Annual Meeting on “Desert Margin Research”, Rauischholzhausen, 03-04 Feb 2017

The Annual Meeting of the working group “Desert Margin Research” of the Deutsche Gesellschaft für Geographie (DGfG) was held in the castle of Rauischholzhausen near Gießen on 03-04 Feb 2017. Project CLEAR was present with a poster gathering the most striking palaeobiological evidence for a the early Holocene lake as well as preliminary results of the shoreline survey.

The meeting provided the opportunity for several exiled Syrian geoscientists to report on the current situation of academic life threatened by the ongiong civil war, thereby dwarfing all the aspects of European academia that we consider as problems or deficiencies in our daily work.

Regarding the identification of shorelines of the contracting palaeolake at Tayma during the mid- to late Holocene aridisation, Peter Felix-Henningsen of the University of Gießen gave a fascinating talk about how he uses swamp ores and calcretes formed in shoreline positions in order to reconstruct a shirinking lake in space and time in Niger. In densely vergetated, flat lake-shore areas, vertical rhizoconcretions form through the accumulation of goethite. These swamp ores preserve the underlying sands and can be reliably dated by 14C. Unfortunately, these features have not yet been found at Tayma…

Poster presentation at the Annual meeting "Desert Margin Research"
Poster presentation at the Annual meeting “Desert Margin Research”

Wetlands or Lakes Pt. II – Discussion Papers published!

Based on some doubts on the reinterpretation of sedimentary palaeo-lake records on the Arabian Peninsula in a paper by Enzel et al. (2015), which were already raised in an earlier blogpost, a Discussion Paper was published this month led by Project CLEAR PI Max (Engel et al., 2017). In their initial contribution, Enzel et al. (2015) conclude that sites, reconstructed as perennial lakes during the Early Holocene Humid Period (EHHP) in earlier studies, rather represent palaeo-wetland environments and that the majority of the Arabian Peninsula experienced no or, if at all, only a very minor increase of rainfall at that time. The new Discussion Paper, however, backed by field geomorphologists, Quaternary geologists and (geo-)archaeologists from the Universities of Bern, Oxford Brookes, Oxford and Freiburg as well as the MPI for the Science of Human History Jena, identifies key sedimentolgical and palaeobiological indicators for lake environments (e.g. foraminifers, barnacles etc.), some of which are not referred to in the initial study. In their reply, Enzel et al. (2017) acknowledge the robust evidence brought up for perennial water bodies, whereas disagreement still exists regarding their definition: Were they shallow and spatially limited to be defined as wetlands or let their size, ecology and chemistry categorize them as lakes? Enzel et al. (2017) emphasize the presence of geomorphic remnants of shorelines as a mandatory feature of palaeo-lakes, a view challenged in the comment (Engel et al., 2017). Anyway, at Tayma, a systematic mapping campaign was carried out during fieldwork in December 2015. The debate is ongoing and genuinely appreciated by both sides!

Fig. 1 in Engel et al. 2017: Overview of key Holocene palaeo-lake sites on the Arabian Peninsula.
Fig. 1 in Engel et al. (2017): Overview of some key Holocene palaeo-lake sites on the Arabian Peninsula.

References

Engel, M., Matter, A., Parker, A.G., Parton, A., Petraglia, M.D., Preston, G., Preusser, F., 2017. Lakes or wetlands? A comment on ‘The middle Holocene climatic records from Arabia: Reassessing lacustrine environments, shift of ITCZ in Arabian Sea, and impacts of the southwest Indian and African monsoons’ by Enzel et al. Global and Planetary Change 148, 258-267.

Enzel, Y., Quade, J., Kushnir, Y., 2015. The middle Holocene climatic records from Arabia: Reassessing lacustrine environments, shift of ITCZ in Arabian Sea, and impacts of the southwest Indian and African monsoons. Global and Planetary Change 129, 69-91.

