Actively decaying or just poorly preserved? Can we tell when plant and invertebrate remains in urban archaeological deposits decayed?

We have recendy argued that poorly preserved delicate macrofossil remains of plants and invertebrates in near-surface deposits in York are in active decay, rather than being preserved in stasis, part-way down the decay trajectory. Observations of both archaeological and modern deposits suggest empirically that remains either survive for a long period (if conditions are conducive) or decay rapidly (if they are not). The hypothesis that very gradual decay has led to large numbers of deposits containing remains in a similar state appears illogical. It is more likely that, where poorly preserved biological remains are found, they either decayed in the past and then were stabilised when ground conditions became anoxic, or are currently in decay. Long-term patterns of decay cannot easily be investigated experimentally, but arguments concerning patterns and rates of decay can be. Apart from the question of in-ground preservation, understanding patterns of decay will allow us to address a range of taphonomic problems fundamental to drawing archaeological information from these remains.