Silurian Bio-Events

Kaljo, Dimitri; Boucot, A. J.; Corfield, Richard; Hérissé, Alain Le; Koren, T. N.; Kříž, Jiří; Männik, Peep; Märss, Tiiu; Nestor, Viiu; Shaver, Robert; Siveter, Derek J.; Viira, Viive

doi:10.1007/978-3-642-79634-0_10

Cited by 39 publications

(24 citation statements)

References 47 publications

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“…Much of this evidence is summarized in the works of Lenz (1982), Johnson & McKerrow (1991) and, particularly, Kaljo et al (1995). Kaljo et al (1995, p. 214) stated: 'The global character of the latest Wenlock sealevel lowering has been advocated by many authors... and can be taken as proved.'…”

Section: M Mid Homerian Sea-level Fall and Late Homerian Sealevel mentioning

confidence: 96%

Early Silurian sea-level changes

1998

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Of the various mechanisms suggested (Donovan & Jones, 1979), that most likely to be responsible for the eustatic sealevel changes in the early Silurian is variation in the amount of water incorporated in land-based ice-sheets. This conclusion is based first on the apparent rapidity of many of the sea-level changes (see, e.g. Loydell, 1994) and secondly on the direct evidence of glacial deposits present in the Silurian sequences of Brazil (Grahn & Caputo, 1992) and elsewhere in South America (see Hambrey, 1985).Obviously, the third (and possibly fourth) order cycles being discussed here are superimposed upon the longer term second order and first order cycles (Haq, Hardenbol & Vail, 1988) linked to global tectonic processes. It is likely, for example, that the particularly high sea-levels of the Telychian and early Sheinwoodian reflect the coincidence of interglacial 'greenhouse' conditions with an increase in the volume of oceanic ridges. Abstract -Global sea-level fluctuated markedly during the early Silurian, probably as a result of the waxing and waning of ice-sheets in the South American portion of Gondwana. The highest sea-levels of the Silurian are recorded by the Telychian upper crispus-lower griestoniensis and spiralis-lower lapworthi biozones. Other highstands occurred in the early Aeronian, during the convolutus Zone (mid Aeronian), guerichi Zone and late turriculatus Zone (early Telychian), and early Sheinwoodian. Low sea-levels characterized much of the argenteus and sedgwickii zones (Aeronian), the utilis Subzone (late guerichi-early turriculatus zones, early Telychian), the late Telychian (commencing in the mid lapworthi Zone) and, after a period of apparently only small amplitude sea-level fluctuations in the late Sheinwoodian and earliest Homerian, the mid-late Homerian, in particular the early nassa Zone. Facies (and faunal) changes in the Lower Silurian do not support the P and S model of Jeppsson and others, but are consistent with the sea-level changes proposed herein. Mid Telychian marine red beds appear to have been deposited during a minor sea-level fall immediately after a period of very high sea-levels, rather than during a transgressive episode as previously suggested. Comparison of the sea-level curve presented herein with those constructed in the past is hampered by the lack of precision currently possible in the correlation of early Silurian deep water (graptolitic) and shallow water (shelly) sequences. Improving the precision of this correlation should be a priority for future research.*

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Section: M Mid Homerian Sea-level Fall and Late Homerian Sealevel mentioning

confidence: 96%

Early Silurian sea-level changes

1998

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“…Calner, 1999;Calner & Säll, 1999;Calner, 2002; see also references in Kaljo et al 1995 andLoydell, 1998). The maximum lowstand has, based on East Baltic sections, previously been suggested to be in the 'early nassa time' (Nestor & Nestor, 1991, p. 58).…”

Section: B Mid-late Homerian Sea-level and Sequence Stratigraphymentioning

confidence: 97%

Carbonate platform evolution and conodont stratigraphy during the middle Silurian Mulde Event, Gotland, Sweden

