Lithostratigraphy, biostratigraphy and radiometric dating of the Early Eocene at Helmstedt (Lower Saxony)

Ahrendt, H.; Köthe, Angelika; Lietzow, Axel; Marheine, Dirk; Ritzkowski, Siegfried

doi:10.1127/zdgg/146/1995/450

Cited by 10 publications

(17 citation statements)

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“… The age model for the succession is based on K/Ar-ages [ 43 , 45 ], nannoplankton zones [ 43 ], dinoflagellate zones [ 46 ] and palynological zones [ 27 , 28 ]. Data for global changes in Paleogene sea-level [ 47 ] and higher order orbital cyclicity (long eccentricity >589 kyr) [ 48 ] are used for a putative correlation to seams in the Schöningen Südfeld section.…”

Section: Geological Settingmentioning

confidence: 99%

“…The conventional age model ( Fig 3 ) for the coal-bearing part of the Paleogene succession of the Helmstedt Lignite Mining District is mainly based on scattered radiometric ages from glauconites [ 43 , 45 ] as well as biostratigraphic data from nannoplankton [ 43 ], dinocysts [ 45 , 46 ] and palynomorphs [ 27 , 28 ]. The data for the Schöningen, Emmerstedt and Helmstedt formations were mostly derived from wells near Helmstedt in the eastern Syncline and have simply been transferred by lithologic correlation to both synclines in the rest of the area.…”

Section: Geological Settingmentioning

confidence: 99%

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Greenhouse conditions in lower Eocene coastal wetlands?—Lessons from Schöningen, Northern Germany

2021

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The Paleogene succession of the Helmstedt Lignite Mining District in Northern Germany includes coastal peat mire records from the latest Paleocene to the middle Eocene at the southern edge of the Proto-North Sea. Therefore, it covers the different long- and short-term climate perturbations of the Paleogene greenhouse. 56 samples from three individual sections of a lower Eocene seam in the record capture the typical succession of the vegetation in a coastal wetland during a period that was not affected by climate perturbation. This allows facies-dependent vegetational changes to be distinguished from those that were climate induced. Cluster analyses and NMDS of well-preserved palynomorph assemblages reveal four successional stages in the vegetation during peat accumulation: (1) a coastal vegetation, (2) an initial mire, (3) a transitional mire, and (4) a terminal mire. Biodiversity measures show that plant diversity decreased significantly in the successive stages. The highly diverse vegetation at the coast and in the adjacent initial mire was replaced by low diversity communities adapted to wet acidic environments and nutrient deficiency. The palynomorph assemblages are dominated by elements such as Alnus (Betulaceae) or Sphagnum (Sphagnaceae). Typical tropical elements which are characteristic for the middle Eocene part of the succession are missing. This indicates that a more warm-temperate climate prevailed in northwestern Germany during the early lower Eocene.

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Section: Geological Settingmentioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

Greenhouse conditions in lower Eocene coastal wetlands?—Lessons from Schöningen, Northern Germany

2021

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“…Dinoflagellate cyst assemblages from marine horizons at Emmerstedt (Ahrendt et al, 1995) indicate that the Schöningen Formation can be assigned to the lower Eocene dinoflagellate zones D5b to D9na for northwestern Germany (Costa and Manum, 1988;Köthe, 1990Köthe, , 2003. Cysts of dinoflagellates have also been recorded in interbeds with marine influence at Schöningen, but their provisional assignment to dinoflagellate zones by Riegel et al (2012) is slightly modifed here.…”

Section: Dinoflagellatesmentioning

confidence: 99%

“…Furthermore, these ages fit the K/Ar ages from the drill core at Emmerstedt, ca. 20 km N of Schöningen (Ahrendt et al, 1995).…”

Section: Eustatic Sea Levelmentioning

confidence: 99%

“…The lower Eocene part of the succession terminates with Seam 8. If the following Interbed 9 is regarded as equivalent to the greensand of the Emmerstedt Formation further to the NW and in the eastern syncline, the K/Ar glauconite age of 46.0 ± 1.1 Ma (Ahrendt et al, 1995) from Emmerstedt implies that it already has a middle Eocene age. The change from the Schöningen Formation to the Emmerstedt Formation is characterized by a significant hiatus at the top of Seam 8 (Osman et al, 2013), which may be represented at Schöningen by a deep channel reaching down from slightly above Seam 8 to a level well below Seam 7.…”

