Biostratigraphy & Taxonomy

Biostratigraphy is using the first (evolution) and last (extinction) events of fossil species to determine the age of rocks and sediments. Taxonomy is the classification and naming of organisms. I conduct biostratigraphies with planktic foraminifera, and update their taxonomic associations.

Biostratigraphy

Fossil plankton are the primary means to decipher the age of deep-marine sediments. Robust biostratigraphic zonation schemes, in part, rely on calibrating the evolution and extinction events of species to the geomagnetic and/or astronomical time scales at certain places in the world ocean. In this way, paleontologists can then use these dates at other places in the ocean. However, not all zonation schemes are appropriate for all regions of our oceans.

Over the past several decades, micropaleontologists have built very robust tropical-subtropical planktic foraminiferal zonation schemes. These schemes are not appropriate for higher-latitude sites, however, as the distribution of foraminifera are strongly controlled by temperature.

My goal is to create robust mid-latitude planktic foraminiferal zonation schemes, especially within and across major ocean current systems (e.g., western boundary currents). These regions remain understudied with respect to biostratigraphy, with several species lacking magnetostratigraphically- or orbitally-calibrated first and last appearance dates.

A planktic foraminiferal biostratigraphic zonation scheme for Ocean Drilling Program Hole 1207A, on the northern edge of the Kuroshio Current Extension. Figure from Lam and Leckie (in review).

Taxonomy

Robust biostratigraphic schemes, paleoceanography using fossil plankton, and paleobiogeography of plankton all require that species are being identified correctly and consistently by different micropaleontologists. Species identifications rely on detailed and robust images of fossil plankton, with descriptions of how different workers identify these species. To date, there have been taxonomic atlases published for planktic foraminifera through the Cenozoic, except for the Neogene.

Similar to biostratigraphy, tropical species of foraminifera have been studied extensively and have robust taxonomic guides, atlases, and publications. The mid-latitude species, or those that prefer cooler waters, have not been studied in as much detail.

Another goal of mine is to create robust taxonomic atlases of Neogene mid-latitude planktic foraminifera. Currently, my focus is on species that inhabit the North Pacific area, and compare those species to the southwest Pacific. Since 2018, I have been a member of the Neogene Working Group, an international team of micropaleontologists who will create a taxonomic atlas of Neogene planktic foraminiferal species.

Scanning electron microscope (SEM) images of two species of mid-latitude foraminfiera: Globoconella miotumida (1-3) and Globoconella conomiozea (4-6). These species have been confused in the literature for some time, so I devised a way to differentiate them more clearly. Figure from Lam and Leckie (in press).

Publications Related to Biostratigraphy & Taxonomy

Lam, A. R., Crundwell, M. P., Leckie, R. M., Albanese, J., and Uzel, J. P., 2022. Diachroneity rules the mid-latitudes: A test case using late Neogene planktic foraminifera across the western Pacific. Geosciences, 12, 190. https://doi.org/10.3390/geosciences12050190

Lam, A. R., and Leckie, R. M., 2020. Late Neogene and Quaternary Diversity and Taxonomy of Subtropical to Temperate Planktic Foraminifera across the Kuroshio Current Extension, northwest Pacific Ocean. Micropaleontology, 66 (3), 177–268.

Lam, A. R., and Leckie, R. M., 2020. Subtropical to temperate late Neogene to Quaternary planktic foraminiferal biostratigraphy across the Kuroshio Current Extension, Shatsky Rise, northwest Pacific Ocean. PLOS ONE, 15 (7), e0234351. https://doi.org/10.1371/journal.pone.0234351 

Abstracts Related to Biostratigraphy & Taxonomy

Lam, A. R., and Leckie, R. M., 2020. Mid-Latitude Planktic Foraminiferal Biostratigraphy for the Northwest Pacific Ocean, Shatsky Rise, Ocean Drilling Program Holes 1207A, 1208A, and 1209A. Northeast/Southeast GSA Meeting, Reston, VA. (Conference canceled)

Lam, A. R., and Leckie, R. M., 2018. A new high-resolution Late Neogene mid-latitude planktic foraminiferal biostratigraphy, Shatsky Rise, northwest Pacific. FORAMS 2018 Conference, Edinburgh, Scotland.

Lam, A. R., St. John, K., Leckie, R. M. 2013. Planktic foraminiferal biostratigraphy of Holocene-Late Pleistocene Core MD02-2535, Tunica Mound, Gulf of Mexico. Geologic Problem Solving with Microfossils III, Houston, Texas, USA.

Lam, A. R., St. John, K., Leslie, S. A., Robinson, M. 2012. Planktonic foraminiferal biostratigraphy of Holocene-Late Pleistocene Core MD02-2535, Tunica Mound, Gulf of Mexico. Geological Society of America Abstracts with Program, 44 (7). Online