How are fossil small remains recovered?

Figure 1. Myself (B. Moncunill-Solé) and my colleague A. Blanco in the lab conducting the workshop. CC BY-NC-ND 4.0 DEED B. Moncunill-Solé.

These days, we participated in the 12th Symposium on Geology Education that took place in Quiroga (Courel, Galicia) from July 8th to 13th. During the symposium we conducted a screen-washing workshop,so that elementary and secondary school teachers can apply these techniques in their geology classes.

Screen-washing techniques in paleontology are methods used to recover small fossil remains (such as microvertebrates, small invertebrates, and plant remains) from sediment. This technique is crucial because it allows for the retrieval of tiny and delicate fossils that might be overlooked using traditional excavation methods. The process involves several key steps:

1) Collection of Sediment Samples: Sediment samples are gathered from field sites where fossils are likely to be found, such as riverbeds, ancient lake deposits, or other sedimentary environments. The quantity of samples collected depends on the fossil richness of the area, and wether it is a preliminary survey or a larger-scale excavation. 

2) Initial Processing: The collected sediment is first dried, and then soaked in water to disaggregate the particles. This step helps to loosen any fossils embedded within the sediment.

3) Screen-Washing: The disaggregated sediment is poured through a series of nested sieves or screens with different mesh sizes. Water is used to wash the sediment through the screens. The finest mesh screens capture the smallest fossil remains, while allowing smaller sediment particles to pass through.

4) Drying and Sorting: The material caught in the screens is carefully dried and then sorted under a stereomicroscope. Fossil remains, such as tiny bones, teeth, or shells, are meticulously separated from the remaining sediment particles.

Finally, the recovered remains are curated in collections until researchers are ready to identify and analyze them.

Figure 2. A (left). Screenshot of the first slide of the presentation. B (right). Students attending the workshop. CC BY-NC-ND 4.0 DEED B. Moncunill-Solé.

In addition, we visited the small Geological Museum of Quiroga. The Geological Museum of Quiroga is one of the cornerstones of the Montañas do Courel Geopark and is part of its network of museums and interpretation centers. It is also the first museum in Galicia dedicated entirely to interpreting geological heritage. The museum was inaugurated in December 2011 and expanded in September 2020. In a space of about 250 square meters, the Quiroga Museum includes the most representative geological contents of the area, arranged from the oldest to the most recent.

Figure 3. A (left). Entrance of the Geological Museum of Quiroga. B (right). Exposed remains of a cave bear (cast) from the Courel Moutains. CC BY-NC-ND 4.0 DEED B. Moncunill-Solé.

Both the participation in the workshop and the visit to the Geological Museum of Quiroga were very nice experiences!