22-5 Pliocene Laminated Sediments from Lake El’gygytgyn, NE Arctic Russia

Abstract:

Lake-bed sediment records are often key datasets for scientific inference of paleoclimates. Even more so if the lacustrine environment produces an annual layering cycle, or varves, which can give yearly fidelity of past climates, especially during the warm Pliocene. Lake El’gygytgyn is a lake situated in a meteorite impact site in northeastern Arctic Russia. The impact is dated to 3.6 million year BP. The lake has provided several lacustrine sediment cores ranging from the Quaternary to the Pliocene. The core sample analyzed for this project comes from ICDP site 5011-1, hole C, and originates in the Pliocene segment of this sediment record, approximately spanning 3.550 to 3.551 mya. Annual varves in Pliocene sediments are rare. The aim of this research is to determine if the laminae present in the core segment represent annual varves as well as any evidence of known cyclicity, such as the sun-spot cycle. Analysis is being conducted based on the existing thin-sections that were sampled from the lower half of the core. This involves the counting of the laminae in each thin-section via ImageJ and a custom made program. This counting is conducted optically, with spectral analysis being performed on the resultant data in R and the PAST software. This spectral analysis has indicated the possible presence of an 11-year sunspot cycle. The laminae of the nine thin-sections analyzed comprise approximately 48.8 cm of the core, starting at the bottom and ascending towards the mid-point. In total 517 laminae were recorded with the average thickness of the laminae recorded was approximately 1 mm. According to the chronology established by Brigham-Grette et. al (2013, Science) this bottom section accounts for approximately 600 years. This chronology roughly aligns with the total layer count, possibly indicating the laminae being varves. Should this core be an example of lacustrine varves it would provide a new source of climatic and environmental information from the mid-Pliocene.

© Copyright 2026 The Geological Society of America (GSA), all rights reserved.