Habilitation
Hartenfels, S. (2021): Upper Devonian to Lower Carboniferous global environmental change and impact on conodonts.
The Upper Devonian and to a less extent the Mississippian were characterized by a complex sequence of global 1st to 4th order events and crises. Bioevents, in the form of extinction, innovation, and radiation pulses, short-termed eustatic fluctuations, hypoxic/anoxic pulses, organic-rich facies, geochemical anomalies as well as isotope spikes that reflect sudden changes of palaeotemperatures, nutrient fluxes, oceanic palaeoproductivity, and volcanic events, as well as tectonics, magmatism, fluctuations of magnetic susceptibility, or the interference of Milankovitch cyclicity are thought to have triggered environmental changes and hazards of different magnitude, duration, and intensity (e.g., overviews in Myrow et al. 2011; Kaiser et al. 2015; Becker in prep.). Impact event scenarios were developed, e.g., for the Kellwasser Crisis, but these led often to more open questions than answers (Racki 2005). UV-B radiation as a trigger of terrestrial extinctions in land plants at the Devonian/Carboniferous Boundary was proposed by Marshall et al. (2020). Fields et al. (2020) brought a supernova scenario, leading to destruction of the ozone layer, for the end-Devonian mass extinctions in discussion.
Between the two well-known 1st order mass extinction intervals at the Frasnian/Famennian Boundary (Upper Kellwasser Event, e.g., Schindler 1990) and the Hangenberg Crisis near the Devonian/Carboniferous Boundary (e.g., Kaiser et al. 2015; Becker et al. 2016b, 2020b; Hartenfels et al. in prep., see appendix), other global 2nd to 4th order events or crises occurred (Fig. 1). Amongst others, the regressive Lower and Upper Condroz Events (e.g., Becker 1993b; Hartenfels et al. 2013; Ma et al. 2017) or the transgressive Lower and Upper Annulata Events (e.g., Hartenfels 2011; Hartenfels & Becker 2016a) and the Dasberg Crisis (e.g., Hartenfels & Becker 2009; Hartenfels 2011). This sequence was first summarized by House (1983, 1985) and Walliser (1984a, 1985) and later updated and/or reviewed by Becker (1993b), House (2002), and Becker et al. (2012, 2016a). As pointed out by Hartenfels & Becker (2009), there is a clear distinction between global events and crises based on their duration. Events are understood as sudden sedimentary changes (e.g., onset of black shales or sudden transgressions) and extinctions within one biozone, whereas crises consist of narrowly spaced, distinctive steps (individual events) of environmental perturbation and extinction within several biozones. Many Upper Devonian events bear similarities with specific episodes of the longer-lasting crisis and can especially be recognized, in weakly tectonised pelagic facies, globally in a pan-tropical belt from North America to North Africa, Europe, Asia, and Australia. It is understood that not necessarily all palaeoclimatic zones were affected during events or crises episodes. Apart from the Hangenberg Crisis Interval, the Upper Devonian was a time of global warm temperatures (e.g., Lakin et al. 2016), interrupted briefly by cooling pulses, e.g., associated with the Lower and Upper Kellwasser Events (e.g., Joachimski & Buggisch 2002; Joachimski et al. 2009; Hartenfels et al. 2016b). As pointed out by Becker (in prep.), greenhouse climates seem to be more prone to global perturbations than icehouse times. In the Famennian, the predominantly transgressive nature of the events/crises interrupted the overall regressive trend (compare the famous eustatic sea-level curve of Johnson et al. 1985, Cycle IIe-f; updated, e.g., in Johnson & Sandberg 1989, Hartenfels & Becker 2009, 2016a, 2016b, and Becker et al. 2012; Fig. 1). This trend was partly accompanied by a multiphased, but gradual decrease of seawater surface temperature within the palaeo(sub)tropics (Joachimski et al. 2009). However, oxygen and carbon isotope data suggest intercalated, sudden climatic changes and variations of organic palaeoproductivity within the oceans (e.g., Joachimski & Buggisch 2002; Joachimski et al. 2002, 2009; Kaiser et al. 2006, 2008; Myrow et al. 2011; Hartenfels et al. 2018).