Enzel, Y., Quade, J., Kushnir, Y., 2017. Response to Engel et al. (in press): Lakes or wetlands? A comment on “The middle Holocene climatic records from Arabia: Reassessing lacustrine environments, shift of ITCZ in Arabian Sea, and impacts of the southwest Indian and African monsoons” by Enzel et al. (2015). Global and Planetary Change 148, 268-271.

Ostracod sieve pores as salinometers – Paper published

A paper with first results from the microcosm component of WP B (Micropalaeontology) of Project CLEAR recently went online with the Journal of Micropalaeontology. By investigating shapes of sieve pores in the species Cyprideis torosa (Jones) under a range of different salinities (0.6-14.8 psu), Peter Frenzel (FSU), Judith Ewald and Anna Pint (both UC) were able to identify a significant inverse correlation between the amount of rounded sieve pores and ambient water salinity, with minor influences of ionic composition. The outcome of the microcosm experiments corroborate results from studies of ostracod sieve pores in marginal marine environments, where this relationship has been proposed previously. The dataset established by Peter, Judith and Anna provides an important reference for systematically applying the proxy of sieve-pore variability to the palaeo-record of Tayma.

Frenzel_et_al_2016_fig1
Figure 1 from Frenzel et al. (2016): Left valve of Cyprideis torosa from a low-salinity microcosm. On the scanning electron microphotographs below, the different sieve-pore categories are depicted (from left to right): round (fossil), round (recent), irregular, elongate.

 

Reference

Frenzel, P., Ewald, J., Pint, A., 2016. Salinity-dependent sieve pore variability in Cyprideis torosa: an experiment. Journal of Micropalaeontology, DOI: .

New book chapters on the Tayma pollen record

Michèle Dinies and colleagues from the palynology component of Project CLEAR published two new book chapters on the recent state of knowledge in the analysis of the pollen record from the first master profile, i.e. a series of sediment cores from the southeastern part of the Tayma sabkha. Both contributions target a readership rooted in the field of Arabian archaeology.

The contribution published in a supplement volume of “Routes de l’Orient” adopts a specific perspective on the palaeo-vegetation reconstructed from pollen of the sabkha at Tayma as a natural resource for (semi-)nomad and later sedentary populations at the oasis. A significant increase in grassland – potential pastures – 8700-8000 cal yrs. BP along with limited woodland resources is reported. However, neither this type of vegetation, nor the afterwards dominating desert shrublands show any significant control by humans. Michèle still leaves the case open, whether the increase of olive frequencies identified around 7500 cal yrs. BP is related to cultivation or represents wild species.

Following her talk at the International Congress “The Archaeology of North Arabia – Oases and Landscapes” held at the University of Vienna, 5-8 December 2013, Michèle prepared an insightful overview paper on the reconstruction of vegetation based on her analysis of the pollen record from Tayma along with implications on climate, land use and plant cultivation.

 

References

Dinies, M., Neef, R., Plessen, B., Kürschner, H., 2016. Holocene vegetation, climate, land use and plant cultivation in the Tayma region, northwestern Arabia. In: Luciani, M. (ed.), The Archaeology of North Arabia – Oases and Landscapes. Proceedings of the International Congress held at the University of Vienna, 5-8 December, 2013 (=Oriental and European Archaeology 4). Austrian Academy of Sciences Press, Vienna, pp. 57-77.

Dinies, M., Neef, R., Plessen, B., Kürschner, H., 2016. Holocene vegetation in northwestern Arabia – changing natural resources. In: Goy, J., Bessenay-Prolonge, J., Betouche, A., Decaix, A., Havé, A., Hiblot, S., Perriot, C., Pichon, F. (eds.), Actualités des recherches archéologiques en Arabie. Routes de l’Orient, Hors-Séries 2, 1-19.

