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 Trovão(Peniche,Lusitanian Basin,Portugal;coordinates:39&#...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 Trovão(Peniche,Lusitanian Basin,Portugal;coordinates:39°22′15″N,9°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.展开更多
Lake-level changes can significantly affect paleoenvironmental evolution,resource occurrence,terrestrial carbon budget,and biodiversity in continental basins.Climate is one of the most critical factors controlling lak...Lake-level changes can significantly affect paleoenvironmental evolution,resource occurrence,terrestrial carbon budget,and biodiversity in continental basins.Climate is one of the most critical factors controlling lake-level changes.Paleoclimate of the Early Jurassic has been evidenced by oscillating icehouses to(super)greenhouses with interrupted intermittent extreme climatic events(hyperthermal and cooling),e.g.,the Toarcian oceanic anoxic event(~183 Ma)and the late Pliensbachian cooling event(~185 Ma).Lake-level evolution and hydrologic cycling on Earth’s surface during the Early Jurassic icehouses-to-(super)greenhouses are thus far poorly understood due to a lack of continuous high-resolution nonmarine evidence.Here we present a super-long nonmarine lake level record for this pivotal interval from the early Pliensbachian to Toarcian by sedimentary noise modeling,and construct a 16.7-Myr-long astronomical time scale(174.2 Ma to 190.9 Ma)based on cyclostratigraphy analysis of rock color datasets(CIE b*)of the Qaidam Basin.Our results document lake-level oscillations on a 5-to 10-million-year(Myr)scale which shows a pronounced correlation with long-term climate variation and extreme climatic events,and 1-to 2.5-Myr-scale lake-level changes that are prominently paced by the 2.4-Myr long-eccentricity forcing and the 1.2-Myr obliquity forcing.At the Pliensbachian Stage,the 1.2-Myr-scale lake-level changes are in phase with the coeval sealevel variations.Orbitally forced growth and decay of the ephemeral or permanent ice sheets in polar regions are interpreted to control the synchronous ups-and-downs of continental lake level and global sea level.However,during the Toarcian ice-free greenhouses to(super)greenhouses,the 1.2-Myr-scale lake-level variations show an anti-phase relationship with global sea level,indicating a‘seesaw’interaction between continental reservoirs(lakes and groundwater)and global oceans.The 2.4-Myr longeccentricity cycles mainly regulate variations of lake level and sea level by controlling the growth and decay of small-scale continental ice sheets,which is especially notable during the Pliensbachian Stage.These findings indicate a remarkable transition of hydrological cycling pattern during the Pliensbachian-Toarcian icehouses to(super)greenhouses,which provides new perspectives and evidence for investigating the hypothesis of global sea-level changes(e.g.,glacio-eustasy and aquifer-eustasy)and long-period astronomical forcing in nonmarine stratigraphy.展开更多
基金supported by the BIOSCALES Project(POCTI/36438/PAL/2000)coordinated by the Universidade NOVA de Lisboa+1 种基金R.B.Rocha thanks the support of A.F.Soares,J.C.Kullberg,P.S.Caetano and P.H.VerdialFinancial support was provided to L.V.Duarte,S.Pinto and M.C.Cabral by Projects PDCTE/CTA/44907/2002 and PTDC/CTE-GIX/098968/2008.
文摘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 Trovão(Peniche,Lusitanian Basin,Portugal;coordinates:39°22′15″N,9°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.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.41502108,42372206&41602123)the China Postdoctoral Science Foundation(Grant No.2016T90667)+1 种基金the China Scholarship Council Project(Grant No.201907770004)the Fundamental Research Funds for the Universities of Henan Province(Grant No.NSFRF220401).
文摘Lake-level changes can significantly affect paleoenvironmental evolution,resource occurrence,terrestrial carbon budget,and biodiversity in continental basins.Climate is one of the most critical factors controlling lake-level changes.Paleoclimate of the Early Jurassic has been evidenced by oscillating icehouses to(super)greenhouses with interrupted intermittent extreme climatic events(hyperthermal and cooling),e.g.,the Toarcian oceanic anoxic event(~183 Ma)and the late Pliensbachian cooling event(~185 Ma).Lake-level evolution and hydrologic cycling on Earth’s surface during the Early Jurassic icehouses-to-(super)greenhouses are thus far poorly understood due to a lack of continuous high-resolution nonmarine evidence.Here we present a super-long nonmarine lake level record for this pivotal interval from the early Pliensbachian to Toarcian by sedimentary noise modeling,and construct a 16.7-Myr-long astronomical time scale(174.2 Ma to 190.9 Ma)based on cyclostratigraphy analysis of rock color datasets(CIE b*)of the Qaidam Basin.Our results document lake-level oscillations on a 5-to 10-million-year(Myr)scale which shows a pronounced correlation with long-term climate variation and extreme climatic events,and 1-to 2.5-Myr-scale lake-level changes that are prominently paced by the 2.4-Myr long-eccentricity forcing and the 1.2-Myr obliquity forcing.At the Pliensbachian Stage,the 1.2-Myr-scale lake-level changes are in phase with the coeval sealevel variations.Orbitally forced growth and decay of the ephemeral or permanent ice sheets in polar regions are interpreted to control the synchronous ups-and-downs of continental lake level and global sea level.However,during the Toarcian ice-free greenhouses to(super)greenhouses,the 1.2-Myr-scale lake-level variations show an anti-phase relationship with global sea level,indicating a‘seesaw’interaction between continental reservoirs(lakes and groundwater)and global oceans.The 2.4-Myr longeccentricity cycles mainly regulate variations of lake level and sea level by controlling the growth and decay of small-scale continental ice sheets,which is especially notable during the Pliensbachian Stage.These findings indicate a remarkable transition of hydrological cycling pattern during the Pliensbachian-Toarcian icehouses to(super)greenhouses,which provides new perspectives and evidence for investigating the hypothesis of global sea-level changes(e.g.,glacio-eustasy and aquifer-eustasy)and long-period astronomical forcing in nonmarine stratigraphy.
