Palynological and Paleobotanical Investigations of Paleogene ...

ISSN 08695938, Stratigraphy and Geological Correlation, 2015, Vol. 23, No. 3, pp. 300–325. © Pleiades Publishing, Ltd., 2015. Original Russian Text © G.N. Aleksandrova, T.M. Kodrul, J.H. Jin, 2015, published in Stratigrafiya. Geologicheskaya Korrelyatsiya, 2015, Vol. 23, No. 3, pp. 69–95.

Palynological and Paleobotanical Investigations of Paleogene Sections in the Maoming Basin, South China G. N. Aleksandrovaa, T. M. Kodrula, and J. H. Jinb a

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Geological Institute (GIN), Russian Academy of Sciences, Pyzhevskii per. 7, Moscow, 119017 Russia State Key Laboratory of Biocontrol and Guangdong Provincial Key Laboratory of Plant Resources, School of Life Sciences, Sun Yatsen University, Guangzhou, China email: [email protected], [email protected] Received February 3, 2014; in final form, August 25, 2014

Abstract—The complex paleobotanical investigations carried out in the Maoming sedimentary basin (Guangdong Province, South China) yielded first data on the taxonomic composition and ecological prop erties of two large paleofloras from the Youganwo and Huangniuling formations. The palynomorph assem blages from these formations indicate their middle–late Eocene age (Lutetian–Bartonian and Priabonian for the former and latter, respectively). It is shown that sediments of the Youganwo Formation were deposited in an intermittently swamped lacustrine–fluvial plain, which gave way to a freshwater lake. Vegetation of this period was represented by wet subtropical forests with evergreen Fagaceae, Lauraceae, and Palmae. The Hua ngniuling flora reflects the biome of seasonal tropical forests developed in a broad fluvial plain and its margins. The Eocene floras of the Maoming Basin are marked by the appearance of several recent plant genera, which is also evident from finds of remains of their reproductive structures. The Eocene flora from low latitudes of South China exhibits a notable share of floral elements from middle and high latitudes of East Asia. Keywords: Eocene, South China, spores, pollen, fossil plants, climate DOI: 10.1134/S0869593815030028

INTRODUCTION The Late Mesozoic–Cenozoic biota and climate of low latitudes are objects of recent extensive paleonto logical and paleoecological investigations. Such inter est in the study of the paleofloras from these regions is explained by the need to understand factors responsi ble for the formation of highly diverse floral commu nities of recent tropical forests and its dating, recon struct an evolutionary trend of this biome, and predict its probable future changes. At present, evidence for the existence of Late Cretaceous, Paleocene, and Eocene tropical floras originates mostly from the recent Neotropical biogeographic region and southern areas of North America (Johnson and Ellis, 2002; Burnham and Johnson, 2004; Jaramillo et al., 2010). The data on southeastern Asian tropical paleofloras, especially characterizing the Eocene epoch marked by the appearance of many recent taxa mostly of the generic rank, remain scarce. In southern Asia, paleobotanical investigations of such kind were largely conducted on the Hindustan Peninsula (Bhattacharyya, 1983, 1985; Lakhanpal and Guleria, 1983; Lakhanpal et al., 1984; Bande and Prakash, 1986; etc.). During the last decade, such investigations were substantially intensified (Bande, 1992; Mehrotra, 2000, 2003; Mehrotra et al., 2003; Srivastava and Mehrotra, 2010; Dutta et al., 2011;

Kumar et al., 2012; Srivastava et al., 2012; etc.). Exten sive information on Paleogene and Cenozoic (mostly Oligocene and Miocene) lowlatitude floras of China has recently been obtained in Yunnan, Guangxi, and Fujian provinces and on Hainan Island (Jin, 2009; Jin et al., 2009, 2010; Yao et al., 2009; Shi and Li, 2010; Xie et al., 2010; Xing et al., 2010; Su et al., 2011; Feng and Jin, 2012). For a long time, the Cretaceous and Paleo gene–Neogene climate and floras of southeastern Asia have been investigated by R. Morley using palynological data (Morley, 1991, 1998, 2000, 2001, etc.). The Maoming sedimentary basin, which contains one of the largest oil shale deposits of China is located in the southwestern part of Guangdong Province (Fig. 1). This NWextending grabenlike structure filled with Upper Cretaceous, Paleogene, and Neo gene terrigenous sediments (Nan and Zhou, 1996; Ye et al., 1996) is approximately 50 km long and 10 km wide. The section of Paleogene fluvial and lacustrine sedimentary rocks approximately 2700 m thick is rep resented from the base upward by the following forma tions: Tongguling, Youganwo, Huangniuling, Shang cun, Laohuling, and Gaopengling. The Tongguling Formation is composed of red colored feldspar siliceous calcarenites, sandy con glomerates, and volcanic rocks. No fossils have been recorded from this formation. The formation is condi

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Fig. 1. Schematic location of examined sections.

tionally dated back to the Late Cretaceous (Nan and Zhou, 1996) or Paleocene–early Eocene (Ye et al., 1996). The Youganwo Formation is 70–150 m thick. Its lower part consists of sandy conglomerates, sand stones, graygreen to purplered clayey shales, and coal seams; the upper part is dominated by dark gray to dark brown oil shales with subordinate yellowish brown mudstones alternating with coals. The oil shales yielded remains of fishes (Cyprinus maomingensis Liu), reptilians (Anosteira maomingensis Chow et Liu, Isometremys lacuna Chow et Yeh, Aspideretes impres sus Yeh, Adocus inexpectatus Danilov, Syromyatni kova, Skutschas, Kodrul et Jin, Tomistoma petrolica Yeh, Alligatoridae gen. et sp. indet.), and mammals (Lunania cf. youngi Chow) (Chow and Liu, 1955; Liu, 1957, Yeh, 1958, 1963, Chow and Yeh, 1962; Li, 1975; Wang et al., 2007; Tong et al., 2010; Danilov et al., 2013; Skutschas et al., 2014). The Youganwo Forma tion was considered to be the middle Eocene–early Oligocene in age on the basis of palynological data (Yu and Wu, 1983; Li et al., 2006) or late Eocene in age on the basis of mammal Lunania cf. youngi remains (Wang et al., 2007; Jin, 2008). The overlying Huangniuling Formation (60–200 m thick) is largely formed by grayish yellow, graywhite, and pale red sandy conglomerates, sandstones, and grayish green mudstones with intercalations of oil and asphaltbearing sandstones in the upper part. The for mation is presumably the Miocene in age (Nan and Zhou, 1996). According to Ye et al. (1996), the sedi mentary complex of the Maoming Basin including the Youganwo, Huangniuling, Shangcun, and Laohuling formations should be dated back to the middle–late Eocene. The organic remains in the Huangniuling For mation are represented by leaf impressions of Alnus cf. kefersteinii (Goepp.) Unger and Castanea cf. miomollis sima Hu et Chaney (Nan and Zhou, 1996; Ye et al., 1996). The Shangcun Formation (300–500 m thick) is dominated by grayish brown and greenish gray com pact mudstones, sandy shales, and siltstones with sub ordinate intercalations of oil shales and coal seams in the lower part. It contains fossil: plants Zelkova ungeri Kovats, Liquidambar miosinica Hu et Chaney, and Castanea miomollissima; gastropods Viviparus sp., Tulotomoides kuangsiensis, and Melania sp.; and palynomorphs (Nan and Zhou, 1996; Ye et al., 1996). The Laohuling Formation (over 300 m thick) is composed of graywhite and grayyellow sandy con glomerates and gravely sandstones with mudstone lenses. No organic remains are found in this unit. The Gaopengling Formation (500–1800 m thick) consists of poorly sorted conglomerates, medium to coarsegrained sandstones, and grayish yellow to pur plered siltstones barren of organic remains. The for STRATIGRAPHY AND GEOLOGICAL CORRELATION

