What if there are several materials found in sediment (e.g. wood, charcoal, seeds) but each one does not meet the lab’s minimum sample size requirement, can a mixture of materials be dated?
The first thing to do is to consult the lab which component in the mixture is best for radiocarbon dating. Sending a mixture for dating is okay, but the accuracy of the date may be compromised. If all the materials are the same age, then there is no effect to the accuracy. If the materials are of different ages (wood from very old trees mixed with seeds from the time of sediment formation), then the result will be biased towards the older result. It is up to the researcher to decide which is best for their study.