Jen here –
This past weekend several students, myself, and my lab mate Maggie went to a fossil locality near Hopkinsville, Kentucky. This rock is from the Mississippian and this locality is particularly interesting to me because of the amount of blastoids you can find in a single moment. They are falling right out of the rock! So we went with a specific question to answer. We are looking to better understand the gap in fossil preservation within some of the blastoids there. Let me explain some – there are specimens that range from 0.25 – 15 mm in height. But most scientists ignore everything below 5 mm because it falls apart more easily than the larger specimens.
Recently we have examined some of the very tiny (0.25 mm) specimens and we are interested to see how the growth of the organism may be affecting its ability to preserve in the rock record! So we did some surface collecting – looking around on the ground and picking up specimens that we can see with our eyes. We also did a lot of bulk collecting. By bulk collecting I mean we filled buckets of sediment with a shovel to take home with us. We will then sieve all the sediment to differentiate the different sizes of the specimens. We will have several different sieve sizes from 5 mm all the way to 64 microns (very tiny material). We will clean everything so that we can sort through the different sizes to find what we are looking for – pieces of small blastoids!
The fossils are found in limestone beds (see by Maggie’s leg – there is a bench like extension from the rock) and in the shale layers (drab gray colored rock that makes up most of the bottom) that occur between the limestone beds. The big rock on top of them is sandstone and is part of an ancient river system.