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mation is presumably the Pliocene in age (Ye et al., 1996). On the basis of paleomagnetic data on borehole sections of the Youganwo, Huangniuling, Shangcun, and Laohuling formations (Wang et al., 1994), the whole sedimentary complex was considered as corre sponding to the interval of normalpolarity magnetic zones (C18n–C11n) of the geomagnetic polarity time scale (GPTS), which comprises the time interval of 42 to 32 Ma (middle Eocene–early Oligocene). Thus, age of most lithological units in the Mao ming Basin remains debatable. The purpose of this investigation is to specify the age of the Youganwo and Huangniuling formations and reconstruct lowlatitude plant communities, paleoland scapes, and paleoclimatic parameters for this region of southeastern China, which belonged in the Eocene pre sumably to the ecotone zone between two climatic belts: tropical and arid subtropical (Scotese, 2003). MATERIAL AND METHODS The bedbybed description of the upper part of the Youganwo Formation and the lower part of the Hua ngniuling Formation and their sampling were per formed in three sections recovered by the Zhengjiang, Shigu, and Jintang quarries in the southwestern part of the Maoming Basin during field works in spring of 2011 (Fig. 1). The description was accompanied by bedbybed sampling of organic macroremains, palynological samples, and taphonomic analysis of fossil plant local ities in both formations. The upper part of the You ganwo Formation yielded remains of fishes, croco diles, and turtles. Two horizons with very abundant and diverse oryctocoenoses formed by vegetative and reproductive plant remains were first defined in the Huangniuling Formation. In total, 40 samples for the palynological analysis and collection of bedbybed sampled plant remains were obtained during these field works. A complex of paleobotanical, biostratigraphic, and statistical methods were used for these investigations. The paleobotanical methods included (1) the tapho nomic analysis of fossil plants on the basis of their mac romorphological and microstructural features; (b) anal ysis of palynomorph assemblages (spores, pollen of ter restrial plants, and microalgal remains), which yields information on regional vegetation and depositional environments and allows the age of host sediments to be specified; and (c) analysis of the geographical and stratigraphic distribution of taxa, their paleoecologii cal properties, and probable migration routes. The biostratigraphic investigations were accompanied by the study of sedimentological features of host deposits and analysis of taphocoenoses for reconstructing the composition of the paleobiota and its habitat condi tions. The analysis of the taxonomic composition,

structure, and diversity of floral assemblages provided grounds for the preliminary qualitative assessment of the past climate. For the preliminary treatment of palynological samples, the technique accepted in the Laboratory of Paleofloristics (GIN, Moscow) was used. It includes several successive procedures: (1) treatment of sam ples with 10% HCl solution for elimination of carbo nates; (2) treatment of samples with 5% Na4P2O7H2O solution and subsequent elutriation in distilled water for removal clayey particles; (3) centrifugation of the residual sediment in a solution of heavy liquid K2(CdI4) with the specific weight of 2.25. For remov ing silicate minerals, the treatment of the macerate with HF was applied. The obtained macerates were placed into a test tube with glycerin. The examined samples are stored in the Laboratory of Paleofloristics (GIN, Moscow). Practically all the examined samples contain fossil palynomorphs. Their preservation is variable: poor and moderate in the Youganwo Formation; good and excellent in the Huangniuling Formation. The taxo nomic and statistical analyses of palynomorphs were performed for all the samples: at least 200 specimens or all of them in samples with low abundances were counted. The qualitative and quantitative changes in the composition of palynomorphs served as a basis for defining assemblages characteristic of bedranked bio stratigraphic units. These assemblages were compared mainly with Paleogene palynological assemblages in southern areas of China (Ye et al., 1996). Figures 2–4 illustrate the stratigraphic distribution of palyno morph taxa; Figs. 5–7 show variations in percent pro portions of different palynomorph groups through the examined sections; Plates I–VII present characteristic taxa of palynomorphs. DESCRIPTION OF SECTIONS The sections are characterized from the base upward; no contacts with under and overlying strata are observable. Zhenjiang quarry section (21°52′47.5′′ N; 110°40′06.3′′ E) Yo u g a n w o F o r m a t i o n Bed 1. The observable basal part of the section is rep resented by a member of greenish gray clay with some admixture of silt, massive, compact, fissured, ferrugi nate along fissures. The apparent thickness is 5 m. Bed 2. Dark brown to black clay, plastic, fissured, with thin lenticular coal seams, ferruginate at the base. The thickness is 1.0–1.1 m. Bed 3. The sediments of the previous bed grade into light brownish gray clay 0.3 m thick overlain by light gray siltstones 0.8 m thick with three intercalations (0.05 m each) of inequigranular poorly consolidated sandstones with gravel admixture. The bed is crowned

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Bed 5. Greenish gray (tobacco gray in the wet state), silty, compact, massive, highly fissured, enclos ing an intercalation (1 m above the base) of yellowish gray finegrained sand with vague horizontal bedding and cherrycolored spots of Fe hydroxides. The thick ness is 5 m. Vol. 23

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ALEKSANDROVA et al. Fig. 5. Spore–pollen diagram for the Jintang section.

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Bed 6. Browngray plastic clays with slickensides and plant detritus overlie the previous bed with gradual transition. The upper part of the bed contains black semilustrous bedded coals with remains of ferns Osmunda lignitum (Giebel) Stur and Equisetales. The surface of the bed is uneven. The thickness is 0.5 m. Bed 7. Greengray clays laterally replaced by sands and poorly lithified sandstones, intensely ferruginate at the base. The upper part of the bed encloses brown ish gray inequigranular massive sands with small gravel admixture and abundant plant detritus. Its uppermost part contains black foliated coals and carbonaceous clays with impressions of fronds and segments of ferns from the family Polypodiaceae and abundant remains of seeds and rhizomes of Nelumbo Adans. The thick ness is 3 m. Bed 8. Browngray and black clays with coal lenses. The thickness is 3 m. Bed 9. Greenish gray clay, plastic, with low silt admixture and rusty spots of Fe hydroxides. In the uppermost part of the bed, clay is light brown, massive, plastic (0.6 m). The thickness is 3.6 m. Bed 10. Carbonaceous clays and black coals with impressions of plants (Osmunda lignitum). The thick ness is 0.1–0.5 m. Bed 11. Brown clays, plastic, clotted, with plant detritus and small lenses of greenish gray sand. The thickness is 0.4 m. Bed 12. Brown clay with platy jointing and single fish remains, resting upon the previous bed with the uneven surface. The thickness is 1 m. Bed 13. Alternating dark gray carbonaceous clays and black foliated coals with abundant impressions of Osmunda lignitum and angiosperm leafs. The thickness is 1.2 m. Huangniuling Formation Bed 14. Conglomerates and light greenish gray gravelites (up to 1 m thick) corresponding to its basal part are overlain by light reddish brown clays with par allel bedding and lenticular intercalations of light gray to reddish gray sands (2.5 m) and gray foliated silty clays with abundant plant detritus along bedding sur faces and thin coal lenses in the upper part. The total thickness is 6 m. Bed 15. Greenish gray clays, compact, plastic, fis sured, ferruginate along fissures. The thickness is 1.8 m. Bed 16. Reddish and greenish gray sandstones (gray in the wet state), finegrained, compact, forming three intercalations up to 0.7 m thick, alternating with poorly consolidated sandstones and gray poorly sorted conglomerates and enclosing thin lenses of gray and greenish gray clays and silts. The thickness is 7 m. Bed 17. Greenish gray silty clays, compact, highly fissured. The thickness is 5.5 m.

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Fig. 6. Spore–pollen diagram for the Shigu section.

