Cretaceous Algal Palynomorphs from Northeast Sinai, Egypt: Systematics and Paleoenvironmental Implications Zainab M

6 Egypt.J.Bot. Vol. 58, No.1, pp. 63 - 72 (2018) Cretaceous Algal Palynomorphs from Northeast Sinai, Egypt: Systematics and Paleoenvironmental Implications Zainab M. El Noamani# and Amal I. Saleh Botany Department, Faculty of Science, Ain Shams University, Cairo, 11566, Egypt. HE microalgal palynomorphs considered one of the main categories of non-pollen Tpalynomorphs recognized in palynological slides which characterized by their potential paleoecological and stratigraphical values especially in the pre-Quaternary deposits. For this importance, four subsurface cutting samples recovered from two Cretaceous (Aptian/Albian and Turonian) geological units in Bougaz-1 well, northeast Sinai have been palynologically analyzed in order to study their algal content. Seven species of algae related to four genera from two divisions have been described and illustrated: Pediastrum boryanum, P. duplex, P. kawraiskyi, P. simplex, Scenedesmus acuminatus, and Chomotriletes minor (Chlorophyta); and Pterospermella sp. (Prasinophyta). Of these, two species (Pediastrum kawraiskyi and Scenedesmus acuminatus) are recorded for the first time from the Cretaceous of Egypt. Notes on the stratigraphic range and the geographical distribution of the most important recorded genera are given. The cell wall nature and its role in resistance to degradation are also discussed. The ecology of extant taxa has been used to determine the paleoenvironment and paleoecology prevailed in the studied area during the Cretaceous period. Keywords: Chlorophycean algae, Cretaceous, Egypt, Non-pollen palynomorphs, Paleoecology, Palynology. Introduction coenobia), filamentous zygnemataceans (a group of green algae produce resting spores with a In paleopalynology, in addition to spores and sporopollenin-like cell wall) and prasinophyte pollen of vascular plants, there are different phycomata (the fossilized cyst that represent non-pollen palynomorphs (NPPs) which the non-motile stage of prasinophyceae). contribute the total organic matter in sediments Prasinophyte represents the oldest group of the such as dinoflagellate cysts, chitinous fungal green algae; their extant forms occur in fresh to remains, certain types of microscopic algae, hypersaline water, but fossil forms (non-motile acritarchs, microforaminifera linner test linings, stage) are exclusively marine (Mendonça Filho scolecodonts, chitinozoans and arthropod remains et al., 2012). can be recognized in palynological slides. These NPPs consisted of organic-walled microfossils Most cyanobacteria and algal taxa have a which composed of sporopollenin-like or chitin/ much longer geological history than miospore pseudochitin polymers which are often making producing groups (bryophytes, pteridophytes, them more resistant to corrosion and oxidation gymnosperms and angiosperms). Like most than pollen and spores, and they are not destroyed aquatic organisms, algae has an important during chemical treatment of the sample with ecological advantage in that its ability to react strong acids (HCL-HF acid treatments) (Traverse, quickly to environmental changes and respond 2007). to different parameters (e.g., length of open- water season, nutrient availability and water Of the main categories of NPPs is microalgal temperature) than the terrestrial vegetation palynomorphs which represented by a group (Sarmaja-Korjonen et al., 2006). In addition, the of acid resistant organic walled microfossils presence of some colonial algae in sediments attributed to various types of fresh and marine of different ages has been largely recognized as water algae including cyanobacteria (blue green one of the most reliable paleoecological markers algae), unicellular and colonial chlorophytes (such of fresh water environments, in particular, of as Botryococcus, Pediastrum and Scenedesmus #Corresponding author email: [email protected] DOI: 10.21608/ejbo.2017.1838.1127 ©2018 National Information and Documentation Center (NIDOC) 64 ZAINAB M. EL NOAMANI ANDAMAL I. SALEH standing water bodies such as ponds and lakes common chlorococcale colonial genera present in (Tell & Zamaloa, 2004).Therefore, some of them the palynological slides based on their previous are interesting for palynologists especially in the records compiled from Palynodata Inc. & analysis of pre-Quaternary deposits (Gawlik & White (2008). Finally, interpretations about the Millington, 1969). paleoecology of the recorded genera are discussed. Despite their potential paleoecological and Materials and Methods stratigraphical values, the algal elements are rarely illustrated and/or identified below the genus The algal assemblage which is the subject of level in the palynological studies. Nevertheless, this study is recorded