The Quaternary period begun around 2.4 million years ago (Gibbard et al., 2005).
Its onset is defined by a change in Earth’s climate from stability slow cooling to periods of great instability and fluctuation (Holden, 2005). Subsequently this has been reflected in a great deal of terrestrial environmental change meaning there is a great deal of complexity that lies behind the reconstruction of this period (Lowe & Walker, 2015). One aspect that facilitates reconstruction is through the use of Biological remains (Battarbee, 2000). Biological remains take a variety of aspects; from plants, insects and other animal remains, but also come in a variety of forms, through fossilisation, bone discovery or from samples taken from sedimentary sequences (Holden, 2005).
Further variety is provided through the array of dating techniques; no technique is perfect, all come with a ‘range of problems’ which lead to difficulties in interpreting data, ultimately this means their value can come under scrutiny, and thus undermine their value to reconstruction (Holden, 2005). This essay will explain how if considered individually each element of biological remains are somewhat less valuable than if they are used in conjunction with each other. Biological evidence stemming from plants and animals has ‘always been the cornerstone in the reconstruction of quaternary environments’ (Lowe & Walker, 2015). As such this essay will evaluate the value of plant matter; focusing on pollen, insects and other animals, considering their strengths as well as their shortcomings, to provide an assessment of their overall value to reconstruction.
Some of the earliest attempts of quaternary reconstruction were through pollen analysis (Gajewski, 2008). Since this point its continual use has made it a ‘cornerstone’ in reconstruction (Lowe & Walker, 2015). Meaning experts have been modifying and evolving the process to make it more accurate and thus provide greater value to reconstruction (Bell & Walker, 2005). Palynology is used to reconstruct the quaternary climate, depending on the make-up of pollen assemblage which is preserved in abundance with great diversity enables the deduction of the type of climate that existed at a time (Seppä & Bennett, 2003). The intrinsic link between vegetation, animals and humans means pollen provides an insight into the structure and biomass involved in ecosystems (Holden, 2005). Furthermore, we can make inferences on other aspects of the environment through pollen analysis. By considering the climatic preferences of certain species we are able to make more precise reconstructions of the palaeoclimate. These reconstructions can then be compared either in terms of timescale or location using Isopollen maps (Fig.
1). Figure 1 highlights why this comparative tool is so valuable. Showcasing how one area’s vegetation cover changed with time, based on 11,700 pollen samples provides an informative, well referenced explanation of the terrestrial environmental change (Lowe & Walker, 2015). In Figure 1 we can compare the reduction of ice from being largest in 18 ka, to being completely removed in 6ka, with the growth in deciduous forest from 18 ka to the modern day.
It shows us that the climate has become increasingly temperate and conducive to vegetation growth, this reconstruction is facilitated through palynology which highlights its value.However, whilst this type of biological remains is undoubtedly of great value, it is somewhat undermined by its imperfections. We must also consider the effect degradation can have on the value of pollen analysis. Many fossils show signs of deterioration that stems from leaching and capillary action (Twiddle & Bunting, 2010). Corrosion has been observed in high frequencies where spectra has been fluvially deposited, and often fossil pollen grains show more than one aspect of deterioration (Tweddle & Edwards, 2010). Whilst this does of course degrade the value of this form of biological remains, In some cases, it has been proven that plant communities may have never been in equilibrium with pre-existing conditions. This issue is compounded by limits from instrumental imprecision, and identification is more often on a generic level. Despite the ‘considerable progress’ made in the quality of instrumentation this can lead to incorrect inferences being made (Lowe & Walker, 2015).
The use of pollen influx diagrams (Fig. 2) enables us to overcome the issue of statistical independence, but this still has problems of application and interpretation because variations in rates of deposition will affect pollen accumulation (Lowe & Walker, 2015). These diagrams represent the most difficult part of pollen analysis due to the need for knowledge regarding the production and dispersal of pollen as well as its preservation and connection to plant communities. As a result, it is fair to conclude that when utilising palynologic analysis singularly its value is somewhat marginalised by its imperfections, however when used in line with other aspects of biological remains it formulates the ‘cornerstone’ and is vital to quaternary reconstruction.