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Bed 18. Brownish and greenish gray sandstones, vaguely bedded, poorly consolidated to compact in the upper part, with gravelite lenses. The thickness is 1.0– 3.3 m. Bed 19. Light greenish to brownish gray clays and clayey siltstones with an even lower contact. The thickness is 6.2 m. Bed 20. Gray, rusty, and reddish brown sandstones, largely coarsegrained, with pebbles and gravel, inter calated by abundant thin (2–3 mm) carbonaceous laminae in the lower part, and ferruginate at the top. The thickness is 3.5 m. Bed 21. Greenish and cherry–gray clays, com pact, silty, with an uneven lower contact. The thick ness is 4.2 m. Bed 22. Gray sandstones (rusty in the weathered state), vaguely bedded with coalified plant detritus along bedding surfaces and wood fragments in the lower third of the unit and lenticular intercalations of gravel and pebbles in its upper part. The thickness is 5 m. Bed 23. Greenish gray compact clays. The thick ness is 3 m. Bed 24. Gray (cherrycolored in the wet state) sandstones, poorly consolidated, fine to coarse grained. The thickness is 4 m. Bed 25. Greenish gray (cherrygray in the wet state) clays. The thickness is 3 m. Higher, the section is unexposed.

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Shigu quarry section (21°50′44.9′′ N; 110°45′40.7′′ E) Yo u g a n w o F o r m a t i o n Bed 1. The observable basal part is represented by brown to graybrown clay, compact, with slickensides. The apparent thickness is 1.5 m. Bed 2. Pale green silty clay. The thickness is 1.1 m. Bed 3. Gray quartz sand, coarsegrained, unsorted, poorly cemented. The thickness is 0.5 m. Bed 4. Pale green silty clay, brown in the uppermost part. The thickness is 2–3 m. Bed 5. Dull black coal. The thickness is 0.05– 0.10 m. Bed 6. Gray to brownish gray clay, with fine parallel lamination and plant detritus along bedding surfaces (particularly at the base). The thickness is 0.85 m. Bed 7. Light gray silty clay, slightly ferruginate along fissures. The thickness is 1.2–1.3 m. Bed 8. Black carbonaceous clay and coals. The thickness is 0.15–0.20 m. Bed 9. Greenish gray clay, brown in the upper part. The thickness is 1.2 m. Bed 10. Black carbonaceous clays, compact, fis sured. The thickness is 0.25–0.30 m.

ALEKSANDROVA et al. Fig. 7. Spore–pollen diagram for the Zhenjiang section.

Bed 11. Greenish gray (brown in the wet state) clay, massive, fissured. The thickness is 2.5 m. Bed 12. Browngreen clay, splintered into small acuteangled fragments (joint), with intercalation of carbonaceous clay (0.10–0.15 m) 0.8 m above the base. The thickness is 2 m. Bed 13. Dark brown clay with angular joint. The thickness is 1 m. Bed 14. Dark brown oil shale, laminated. The thickness is 0.4 m. Bed 15. Greenish gray clay, tobaccocolored in the weathered state, massive. The thickness is 2 m. Bed 16. Black coal, clayey at the top. The thickness is over 1 m. Bed 17. Chocolate clay, plastic, massive. The thick ness is 0.2 m. Bed 18. Black coal, foliated, forming lenticular laminae. The thickness is 0.10–0.15 m. Bed 19. Greengray clay (tobaccocolored in the weathered state), locally silty, plastic, massive. The thickness is 2.1 m. Bed 20. Dark brown oil shale, laminated, alternat ing with black carbonaceous shale and coal, and con taining remains of Nelumbo rhizomes and fruit of the legume genus Podocarpium A. Braun ex Stizenberger. The thickness is 1.7 m. Bed 21. Chocolate clay, greenish gray in the upper part, massive, plastic, overlying the previous bed with gradual contact. The thickness 1.4 m. Bed 22. Rhythmically alternating (from the base upward) brown massive compact clay (0.5 m), dark brown oil shale with thinplaty joint (0.25 m), and black semilustrous coal overlying the previous bed with a sharp contact. The thickness is 0.95 m. Bed 23. Chocolate clay, massive, compact, resting with gradual transition upon underlying sediments. The thickness is 0.7 m. Bed 24. Rhythmically alternating (from the base upward) dark brown to black carbonaceous clays (0.6 m), oil shale (0.3 m), and black lustrous foliated coal with a shelly fracture. The thickness is 1.3 m. Bed 25. Light brown siltstone, light gray in the wet state. The thickness is 0.55 m. Bed 26. Greenish gray clay, compact, massive, highly fissured, replacing siltstones with a gradual transition. The thickness is 1.2 m.

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Plate I. Characteristic palynomorphs from Paleogene sec tions of the Maoming Basin. (1) Laevigatosporites hardtii; (2) Extrapunctatosporites alveolatus; (3, 8) Cyclophorus sisporites spp.; (4) Deltoidospora sp.; (5) aff. Asplenium sp.; (6) Riccia sp.; (7) Polypodiaceoisporites potonei; (9) Osmun dacidites semiprimarius; (10) Crassoretitriletes sp., (11) Poly podiisporites favus. Magnification for all figures ×1000.

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Bed 27. Rhythmically alternating (from the base upward) chocolate and dark brown clays (0.1 m), black lustrous coal, with shelly fracture (0.2 m) and brown oil shales (0.25 m). Total thickness is 0.8 m. Bed 28. Greenish gray clay (gray in the wet state), compact, massive, fissured, ferruginate along fissures. The thickness is 1.2 m. Bed 29. Dark brown oil shale (0.75 m) replaced higher in the section by dark gray to black clays with lenses of lustrous coal characterized by shelly fracture and resting upon Bed 28 with a gradual transition. The thickness is 0.85 m. Bed 30. Brown sandstone, poorly consolidated, with lenticular parallel thin intercalations of light gray sandstone. The thickness is 1.15 m. Bed 31. Dark gray to black oil shale, with lenticu lar intercalations of foliated dull and lustrous coals with a shelly fracture in the upper part. The thickness is 2.15 m. Bed 32. Light brown sandstone, poorly consoli dated, finegrained, with lenticular intercalations of light gray sandstone and concretions of presumably marcasite composition, and becoming dark brown in the upper part, where the admixture of clayey material and organic matter, including plant detritus, increases. The thickness is 1.5 m. Huangniuling Formation Bed 33. The basal part with an uneven lower con tact is composed of rusty clay overlain also with an uneven contact by rusty sandstone, unsorted, cemented by Fe hydroxides, with gravel and quartz pebbles. The thickness is 1.8 m. Bed 34. White finegrained clayey sandstone, poorly consolidated, resting upon the previous bed with a grad ual transition. The apparent thickness is 3 m. Higher, the section is unexposed. Jintang quarry section (21°42′33.2′′ N; 110°53′19.4′′ E) Yo u g a n w o F o r m a t i o n Bed 1. The observable basal part is represented by dark brown to black dull coals alternating with carbon aceous siltstones congaing plant detritus. The appa rent thickness is 1 m. Bed 2. Greenish gray clay (brown in the wet state) with slickensides. The thickness is 0.3 m. Bed 3. Dark brown to black dull coals. The thick ness is 0.3 m. Bed 4. Greenish and bluish gray clays, massive, vaguely bedded. The middle part encloses lenses of

