GSSP of the Barremian Stage
Definition
The GSSP for the base of the Barremian Stage is defined at the base of bed 171 of the Río Argos section, near Caravaca (SE Spain) and correlated by the first appearance of the ammonite species Taveraidiscus hugii.
Location
The GSSP section is located some 8 km WSW of Caravaca and 1.5 km NW of the small village of Benablón (Region of Murcia, SE Spain), on the southern bank of the river Río Argos. Geographic coordinates of the base of the section are 38º4’13.5”N 1º56’54.3”W, altitude: 771 m.
Sedimentology and ammonite stratigraphy
The GSSP section is thick, well exposed, and tectonically almost undisturbed. It encompasses the Berriasian–Upper Albian interval, and sedimentation seems continuous with no evidence of interruption or condensation except for a hiatus comprising the Upper Aptian–Middle Albian (van Veen, 1969; Gea, 2004). Sedimentological, palaeontological, taphonomic and palaeoichnological data indicate that the Río Argos succession was deposited in a stable, distal, low-energy, deep-water marine environment.
The lower 8 m of the section (beds 144 to 154; bed numbering of Hoedemaeker and Leereveld (1995), belonging to the Pseudothurmannia ohmi ammonite Subzone (ASz) and most of the Pseudothurmannia mortilleti ASz, consist of a rhythmic alternance of light gray limestone beds (10–75 cm thick) and dark gray marlstone interbeds (10–65 cm thick). A thin laminated black shale interval occurs at the base of the Pseudothurmannia mortilleti ASz (bed 148), which represents the local equivalent of the Faraoni Level (Baudin, 2005; Company et al., 2005; Sauvage et al., 2013; Baudin and Riquier, 2014). The uppermost part of the P. mortilleti ASz and the Pseudothurmannia picteti ASz (beds 155 to 170b, with a thickness of 15 m) are represented by a predominantly marly interval with yellowish limestone and marly limestone beds (10–45 cm thick) and light grey marlstone layers up to 120 cm thick. The following 9 m of the section (beds 171 to 182, T. hugii ASz) correspond to a more regular succession of yellowish limestone beds (10–45 cm thick) and greyish marlstone interbeds (10–60 cm thick). The uppermost 8 m of the section (beds 183 to 192, Psilotissotia colombiana ASz) are made of thick marlstone layers (up to 100 cm) alternating with thinner marly limestone beds (10–40 cm thick).
Texturally, the sediments composing the lithological successions are mudstones with calcitised radiolarians and scarce foraminifera. The lime fraction is mostly made up of calcareous nannofossil remains (Hoedemaeker and Leereveld, 1995; Gressier, 2010), while clay minerals (illite, smectite, chlorite and kaolinite) are the main components of the detrital fraction (Moiroud et al., 2012).
Primary Marker
The first appearance of the ammonite species Taveraidiscus hugii at the base of bed 171 (at 22.8 m from the base of the section).
Secondary Markers
Listed below from the stratigraphic bottom to the top: (Abbreviations: FO= First Occurrence; LO= last occurrence; FLE= Faraoni Level Equivalent)
• Bed 138: FO of the planktonic foraminifera species Lilliputianella roblesae and Lilliputianella semielongata. These events mark the base of the L. semielongata Zone.
• Bed 144: FO of the ammonite genus Pseudothurmannia (species Pseudothurmannia ohmi).
• Bed 148: LO of the calcareous nannofossil species Lithraphidites bollii. This event, which coincides with the base of the FLE, marks the boundary between NC5B and NC5C calcareous nannofossil Subzones.
• Bed 148: FO of the ammonite species Pseudothurmannia mortilleti and Sabaudiella simplex.
• Bed 149: FO of the ammonite species Pseudothurmannia pseudomalbosi and Sabaudiella argosensis.
• Interbed 154–155: FO of the calcareous nannofossil species Nannoconus circularis (typical forms).
• Interbed 154–155: FO of the dinoflagellate species Subtilisphaera senegalensis, and LO of the dinoflagellate species Palaecysta complicate.
• Bed 155: FO of the ammonite species Discoidellia favrei.
• Bed 156: FO of the ammonite species Pseudothurmannia picteti and Garroniceras morloti.
• Bed 158: LO of the belemnite species Duvalia dilatate.
• Bed 160: LO of the ammonite genus Pseudothurmannia, and FO of the ammonite species Barremites tenuicinctus.
• Bed 164: LO of the ammonite species Sabaudiella argosensis.
• Bed 169: LO of the ammonite species Garroniceras morloti.
• Bed 170: FO of the ammonite species Taveraidiscus intermedius.
• Interbed 170–171: LO of the dinoflagellate species Exiguisphaera phragma.
• Bed 171, primary marker: FO of the ammonite species Taveraidiscus hugii (base of the Barremian).
• Bed 174: FO of the ammonite species Psilotissotia chalmasi.
• Interbed 175–176: FO of the benthic foraminifera species Gavelinella barremiana and Conorotalites bartensteini. The two species have a wide geographic distribution.
• Bed 182: LO of the ammonite species Discoidellia favrei.
• Bed 183: FO of the ammonite species Psilotissotia colombiana.
• Interbed 185–186: LO of the calcareous nannofossil species Micrantholithus spinulentus.
• Interbed 185–186: FO of the benthic foraminifera species Conorotalites intercedens.
• Bed 188: FO of the belemnite species Duvalia silesiaca.
• Bed 193: FO of the ammonite species Kotetishvilia nicklesi.
• Bed 195: FO of the belemnite species Duvalia pontica.
• Interbed 195–196: LO of the benthic foraminifera species Dorothia kummi.
Geochronology
According to the astrochronological analysis, the base of the Barremian is dated at 125.77 Ma, and it is separated by a time interval of 0.74 myr from the start of the Faraoni Episode.
Correlation Events
Further auxiliary marker criteria, with global correlation potential, are provided by non-biostratigraphic methods:
• The base of the Barremian correlates with the beginning of a gradual negative trend in the C-isotope curve near bed 170. The trend to lower C-isotope values is preceded by a 10-meter interval with stable C-isotope compositions. The positive C-isotope excursion related to the Faraoni Episode is below the stable interval.
• Bodin et al. (2009) provide a Sr-isotope value of 0.707470 for the lowermost Barremian in the Angles section.
• Indirect calibration to the magnetostratigraphic scale suggests that the Hauterivian–Barremian boundary falls in the lowermost part of polarity chron M3r.
• The boundary is located in the depositional sequence Ha7, corresponding approximately to the transgressive surface of the sequence.
• The cyclostratigraphic analysis indicates a duration of 0.80 myr for the P. ohmi ammonite Zone (AZ) and of 0.56 myr for the T. hugii AZ. The time interval from the start of the Faraoni Episode to the Hauterivian–Barremian boundary is assessed at 0.74 myr. The base of the Barremian Stage is dated at 125.77 Ma.
Links
Company, M., Aguado, R., Baudin, F., Coccioni, R., Martinez, M., Rawson, P. F., Weissert, H., Boulila, S., Deconinck, J.-F., Frontalini, F., Giusberti, L., Granier, B., Janssen, N. M. M., Moiroud, M., Monna, F., O’Dogherty, L., Pellenard, P., Riquier, L., Romero, G., Sandoval, J., Tavera, J.M. (2024). The Global Boundary Stratotype Section and Point (GSSP) of the Barremian Stage at Río Argos (Caravaca, SE Spain). Episodes 2024; published on line 1 June 2024; 47(2): 335-379 https://doi.org/10.18814/epiiugs/2023/02330 GSSP Table