The Paleocene/Eocene boundary Global Standard Stratotype-section and Point (GSSP): Criteria for Characterisation and Correlation

The choice of a Paleocene/Eocene (P/E) Global Standard Stratotype-section and Point (GSSP) is complicated by the fact that there exists confusion on the exact denotation of the Paleocene and Eocene Series and their constituent lower rank (stage) units. While we can now resolve this problem by recourse to rigorous historical analysis, actual placement of the GSSP is further exacerbated by an embarrassment of riches (in regards to 7 criteria suitable for characterising and correlating a PIE GSSP but which span a temporal interval of greater than 2 my). Following the precept that the boundaries between higher level chronostratigraphic units are to be founded upon the boundaries of their lowest constituent stages in a nested hierarchy, we note that one of the criteria providing global correlation potential (a stable isotope excursion in marine and terrestrial stratigraphies) lies at a stratigraphic level more than !my older than the base of the stratotypic Ypresian Stage to which the base of the Eocene Series has been subordinated until now. Lowering a chronostratigraphic unit by this extent risks a significant modification to the original geohistorical denotation of the Ypresian Stage and the Eocene Series. We discuss here four options that are open to Voting Members of the Paleogene Subcommission. One solution consists in adjusting slightly the base of the Ypresian Stage (and, thus, the Eocene Series) so as to be correlatable on the basis of the lowest occurrence/First Appearance Datum (LO/FAD) of the calcareous nannofossil species Tribrachiatus.digitalis. Another solution would be to decouple series and stages so that the Ypresian Stage remains essentially unaltered but the base of tbe Eocene is relocated so as to be correlated on the basis of the Carbon Isotope Excursion (CIE). Two (compromise) solutions consist in erecting a new stage for the upper/terminal Paleocene (between the Thanetian [sensu Dollfus] and Ypresian Stages) characterised at its base by the global stable isotope excursion. The P/E GSSP may then be placed at the base of the stratotypic Ypresian Stage (thus preserving historical continuity and conceptual denotation and stability) or at the base of the newly erected stage (facilitating correlation of the base of the Eocene series, at least in principle). Both GSSPs should be placed in suitable marine stratigraphic sections yet to be determined but upon which there is considerable current investigative activity

The Global Stratotype Sections and Points for the bases of the Selandian (Middle Paleocene) and Thanetian (Upper Paleocene) stages at Zumaia, Spain

The global stratotype sections and points for the bases of the Selandian (Middle Paleocene) and Thanetian (Upper Paleocene) stages have been defined in the coastal cliff along the Itzurun Beach at the town of Zumaia in the Basque Country, northern Spain. In the hemipelagic section exposed at Zumaia the base of the Selandian Stage has been placed at the base of the Itzurun Formation, ca. 49 m above the Cretaceous/ Paleogene boundary. At the base of the Selandian, marls replace the succession of Danian red limestone and limestone-marl couplets. The best marine, global correlation criterion for the basal Selandian is the second radiation of the important calcareous nannofossil group, the fasciculiths. Species such as Fasciculithus ulii, F. billii, F. janii, F. involutus, F.pileatus and F. tympaniformis have their first appearance in the interval from a few decimetres below up to 1.1 m above the base of the Selandian. The marker species for nannofossil Zone NP5, F. tympaniformis, first occurs 1.1 m above the base. Excellent cyclostratigraphy and magnetostratigraphy in the section creates further correlation potential, with the base of the Selandian occuring 30 precession cycles (630 kyr) above the top of magnetochron C27n. Profound changes in sedimentology related to a major sea-level fall characterize the Danian-Selandian transition in sections along the margins of the North Atlantic. The base of the Thanetian Stage is placed in the same section ca. 78 m above the Cretaceous/Paleogene boundary. It is defined at a level 2.8 m or eight precession cycles above the base of the core of the distinct clay-rich interval associated with the Mid-Paleocene Biotic Event, and it corresponds to the base of magnetochron C26n in the section. The base of the Thanetian is not associated with any significant change in marine micro-fauna or flora. The calcareous nannofossil Zone NP6, marked by the first occurrence of Heliolithus kleinpelli starts ca. 6.5 m below the base of the Thanetian. The definitions of the global stratotype points for the bases of the Selandian and Thanetian stages are in good agreements with the definitions in the historical stratotype sections in Denmark and England, respectively

Integrated stratigraphic analysis of Lower Rupelian deposits (Oligocene) in the Belgian Basin

Information from new borehole sections and cone penetration tests in the Rupelian type area has led to a reassessment of Lower Rupelian stratigraphy in the Belgian Basin. Deposits underlying the Boom Clay Formation in the type area are reclassified into the newly introduced Niel Sand Formation, including a lower Wintham Silt Member (new) and an upper Ruisbroek Sand Member (redefined). A new integrated stratigraphic framework is established for the Lower Rupelian, on the basis of grain-size, natural radioactivity, point resistance and calcareous nannoplankton data. These data are interpreted in terms of sequence stratigraphy. It is concluded that the lower part of the Rupelian stratotype is correlatable with the traditional «Upper Tongrian deposits» of Eastern Belgium, demonstrating once again the ambiguity of previous chronostratigraphic terminology.status: publishe

Trochastrites Stradner 1961

Genus Trochastrites Stradner, 1961 urn:lsid:zoobank.org:act: 9DFE30A4-E474-4861-8FDD-DE1A1491F8D4 TYPE SPECIES. — Discoaster bramlettei Martini, 1958 by subsequent designation of Stradner (1961).Published as part of Steurbaut, Etienne & Nolf, Dirk, 2021, The Mont-des-Récollets section (N France): a key site for the Ypresian-Lutetian transition at mid-latitudes - reassessment of the boundary criterion for the base- Lutetian GSSP, pp. 311-363 in Geodiversitas 43 (11) on page 347, DOI: 10.5252/geodiversitas2021v43a11, http://zenodo.org/record/489110