gray coarsegrained sand and contains plant detritus along bedding surfaces and leaf remains of dicotyle donous plants including Platanaceae. In the upper part of the section, clay is gradually replaced by its browngray silty variety. The thickness is 4.5 m. Bed 5. Black dull coal. The thickness is 0.3 m. Bed 6. Brown clay (light green in the weathered state), massive. The thickness is 1 m. Bed 7. Double coal seam with a thin clay intercala tion in the middle part. The thickness is 0.5 m. The unexposed interval of 1.5 m. Bed 8. Brownish clay at the base (0.1 m), overlain by black coal. The thickness is 0.4 m. Bed 9. Brown clay, massive, with slickensides and coal seam (0.1 m) in the middle part. The thickness is 1.5 m. Bed 10. Dark brown oil shale, coarseplaty, with rare plant remains, including fragments of Nelumbo rhizomes and dicotyledonous plant leaves with ser rated margin. The sediments 8 m above the base con tain scattered small (up to 4 cm) rounded concretions of light brown siderite (?) coated with sediments. The upper part of the bed yielded crocodile and turtle remains. The thickness is approximately 39 m. Bed 11. Light brown clays, gray to lilac gray and vio let in the middle part of the section, and greenish gray in its upper part, plastic, massive, with slickensides and rare dark gray carbonate concretions, gradually replac ing shales of the previous bed. The thickness is 4 m. Huangniuling Formation Bed 12. Bluish gray coarsegrained sandstone, vaguely bedded, with an uneven lower contact compli cated by pockets. The thickness is 0–0.5 m. Bed 13. Light gray to gray (at the top) sands, rusty in the weathered state, inequigranular, unsorted, crossbedded, with gravel and pebbles, ferruginate at the base (0.02–0.03 m). The thickness is 6 m. Bed 14. Clay with thin intercalation of rusty sand stones at the base, resting with an uneven contact upon the previous bed. The clay is sandy, with abundant plant detritus, coniferous megastrobiles, and plant shoots in the lower part, higher in the section replaced by light rose, browngray, and greenish gray plastic clays with plant remains (leaves and reproductive structures of Pinaceae, Podocarpaceae, Lauraceae, Fagaceae, and others). The thickness is 7 m. Bed 15. Yellowish gray sandstone, coarsegrained in the lower part and finegrained in the upper part, crossbedded, with an uneven lower contact and thin intercalation of rusty sandstone cemented by Fe hydroxides at the base. The uppermost part of the bed

Plate II. Characteristic palynomorphs from Paleogene sections of the Maoming Basin. (1) Tricolpopollenites liblarensis; (2) Quer cus gracilis; (3, 4) Quercoidites spp. (verrucate morphotype); (5, 7, 8) Quercoidites spp.; (6) Quercus forestdalensis; (9) Anacardi aceae; (10, 24, 28) Rhoipites spp.; (11, 12, 17, 18) Rutaceae; (13) Diospyros sp.; (14, 15) Retitricolpites sp.; (16) Pleurospermaepol lenites sp.; (19, 20) ?Capparidaceae; (21) Rhoipites porrectus; (22, 23) ?Fabaceae; (25, 26) Castanea sp.; (27) Tricolporopollenites scabratus; (29) Menispermum sp.; (30) Ilexpollenites sp.; (31) Cornaceae; (32) Tricolporopollenites satzveyensis; (33) Sapotaceae; (34) Tricolporopollenites mansfeldensis. Magnification for all figures ×1000. STRATIGRAPHY AND GEOLOGICAL CORRELATION

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includes rare intercalations of rusty sandstone similar to that at the base. The thickness is 7 m. Bed 16. Gray sandstone, poorly consolidated, crossbedded, coarsegrained, with ferrugination spots. The lower part encloses intercalations satu rated with rounded kaolinite concretions 1–7 cm across and lenses of white finegrained sandstones. The thickness is 3 m. Bed 16. Gray sands, poorly consolidated, coarse grained, with ferrugination spots. The lower part of the section contains intercalations saturated with rounded kaolinite concretions 1–7 cm in diameter and lenses of white finegrained sandstones. The thickness is 3 m. Bed 17. White finegrained sands, kaolinized, with siltstone intercalations exhibiting thin parallel bedding and an uneven lower contact complicated by a thin ferruginate layer at the base. Up the section, the sedi ments become gradually coarsegrained. The thick ness is 2.5–3.0 m. Bed 18. Pinkish and gray clays, bedded, with an uneven lower contact and ferrugination crust at the base, abundant wellpreserved plant remains: Pinaceae, Podocarpaceae, Lauraceae, Fagaceae, Hamamelidaceae, Altingiaceae, Fabaceae, Myri caceae, Juglandaceae, Myrtaceae, Rhamnaceae, Ulmaceae, Celastraceae, Dipterocarpaceae, and others. The thickness is 3 m. Bed 19. Gray coarsegrained sandstone and grav elite, crossbedded, with an uneven lower contact and ferrugination crust at the base. The lower part of the bed is saturated with kaolinite concretions similar to those in Bed 16. The thickness is 5.5 m. Bed 20. Pale, gray, and variegated (green and cherry) clays, compact, massive, with an insignificant silt admixture and ferrugination crusts at the base and top of the bed. The thickness is 0.2–6.0 m. Bed 21. Gray vaguely bedded gravelite. The thick ness is 3 m. Up the section, an unexposed interval.

PALYNOLOGICAL ASSEMBLAGES Two palynological spore–pollen assemblages replacing each other up the section are defined in the Youganwo Formation (Figs. 2–7). Its lower (coalbear ing) part is characterized by the palynological assem blage PA1 with a high amount of spores (40–60% on average). They are dominated by forms belonging to the family Polypodiaceae: Laevigatosporites hardtii Thom son et Pflug, Polypodiisporites favus Potonie, Polypodia ceoisporites potonei (Potonie et Gelletich) Kedves, and aff. Asplenium sp. Locally, they are accompanied by abundant megaspores, massulae, glochidiums, and

spores of Azolaceae and Salvinaceae associated with spores of Ischyosporites convolutes Song et Zeng and Ischyosporites sp. A, rare Osmundacidites semiprimarius (Krutzsch) Ke et Shi, Deltoidospora sp., (Cyatheaceae?), Crassoretitriletes sp. (Lygodiaceae), and Riccia sp. (Hepataceae). The group of angiosperms is mostly rep resented by small tricolpate pollen such as Quercoidites henrici (Potonie) Potonie, Q. microhenrici (Potonie) Potonie, Quercoidites sp., Quercus gracilis Boitz., and Q. graciliformis Boitz., as well as by Tricolpites and Tri colporopollenites representatives (mostly T. cingulum (Potonie) Thomson et Pflug and T. liblarensis (Thomson) Thomson et Pflug). Other angiosperms are represented by pollen grains of Palmae, Ulmaceae (Ulmodeipites tricostatus And., U. planeraeformis And., U. krempii And., Ulmodeipi tes sp.), Rhoipites spp., and Alnipollenites precordata Simpson in considereble amounts. The assemblage is characterised by the presence of Hamamelidaceae (Hamamelis sp., Fothergilla sp., Corylopsis princeps Lyubom.), Liquidambarpollenites sp., Caryapo llenites sp., Platycaryapollenites sp., Juglanspollenites sp., Engelhardia sp., Momipites coryloides Wodehouse, Ilex pollenites sp., Rutaceae, Potamogeton sp., Sparganium sp., single Dipterocarpaceae, Loranthus sp., Corsinipol lenites triangulus (Zakl.) Ke et Shi, Lonicerapolis sp., Margocolporites sp., Moraceae, Retitricolpites sp., ?Pan danus sp., and others. Gymnosperms are scarce being of low diversity: solitary pollen grains of Pinuspollenites and alete pollen close to that of Taxodiaceae–Cupres saceae. The taxonomic composition of PA1 and its quantitative structure imply deposition of sediments constituting the lower part of the Youganwo Formation in swamped plain environments, which is also indicated by lithological properties of the host section. The second palynological assemblage (PA2) is established in oil shales of the upper part of the You ganwo Formation. It differs distinctly from the assem blage in the lower part of the formation in the propor tions between its main constituting components rather than in the taxonomic composition. The dominant role in this palynological assemblage belongs to small tricolpate angiosperm pollen (Quercoidites sp., Tricol pites sp., Tricolporopollenites spp.) and freshwater alga Pediastrum sp. (aff. Pediastrum simplex var. sturmii (Reinsch) Wolle). As compared with the previous assemblage, the abundance of spores is reduced, although their diversity becomes notably higher toward the top of the formation owing to the appear ance of Baculatisporites primarius (Wolff) Pflug et Thomson, Cyclophorusisporites sp., C. bullis Song, Lee et Zhang, Extrapunctatosporites microalveolatus Krutzsch, Mediobaculisporites sp., Polypodiisporites communicus Song et Li, and others. Angiosperms are

