Revision of annulated orthoceridan cephalopods of the Baltoscandic Ordovician

The annulated orthoceridans of the Middle and Late Ordovician of Baltoscandia are described and their systematic frame is revised. The revision of these nautiloids, which are part of the Orthocerida and Pseudorthocerida, is based on the investigation of characters of the septal neck, the siphuncular tube, and the apex. An unequivocal terminology of these characters is suggested and applied. The shape of the septal neck and the siphuncular tube are described for the first time in Palaeodawsonoceras n. gen., Striatocycloceras n. gen., Dawsonoceras fenestratum Eichwald, 1860, and Gorbyoceras textumaraneum (Roemer, 1861). Ctenoceras sweeti n. sp. is erected. The apex of Dawsonoceras barrandei Horný, 1956 is figured and described for the first time. The distribution of the character states of the apex and the septal neck support the emendation of the families Orthoceratidae, Dawsonoceratidae, and Proteoceratidae. The analysis shows also that the families Kionoceratidae, and Leuroceratidae must be refused because they represent not natural groups. However, it is also shown that the present knowledge is not sufficient to establish an unequivocal classification of the Middle, and Late Ordovician annulate cephalopods. Die orthoceriden Cephalopoden des Mittleren bis Späten Ordoviziums im Baltoskandium werden beschrieben und revidiert. Die Revision dieser Cephalopoden, welche zu den Orthocerida und Pseudorthocerida gehören, stützt sich auf die Untersuchung der Apikalenden, der Septalduten und der Form der Siphonalröhre. Eine eindeutige Terminologie für diese Merkmale wird vorgeschlagen und angewandt. Die Form der Septalduten und der Siphonalröhre von Palaeodawsonoceras n. gen., Striatocycloceras n. gen., Dawsonoceras fenestratum, Eichwald, 1860 und Gorbyoceras textumaraneum (Roemer, 1861) wird erstmals beschrieben. Die Art Ctenoceras sweeti n. sp. wird aufgestellt. Der Apex von Dawsonoceras barrandei Horný, 1956 wird erstmals beschrieben und dargestellt. Die neu gefundenen Merkmale stützen eine Emendation der Familien Orthoceratidae, Dawsonoceratidae und Proteoceratidae. Es wird daher dafür plädiert, die Familien Kionoceratidae (Hyatt, 1900) und Leuroceratidae (Sweet, 1964) nicht mehr zu verwenden, da diese keine natürlichen Gruppen repräsentieren. Die Untersuchung zeigt aber auch, dass es derzeit noch nicht möglich ist die annulaten Cephalopoden des Mittleren und Oberen Ordoviziums zweifelsfrei zu klassifizieren. doi:10.1002/mmng.200600005</a

Revision of annulated orthoceridan cephalopods of the Baltoscandic Ordovician

The annulated orthoceridans of the Middle and Late Ordovician of Baltoscandia are described and their systematic frame is revised. The revision of these nautiloids, which are part of the Orthocerida and Pseudorthocerida, is based on the investigation of characters of the septal neck, the siphuncular tube, and the apex. An unequivocal terminology of these characters is suggested and applied. The shape of the septal neck and the siphuncular tube are described for the first time in Palaeodawsonoceras n. gen., Striatocycloceras n. gen., Dawsonoceras fenestratum Eichwald, 1860, and Gorbyoceras textumaraneum (Roemer, 1861). Ctenoceras sweeti n. sp. is erected. The apex of Dawsonoceras barrandei Horný, 1956 is figured and described for the first time. The distribution of the character states of the apex and the septal neck support the emendation of the families Orthoceratidae, Dawsonoceratidae, and Proteoceratidae. The analysis shows also that the families Kionoceratidae, and Leuroceratidae must be refused because they represent not natural groups. However, it is also shown that the present knowledge is not sufficient to establish an unequivocal classification of the Middle, and Late Ordovician annulate cephalopods.Die orthoceriden Cephalopoden des Mittleren bis Späten Ordoviziums im Baltoskandium werden beschrieben und revidiert. Die Revision dieser Cephalopoden, welche zu den Orthocerida und Pseudorthocerida gehören, stützt sich auf die Untersuchung der Apikalenden, der Septalduten und der Form der Siphonalröhre. Eine eindeutige Terminologie für diese Merkmale wird vorgeschlagen und angewandt. Die Form der Septalduten und der Siphonalröhre von Palaeodawsonoceras n. gen., Striatocycloceras n. gen., Dawsonoceras fenestratum, Eichwald, 1860 und Gorbyoceras textumaraneum (Roemer, 1861) wird erstmals beschrieben. Die Art Ctenoceras sweeti n. sp. wird aufgestellt. Der Apex von Dawsonoceras barrandei Horný, 1956 wird erstmals beschrieben und dargestellt. Die neu gefundenen Merkmale stützen eine Emendation der Familien Orthoceratidae, Dawsonoceratidae und Proteoceratidae. Es wird daher dafür plädiert, die Familien Kionoceratidae (Hyatt, 1900) und Leuroceratidae (Sweet, 1964) nicht mehr zu verwenden, da diese keine natürlichen Gruppen repräsentieren. Die Untersuchung zeigt aber auch, dass es derzeit noch nicht möglich ist die annulaten Cephalopoden des Mittleren und Oberen Ordoviziums zweifelsfrei zu klassifizieren.doi:10.1002/mmng.20060000

