The extent of documentation varied considerably in 'historical' cultures and the information that survives is determined by a variety of factors.
If a context containing burnt debris and broken artefacts is excavated on a site from a historical period, it is tempting to search the local historical framework for references to warfare or a disaster in the region, and to date the excavated context accordingly.
These techniques both place assemblages of artefacts into relative order.
They identified a succession of Ice Ages alternating with temperate conditions (glacials and interglacials) which - if they could be dated - would reveal much about the evolution of early humans in the context of changing environmental conditions.
Cores extracted from ocean floor deposits reveal variations in oxygen isotopes in the shells and skeletal material of dead marine creatures, which reflect fluctuations in global temperature and the volume of the ocean.