Plate III. Characteristic palynomorphs from Paleogene sections of the Maoming Basin. (1, 2) Ericaceae; (3, 4) Proteacidites sp.; (5, 9, 13, 17–19) Liquidambarpollenites spp., (8, 12, 16) ?Cyperaceae; (10, 11, 14, 15) Fupingopollenites sp. Magnification for all figures ×1000. STRATIGRAPHY AND GEOLOGICAL CORRELATION

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characterized by the increase in the pollen amount of Moraceae, Rutaceae, Retitricolpites sp., Rhoipites sp., and Momipites sp. The assemblage is marked by the appearance and permanent occurrence of pollen Ephedripites spp., Cycadaceae–Ginkgoaceae, ex gr. Sciadopitys sp., Quercus conferta Boitz., Q. forestdalensis Trav., Castanopsis pseudocingulum (Potonie) Boitzova, Sapotaceae, Araliaceae, Menispermum sp., Myrica sp., Cyperaceae, single Pleurospermaepollenites sp., Ole aceae, Anacolosa sp., Retimultiporopollenites sp., Alan giopollis sp., Bombacites sp., and others. The terminal part of the section characterized by PA2 exhibits the decrease in abundance of Quercus conferta Boitz. and Q. forestdalensis Trav., which makes the last palynolog ical assemblage similar to that from the Huangniuling Formation. The amount of gymnosperm pollen increases mostly owing to development of Taxodiaceae–Cupres saceae representatives. Freshwater phytoplankton is represented by Tetraedron sp., Chomotriletes sp., and sporadically occurring Botryococcus sp. in addition to Pediastrum sp. A notable role in this assemblage belongs also to fungi spores and gyphae. The presence of remains of microalga Pedia strum sp., which is a typical inhabitant of mostly small shallowwater wellheated meso and eutrophic basins, allows the assumption that the upper part of the Youganwo Formation was formed in lacustrine settings. The palynological spectra from the middle and upper parts of the oil shale sequence in the Jintang section contain in abundance amorphous organic matter, which may indicate more stagnant and deepwater con ditions in this part of the Maoming Basin. For the Huangniuling Formation, representative palynological assemblages are observed only in samples obtained from clayey lenses with plant macrofossils in the Jintang and Zhenjiang sections (Figs. 2, 4, 5, 7). The palynological assemblage from the examined part of the Huangniuling Formation (PA3) includes found in the Youganwo Formation (assemblages PA1 and PA2), however complex PA3 generally is more diverse. The dominant angiosperm group is represented by pollen of Anacardiaceae, Tricolpopollenites spp., Tricolpoporopol lenites satzveyensis Pfl., T. mansfeldensis Krutz., T. taugourdae Gr.Gav. (=Rosaceae), T. megaexatus (Pot.) Th. et Pfl. (=Cyrillaceae–Clethraceae), Cory lopsis princeps Lubm., Corylopsis sp., Hamameli daceae, Fagaceae (Quercoidites spp., Quercus type8 sensu Liu et al., 2007, Quercus graciliformis, Q. con ferta Boitz., Q. forestdalensis Trav.), Liquidambar spp., Rhus sp., Pleurospermaepollenites sp., Sterculiaceae, Rhoipites porrectus Boitz., Rhoipites spp., Fabaceae, Araliaceae, Aralia sp., Nyssa sp., Tetracolpopollenites

rotundus Roche (=Sapotaceae), Rutaceae, Salixpolle nites sp., Cornaceoipollenites sp., Diospyros sp., Menispermum sp., Ilexpollenites spp., ?Capparidaceae, Loranthaceae, Symplocaceae, Fupingopollenites sp., Corsinipollenites trinagulus Zakl. (=Onagraceae), Eri caceae, Euphorbiaceae, Moraceae, Ulmaceae, Myrt aceae, Engelhardia sp., Platycaryapollenites sp., Juglans horniana Trav., Subtriporopollenites subporatus Krutz. (=Juglandaceae), Carya spp., Triatriopollenites plicoides Zakl., Alnipollenites sp., Palmae, and others. In the angiosperm spectrum, small pollen of Quercoid ites spp. belonging to evergreen oaks looses its domi nant position, giving way to taxa close to deciduous oaks (Qeurcus conferta Boitz., Q. forestdalensis Trav.) and tricolpate pollen of oaks with verrucate exine. Pollen of gymnosperm plants is still of low abun dance, being mostly represented by Pinuspollenites spp. with a subordinate amount of Ephedripites spp., Podocarpidites sp., Sciadopitys sp., and Taxodiaceae– Cupressaceae. Spores are locally dominated by Poly podiaceae and Hepataceae (Riccia sp.) representa tives, accompanied by subordinate Grassoretitriletes sp. and Osmundaceae. The palynological spectra con tain abundant and diverse fungi spores and gyphae. The lithological features indicate deposition of sedi ments constituting the Huangniuling Formation in fluvial environments. Six palynological assemblages corresponding to the early and late Paleocene, early, middle, and late Eocene, and Oligocene (PA1–PA6) are defined in Paleogene sections of China (Zhang, 1995). The first three palynological assemblages (PA1–PA3) demon strate many features in common with middle–late Eocene assemblages, which are characterized by the dominant role of tricolpate and tricolpoporate pollen close to Fagaceae, presence of Ulmaceae, Juglan daceae, and Myricaceae pollen, and absence of pollen of the Normapolles stemma characteristic of Pale ocene and lower Eocene sections (Song et al., 1999). This level is also marked by the appearance of the majority of recent taxa. Against the background of the dominant role of pollen close to Fagaceae, the late Eocene palynological assemblages of South China are characterized by the presence of Alnipollenites pollen. The latter is established in palynological assemblages from both formations. The Oligocene palynological assemblages of China differ significantly from late Eocene assemblages in the dominant role of Pinacae pollen and appearance of Gramineae pollen. The last group (Chenopodiaceae, Artemisia, Graminea, and others) is missing from the palynological assemblages of the Maoming Basin. Betula pollen, which is charac teristic of Neogene sections in different regions of

Plate IV. Characteristic palynomorphs from Paleogene sections of the Maoming Basin. (1–4) Platycaryapollenites sp.; (5–10) Momi pites sp.; (11, 12) Engelhardiapollenites sp.; (13, 14) Juglans horniana; (15, 16) Alnipollenites precordata; (17, 18) Myrica sp.; (19) Symplocoipollenites sp.; (20, 21, 25–30) Ulmoideipites spp.; (22, 23) Loranthus sp.; (24, 31, 32) Caryapollenites spp. Magnifica tion for all figures ×1000. STRATIGRAPHY AND GEOLOGICAL CORRELATION

