First Report of Araucariaceae Wood (Agathoxylon Sp.) from the Late Cretaceous of Turkey

Home , Narman, Oltu

IAWA Journal, Vol. 33 (3), 2012: 319–326 fIrst Report of Araucariaceae wood (Agathoxylon sP.) from the Late Cretaceous of Turkey

Hatice Kutluk1, Osman Kır1 and Ünal Akkemik2*

SUMMARY Oltustone is a semi-precious gemstone found only in the Late Cretaceous (Upper Maastrichtian) Dutlu Formation of Turkey. Microscopic exami- nation of oltustone reveals that it consists of fossilized Agathoxylon wood (Araucariaceae). This represents one of the latest occurrences of the Araucariaceae in southern Eurasia and is also the southernmost recorded for the Laurasian continent. Key words: Agathoxylon, Araucariaceae, oltustone, wood anatomy, Dutlu Formation, Cretaceous, Erzurum-Turkey.

Introduction

Oltustone, also known as ‘Black Amber’, is a semiprecious gemstone unique to Turkey. Natural oltustone is dull and black in appearance, but when polished it acquires an attractive black sheen. The name ‘oltustone’ derives from the town of Oltu, province of Erzurum (Fig. 1), where it is most commonly excavated. Skillful artisans have used oltustone for centuries to manufacture jewelry and decorative items. Although several studies have treated the geology and petrology of oltustone (e.g., Göymen 1976; Çiftçi et al. 2002; Karayiğit 2007), no previous study has been done to determine the source plants. The aims of this paper are: 1) to describe and then discuss the affinities of the wood from which the oltustone originated, and 2) to discuss the palaeobiogeographic significance of the wood.

MATERIALS AND METHODS

The oltustone samples analyzed in this study were collected at a point approximately 20 m inside a 70 m long pithole that is close to Günlüce village (40° 41' 01.57" N by 42° 02' 52.54" E) at an altitude of 2200 m above sea level (Fig. 1). Four small (3–5 cm) cubic samples were taken from pieces of trunks occurring in thin horizons in the Dutlu Formation. Cross, radial, and tangential thin sections were prepared from all four samples. The thin sections are deposited in the Geology Department of Eskişehir Osmangazi University. The description primarily uses terms from the IAWA Softwood List (IAWA Committee 2004).

1) Osmangazi University, Department of Geology, 26480 Batı Meşelik, Eskişehir, Turkey. 2) İstanbul University, Faculty of Forestry, Department of Forest Botany, 34473 Bahçeköy, İstanbul, Turkey. *) Corresponding author [E-mail: [email protected]].

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Figure 1. Location map of the oltustone site.

GEOLOGICAL SETTING

The age of the Dutlu Formation is considered Late Cretaceous, most probably Maastrich- tian (Nebert et al. 1964; Özkan et al. 1984; Bozkuş 1990; Dönmez & Işık 1999). The Late Cretaceous marine deposits where oltustone is found form the basal sedimentary units of the Oltu-Narman Basin. Located in the northeastern part of eastern Anatolia, the Oltu-Narman landscape extends along an 8–15 km wide and 80 km long, NE-SW trending basin (Nebert et al. 1964; Bozkuş 1990; Dönmez & Işık 1999). Marly layers of the Dutlu Formation, 70–80 cm thick, exhibit oltustone in the form of thin, discrete horizons and lenses ranging in thickness from 3 to 15 cm. The Oltu-Narman Basin once formed part of the İzmir-Ankara-Erzincan (İAE) Ocean (Bozkuş 1990; Yılmaz et al. 1997; Dönmez & Işık 1999; Görür & Tüysüz 2001; Okay 2008). The İAE Ocean, together with Intra-Pontide and Inner Taurid Oceans, formed branches of the Tethys Ocean that divided Pangea into two mega-continents: Laurasia and Gondwana. The branches of the Tethyan ocean separated six continental units that ultimately combined to form the land mass of modern Turkey. This proc- ess occurred over a time span extending from the early Triassic to the Eocene. The Strandja, the İstanbul, and the Sakarya continents belonged to Laurasia, whereas the Kırşehir Block, the Menderes-Taurid platform, and the southeastern part of Anatolia belonged to Gondwana. Continental units that were situated either as the marginal areas of Laurasia and Gondwana or as isolated islands emerging from the Tethyan ocean appear to have stood at low elevations with no major mountain ranges. The vegetation cover would have included coniferous forests during the warm and equitable climate that prevailed globally during the Late Cretaceous (Şaroğlu & Yılmaz 1986; Yılmaz et al. 1997; Görür & Tüysüz 2001; Okay 2008).

