부산대학교 도서관

Integrated lithostratigraphical, cyclostratigraphical, graptolite and conodont biostratigraphical and chemostratigraphical (δ13C) data are presented from the upper Jaagarahu, Gėluva and Dubysa regional stages, including thelundgreniEvent (middle Homerian) in the Viduklė-61 well, Lithuania. The Viduklė-61 well is located in the west of Lithuania in the deep-water facies zone. Because of its completeness, this section is the “keystone” for middle–upper Homerian stratigraphy that allows us to combine different kinds of data into a coherent picture of large-scale biotic and environmental turnover. Three formations are distinguished: the upper part of the Riga Formation, with the Ančia Member in the uppermost part, the Siesartis Formation and the lower part of Dubysa Formation. The Grötlingbo bentonite is in the upper part of Ančia Member. In the Gėluva regional stage, two 4th-order and six 5th-order cycles have been distinguished. In the studied interval of the Viduklė-61 core, the following graptolite biozones were recognized:lundgreni(upper part),parvus,nassa,praedeubeli,deubeli,ludensisandnilssoni(lower part). Conodonts enabled recognition of thebohemica longaBiozone. A single find ofCtenognathodus murchisoniPander in thenassagraptolite interzone indicates an earlier than previously thought origin of this species. [ABSTRACT FROM AUTHOR]