Apart from Herbig (2016) for the Rhenish Basin, good summaries for the global Mississippian event sequence do not exist. However, since the Tournaisian was probably mostly free of ice sheets (e.g., Buggisch et al. 2008; Kaiser et al. 2008) and, therefore, predominantly a recurrent greenhouse time (Lakin et al. 2016), Devonian event/crisis patterns can also be used to explain basal Carboniferous events, such as the global Lower Alum Shale (e.g., Kalvoda 1989; Becker 1993b; Becker et al. 2016d; Kaiser et al. 2018; Herbig et al. 2019).
The impact of Upper Devonian to Mississippian events/crises on faunal groups, such as ammonoids or trilobites, attracted many researches in the past, which resulted in a huge number of publications. Partly with special emphasis on the ammonoid evolution, reviews of Upper Devonian events/crises in the (hemi)pelagic realm were published by Becker (1993b), House (1996, 2002), and Walliser (1996). Although, living in identical outer shelf settings, the effects on conodonts have not yet received the attention they deserved in the context of our aim to understand the global environmental hazards of the past. Therefore, one of the key questions is to understand how environmental change influenced and/or stimulated the evolution of conodonts. Furthermore, it is of utmost interest to clarify, if there are different extinction/innovation patterns in widely separated basins and, especially, in different facies settings. There are only few publications, which (partly) addressed these topics (e.g., Austin et al. 1970; Dreesen et al. 1986; Sandberg et al. 1988; Girard et al. 2005; Kaiser et al. 2009; Mossoni et al. 2013, 2015). In their pioneer work, Ziegler & Lane (1987) attempted for the first time to record “conodont diversity cycles” within Devonian and Lower Carboniferous strata. Later, based on lower Famennian high-resolution conodont studies, Schülke (2003) postulated a cyclic distribution within European conodont diversity patterns, which correlates with 3rd order sea-level fluctuations. The regional impact of the Annulata Events (Hartenfels 2011, Hartenfels & Becker 2016a) and Dasberg Crisis (Hartenfels 2011) on conodont faunas was analyzed, in each case, for Europe and SE Morocco, indicating significant regional differences within diversity patterns of contemporaneous conodont faunas. In particular, such research scarcity is remarkable, because almost all Devonian series and stage boundaries are defined by conodonts.
High-resolution conodont studies lead to more precise ranges of (sub)species/morphotypes in time and space and provide finally a much finer time resolution for global correlation. It enables a more precise dating of geochemical spikes or isotope-based palaeotemperature reconstructions, on the one hand, and of eustatic sea-level fluctuations, on the other hand. A refined sea-level curve forms the base for a correlation between climate pulses and conodont diversity patterns.
However, conodont stratigraphic studies lead to essential secondary aspects. In the course of taxonomic investigations, great importance should be given to capture the entire range of intraspecific variations. Moreover, “unusual” taxonomic and/or stratigraphic records from the literature have to be evaluated critically since they may merely reflect poor taxonomy or crude sampling. The taxonomic consistency of datasets demands that within all genera a similar distinction of (sub)species and morphotypes has to be applied. Based on a critical comparison of rare forms with the well-known intraspecific variations of similar but more frequent ones, well defined new and often rare (sub)species/morphotypes can be established. In the papers, which are summarized here, a total of ten new taxa and five morphotypes were introduced:
- Icriodus plurinodosus Wang, Becker, Aboussalam, Hartenfels, Joachimski & Gong, 2016
- I. praealternatus ferus Wang, Becker, Aboussalam, Hartenfels, Joachimski & Gong, 2016
- I. stenoancylus junggarensis Wang, Becker, Aboussalam, Hartenfels, Joachimski & Gong, 2016
- Neopolygnathus huijunae Wang, Becker, Aboussalam, Hartenfels, Joachimski & Gong, 2016
- “Polygnathus” pseudocommunis Wang, Becker, Aboussalam, Hartenfels, Joachimski & Gong, 2016
- Bispathodus spinulicostatus M3 sensu Hartenfels & Becker 2016b
- Neo. fibula Hartenfels & Becker, 2016b
- Pseudopolygnathus primus primus M1–M3 sensu Hartenfels & Becker 2016b
- Ps. primus tafilensis Hartenfels & Becker, 2016b
- I. ballbergensis Lüddecke, Hartenfels & Becker, 2017
- B. ultimus corradinii Söte, Hartenfels & Becker, 2017
- Siphonodella (Siphonodella) lobata M2 sensu Becker in Becker et al. 2020b
- Protognathus semikockeli Hartenfels, Becker, Herbig, Qie, Kumpan, De Vleeschouwer & Weyer, in prep., see appendix
The analyzed faunal assemblages consisted of more than 10.000 platform elements. Several further taxa remained in open nomenclature. Future studies have to clarify, if some of these represent in fact new (sub)species or not.
