The preservation of total organic carbon of the Silurian Pridoli strata in the Milaičiai-103 well core of Western Lithuania

Gelūnaitė, Augustė; Spiridonov, Andrej

doi:10.6001/geol-geogr.v1i2.3116

Cited by 2 publications

(1 citation statement)

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“…The combined fourth-and fifth-order cycles show periodic trends at the regional scale by reducing local noise, allowing for correlation with the regional scale graptolite data composited from multiple sites in the Baltic Basin. The close relationship between natural gamma values and the preserved carbon was previously clearly found in integrated studies of the Silurian Baltic Basin (Gelūnaitė& Spiridonov 2015;Cichon-Pupieni et al 2020;Spiridonov et al 2020). Moreover, no bentonites, which may affect gamma ray logs if present, have been recorded from nassa-scanicus biozones of the studied cores (Kiipli et al 2008).…”

Section: Discussionsupporting

confidence: 77%

Dynamic ecophenotypy in the Silurian Monograptidae (Graptolithina)

Whittingham

Spiridonov

Radzevičius

2021

Earth and Environmental Science Transactions of the Royal Society of Edinburgh

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The monograptids from the Wenlock and Ludlow (mid- to late Silurian) of the palaeotropical Baltic Basin exhibit thickened ring structures (sicular annuli) over their initial phase of growth. Appearing before the lundgreni extinction event, they persisted throughout the remainder of the Silurian, fluctuating in number over that period. To better understand the mechanisms controlling their development and variation, counts of sicular annuli were taken from three well cores in Lithuania, compared between species in each sample and compared with contemporaneous gamma ray data, accompanied by the stable isotope (δ13C), and acritarch diversity data. Mean counts of annuli fluctuated greatly over the studied interval, but showed negligible variation between species, indicating that the trait is ecophenotypic. The fluctuation in annulus presence aligned with variations in fourth- and fifth-order cycles derived from the gamma ray trends, which represent significant sea level fluctuations, δ13C ratios, and primary productivity, suggesting that annuli were more plentiful in high-stand states which are associated with the wetter climate and more productive conditions, whereas dryer, less productive conditions were not conducive to annulus development. In light of this evidence, we hypothesise that the action of upwelling as a result of intensified storm events during wetter periods would have encouraged phytoplankton blooms, increasing construction of annuli. These results show the potential utility of sicular annuli in the study of Silurian climate change and give new insights into graptolite palaeoecology.

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Section: Discussionsupporting

confidence: 77%