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Jurassic Forum » JURASSIC references & paper reviews » Jurassic around the world » Toarcian GSSP (Special issue of "Ciências da Terra", 2007)
Toarcian GSSP
mhornДата: Sunday, 16.01.2011, 10:08 | Сообщение # 1
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Elmi S., Mouterde R., Rocha R.B., Ruget Ch. (2007) Toarcian GSSP candidate: the Peniche section at Ponta do Trovão // Ciências da Terra. Nº 16. P.25-35.
Pdf: http://run.unl.pt/bitstream/10362/4789/1/CT_16_03_S_Elmi_et_al.pdf
The Peniche section (Ponta do Trovão) in Portugal is presented as potential stratotype (GSSP) for the Pliensbachian/Toarcian boundary. The lithostratigraphic succession is described and the chronostratigraphy, based on ammonite assemblages, is presented; the change in foraminifera assemblages occurs later, only at the base of beds 16 (base of Semicelatum Subzone, Crosbeyi ? Horizon). An extensive bibliographical list of all scientific articles containing specific reference to this stratigraphic boundary, whether from the Lusitanian or Algarve basins, is also presented. Some lowermost Toarcian ammonites are figured.

Mailliot S., Elmi S., Mattioli E., Pittet B. (2007) Calcareous nannofossil assemblages across the Pliensbachian/Toarcian boundary at the Peniche section (Ponta do Trovão, Lusitanian Basin) // Ciências da Terra. Nº 16. P. 51-62.
pdf: http://run.unl.pt/bitstream/10362/4792/1/CT_16_06_S_Mailliot_et_al.pdf
The Peniche section has revealed moderately-to-well preserved calcareous nannofossil assemblages across the Pliensbachian/Toarcian boundary. This good record has allowed the proposition of a refined biostratigraphic scheme. The stage boundary, as defined by ammonites, is comprised within the NJ5b C. impontus (NW Europe; BOWN & COOPER, 1998) or the NJT5b L. sigillatus (Mediterranean Tethys; MATTIOLI & ERBA, 1999) nannofossil subzones. Since in the Lusitanian Basin a mixing of N- and S-Tethyan taxa is observed, both biozonation schemes can be applied. Some nannofossil events (mainly first occurrences) are observed earlier in Portugal than in other Tethyan settings. It is still unclear if these events are real first occurrences. A diversification phase occurred across the Pliensbachian/Toarcian boundary. This phase is well recorded at Peniche, where a change is observed passing from the Pliensbachian, when assemblages are dominated by muroliths, to the Toarcian showing assemblages where placoliths are abundant. A quantification of nannofossils per gram of rock shows that absolute abundances are the highest across the Pliensbachian/Toarcian boundary. Indeed, Peniche exhibits nannofossil abundances very high with respect to correlative levels in other Tethyan settings. The pelagic carbonate fraction (produced by nannofossils) is important in the marly hemi-couplets of Peniche. In some levels, nannofossils account for more than 50% of the total carbonate fraction.Pliensbachian/Toarcian boundary: the proposed GSSP of Peniche
(Portugal)

Elmi S. (2007) Pliensbachian/Toarcian boundary: the proposed GSSP of Peniche (Portugal) // Ciências da Terra. Nº 16. P.7-16.
Pdf: http://run.unl.pt/bitstream/10362/4787/1/CT_16_01_S_Elmi.pdf
The Peniche section (Portugal) is considered as a potential stratotype (GSSP) for the Pliensbachian/Toarcian boundary and it is analysed on the background of the available data on the ammonite successions from other Tethyan and NW European areas.

Pinto S., Cabral M. C., Duarte L. V. (2007) Preliminary data on the ostracod fauna from the Lower Toarcian of Peniche // Ciências da Terra. Nº 16. P. 37-43.
pdf: http://run.unl.pt/bitstream/10362/4790/1/CT_16_04_S_Pinto_et_al.pdf
Preliminary results of the systematic and biostratigraphical study of the ostracods from the Lower Toarcian (Polymorphum and Levisoni Zones) of Peniche are presented. Most of the identified species are recognized in other European countries. Biodiversity and species abundance are high in the first Zone, decreasing dramatically in the second one.

Duarte L. V. (2007) Lithostratigraphy, sequence stratigraphy and depositional setting of
the Pliensbachian and Toarcian series in the Lusitanian Basin, Portugal // Ciências da Terra. Nº 16. P.17-23
pdf: http://run.unl.pt/bitstream/10362/4788/1/CT_16_02_L_Duarte.pdf
In the Lusitanian Basin (Central Portugal), the Middle-Upper Liassic series are characterized by an expressive marly limestone accumulation, sediments that were deposited on a homoclinal carbonate ramp. These series belong to the Vale das Fontes, Lemede, S. Gião (and the lateral equivalents Prado and Cabo Carvoeiro Formations) and, partially, to the Póvoa da Lomba
Formations. These units, in great part controlled by an accurate ammonite biostratigraphic scale, are organized into two secondorder transgressive-regressive sequences. The first one (SP) is dated of early Pliensbachian/lowermost early Toarcian age; the second (ST) is dated of early Toarcian to early Aalenian.

Veiga de Oliveira L. C., Perilli N., Duarte L. V. (2007) Calcareous nannofossil assemblages around the Pliensbachian/Toarcian boundary in the reference section of Peniche (Portugal) // Ciências da Terra. Nº 16. P.45-50.
Pdf: http://run.unl.pt/bitstream/10362/4791/1/CT_16_05_L_Oliveira_et_al.pdf
The Pliensbachian/Toarcian boundary (Lower Jurassic) is well represented in the Lusitanian Basin (Portugal), mainly in the Peniche area, recorded by a marl/limestone series. Calcareous nannofossil assemblages are described herein, with the aim to contribute to the Toarcian GSSP definition. Marly samples were collected 3 m below and 7 m above this boundary and analysed
for calcareous nannofossils. The main nannofossils observed were Biscutum finchii, B. grande, Calcivascularis jansae, Crepidolithus crassus, C. granulatus, C. impontus, Lotharingius hauffii, L. sigillatus, L. aff. L. velatus, Schizosphaerella spp. and Tubirhabdus patulus. This assemblage indicates that the Pliensbachian/Toarcian boundary in Peniche lies in the upper part of the
NJ5b Subzone. Schizosphaerella and Lotharingius dominate the assemblage. The abundant occurrence of C. jansae and the common occurrence of B. grande indicate a strong Tethyan influence

Veiga de Oliveira L. C., Duarte L. V., Rodrigues R. (2007) Chemostratigraphy (TOC, δ13C, δ18O) around the Pliensbachian/Toarcian boundary in the reference section of Peniche (Lusitanian Basin, Portugal) // Ciências da Terra. Nº 16. P.63-66.
Pdf: http://run.unl.pt/bitstream/10362/4793/1/CT_16_07_L_Oliveira_et_al.pdf
This work presents the chemostratigraphy analysis based on total organic carbon (TOC) and the evolution of the carbon and oxygen stable isotopes in the whole rock samples around the Pliensbachian/Toarcian boundary in the Peniche section (uppermost part of Lemede Formation and lowermost part of Cabo Carvoeiro Formation). These are partial results which form part of a
group of studies, being processed, that include isotope analyses of 87Sr/86Sr, δ18O, δ13C and major, minor and trace elements in whole rock and belemnites.


Middle Jurassic - Lower Cretaceous ammonites & aptychi
 
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