Thoughts on stratigraphy and sampling

I came across a paper by Tipper (1998) which reminded me of the importance of looking at stratigraphy in multiple dimensions. In the paper he discusses stratigraphic completeness and the notion of ‘‘spatio-temporal masking’’: the effect when primarily spatial variations mask primarily temporal variations. He then tries to estimate the optimum sizes of the sampling area in order to best estimate the stratigraphic completeness in the field. Admittedly, I did not follow Tipper’s calculations at some parts but two things became clear to me: the problems that this paper discusses are very relevant to specifically micromorphology and micromorphological sampling, and that it is very important to have micromorphology samples of at least two orientations when studying a site. 

Unfortunately, at Umhlatuzana it was only possible to sample the west profile. To solve the problem of having only N-S oriented samples, I ended up cutting some of the thicker samples vertically after impregnation. So, even if they were originally sampled at the west profile, they ended up having an E-W orientation.

The term spatio-temporal masking discussed by Tipper reminded me of the Law of Facies (aka Walther’s Law), a stratigraphic term explaining how depositional environments that are laterally related can become superimposed and result in trans-transgressive sedimentary formations (see more at Karkanans and Goldberg 2018, 163). The Law of Facies is for me one of the most complicated stratigraphic principles to fully comprehend but something you always have to take into account when studying a stratigraphic sequence.

Karkanas, P., & Goldberg, P. (2018). Reconstructing archaeological sites: Understanding the geoarchaeological matrix. Hoboken, NJ: John Wiley & Sons.

Tipper, J.C. (1998). The influence of field sampling area on estimates of stratigraphic completeness. Journal of Geology, 106(6), 727-738.