This usually requires what is commonly known as a "dating method".
Several dating methods exist, depending on different criteria and techniques, and some very well known examples of disciplines using such techniques are, for example, history, archaeology, geology, paleontology, astronomy and even forensic science, since in the latter it is sometimes necessary to investigate the moment in the past in which the death of a cadaver occurred.
Radiocarbon analysis of the early archaeological site of Nauwalabila I, Arnhem Land, Australia: implications for sample suitability and stratigraphicintegrity Auteur(s) / Author(s) BIRD M. has been recently been significantly strengthened by their announcement of a similar age for the basal deposits of a second Arnhem Land site, Nauwalabila I, 65-70 km south of Malakunanja II. At Nauwalabila I a sequence of five OSL dates are also in stratigraphic order The three oldest samples are 30,000 2400 years (Ox ODK166) from 1.70-1.75 m depth below surface; 53,400 5400 years (Ox ODK168) from 2.28-2.40 m; and 60,300 6,700 years (Ox ODK169) from 2.85-3.01 m. (1991) propose a maximum underestimation of 3000 years between 18,000 years ago and 40,000 years ago and a negligible difference between 45,000 years ago and 50,000 years ago. (1993) indicate that a determination of 18,000 radiocarbon years represents almost 22,000 calendar years.
A very old, but not impossibly old, date for Aborigines in Northern Australia. I’ve had a look around and the thermoluminesence dates from the site seem to agree with the 50,000 date, as do dates from Malakunanja II The case of Roberts et al.
So a 60,000 year old entry date to Australia is completely possible.
When did humans first arrive in greater Australia and why is it important to know? O’Connell, Jim Allen James O’Connell is Professor of Anthropology at the University of Utah.
Strategies for screening samples for suitability include (i) microscopic examination, (ii) not analysing samples unless they survive the full ABOX pretreatment, (iii) not analysing samples unless the material is significantly larger than the sediment matrix, (iv) using CHN analysis on both untreated and pretreated material to check for organic contamination and (v) using stepped combustion to check for concordancy in the ages of carbon released at successively higher temperatures.
The results point to the need for careful assessment of the suitability of charcoal for radiocarbon dating prior to analysis and to the dangers of relying on a small number of radiocarbon dates in the development robust site chronologies.
Both chemical alteration and physical translocation of charcoal contributed to the aberrant ages at depth in the deposit.
Based on sediment characteristics and the distribution of quartz, chert, quartzite and quartz crystal’ artefacts, there is no evidence that there has been significant vertical displacement of artefacts relative to the surrounding sand matrix.
Prior to this he was the Foundation Professor of the same department.