Lanternithus minutus Stradner 1962

Lanternithus minutus Stradner, 1962 (Fig. 18E) Lanternithus minutus Stradner, 1962: 375, pl. 2, figs 12-15. DISTRIBUTION. — L. minutus is biostratigraphically significant, despite its rather long range (upper lower Eocene-lower Oligocene). In the North Sea Basin it has a synchronous lowest consistent occurrence (LCO) within the upper middle of NP14: from the base of unit B4 (upper part of the Brussel Sand Formation) at the Mont-des-Récollets, where its occurrence coincides with the LO of Nummulites laevigatus, from about 2.5 to 3 m above the base of the ‘Glauconie Grossière s.s.’ (as defined by Blondeau 1980) in the Paris Basin (appearance level of Blackites inflatus) and from the Nummulites laevigatus Bed (F6) at Bracklesham Bay, UK. Isolated specimens occur earlier. In the Belgian Basin they are known from many localities within the lower middle of unit B3, which corre- lates with lower middle NP14. A single specimen is known from the lower part of Unit A4 (top of the Aalter Sand Formation) in the Vlakte van de Raan borehole, one from the turritellid level at Whitecliff Bay (at 225 m above the base of the London Clay, dixit D. Curry), and two from the upper part of the ‘Chaumont-en-Vexin sands’ in the Paris Basin, all attributable to the base of NP14. In west Kazakhstan (e.g. Aktulagay), L. minutus seems to appear still earlier (within the middle of NP13) (King et al. 2013). DISCUSSION This small nannolith with a box-like shape has a very distinctive morphology and optical interference pattern, allowing unambiguous and easy recognition.Published as part of Steurbaut, Etienne & Nolf, Dirk, 2021, The Mont-des-Récollets section (N France): a key site for the Ypresian-Lutetian transition at mid-latitudes - reassessment of the boundary criterion for the base- Lutetian GSSP, pp. 311-363 in Geodiversitas 43 (11) on pages 342-344, DOI: 10.5252/geodiversitas2021v43a11, http://zenodo.org/record/489110

Trochastrites hohnensis Bouche 1962

Trochastrites hohnensis (Martini, 1958) Bouché, 1962 (Fig. 20S) Discoaster hohnensis Martini, 1958: 358, pl. 1, fig. 10a-b. Trochastrites hohnensis – Bouché 1962: 91, pl. 4, figs 13, 14. DISTRIBUTION. — At the Mont-des-Récollets it is known from Unit B4 at the top of the Brussel Sand Formation and in the overlying Lede Sand Formation, up into the base of the Wemmel Sand Member. It rarely occurs elsewhere in the Lede Sand Formation (e.g. recorded at Balegem, Oosterzele, etc.). DISCUSSION Three rather long thin arms with bifurcating endings, which are lined with a narrow weblike fringe.Published as part of Steurbaut, Etienne & Nolf, Dirk, 2021, The Mont-des-Récollets section (N France): a key site for the Ypresian-Lutetian transition at mid-latitudes - reassessment of the boundary criterion for the base- Lutetian GSSP, pp. 311-363 in Geodiversitas 43 (11) on page 347, DOI: 10.5252/geodiversitas2021v43a11, http://zenodo.org/record/489110

Martiniaster Loeblich & Tappan 1963

Genus Martiniaster Loeblich & Tappan, 1963 urn:lsid:zoobank.org:act: D80B2B4E-D12E-4D53-8DBB-5081853FBC7D TYPE SPECIES. — Coronaster fragilis Martini, 1961 by subsequent designation of Loeblich & Tappan (1963).Published as part of Steurbaut, Etienne & Nolf, Dirk, 2021, The Mont-des-Récollets section (N France): a key site for the Ypresian-Lutetian transition at mid-latitudes - reassessment of the boundary criterion for the base- Lutetian GSSP, pp. 311-363 in Geodiversitas 43 (11) on page 346, DOI: 10.5252/geodiversitas2021v43a11, http://zenodo.org/record/489110

Martiniaster fragilis

Martiniaster fragilis (Martini, 1961) Loeblich & Tappan, 1963 (Fig. 18N) Coronaster fragilis Martini, 1961: 102, text-fig. 2. Martiniaster fragilis – Loeblich & Tappan 1963: 193. DISTRIBUTION. — This species is consistently but rarely present in the shallow marine Middle Eocene strata from the North Sea Basin. At the Mont-des-Recollets it ranges from the upper part of the Brussel Sand Formation (Unit B4) to the middle of the Lede Sand Formation. This does not represent its total range, as in other Belgian localities it is known to occur up to the Asse Clay Member (upper NP15) (Steurbaut 1986). Additional occurrences in adjacent basins are from the lower Lutetian sands at Grand-Alléré (NP14) in the Paris Basin (see Appendix 1) and from Fisher Beds 20 and 21 in the Hampshire Basin (NP15) (Aubry 1983). Hence, its occurrence seems to be restricted to upper NP14 and NP15. DISCUSSION With its globular outline consisting of 12 radially arranged peripheral ridges and several large central openings this taxon is easily recognisable.Published as part of Steurbaut, Etienne & Nolf, Dirk, 2021, The Mont-des-Récollets section (N France): a key site for the Ypresian-Lutetian transition at mid-latitudes - reassessment of the boundary criterion for the base- Lutetian GSSP, pp. 311-363 in Geodiversitas 43 (11) on pages 346-347, DOI: 10.5252/geodiversitas2021v43a11, http://zenodo.org/record/489110