Cryptic encrusting fauna inside invertebrate fossils from the Ordovician of Estonia

This is the first report of encrusted cryptic surfaces in the Ordovician of Estonia. Only bryozoans and cornulitids occurred in nautiloids and trilobites. Bryozoans were the dominant encrusters, in terms of both the number of specimens and the encrustation area. Stalked echinoderms are common on the hardgrounds in the Middle and Upper Ordovician of Baltica, but the restricted space in nautiloid living chambers and trilobites probably prevented colonization by stalked echinoderms. Cryptic surfaces in nautiloids and trilobites usually are somewhat more encrusted than the open surfaces of hardgrounds in the Ordovician of Estonia. Encrusters presumably favoured cryptic surfaces, as these were less accessible for predators and grazers. Low encrustation densities, compared to North American hard substrates, seem to be characteristic for the Ordovician Baltic Basin

Relevant radionuclides in Estonian drinking and ground waters – measurement techniques and activity concentrations

First comprehensive studies of the radionuclides’ concentration and its composition in Estonian ground water began in 1990s. It was quickly realized that the activity concentration of 226Ra and 228Ra in Cambrian-Vendian (Cm-V) aquifer are the highest contributors to the total indicative dose (TID). About 22% of the population in Estonia uses Cm-V ground water for drinking water supply. In recent study [1], it was concluded, that about 91% of Cm-V aquifer consumers (20% of the Estonian population) obtain higher TID doses (TID exceeding 0.1 mSv/y) than set by European Commission and national regulations. Over the years, a good representation level by the number of measured samples for 226Ra and 228Ra from Cm-V aquifer has been obtained. However, for other widely used aquifers – Ordovician-Cambrian, Silurian-Ordovician and Devonian – only poor data is available. In several southern counties, only few percent of the water supplies have been surveyed. Data for other natural radionuclides (234,238U, 210Po and 210Pb) is also poor. Scarce data has been partly due to the lack of analysis techniques available in Estonian nuclear analysis laboratories. This has been the motivation in the development of gamma spectrometric and liquid scintillation (LSC) counting techniques for ground and drinking water applications

Applying gross alpha and beta measurements as an estimate to the total indicative dose of Cambrian-Vendian ground water in Estonia

Gross alpha and beta measurements are common procedures for screening water samples in order to estimate the level of total indicative dose (TID) from the radionuclides in water. However, it has been pointed out that gross alpha and beta measurements are not suitable for waters containing high concentrations of natural radionuclides, especially Ra-226 and Ra-228. Cambrian-Vendian aquifer system is the major source of public water supply in northern and north-eastern Estonia. The aquifer is known for its high radionuclide concentrations. The main sources of TID are Ra-226 and Ra-228, but the water also contains K-40. Other nuclides from uranium and thorium series may be present as well. A set of Ra-226, Ra-228 and K-40 activity concentrations measured by gammaspectrometry are studied to analyze the applicability of gross alpha and beta measurements in case of Cambrian-Vendian ground water. The calculations indicate that the levels suggested by WHO guidelines are not suitable for the Cambrian-Vendian ground water. Results on the applicability analysis are given