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The woods that became oltustone must have originated from forest detritus on the eastern part of the Sakarya continent and were transported by streams and deposited as sediments in the İAE Ocean. The uplifts in the region during the Neogene were so rapid and forceful that the study area rose to the present-day elevation of 2000–2500 m (Şaroğlu & Yılmaz 1986). Today oltustone is excavated at altitudes above 2200 m. The unique qualities of Turkish oltustone possibly resulted from unique physico- chemical conditions that the fossil wood comprising oltustone endured in the volcano- sedimentary units of the Oltu-Narman basin. Contact metamorphism resulting from nearby volcanic activities possibly caused resinuous woody materials to undergo an unusually high degree of coalification.

RESULTS Description Araucariaceae Genus Ag a t h o x y l o n Hartig Agathoxylon sp. (Fig. 2 & 3) Indistinct growth rings, with 1–2 rows of radially narrowed tracheids. Resin canals absent. Tangential and radial diameters of tracheids 49 (26–72) µm and 53 (30–77) µm, respectively. Tangential walls of tracheids are unpitted. Radial walls with araucarioid type bordered pits that are uni- to biseriate, generally contiguous, with round to polygonal borders of 22 (16–25) µm in diameter. Rims of Sanio absent. Helical thickening absent. Resin plugs occasional. Rays exclusively uniseriate. Ray tracheids absent. Rays 2–9 (1–15) cells or 28 (21–40) µm high, 2–4(–5) rays per mm. Araucarioid cross-field pits, 4–11 per cross-field and 7.6 (5.4 –9.8) µm in diameter. Crystals absent. Axial parenchyma not observed.

Affinities The following features seen in the oltustone wood are considered diagnostic of the Araucariaceae: 1) poorly defined growth rings; 2) bordered pits on radial walls of tracheids commonly uniseriate to biseriate, uniseriate pits often separate and circular, but they may also be flattened above and below, biseriate pits alternate and mostly polygonal; 3) one to fifteen simple circular or elliptical bordered pits per cross-field; 4) rays uniseriate, rarely biseriate; and 5) resin canals and axial parenchyma absent or rare (e.g., Kraus 1870; Phillips 1948; Savidge 2007). We used Philippe and Bamford’s (2008) key for Mesozoic conifer-like woods. Ac- cording to that publication, these samples can be assigned to Agathoxylon, because of the following features: 1) more than 90% of pits on the radial wall of tracheids are contiguous to neighbouring pits and these pits are often somewhat flattened, 2) when multiseriate, they are always alternately arranged, 3) Sanio rims are absent, 4) cross- fields are araucarioid with numerous contiguous unordered cupressoid to taxodioid pits, 5) helical thickenings are absent, and 6) end walls of ray cells are perpendicular. All these features are visible in Figures 2 and 3.

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Figure 2. Agathoxylon sp. – 1: Tracheids rounded in outline, indistinct growth ring boundary, XS. – 2 & 3: Tracheids with possible resin plugs, XS. – 4: Possible resin plugs (white arrow), and perpendicular end wall of ray cells (black arrow), RLS. – 5: Araucarioid type cross-field pitting, RLS. – 6: Perpendicular end wall of ray cells, RLS. — Fig. 2.1 & 2.4 from sample 1; Fig. 2.2, 2.3, 2.5 & 2.6 from sample 2. — Scale bars = 100 µm in 2.1–2.3; 60 µm in 2.4; 20 µm in 2.6; 10 µm in 2.5.