 

Swiss Geoscience Meeting 2016

On 18-19 November 2016, Ina Neugebauer presented the isotope geochemistry component of Project CLEAR at the Swiss Geoscience Meeting 2016, Geneva, on her poster “Centennial-scale variability of the Early Holocene Humid Period in NW Arabia inferred from high-resolution geochemistry and microfacies of the Tayma palaeolake” (Book of Abstracts, p. 41). A good opportunity for Ina to present her research at her new affiliation, the University of Geneva, where she took up a position as Research Associate in June 2016.

EGU General Assembly 2016, Vienna

Recent progress of Project CLEAR was presented during the European Geoscience Union General Assembly 2016 (17-22 April) in Vienna.

During the session “New insights in past African and Middle Eastern climates: A tribute to Françoise Gasse (CL1.16)”, Ina Neugebauer compiled new data on her TOC, CaCO3, C/N, d18O, d13C, d13C (carbonates and organic fraction), and d15N measurements from the mastercore of the Tayma palaeolake on the poster “The early Holocene humid period in the Tayma palaeolake, NW Arabian Peninsula – A high-resolution micro-facies and geochemical approach“. The data cover the stratigraphic section of c. 8500 to 8000 cal yrs. BP which is anticipated to represent the peak moisture phase during the early to mid-Holocene pluvial phase around Tayma. Ina identifies three different sub-stages: (i) aragonitic-organic varves (c. 8500 to 8300 cal. yrs BP), (ii) diatom-organic varves (c. 8300 to 8100 cal. yrs BP), frequently incorporating aragonite laminae as well as some gastropod and ostracod shells, and (iii) organic varves (c. 8100 to 8000 cal. yrs BP) with lower abundance of diatom and aragonite laminae and an increase of gypsum layers, likely heralding drier conditions.

In the same session, Anna Pint provided insights in the state of ostracod and foram analyses of the palaeo-lake deposits on her poster Ostracoda and Foraminifera associated with macrofauna of marginal marine origin in continental sabkha sediments of Tayma (NW Saudi Arabia). After an providing an overview on the microfuanal taxa representing the lake phase, Anna demonstrates how the morphology and chemistry of ostracod shells leads to quantitative reconstructions of the water chemistry.

During the session “Sediment archives and landscape evolution in dryland areas: New approaches, perspectives and challenges (GM3.4/CL1.27/HS11.11/SSS3.9)”, preliminary results of the shoreline mapping survey conducted in December 2015 were presented on the poster “Barnacles Tell no Lies – Bioclastic deposits and in-situ balanid colonies delineate shorelines of the Holocene palaeolake at Tayma (NW Saudi Arabia)“. In order to further substantiate the hypothesis that the early to mid-Holocene aquatic environment of Tayma can be categorized as a perennial lake – a view recently challenged in literature – a clear documentation of a variety of shoreline indicators (in-situ populations of the barnacle Amphibalanus amphitrite, in-situ or parautochthonous shell detritus in varying thickness) was provided.

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Fieldwork December 2015

Supported by the Scientific Committee of the Saudi Commission for Tourism and National Heritage and the German Archaeological Institute, Berlin, an interdisciplinary team of the CLEAR project spent 10 days of intense fieldwork at the oasis of Tayma in December 2015. Fieldwork was dedicated to two main tasks:

  • Excavation of a large stratigraphic trench in the northeastern part of the sabkha of Tayma in order to generate a second master profile of varved lake deposits. Sampling from the trench guaranteed a high number of seamless, unbiased composite profiles  for all working groups.
  • Systematic mapping survey of shoreline deposits along the highest Holocene lake level as these geomorphic or sedimentary features represent strong evidence for prennial lake conditions. Using precise DGPS measurements, remnant shoreline deposits were identified and mapped and sampled between elevations of 808-813 m above sea level all along the unurbanized western, northern and eastern palaeo-shores.

A small group conducted a survey to identify further potential palaeo-lake sites around the provincial capital of Tabuk, northwest of Tayma.