ACADEMIA Letters First report of occurrence of palynomorphs in the beachrocks and their paleoecological implications Arun Kumar, Carleton Climate and Environment Research Group (CCERG) Department of Earth Sciences Carleton University Ottawa, Ontario K1S 5B6, CANADA Abstract A diverse assemblage of palynomorphs is being reported for the first time from the beachrocks of the southeastern Mediterranean Sea coast of Brega, Libya. There is no record of palynomorph assemblages from beachrocks from anywhere. The objective of this study was to explore the possibility of presence of palynomorphs from beachrocks, and if present, demonstrate their paleoenvironmental significance. The recovered palynomorph assemblages from the beachrock samples are sourced from the shallow marine environments and coastal region plants. Presence of few angiosperm pollen reflect a low floral diversity of the coastal desert environment. Algal and marine invertebrate palynomorphs suggest a low diversity in the intertidal zone of this coast. This study demonstrates that rocks that apparently are not suitable for pollen analysis can provide palaeoenvironmental information. Introduction Brega (30°26’06.0”N 19°40’01.0”) is situated on the southeastern corner of the Gulf of Sirte in southern Mediterranean Sea. Geology of Brega and presence of beachrocks was described by Kumar (2014, 2015, 2016). Mediterranean coastal Quaternary deposits of NE Libya are represented by large numbers of sabkhas, aeolian deposits, beach and coastal sand dunes and Academia Letters, November 2021 ©2021 by the author — Open Access — Distributed under CC BY 4.0 Corresponding Author: Arun Kumar, arunkumarlko@hotmail.com Citation: Kumar, A. (2021). First report of occurrence of palynomorphs in the beachrocks and their paleoecological implications. Academia Letters, Article 3884. https://doi.org/10.20935/AL3884. 1 alluvium deposits, along with outcrops of the Ajdabiya Formation (Tawadros, 2012). According to Fowler (2021) “Libya’s climate is dominated by the hot, arid Sahara, but it is moderated along the coastal littoral by the Mediterranean Sea. Libya has 2,103 species of tropical and Mediterranean plants that belong to 856 genera and 155 families and herbs (annual to perennial) dominate over woody (tree and shrub) species (Feng et al. 2013). Beachrocks are consolidated deposits resulting from lithification by calcium carbonate of sediments in the intertidal and spray zones and are formed in the tropical to subtropical climate belts between latitudes 350 N and 350 S, but they are also known from higher latitudes such as the Mediterranean Sea (Scoffin and Stoddart, 1987). An extensive review on various aspects of beachrock studies was provided by Vousdoukas et al. (2007) in which they reported on the occurrences, characteristics, and formation mechanisms of beachrocks and discussed their impacts on the coastal zones. They concluded that beachrock formation is a global and diachronic phenomenon and an overwhelming majority of beachrocks are found in tropical/subtropical and low temperate latitude, microtidal coasts. The history of beachrock distribution and theories of origin has been discussed by Gischler (2007). Moissette et al. (2013) reported abundant and diverse skeletal organisms from the beachrocks associated with the siliciclastic shallow-water lower Pleistocene deposits of Rhodes, Greece. These fossil communities indicate repeated drowning episodes; thus, they are valuable indicators of relative sea-level changes. Edwards and Mitchell (2018) described trace fossils preserved in the clastic beachrocks from the southern section of the Yallahs Salt Ponds on the southeastern coast of Jamaica. Material and Methods Five surface samples of beachrocks were collected at different places on the Brega beach. Samples are hard and compact, were macerated following the techniques described by Traverse (2007) and two slides of each sample were made. The slides were studied under an OMAX Optical Microscope (MD827S30L Series) using transmitted light. Each slide was scanned under x 400 magnification. Palynomorphs were photographed (x400 and x1000) for description and illustration. Results The palynomorph assemblage is impoverished yet diverse; are divided into five groups based on their biological affinities: (1) Angiosperm pollen grains (2) Algal palynomorphs (3) Fungal palynomorphs (4) Marine invertebrate palynomorphs, and (5) Miscellaneous palynomorphs. Academia Letters, November 2021 ©2021 by the author — Open Access — Distributed under CC BY 4.0 Corresponding Author: Arun Kumar, arunkumarlko@hotmail.com Citation: Kumar, A. (2021). First report of occurrence of palynomorphs in the beachrocks and their paleoecological implications. Academia Letters, Article 3884. https://doi.org/10.20935/AL3884. 