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Figure 3. Agathoxylon sp. – 1: Predominantly araucarian pitting, RLS. – 2: Resin plugs in tracheids (white arrow), RLS. – 3: Short uniseriate rays, less than 10 cells high, TLS. – 4: Alter- nately arranged biseriate bordered pits. – 5–7: Araucarioid cross-field pitting. — Fig. 3.1 from sample 1; Fig. 3.2 from sample 2; Fig. 3.3–3.5 from sample 3; Fig. 3.6 & 3.7 from sample 4. — Scale bars = 100 µm in 3.1–3.3; 30 µm in 3.4; 10 µm in 3.5–3.7.

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We are referring to the oltustone woods as Agathoxylon sp. Many species of fossil Araucarioid wood have been described. Differences between many of these species are slight and are of the type of variation that can be seen in a single extant species or with a single tree. Consequently, we leave this wood as Agathoxylon sp. Agathoxy- lon ulmitus (Iamandei & Iamandei 2004) from Romania is the species of Agathoyxlon that is closest geographically and it is of similar age. It differs from the Turkish wood as it has narrower tracheids (20–35 µm diameter) and more rays per mm (8–12).

DISCUSSION

The history of the Araucariaceae, today native to the Southern Hemisphere, has been reviewed by Kershaw and Wagstaff (2001). Due to the limited survival of land areas of the Late Cretaceous in Anatolia, limited information is available regarding terrestrial vegetation of that time and no fossil record of Araucariaceae has been previously reported in Turkey. Philippe et al. (2006) reported the occurrence of Araucarioxylon in Georgia and Armenia, which are located to the east of Turkey, during the Jurassic– Early Cretaceous. Araucariaceae were found associated with Elatides-Classopollis forests of the mid-latitudes in North America and Eurasia in mid-Cretaceous (Krassilov 1978). A flora of Cheirolepidiaceae (Classopollis) together with the pollen of other coniferales such as Tsugaepollenites, Pityosporites, Clavatipollenites and Circumpol- lis existed in the shallow marine Jurassic sequences in the vicinity of Bayburt (Ağralı et al. 1965), a town very close to the study site; however, no pollen of Araucariacites has ever been reported for the Jurassic or Cretaceous of Turkey. The affinity of the latest known occurrence of Araucariaceae species, Araucarites pojarkovae, from the Danian strata of Russia (Krassilov 1976, 1978) has been re- examined by Van der Ham et al. (2010). They suggest the Russian species may belong to the family Doliostrobaceae, not Araucariaceae, and that seed-cone scales from the Upper Maastrichtian of the Netherlands represent the last appearance of the family in Europe. Since the Dutlu Formation is considered Upper Maastrichtian, the oltustone Agathoxylon wood may be considered as one of the latest occurrences of the family in Eurasia. The Dutlu Formation is approximately 5–10 degrees further south than the other recorded Late Cretaceous European occurrences of Araucariaceae in Belgium, Netherlands, Germany, France and Czech Republic. Assuming that the eastern por- tion of the Sakarya continent was the habitat of Araucariaceae in Turkey, the fossilized wood of our oltustone specimens must also represent the southernmost record of the Araucariaceae family ever recorded for the Laurasian continent.

CONCLUSION

This study details the first record of fossil Araucariaceae wood from Turkey, but with an age of 65–70 million years (Maastrichtian). This is the oldest fossil wood ever recorded from Turkey. The occurrence of Araucariaceae in Turkey possibly reflects the southernmost record of the this family in the Laurasian continent, as well as one of the latest examples ever recorded in southern Eurasia.

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ACKNOWLEDGEMENTS

Dr. B. Aytuğ, Emeritus Professor of the Faculty of Forestry, who was born in Erzurum, in the province of Oltustone, suggested that H. Kutluk investigate its origin during her doctorate study in İstanbul University. Dr. L.V. Hills (University of Calgary) critically reviewed the manuscript. Dr. N. Rauh (Purdue University) edited the English language of the paper. Mr. H. Can ([email protected]) skillfully prepared thin sections of the woods. Sincere gratitudes to them are hereby expressed.

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