Base of the Toarcian Stage of the Lower Jurassic defined by the Global Boundary Stratotype Section and Point (GSSP) at the Peniche section (Portugal)
Base of the Toarcian Stage of the Lower Jurassic defined by the Global Boundary Stratotype Section and Point (GSSP) at the Peniche section (Portugal)
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DOI：
10.18814/epiiugs/2016/v39i3/99741
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发表时间：
2016-09-01
期刊：
影响因子：
3.1
通讯作者：
Suan, Guillaume
中科院分区：
文献类型：
--
作者：
da Rocha, Rogerio Bordalo;Mattioli, Emanuela;Suan, Guillaume
下侏罗统陶塔良期基底的全球层型剖面和点（GSSP）位于葡萄牙卢西塔尼亚盆地佩尼切Ponta do Trovao（坐标：北纬39度22′15”，西经9度23′07”）15e泥晶灰岩基底，位于里斯本以北80km处，与鹦鹉石Dactylioceras（始动岩）的大量产状一致。Pliensbachian/Toarcian边界（PLB/TOA）包含在一个超过450米的富碳酸盐沉积物的连续剖面中。构造、同沉积扰动、变质作用或显著的成岩作用对本区影响不大。在PLB/TOA，没有记录到垂直相变化、地层间隙或裂缝。陶塔良期的底部在15e层首次出现单纯性D. (E.)，与D. （E.）伪公社和D. （E.）多形体同时出现。d.p (Eodactylites) ssp.的菊石组合。而其他物种如Protogrammoceras (Paltarpites) cf. paltum、Lioceratoides aff.ballinense和Tiltoniceras aff.capillatum对不同盆地的边界界定和剖面对比尤为重要。PLB/TOA的菊石是地中海和西北欧省份的特征分类群，可以提供可靠的全球相关性。PLB/TOA还具有其他生物地层标记（腕足类、钙质纳米化石、介形类和底栖有孔虫）和高分辨率稳定碳氧同位素的特征，Sr-87/Sr-36比值在PLB/TOA上方显示出明显的变化，从而为全球相关性提供了额外的、强大的工具。PBL-TOA位于海平面变化的第二（和第三）级旋回的末端，15e层顶被解释为层序边界。旋回地层学分析可用于蓬塔多特罗沃的下托瓦西亚。与Almonacid de la Cuba剖面（西班牙伊比利亚山脉）的详细对比提供了欧洲西北部Hawskerense和Paltum亚带菊石演替的补充数据，以及允许超区域对比的磁地层数据。该提案于2012年6月由Toarcian工作组投票通过，2012年9月由国际侏罗纪地层学小组委员会投票通过，2014年11月由ICS批准，2014年12月由IUGS批准。有了这个Toarcian GSSP，下侏罗纪的所有国际阶段都被正式定义了。
The Global Stratotype Section and Point (GSSP) for the base of Toarcian Stage, Lower Jurassic, is placed at the base of micritic limestone bed 15e at Ponta do Trovao (Peniche, Lusitanian Basin, Portugal; coordinates: 39 degrees 22'15 '' N, 9 degrees 23'07 '' W), 80km north of Lisbon, and coincides with the mass occurrence of the ammonite Dactylioceras (Eodactylites). The Pliensbachian/Toarcian boundary (PLB/TOA) is contained in a continuous section forming over 450m of carbonate-rich sediments. Tectonics, syn-sedimentary disturbance, metamorphism or significant diagenesis do not significantly affect this area. At the PLB/TOA, no vertical facies changes, stratigraphical gaps or hiatuses have been recorded. The base of the Toarcian Stage is marked in the bed 15e by the first occurrence of D. (E.) simplex, co-occurring with D. (E.) pseudocommune and D. (E.) polymorphum. The ammonite association of D. (Eodactylites) ssp. and other species e.g. Protogrammoceras (Paltarpites) cf. paltum, Lioceratoides aff. ballinense and Tiltoniceras aff. capillatum is particularly significant for the boundary definition and correlation with sections in different basins. Ammonites of the PLB/TOA are taxa characteristic of both the Mediterranean and Northwest European provinces that allow reliable, global correlations. The PLB/TOA is also characterized by other biostratigraphical markers (brachiopods, calcareous nannofossils, ostracods and benthic foraminifers) and by high-resolution stable carbon and oxygen isotopes, and Sr-87/Sr-36 ratios that show distinctive changes just above the PLB/TOA, thus providing additional, powerful tools for global correlations. The PBL-TOA lies at the end of a second (and third) order cycle of sea-level change, and the top of bed 15e is interpreted as a sequence boundary. Cyclostratigraphy analysis is available for the Lower Toarcian of Ponta do Trovao. Detailed correlations with the Almonacid de la Cuba section (Iberian Range, Spain) provide complementary data of the ammonite succession in the Northwest European Hawskerense and Paltum Subzones, and magnetostratigraphical data that allow supra regional correlations. The proposal was voted on by the Toarcian Working Group in June, 2012, and by the International Subcommission on Jurassic Stratigraphy in September, 2012, approved by the ICS in November, 2014, and ratified by the IUGS in December, 2014. With this Toarcian GSSP, all international stages of the Lower Jurassic have been officially defined.