2 The presence of diatoms in these assemblages is problematic because with 15 % hydrofluoric acid (HF) treatment they should have been destroyed. However, it is possible that not all siliceous matter was destroyed; few diatoms survived. The possibility of contamination during palynological preparation is ruled out since these diatoms are marine. The palynomorph list is as follows. Pollen grains: Periporate pollen of the families Chenopodiaceae/Amaranthaceae, Tricolpate, psilate pollen, Juniper (inaperturate, verrucate) pollen, and Arecaceae (monosulcate, psilate) pollen types 1, 2 and 3. Algal palynomorphs: Cyanobacterial trichome, Algal cell types A, B and C, Algal filaments, Diatoms: Amphora ovalis (Kützing) Kützing, 1844, Amphora sp., Licmophora cf. debilis (Kützing) Grunow ex Van Heurck, 1881, Nitzschia cf. frustulum (Kützing) Grunow in Cleve & Grunow 1880, Nitzschia cf. perspicua Cholnoky 1960 non Sovereign 1963, and chemically altered diatoms. Fungal palynomorphs:cf. Dictyosporites moruloides (Salard-Cheboldaeff and Locqin) Kalgutkar and Jansonius 2000, Fungites sp., Glomus spore, Inapertisporites typicus van der Hammen, 1954, Inapertisporites types 1, 2 and 3, Laevitubulus laxus Burgess and Edwards 1991, Polyadosporites suescae van der Hammen 1954, Reduviasporonites ramosus Kalgutkar 1993, and Xylohyphites sp. Marine invertebrate remains:Scolecodonts, Resting egg capsule, and Marine ostracod carapace. Miscellaneous forms:Trichomes (wind-blown), Cuticles, Woody fragments, and Charcoal. Discussion and conclusions Angiosperm families Chenopodiaceae/Amaranthaceae inhabit hot and arid environments in Libya (Feng et al. 2013). Arecaceae (Palmae) pollen most likely are sourced from tropical palm taxa Borassus, and Phoenix which occur along the coastal areas in Libya (Feng et al. 2013). Juniper pollen is sourced from the Juniperus phoenicea var. turbinata planted along the roadside when this town was built during 1950-1960 (Kumar, 2015). Thus, the angiosperm pollen assemblage indicates the sparse coastal flora of Libya characteristic of desert environments. Pollen of grass and Acacia sp. were not observed in this study; however, they occur along the coastal regions. Study of larger number of beachrock samples may yield such pollen. Different types of algal cells and filaments may be related to Cyanobacteria or green algae common in the Mediterranean Sea. Diatom taxa Amphora occurs in marine habitats as well as in freshwater environments. Licmophora is a benthic diatom that inhabits coastal marine Academia Letters, November 2021 ©2021 by the author — Open Access — Distributed under CC BY 4.0 Corresponding Author: Arun Kumar, arunkumarlko@hotmail.com Citation: Kumar, A. (2021). First report of occurrence of palynomorphs in the beachrocks and their paleoecological implications. Academia Letters, Article 3884. https://doi.org/10.20935/AL3884. 3 environments around the world and is known to thrive in different substrates such as sediments, rocks, and macroalgae. Licmophora cf. debilis occurs along the European coasts. Nitzschia cf. frustulum is a cosmopolitan marine and brackish water species. N. perspicua is a brackish water species that inhabits marine coasts of South Africa, the Mediterranean, and inland saline waters in Austria (Witowski et al. 2000). Taxonomic diversity of fungal palynomorphs is relatively higher in these assemblages than other groups. They include various types of fungal hyphae, spores, and a fruit body. Genus Glomus is an endomycorrhizal fungus that has a symbiotic relationship with roots of higher plants, and inhabits terrestrial habitats, such as, deserts, grasslands, and tropical forests. These spores are not normally transported; their presence is an indicator of soil erosion (Cook et al. 2011). Thus, presence of Glomus spores in these assemblages is an indicator of soil erosion along the coastal region. This fungal assemblage represents dry, hot coastal environments having wet and humid rainfall months. Marine invertebrate palynomorphs include scolecodonts, resting egg capsule of Copepods and marine ostracod carapace. Scolecodonts are any jaw piece of a polychaete annelid worm (Traverse, 2007) that commonly inhabit the coastal regions of Brega. The resting egg capsule is an egg of a marine copepod that commonly inhabits the coastal waters of the Mediterranean Sea (Molinero et al. 2009). A variety of cuticles and wood fragments observed in the assemblage are wind-blown from the coastal plants. Amorphous organic remains of seagrass Posidonia oceanica that commonly inhabit the shallow coastal regions of the Mediterranean Sea were observed among the palynomorphs. Presence of charcoal in the assemblage indicates natural fires or fires due to human activity. The palynomorph assemblages from the beachrock samples of the Brega coast demonstrate that shallow marine environments and nearby coastal region plants contribute to the assemblage. This study demonstrates that rocks apparently not suitable for pollen analysis can be productive and provide paleoenvironmental information. The source and preservation potential of palynomorphs in beachrocks is evident. Academia Letters, November 2021 ©2021 by the author — Open Access — Distributed under CC BY 4.0 Corresponding Author: Arun Kumar, arunkumarlko@hotmail.com Citation: Kumar, A. (2021). First report of occurrence of palynomorphs in the beachrocks and their paleoecological implications. Academia Letters, Article 3884. https://doi.org/10.20935/AL3884. 4 References Cook, E. J., van Geel, B., van der Kaars, S., & van Arkel, J. (2011). A review of the use of non-pollen palynomorphs in palaeoecology with examples from Australia. Palynology, 35,155-178. https://doi.org%2F10.1080%2F01916122.2010.545515 Edwards, T. C. P., & Mitchell, S. F. (2018). Trace Fossils in Clastic Beachrocks at the Yallahs Salt Ponds, Jamaica: Implications for Beachrock Cementation. Journal of Coastal Research, 34, 429–433. https://doi.org/10.2112/JCOASTRES-D-16-00176.1 Feng, Y., Lei, J-Q., Xu, X-W., & Pan, B-R. (2013). Composition and characteristics of Libyan flora. Archives of Biological Sciences, 65, 651-657. Fowler, G. L. (2021). Libya. Encyclopedia Britannica. Retrieved August 16, 2021, from https://www.britannica.com/place/Libya Gischler, E. (2007). 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