Wet-sieving uncovers additional human relics

May 05, 2014 by Geoff Vivian
Dry sieving excavated archaeological deposits in the field at a rockshelter site in the eastern Chichester Range, Pilbara. Credit: Stuart Rapley/Archae-aus

A Western Australian archaeology consultancy has conducted a cost-benefit analysis of improved treatments for sediment samples taken from ancient occupation sites.

Archaeologists examine sediments for evidence of a site's human history.

Archae-Aus research manager Dr Caroline Bird says archaeologists in private practice typically dry-sieve excavated material for private clients, but wet-sieving achieves much better results.

"It was really to see whether the time spent getting the extra data from doing more fine sieving actually was justified in terms of cost," she says.

While wet-sieving is more time consuming than dry-sieving, Dr Bird says it dramatically improves the speed and quality of analysis as it is easier to examine clean gravel than dirty gravel.

She says they prefer to analyse samples of visible strata in a cave floor, but if they detect no change of soil colour they sample "spits" of about five centimetres in depth.

Archae-Aus staff sampled two such spits from one site, and one spit from another, in Nyiyaparli native title lands near Newman in the Pilbara.

They passed the samples through 6mm and 3mm mesh sieves on-site, as per usual practice.

In their Perth laboratory they washed and wet-sieved material caught in the 3mm sieve.

Dr Bird says this resulted in a much better recovery of objects such as charcoal and bone fragments; and artefactual stone remains such as tiny flakes.

She says this gives a much better idea of how the sites were used.

Minute flakes, for example, indicate a tool making site, and also whether toolmakers used local stone or raw materials from another location.

In the paper just published, she cites Langley et al (2011) who notes that wet-sieving can turn up extremely rare items undetectable by dry sieving, such as beads and bone artefacts.

While she is yet to find any of these herself, Dr Bird says they do occasionally occur in Australian ice age sites.

She says samples taken from past excavations in South Africa, and wet-sieved decades later, have resulted in similar finds missed in the original studies.

"In terms of the quality of the result, there's no question that you get a better result," she says.

She says the present study shows wet-sieving costs are 10 – 50 percent higher, depending on the site's complexity.

Consulting archaeologists assess mine sites to comply with the Aboriginal Heritage Act's site protection requirements, and terms laid down under individual Native Title agreements.

Explore further: Archaeologists, tribe clash over Native remains

More information: Bird et al (2014) "Time and efficiency in data recovery: an experiment comparing wet and dry sieving in Pilbara rockshelter excavations," Journal of the Australian Association of Consulting Archeaologists Vol 2 Article 1. 

add to favorites email to friend print save as pdf

Related Stories

Archaeologists, tribe clash over Native remains

Apr 23, 2014

Archaeologists and Native Americans are clashing over Indian remains and artifacts that were excavated during a construction project in the San Francisco Bay Area, but then reburied at an undisclosed location.

Human activity influences beach bacterial diversity

Mar 05, 2014

Human activity influences ocean beach bacterial communities, and bacterial diversity may indicate greater ecological health and resiliency to sewage contamination, according to results published March 5, 2014, in the open ...

Unearthing the history of the Naracoorte Caves

Feb 04, 2014

(Phys.org) —Flinders University researcher Amy Macken has discovered the age of sedimentary layers in the Naracoorte Caves using a cutting-edge computer modelling technique that has never before been used ...

Archaeologists rewrite history of the Trefael Stone

Apr 13, 2012

The Trefael Stone, a scheduled ancient monument in south-west Wales originally thought to be an ancient standing stone is actually the capstone of a 5,500-year-old tomb, according to new research from an archaeologist ...

A wet Moon

Mar 26, 2014

The Moon's status as a "dry" rock in space has long been questioned. Competing theories abound as to the source of the H20 in the lunar soil, including delivery of water to the Moon by comets.

Recommended for you

Secrets of dinosaur ecology found in fragile amber

12 hours ago

Ryan McKellar's research sounds like it was plucked from Jurassic Park: he studies pieces of amber found buried with dinosaur skeletons. But rather than re-creating dinosaurs, McKellar uses the tiny pieces ...

New progress of the Neogene Suidae research

Oct 17, 2014

Dr. Hou Sukuan and Prof. Deng Tao from the Institute of Vertebrate Paleontology and Paleoanthropology(IVPP), Chinese Academy of Sciences reported a new species of Chleuastochoerus from the Linxia Basin, Gansu ...

User comments : 0