The papers are the outcome of extensive field campaigns and fruitful cooperations with colleagues around the globe. They were contributions to the successful UNESCO IGCP 499 “Devonian land - sea interactions: evolution of ecosystems and climate”, IGCP 596 “Climate change and biodiversity patterns in the Mid-Palaeozoic”, and IGCP 652 “Reading geological time in Palaeozoic rocks”. In addition, there was a DFG-CNRST Maroc cooperation project (Be 1367/11-1) on “Eovariscan evolution of the southern and northern Prototethys: high-resolution stratigraphy, facies developments, biogeography, and geodynamic interpretation”. Results much improved our knowledge of Upper Devonian to lower Mississippian event/crisis patterns as well as environmental changes and, therefore, the evolution of palaeoecosystems on different continents and in widely separated depositional environments. In this respect, special emphasis was placed on the impact of events/crises on conodonts – their extinction, innovation, and radiation.
As a titular member of the German Subcommission on Devonian Stratigraphy, a corresponding member of the International Subcommission on Devonian Stratigraphy, as well as an active participant of the Devonian/Carboniferous Boundary Task group, my research is also a contribution to define future Upper Devonian substages (Hartenfels et al. 2009; Hartenfels & Becker 2016a) and to the ongoing revision of the Devonian/Carboniferous Boundary (e.g., Kumpan et al. 2015; Becker et al. 2016d, 2020b; Söte et al. 2017; Feist et al. 2020; Hartenfels et al. in prep., see appendix).
The fundament of my cumulative habilitation thesis is formed by thirteen papers, listed here. These works are chronologically attached in the appendix and separate introduction pages fully reference the contributions of the habilitation candidate and all other authors to the individual papers. The contributions of each paper to the (sub)chapters in the context of the habilitation thesis are given below.
Myrow, P. M., Strauss, J., Creveling, J., Sicard, K., Ripperdan, R., Sandberg, C. A. & Hartenfels, S. (2011). A carbon isotopic and sedimentological record of the Latest Devonian (Famennian) from the western U. S. and Germany. Palaeogeography, Palaeoclimatology, Palaeoecology, 306: 147–159.
contribution to the habilitation thesis: subchapters 5.1, 6.4, 6.5
Hartenfels, S., Becker, R. T., Aboussalam, Z. S., El Hassani, A., Baider, L., Fischer, T. & Stichling, S. (2013). The Upper Devonian at El Khraouia (southern Tafilalt). In: Becker, R. T., El Hassani, A. & Tahiri, A. (eds.), International Field Symposium “The Devonian and Lower Carboniferous of northern Gondwana”. Document de l’Institut Scientifique, Rabat, 27: 41–50.
contribution to the habilitation thesis: (sub)chapters 2, 6.1, 6.3, 6.4
Kumpan, T., Bábek, O., Kalvoda, J., Grygar, T. M., Frýda, J., Becker, R. T. & Hartenfels, S. (2015). Petrophysical and geochemical signature of the Hangenberg Events: an integrated stratigraphy of the Devonian-Carboniferous boundary interval in the Northern Rhenish Massif (Avalonia, Germany). Bulletin of Geosciences, 90(3): 667–694.