from four subsurface cutting the identification of the fossil/subfossil species samples coming from two Cretaceous (Aptian/ provide us with important paleoenvironmental Albian to Turonian) geological units in Bougaz-1 inferences by comparison with the known (B-1) well. Samples no. 1 & 2 was taken from the ecological requirements of the living counterparts Turonian unit at depths 3093 m & 3078 m, while (Tell & Zamaloa, 2004). samples no. 3 & 4 was taken from Aptian/Albian unit at depths 3117 m & 3105 m, respectively. This The purpose of this paper is to identify to the well was drilled to a total depth of about 3540.9 species level and describe the algal assemblage m by Continental Delta Oil Company (Conoco) present in the Cretaceous samples recovered during 1982. It is located at latitude 31° 09′ 24.6″ from Bougaz-1 well, northeast Sinai, in addition N and longitude 32° 40′47.55″ E, near Bardawil to a compilation of the known stratigraphic Lake, northwest Sinai (Fig. 1) range and paleogeographic extent of the most Fig. 1. Location map of Bougaz-1 (B-1) well (modified after Ibrahim et al., 2017). Egypt. J. Bot. Vol. 58, No.1 (2018) CRETACEOUS ALGAL PALYNOMORPHS FROM NORTHEAST SINAI, EGYPT: SYSTEMATICS ... 65 The recovered samples were processed using Division2: Prasinophyta Round the standard palynological preparation technique Class: Prasinophyceae Christensen ex Moestrup for extraction and concentration of palynomorphs, & Throndsen including HCl and HF treatments and subsequent Order: Petrospermatales Schiller sieving with a nylon filtering screen (15 µm Family: Petrospermellaceae Eisenack mesh); no oxidation was applied (cf. Traverse, Genus: Pterospermella Eisenack 2007 and Ibrahim et al., 2017). Two slides per sample were prepared using DPX as mounting Genus: Pediastrum Meyen medium. The smear slides were examined using a The distinctive morphological feature of the DEL binocular biological compound microscope genus is the arrangement of the inner and outer equipped with a Canon PowerShot G12 digital cells into flat circular coenobia. The several camera for photomicrography. Coordinates for species within the genus are distinguished by the all illustrated specimens are cited as England number of cells in coenobia, shape of internal Finder references. Identification of the recorded and external cells, wall ornamentation, presence species was carried out according to Prescott or absence of spaces between the inner cells and (1962), Pocock (1970), Eisenack (1972) and the number, shape and orientation of the horns Hortobagyi (1973). of the outermost ring of cells (Tell & Zamaloa, 2004). The slides and the remaining residues are deposited in the Paleobotany and Palynology In the present study, Pediastrum is Lab, Botany Department, Faculty of Science, represented by four species; P. boryanum, P. Ain Shams University, Egypt. duplex, P. kawraiskyi and P. simplex. Results P. boryanum (Turpin) Meneghini (Plate 1, Fig. 1−3) In the present study seven algal species Description: Colony circular to ovoid, of belonging to two different divisions (Chlorophyta 8, 16, 32 or more cells, without perforations and Prasinophyta) were identified. Out of which between the cells. Inner cells 4−6 sides, with four species were related to genus Pediastrum undulated or straight sides. Outer half of marginal and one species each for Scenedesmus, cells produced into two long horn-like processes. Chomotriletes and Pterospermella. The identity Colony 50−61 μm in diameter. Cells 9−13 μm in of the latter species remains unknown. diameter, 10−17 μm long with the processes. Within the genus Pediastrum, P. boryanum Remarks: The absence of holes in the was the dominant species and recorded in the coenobia and the external cells with two horns four samples, P. simplex and P. duplex were in the same plane clearly distinguish the species. frequent in the four samples and P. kawraiskyi This is the most widely distributed and variable was rare and recorded only in one sample species among Pediastrum. (sample no. 1). Scenedesmus acuminatus was frequent and recorded in two samples no. 1 & P. duplex Meyen (Plate 1, Fig. 4 and 5) − 3; while Chomotriletes minor was recorded only Description: Colony 8 128 celled, the in Aptian/Albian samples (samples no. 3 & 4). walls smooth or granulated (punctate), with Pterospermella sp. was represented by very rare clear spaces between the inner cells; inner and specimens from Aptian/Albian interval (samples peripheral cells quadrate, the outer margin of the no. 3 & 4). peripheral cells extended into 2 tapering, blunt- tipped processes and in some cases the processes Systematic description: ended with globules, distance between processes Division1: Chlorophyta Pascher of one cell about one-half the distance between Class: Chlorophyceae Kützing processes of adjacent cells;

Load more