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China together with Gramineae taxa (Wu et al., 2003; Wang, 2006), is also missing. Taken combined, these features indicate that the examined sediments of the Maoming Basin are older than the Oligocene. As a whole, the palynological assemblages estab lished in the sections of the Youganwo and Huangniul ing formations in the Maoming Basin are very similar to the Quercoidites microhenrici–Pteridophyta spores– Alnipollenites Assemblage from Eocene sections of the South China Sporopollen Region, which comprises Yunnan, Guangxi, and Guangdong provinces and the South China Sea (Ye et al., 1996). Their similarity is evi dent from both the taxonomic composition and abun dances of taxa. The features in common for these assemblages are as follows: (a) the dominant role of tri colpate and tricolpoporate pollen among angiosperms (mostly Quercoidites spp.); the amount of porate pollen in Maoming assemblages is lower, although locally it is abundant due to the presence of Alnipollenites pollen; (b) high concentration of fern spores; (c) low abun dance and taxonomic diversity of gymnosperm pollen. The Quercoidites microhenrici–Pteridophyta spores– Alnipollenites palynological assemblage is established in sediments of the Changchang Basin on Hainan Island assigned to the upper Eocene (Lei et al., 1992; Yao et al., 2009) and in the lower and middle parts of the Nadu Formation in the Bose Basin (Liu and Yang, 1999), the late Eocene age of which is confirmed by finds of mammal remains, dinoflagellates, and ostra cods (Zhang et al., 2003; Zhai et al., 2003). The taxo nomic composition and abundances of taxa in the Eocene Quercoidites microhenrici–Pteridophyta spores–Alnipollenites palynological assemblage are slightly variable, thus providing grounds for defining three stages in palynoflora development: early, middle, and late (Ye et al., 1996). On the basis of the frequent occurrence of porate Ulmaceae and Alnipollenites, dominant role of spores, and low share of gymnosperm pollen, the palynological assemblage from the lower (coaliferous) part of the You ganwo Formation (PA1) may partly be correlated with the early stage of the Quercoidites microhenrici–Pteri dophyta spores–Alnipollenites palynological assem blage. In southern China, the sediments characterized by the palynoflora of the early stage are represented by the Xibu Formation in the Sanshui Basin, the lower part of the Gucheng Formation in the Nanxiong Basin, and upper part of the Changliu (Beibuwan Basin) in the South China Sea area (Ye et al., 1996). By the angiosperm pollen composition, the palynological assemblage from the upper part of the Youganwo Formation (PA2) is close to the regional palynoflora of the middle stage. Their features in com mon are the dominant role of Quercoidites pollen among angiosperms and frequent occurrence of

Ulmaceae, Momipites, and Alnipollenites pollen. The finds of Pediastrum sp. characteristic of this assem blage were previously recorded in the Liushagang Formation of the Beibuwan Basin in the northern part of the South China Sea, which is dated back to the late Eocene–early Oligocene (Yu, 1983), middle Eocene (The South…, 2009), or middle–late Eocene (Ye et al., 1996). The sediments corresponding to the middle stage of the Quercoidites microhenrici– Pteridophyta spores–Alnipollenites palynological assemblage are established in the Huachong Forma tion of the Sanshui Basin, members 2–3 of the Liushagang Formation of the Beibuwan Basin, and the Wenchang Formation of the Zhujiangkou Basin (Ye et al., 1996). The palynological assemblage dom inated by Quercoidites, Ulmipollenites, Taxodiaceae pollenites, Alnipollenites, and Poypodiaceae is recorded in the Bogang Formation of the Bose Basin, which is correlated with a part of the Shahejie For mation in the Bohaiwan Basin, where it is dated back to the terminal middle–late Eocene (Ye et al., 1996). The comparison between the late stage of the Quercoidites microhenrici–Pteridophyta spores– Alnipollenites palynological assemblage (Ye et al., 1996) and the assemblage established in the Huang niuling Formation (PA3) revealed significant simi larity in their taxonomic compositions. Both palyno logical assemblages are characterized by high abun dance of Quercoidites and Retitricolpites pollen, accompanied frequently by Alnipollenites, Liquidam barpollenites, Ulmaceae, Gothanipollis (=Loran thaceae), and Juglanspollenites. Some differences determined likely by deficiency of material obtained only from clay lenses with plant macrofossils from the lower part of the formation are mostly reflected in the slightly higher amount of pollen belonging to deciduous oaks among angiosperms and low abun dance of gymnosperms in the assemblage PA3. In southern China, the sediments with the Quercoidites microhenrici–Pteridophyta spores–Alnipollenites palynological assemblage of the third stage are docu mented in the Yongjiang Formation of the Nanning Basin and in lower part of the Jiuxikeng Formation of the Hepu Basin. They are also correlated with the Nadu and Baigang formations from the Bose Basin, Member 1 of the Liushagang Formation from the Beibuwan Basin (with some conditionality), the lower part of the Enping Formation of the Zhujiangkou Basin, and the Huangniuling Formation in the Maoming Basin (Ye et al., 1996). Thus, the comparison of the palynological assem blages defined in sections of the Maoming Basin with those established for the South China region reveals that their age may be limited to the middle–late Eocene. It is most likely that sediments from the

Plate V. Characteristic palynomorphs from Paleogene sections of the Maoming Basin. (1–7) Pediastrum sp. (aff. Pediastrum sim plex var. sturmii). Magnification for all figures ×900. STRATIGRAPHY AND GEOLOGICAL CORRELATION

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examined parts of the Youganwo and Huangniuling formations were deposited in the Luthetian–Barto nian and Priabonian ages, respectively. The analysis of the taxonomic composition and abundances of palynomorphs from the Maoming Basin allows the middle–late Eocene succession of paleosettings to be reconstructed for the region under consideration. The lower part of the Youganwo For mation was formed in humid climatic, most likely, subtropical environments. The high amount of small tricolpate pollen (Quercoidites sp., Quercus gracilis, Q. graciliformis) in the palynological assemblage from the upper part of the Youganwo Formation, which is close to that of evergreen oaks, may indicate relative aridization of the climate at that time. The intermit tently swamped lacustrine–fluvial plain reconstructed in this region for the period marked by deposition of the coaliferous part of the Youganwo Formation was replaced by a large lake, which accumulated oil shales. Freshwater phytoplankton, mostly Pediastrum sp. and, to a lesser extent, Tetraedron sp., Chomotriletes sp., and Botryococcus sp., served as a source of organic matter for these sediments. The composition of the palynological assemblage from the Huangniuling Formation implies some rise of average annual temperatures and humidity during its formation. It includes pollen of plants characteristic of the tropical and subtropical zones, which verrucate grounds for assuming a climate close to tropical during deposition of sediments constituting the Huangniul ing Formation. The palynological assemblage from these sediments is still dominated by Fagaceae pollen. At the same time, it includes in abundance taxa close to deciduous oaks (Quercoidites sp. with verrucate exine, Quercus conferta Boitz., Q. forestdalensis Trav.). This feature combined with the significant amount of pollen belonging to broadleaved plants indicates a seasonal climate. PLANT MACROFOSSIL ASSEMBLAGES Despite the fact that plant macrofossils in the Maoming Basin were discovered almost two decades ago (Nan and Zhou, 1996; Ye et al., 1996), they were never subjected to thorough taxonomical and paleo ecological investigations. Our biostratigraphic investi gations revealed that plant remains are primarily con fined to the lower coaliferous part of the Youganwo Formation (plant macrofossil assemblages Y1); in the Huangniuling Formation, plant macrofossils are reg istered in lenticular clay intercalations at least at two stratigraphic levels (plant macrofossil assemblages H1 and H2) (Figs. 2, 4).

