.It is only by correlations that the conditions on different parts of Earth at any particular stage in its history can be deduced.In addition, because sediment deposition is not continuous and much rock material has been removed by erosion, the fossil record from many localities has to be integrated before a complete picture of the evolution of life on Earth can be assembled.A coin, vessel, or other common artifact could link two archaeological sites, but the possibility of recycling would have to be considered.
Some method of correlating rock units must be found.These results provide new insight into the evolution of the Moulouya River, which does not appear to be mainly climatically driven, unlike many European rivers.Instead the results highlight the key role of tectonic activity in the landscape evolution of northeast Morocco and suggest and an acyclic and discontinuous sedimentation pattern since 1.5 million years ago, which seemingly rules out climate as a main driver in fluvial deposition.At a regional scale, several indicators point to transient fluvial response resulting from major tectonic activity in this area, especially rock uplift in the Beni Snassen massif.The latter strongly influenced drainage organisation, and therefore landscape evolution, in northeast Morocco.Dating, in geology, determining a chronology or calendar of events in the history of Earth, using to a large degree the evidence of organic evolution in the sedimentary rocks accumulated through geologic time in marine and continental environments.To date past events, processes, formations, and fossil organisms, geologists employ a variety of techniques."This is one of the first large-scale attempts in which we can directly compare different dating approaches on the exact same stratigraphic section," Dr Duval said."The different dating methods have yielded very consistent results, giving us confidence in their robustness." Although additional dating analyses have to be carried out in the area to confirm these initial promising results, the study nevertheless strongly suggests the absence of fluvial deposits younger than 1 million years in the area.This then can be used to deduce the sequence of events and processes that took place or the history of that brief period of time as recorded in the rocks or soil.For example, the presence of recycled bricks at an archaeological site indicates the sequence in which the structures were built.