Section: Eustatic Sea Levelmentioning

confidence: 99%

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Early Eocene carbon isotope excursions in a lignite bearing succession at the southern edge of the proto-North Sea (Schöningen, Germany)

Lenz

Montag

Wilde

et al. 2021

Preprint

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Abstract. Situated at the southern edge of the proto-North Sea the lower Eocene Schöningen Formation of the Helmstedt Lignite Mining District, Lower Saxony, Germany is characterized by several lignite seams alternating with estuarine to brackish interbeds. Here, we present carbon isotope data of bulk organic matter (δ13CTOC), organic carbon content (%TOC), and palynomorphs from a 98 m thick sequence of the Schöningen Formation embedded into a new robust age model. This is based on eustatic sea-level changes, biostratigraphy, and a correlation to existing radiometric ages. Based on the δ13CTOC data we observe six negative carbon isotope excursions (CIEs) reflecting massive short-term carbon cycle perturbations. A strong CIE of −2.6 ‰ in δ13CTOC values in the Main Seam and the succeeding marine interbed can be related to the Paleocene–Eocene Thermal Maximum (PETM). The subsequent CIE of −1.7 ‰ in δ13CTOC values may be correlated with the Eocene Thermal Maximum 2 (ETM2) or slightly older events preceding the ETM2. High-amplitude climate fluctuations including at least 4 minor CIEs with a maximum negative shift of −1.3 ‰ in δ13CTOC in the upper part of the studied section are characteristic for the EECO. Palynological analysis across the Main Seam proved that shifts in δ13CTOC values are correlated with changes in the peat forming wetland vegetation, specifically the change from a mixed angiosperm and gymnosperm flora to an angiosperm dominated vegetation at the onset of the PETM. The PETM-related CIE shows a distinct rebound to higher δ13CTOC values shortly after the onset of the CIE, which is here recognized as a common feature of terrestrial and marginal marine PETM-records worldwide and may be related to changes in the vegetation including different carbon isotope budgets of gymnosperms and angiosperms.

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Sphagnoid spores as tracers of environmental and climatic changes in peatland habitats of the early Eocene

Riegel,

Lenz,

Wilde

2024

Int J Earth Sci (Geol Rundsch)

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Peat mosses have been an important part of the lignite forming vegetation in the early Eocene of the Helmstedt Lignite Mining District. Three genera of Sphagnum-type spores can be distinguished: Tripunctisporis, Distancoraesporis and Sphagnumsporites. The distribution of these sphagnoid spores is traced through seven lignite seams including most of the known hyperthermal events from the PETM to the EECO. In general, Sphagnum-type spores increase in importance from base to top in each seam as a result of acidification and nutrient depletion during peat accumulation. The proportion of Tripunctisporis increases from Main Seam to Seam 6. The lower three seams are characterized by assemblages typical for coastal plain swamp forests including tree stumps and charcoal in distinct layers and lenses. The upper seams, in which Tripunctisporis is dominant and woody material is rare, are thin-bedded with charcoal in numerous thin drapes on bedding planes. The palynomorph assemblages here indicate a low growing mainly herbaceous vegetation typical of ombrogenous bogs. The change from topogenous swamp forests to open ombrogenous bogs takes place along with the hyperthermals of the early Eocene from the PETM to the EECO. The change from a swamp forest to a shrub forest in the middle of the Main Seam coincides with the isotope excursion of the PETM. Similar changes in other seams independent of thermal events indicate that thermal events merely amplify changes in vegetation, which are primarily imposed by edaphic constraints. It is rather the rapid accumulation of hyperthermals during the EECO that exerts sufficient environmental stress to fundamentally alter the peat forming vegetation. Graphical abstract

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Lithostratigraphy, biostratigraphy and radiometric dating of the Early Eocene at Helmstedt (Lower Saxony)

Cited by 10 publications

References 0 publications

Greenhouse conditions in lower Eocene coastal wetlands?—Lessons from Schöningen, Northern Germany

Greenhouse conditions in lower Eocene coastal wetlands?—Lessons from Schöningen, Northern Germany

Early Eocene carbon isotope excursions in a lignite bearing succession at the southern edge of the proto-North Sea (Schöningen, Germany)

Sphagnoid spores as tracers of environmental and climatic changes in peatland habitats of the early Eocene

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