The coal deposits of the Youganwo Formation are largely characterized by concentrated phytoorycto coenoses frequently composed of horsetail or fern and Nelumbo remains. The oryctocoenoses in sediments sandwiched between coal seams are represented by the scattered distribution of plant macrofossils and their polytaxonic composition (mostly leaves, rhizomes, and reproductive structures of woody and aquatic angiosperms; the lenses and intercalations of fluvial sandstones contain abundant wood fragments and large parts of tree stems). The basal part of the observ able section of the Youganwo Formation encloses a member of siltstones and sandstones with large calcar eous concretions with concentrated diverse phytoo ryctocoenoses under the productive coal seam. In the Huangniuling Formation (Jintang section), we found plant remains at two stratigraphic levels (Fig. 2). The lower level (H1) is characterized by oryctocoenoses of two types. The massive sandy clays belonging most likely to floodplain facies contain mostly polytaxonic oryctocoenoses of the irregularly scattered type: plant remains are usually deformed, chaotically oriented, and represented by large organs (coniferous megastrobiles, shoots of plants). The overlying parallelbedded clays (probably, oxbow facies) contain concentrated polytaxonic orycto coenoses with plant remains frequently forming leaf roofs. Similar leaf roofs are also observable in orycto coenoses of the second level (H2) with plant fossils in the upper part of the section of the formation under consideration recovered by the quarry. According to the preliminary study, the macrofloral assemblage from the Youganwo Formation (Y1) includes approximately 65 morphotaxa: Equisetales, Filicales (Osmundaceae, Polypodiaceae, Salviniaceae), conifers (Podocarpaceae), and dominant angiosperms (Nelumbonaceae, Lauraceae, Platanaceae, Hamamel idaceae, Altingiaceae, Fagaceae, Fabaceae, Anacardi aceae, Euphorbiaceae, Myrtaceae, Celastraceae, Ulmaceae, Arecaceae, and others). The presence of a number of characteristic species from the genera Osmunda L., Nelumbo, Laurophyllum Goeppert, Quer cus L., Platimelliphyllum N. Maslova, Liquidambar L., cf. Celastrus L., Leguminophyllum A. EscalupBassi, Podocarpium A. Braun ex Stizenberger, Zelkova Spach, and others in this assemblage in common with the Changchang flora from Hainan Island and also their similar taxonomic composition and other features make it possible to assume their synchronism. Our paleobotanical investigations on Hainan Island and in the Maoming Basin reveal that the Eocene low latitude floras of China have several taxa in common with Cenozoic middle and highlatitude floras of Asia, North America, and Europe (Kodrul et al., 2012).

Plate VI. Characteristic palynomorphs from Paleogene sections of the Maoming Basin. (1–3, 6) Palmae; (4, 8) Ephedripites sp.; (5) Hamamelis sp.; (7, 11) Vitreisporites spp.; (9, 14) Taxodiaceae–Cupressaceae; (10, 12) Chomotriletes sp.; (13, 17) Pinuspolle nites sp., (15) Corsinipollenites triangularis Zakl.; (16) Podocarpus sp. Magnification for all figures ×1000. STRATIGRAPHY AND GEOLOGICAL CORRELATION

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For example, it appeared that the Youganwo and Changchang floras contain remains of Platanaceae leaves first discovered in low latitudes of East Asia, which may be attributed on the basis of their morpho logical features to the genus Platimeliphyllum. Like other species from this genus from middle latitudes of East Asia and North America, the South China spe cies is characterized by significant morphological vari ability of leaves. The leaves of the Chinese Platimeli phyllum are most similar to leaves from Eocene sec tions of Primorye assigned to Platanus sp. (Pavlyutkin, 2007) and some leaves from upper Eocene sediments of the Zaissan Depression described as Dicotylophyl lum sp. (Aver’yanova, 2012). The plant remains from the Youganwo Formation include also abundant leaf impressions, which may belong to the recent genus Zelkova. The fossil leaves are similar to leaves of the recent Chinese species Z. sinica C.K. Schneider, which is considered to be basal for this genus. It is assumed (Denk and Grimm, 2005) that this genus appeared in the northern part of the Pacific region and migrated to Europe after closing of the Turgai seaway in the late Oligocene. The presence of representatives of the genus in the Maoming Basin may indicate that Zelkova is a an inhabitant of its recent distribution area since the Eocene. The fossil leaves from the Maoming Basin are characterized by dimorphism of the leaf blade, which is most likely explained, as for recent species of this genus (Denk and Grimm, 2005), by their belonging to different types of shoots: vegetative and reproductive. The analysis of the anatomic structure of wood first studied in the Youganwo Formation revealed the pres ence of representatives of the families Euphorbiaceae and Myrtaceae. The new species of Euphorbiaceae wood is assigned to the recent genus Bischofia Blume (Feng et al., 2012). Fossil wood Bischofia from the Youganwo Formation represents the oldest find of this genus in China. Wood of Myrtaceae described as a new genus and species Myrtineoxylon maomingensis was first discovered in the fossil state in East Asia (Oskolski et al., 2012). This wood is very similar to that of recent genera Calycolpus O. Berg, Octamyrtis Diels, and oth ers belonging to the Myrteae tribe of the family Myrt aceae, which is characterized by a pantropical distri bution with the highest diversity in South America. The biogeographic analysis of recent representatives of this tribe indicates its Australian origin. The presence of wood belonging to the Myrteae tribe in Eocene sec tions of the southern part of Mainland China may be considered as representing reliable evidence for vicar iation of this group in East Asia.

According to the preliminary taxonomic analysis, the floral assemblages from the Huangniuling For mation (H1 and H2) include at least 150 morpho taxa belonging to ferns (Lygodiaceae), conifers (Pinaceae, Podocarpaceae, Sciadopityaceae, Taxa ceae), and dominant angiosperms from the families Lauraceae, Fagaceae, Hamamelidaceae, Altingia ceae, Fabaceae, Juglandaceae, Myricaceae, Myrta ceae, Dipterocarpaceae, Rhamnaceae, Celastraceae, Nyssaceae, Ulmaceae, and others. As compared with the Youganwo flora, ferns are extremely rare in the Huangniuling flora: only single specimens of fertile fronds belonging to the genus Lygodium Swartz are found in oryctrocoenoses. In contrast, abundance and diversity of conifers repre sented by species from the genera Pinus L., Nageia Gaertner, Sciadopitys Siebold et Zuccarini, and cf. Taxus L. notably increased. On the basis of morphol ogy of megastrobiles and presence of short shoots with five long leaves in the fascicles, the Maoming Pinus species is attributed to the subgenus Strobus. The Podocarpaceae in the Huangniuling flora are repre sented by a new species of the genus Nageia (Liu and Jin, 2012), leaves of which differ in their macromor phological features and epidermal properties from leaves of the recently investigated Eocene species Nageia hainanensis Jin, Qiu, Zhu et Kodrul from the Changchang Formation (Hainan Island) (Jin et al., 2010), which is the first known representative of this genus in Cenozoic sediments of South China. The leading role in this flora belongs to angiosperms dominated with respect to diversity and abundance by representatives of the families Fagaceae, Lauraceae, and Fabaceae, accompanied by subordi nate Altingiaceae, Hamamelidaceae, Myricaceae, Juglandaceae, Rhamnaceae, Dipterocarpaceae, and others. The family Fagaceae in this flora includes seve ral species of the genus Quercus and, probably, Casta nopsis (D. Don) Spach. The oryctocoenoses contain also fruits of Fagaceae in addition to the leaf remains. In Huangniuling oryctocoenoses are also present the reproductive structures (fruit and infructescences) of representatives of the families Altingiaceae (genus Liquidambar), Juglandaceae (genus Paleocarya Saporta), Dipterocarpaceae (genus Shorea Roxburg ex C.F. Gaertner), Rhamnaceae (genus Paliurus Miller), and others. The presence of Dipterocarpaceae forms con firmed by finds of reproductive structures is recorded in the Maoming Basin for the first time. Recent Dipterocarpaceae are confined to the tropical belt on three continents: Asia, Africa, and South America

Plate VII. Characteristic palynomorphs from Paleogene sections of the Maoming Basin. (1) Azollaceae massula; (2) Ovoidites sp.; (3, 4) Foveodiporites cf. anklesvarensis Varma et Rawat; (5) aff. Fisiformisporites sp.; (6) aff. Multicellites sp.; (7, 8) Callimothallus pertusus Dilcher; (9, 17) Trichothyritestype; (10) Dicellaesporites sp.; (11, 12) Ctenosporites cf. esrkerensis Elsik et Jansonius; (13, 14) Tetraedron sp.; (15, 16) Polyadosporitestype; (18) Chaetosphaerites sp.; (19, 20, 23, 24) Trichothyrites spp.; (21, 22) Plu ricellaesporites spp. Magnification for all figures ×1000 (except for fig. 1 ×500). STRATIGRAPHY AND GEOLOGICAL CORRELATION