contribution to the habilitation thesis: subchapters 5.3, 6.7
Wang, Z. H., Becker, R. T., Aboussalam, Z. S., Hartenfels, S., Joachimski, M. M. & Gong, Y. M. (2016). Conodont and carbon isotope stratigraphy near the Frasnian/Famennian (Devonian) boundary at Wulankeshun, Junggar Basin, NW China. Palaeogeography, Palaeoclimatology, Palaeoecology, 448: 279–297.
contribution to the habilitation thesis: (sub)chapters 2, 5.1, 6.1
Hartenfels, S. & Becker, R. T. (2016a). The global Annulata Events: review and new data from the Rheris Basin (northern Tafilalt). In: Becker, R. T., Königshof, P. & Brett, C. E. (eds.), Devonian Climate, Sea Level and Evolutionary Events. Geological Society, London, Special Publications, 423: 291–354.
contribution to the habilitation thesis: (sub)chapters 2, 4, 6.4, 7
Hartenfels, S. & Becker, R. T. (2016b online). Age and correlation of the transgressive Gonioclymenia Limestone (Famennian, Tafilalt, eastern Anti-Atlas, Morocco). Geological Magazine, 155(3): 586–629 [printed 2018, doi:10.1017/S0016756816000893].
contribution to the habilitation thesis: chapters 2, 3, 7
Hartenfels, S., Hartkopf-Fröder, C., Herbig, H.-G., Becker, R. T. & Esteban Lopez, S. (2016a). Middle Famennian to Viséan stratigraphy at Riescheid (Herzkamp Syncline, Rhenish Massif). In: Becker, R. T., Hartenfels, S., Königshof, P. & Helling, S. (eds.), Middle Devonian to Lower Carboniferous stratigraphy, facies, and bioevents in the Rhenish Massif, Germany – an IGCP 596 Guidebook. Münstersche Forschungen zur Geologie und Paläontologie, 108: 102–125.
contribution to the habilitation thesis: subchapter 6.7
Lüddecke, F., Hartenfels, S. & Becker, R. T. (2017). Conodont biofacies of a monotonous middle Famennian pelagic carbonate succession (Upper Ballberg Quarry, northern Rhenish Massif). Palaeobiodiversity and Palaeoenvironments, 97(4): 591–613.
contribution to the habilitation thesis: chapter 4
Söte, T., Hartenfels, S. & Becker, R. T. (2017). Uppermost Famennian stratigraphy and facies development of the Reigern Quarry near Hachen (northern Rhenish Massif, Germany). Palaeobiodiversity and Palaeoenvironments, 97(3): 633–654.
contribution to the habilitation thesis: (sub)chapters 2, 4, 6.7
Kołtonik, K., Pisarzowska, A., Paszkowski, M., Sláma, J., Becker, R. T., Szczerba, M., Krawczyński, W., Hartenfels, S. & Marynowski, L. (2018). Baltic provenance of top-Famennian siliciclastic material of the northern Rhenish Massif, Rhenohercynian zone of the Variscan orogen. International Journal of Earth Sciences (Geologische Rundschau), 107(8): 2645–2669.
contribution to the habilitation thesis: subchapter 6.7
Feist, R., Cornée, J.-J., Corradini, C., Hartenfels, S., Aretz, M. & Girard, C. (2020 online). The Devonian/Carboniferous boundary in the stratotype area (SE Montagne Noire, France). Palaeobiodiversity and Palaeoenvironments [doi:10.1007/s12549-019-00402-6].
contribution to the habilitation thesis: (sub)chapters 2, 6.7
Becker, R. T., Hartenfels, S. & Kaiser, S. I. (2020b accepted). Review of Devonian-Carboniferous boundary sections in the Rhenish Slate Mountains (Germany). Palaeobiodiversity and Palaeoenvironments.
contribution to the habilitation thesis: (sub)chapters 2, 3, 6.7, 7
Hartenfels, S., Becker, R. T., Herbig, H.-G., Qie, W., Kumpan, T., De Vleeschouwer, D., Weyer, D. & Kalvoda, J. (in prep.). The Devonian-Carboniferous transition at Borkewehr near Wocklum (northern Rhenish Massif, Germany) – a potential GSSP section.
contribution to the habilitation thesis: (sub)chapters 2, 6.7