2003

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-Evidence from sedimentology and conodont biostratigraphy is used to reinterpret the mid-Homerian (Late Wenlock) succession on Gotland, Sweden. A new conodont zonation includes from below: the Ozarkodina bohemica longa Zone (including five subzones), the Kockelella ortus absidata Zone and the Ctenognathodus murchisoni Zone (two taxa are named, Ozarkodina bohemica longa and Pseudooneotodus linguicornis). These new zones are integrated with facies in order to correlate strata and infer the major depositional environments and the controls on deposition during the mid-Homerian Mulde Event. Reef-associated and skeletal carbonate deposition predominated before and after the event, i.e. during the uppermost O. s. sagitta Zone and, again, in the C. murchisoni Zone. These periods are characterized by the expansion of reefs and shoal facies across marls in the topmost Slite Group on eastern Gotland and in the lower parts of the Klinteberg Formation on western Gotland, respectively. The intervening O. b. longa and K. o. absidata zones are initially characterized by rapid facies changes, including siliciclastic deposition, and later stabilisation of a carbonate depositional system. The composition of sediments and depositional rates are closely related to the creation and destruction of accommodation space and reflects a classical case of depositional bias of the carbonate and siliciclastic depositional systems. Based on coastline migration, stratal boundaries, and the stratigraphic position of major reef belts, several facies associations can be fitted into a sequence stratigraphic model for platform evolution. A highstand systems tract (HST) situation prevailed prior to, and during the early part of the event; the upper Slite Group including the lower Fröjel Formation. This HST was characterized by prolific skeletal production and regional reef development except for during the latest stage when carbonate production declined at the onset of the Mulde Event. Platform growth was inhibited during a following regressive systems tract (RST) when regional siliciclastic deposition predominated; the Gannarve Member. The subsequent lowstand resulted in regional emersion and karstification, i.e. a complete termination of the platform. The postextinction transgressive systems tract (TST) is exclusively composed of non-skeletal carbonates; the Bara Member of the Halla Formation. Re-occurrence of reefs and a prolific skeletal production marks platform recovery during a second HST; the remaining Halla and the lower Klinteberg formations. Integration of high-resolution biostratigraphy and sequence stratigraphy reveals that the major physical control on platform evolution was a 5th order eustatic sea-level change during an early part of the Mulde Event, and that the bulk of the strata accumulated when the platform aggraded and prograded during the highstand systems tracts. Thus, Silurian oceanic events and associated sea-level changes had profound impact on the neritic carbonate system. The Gotland-based middle and late Homerian...

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“…1. Correlation of the Lithuanian graptolite biozones with generalized graptolite biozones and with regional stages and formations other biotic groups after the lundgreni Event as well (Kaljo et al 1996). During the discussed event there was major perturbation of the global carbon cycle in the middle-upper Homerian, which was called the upper Homerian positive carbon isotopic (δ 13 C) excursion (Kaljo et al 1997).…”

Section: Geological Backgroundmentioning

confidence: 99%

Upper Homerian (Silurian) high-resolution correlation using cyclostratigraphy: an example from western Lithuania

Radzevičius

Tumakovaitė

Spiridonov

2017

Acta Geologica Polonica

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ABSTRACT:Radzevičius, S., Tumakovaitė, B. and Spiridonov, A. 2017. Upper Homerian (Silurian) high-resolution correlation using cyclostratigraphy: an example from western Lithuania. Acta Geologica Polonica, 67 (2), 307-322. Warszawa.The Gėluva regional stage stratigraphically corresponds to the late Wenlock. This time interval witnessed significant graptolite extinctions and turnovers of conodont faunas, as well as a large positive Mulde carbon isotopic excursion. Thus, the development of a detailed stratigraphy is a necessary step in understanding the complex patterns of regional and global variations in the sediments accumulating during the time interval studied. Therefore, in this contribution we present a cyclostratigraphic analysis of gamma ray (GR) logs from four wells, which are located in the deep water facies belt of the Lithuanian part of the Silurian Baltic Basin of the Gėluva regional stage. The analysis was performed using REDFIT spectral estimation, continuous wavelet transform and signal filtering techniques. As a result two 4 th order and five 5 th order cycles were distinguished and named in all sections. The correlation of cycles between sections was calibrated with the graptolite biozones. The comparative analysis revealed that intra-basinal cyclostratigraphic correlation could achieve resolution of the order of several tens of thousands of years.

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Silurian Bio-Events

Cited by 39 publications

References 47 publications

Early Silurian sea-level changes

Early Silurian sea-level changes

Carbonate platform evolution and conodont stratigraphy during the middle Silurian Mulde Event, Gotland, Sweden

Upper Homerian (Silurian) high-resolution correlation using cyclostratigraphy: an example from western Lithuania

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