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(Ashton, 1982; MauryLechon and Curtet, 1998). In Southeast Asia, where most of their recent species (470 of 520) inhabit, they largely populate wet tropical forests, occupying up to 30% of the total area of equa torial forests. At the same time, some of them are fre quently noted in deciduous forests in northeastern India, Burma, Thailand, and Cambodia. The origin of Dipterocarpaceae and its phytogeographic evolution remain debatable topics: both the Gondwanan (Ash ton, 1982; Dayanandan et al., 1999; Ducousso et al., 2004) and the East Asian (Lakhanpal, 1970; Sasaki, 2006) origin are assumed for this family. In China, the 12 known species from five genera are mostly distrib uted in Yunnan and Guangxi provinces and on Hainan Island (Li et al., 2000). In the geological record, Dipterocarpaceae are usually represented by wood fragments (Shi and Li, 2010). In Southeast Asia, their oldest remains represented by pollen grains are reported from Oligocene sections of Borneo (Muller, 1981), although the most abundant Dipterocarpaceae remains are found in Miocene and Pliocene sediments of the region. The recent investigation (Dutta et al., 2011) yielded information on presence of Dipterocar paceae in middle Eocene sediments (approximately 53 Ma) of Western India derived from the chemical analysis of fossil resin and occurrence of pollen grains close to that of Dipterocarpaceae plants. On the basis of several morphological features, the remains of reproductive structures of Dipterocar paceae from the Huangniuling Formation are assigned to the recent genus Shorea; associated leaves also belong to this genus (Feng et al., 2013). The genus Shorea is characterized by the maximum diversity among Dipterocarpaceae taxa, uniting approximately 196 species from India, Sri Lanka, Bangladesh, Burma, Thailand, Laos, Cambodia, Vietnam, China (two species), Malaysia, the Philippines, and Java (Li et al., 2000; Ashton, 2004). Most recent Shorea spe cies colonize wet tropical evergreen forests on plains and lower parts of mountain slopes, although some species populate seasonal semideciduous and decidu ous forests and locally represent a dominant element of savanna forests. The fossil leaves and wood remains of this genus are reported from Cenozoic sediments of India (Awasthi, 1992; Guleria, 1992). The fossil repro ductive structures of Shorea are rare: now, they are known only from Miocene of India (Khan and Bera, 2010; Shukla et al., 2012). The finds of the oldest reli ably identified representatives of the Dipterocar paceae in Eocene of South China are of great signifi cance for understanding the origin, diversification, and phytogeography of this taxon. The presence of the genus Shorea in the Huangniuling flora may indicate the existence of tropical forests in the region under consideration during the late Eocene.

CONCLUSIONS The analysis of palynologial and plant macrofossil assemblages revealed for the first time two large paleo floras in the Cenozoic Maoming Basin. By their diver sity and abundances, these paleofloras are suitable for taxonomic, florogenetic, paleoecological, and paleo climatic investigations and remote regional and inter regional correlations. The comparative analysis of the taxonomic compo sition of fossil floras in the Maoming and Changchang (Hainan Island) basins demonstrated the similarity between the Youganwo and Changchang floras, which allows them to be considered coeval. Noteworthy also is the similar trend in development of sedimentary basins in the continental part of China and on Hainan Island, which is evident from similarity in structure of their sections: both the Youganwo and Changchang formations are composed of coaliferous sediments in their lower part, which are replaced up the section by oil shales, while the overlying Huangniuling (Maom ing Basin) and Wayao (Changchang Basin) formations are formed by fluvial poorly consolidated sandstones with lenses and intercalations of conglomerates and clays. The palynological data provided grounds for specifying the ages of the Youganwo (Luthetian–Bar tonian) and Huangniuling (Priabonian) formations. The analysis of the complex data on plant macrofos sils and palynomorphs made it possible to provide a qualitative characteristic for the regional climate and its changes in the middle–late Eocene. The data derived from the analysis of paleofloras from the Maoming Basin may be used for testing paleoclimatic reconstruc tions based mainly on the study of lithological features of sedimentary sections (Scotese, 2003). The influence of a wide arid zone, which is reconstructed for the Pale ocene–Eocene Epoch in the largest part of continental China (Sun and Wang, 2005) was indistinguishable in the period corresponding to deposition of the coalifer ous sequence of the Youganwo Formation. Slight arid ization of the climate is registered for the period corre sponding to deposition of oil shales from the upper part of this unit. It seems that the reconstructed arid belt provided no serious barrier to the floral exchange between middle and low latitudes of East Asia in the second half of the Eocene. The composition of the Eocene floras provides unambiguous evidence for the appearance of several recent plant genera (Shorea, Liquidambar, Paliurus, and others) at that time, which is confirmed by finds of their reproductive structures. According to palynological data, during deposition of the Youganwo Formation, the region under consid eration was occupied by an intermittently swamped lacustrine–fluvial plain, which was replaced subse quently by a freshwater lake. Vegetation of that period was represented by lowland wet subtropical forests with evergreen Fagaceae, Lauraceae, and Palmae. By the end of its deposition, the climate evolved toward its

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aridization. The Huangniuling flora reflects most likely the biome of seasonal tropical forests developed over the spacious fluvial plain and its margins. The data on the Eocene ecosystems of the region, taxonomic composition, and ecological properties of the fossil floras are of theoretical significance for reconstructing the vegetation and climate of low lati tudes in the Paleogene, understanding the origin of the biome of tropical forests, dating the appearance of recent plant taxa, and defining the ways and directions of floral migrations. ACKNOWLEDGMENTS We are grateful to Liu Xiaoyan and Song Yunsheng (Department of Natural Sciences, Sun Yatsen Univer sity) for their help during field works in the Maoming Basin. This work was supported by the Russian Foundation for Basic Research (grant nos. 110491175GFEN, 140591163GFEN), National Natural Science Foundation of China (grant nos. 41210001, 40972011, 31070200), National Program of China on Basic Research (Program 973, grant no. 2012CB822003), State Leading Laboratory of Paleobiology and Stratig raphy (Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences, grant no. 123110), the Fundamental Research Funds for the Central Universi ties (grant no. 121gjc04), and the Key Project of Sun Yatsen University for inviting foreign teachers. Reviewers S.V. Popov, N.P. Maslova, and Yu.B. Gladenkov REFERENCES Ashton, P.S., Dipterocarpaceae, in Flora Malesiana, Sper matophyta,. Van Steenis, C.G.G.J., Ed., The Hague: Mar tinusNijhoff Publ., 1982, vol. 9, pp. 237–552. Ashton, P.S., Dipterocarpaceae, in Tree Flora of Sabah and Sarawak. Vol. 5, Soepadmo, E., Saw, L.G., and Chang, R.C.K., Eds., Kuala Lumpur, 2004, pp. 61–382. Aver’yanova, A.L., Late Eocene flora of the Zaissan Depression (East Kazakhstan), Extended Abstract of Cand. Sci. (Biol.) Dissertation, St. Petersburg: BIN RAN, 2012. Awasthi, N., Changing patterns of vegetation through Siwa lik Succession, Palaeobotanist, 1992, vol. 40, pp. 312–327. Bande, M.B. and Prakash, U., The Tertiary flora of South east Asia with remarks on its palaeoenvironment and phy togeography of the IndoMalayan Region, Rev. Palaeobot. Palynol., 1986, vol. 49, pp. 203–233. Bande, M.B., The Palaeogene vegetation of Peninsular India (megafossil evidence), Palaeobotanist, 1992, vol. 40, pp. 275–284. Bhattacharyya, B., Fossil plants from the Tura Formation (Eocene) in the Garo Hills, Meghalaya, Indian J. Earth Sci., 1983, vol. 10, no. 1, pp. 1–10. Bhattacharyya, B., Leguminous fruits from the Eocene of Garo Hills, Meghalaya, Q. J. Geol. Min. Metall. Soc. India, 1985, vol. 57, pp. 215–225. STRATIGRAPHY AND GEOLOGICAL CORRELATION

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Translated by I. Basov

Vol. 23

No. 3

2015