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Role of water vapor and CO2 in the paleoclimatic fluctuations along northwestern and southern Syria, and the adjacent Mediterranean Sea
Microchemical Journal 74 (2003) 231–238
Role of water vapor and CO2 in the paleoclimatic fluctuations along northwestern and southern Syria, and the adjacent Mediterranean Sea Robert F. Mahfouda,*, James N. Beckb a
PhysicsyGeology Department, McNeese State University, P.O. Box 93140, Lake Charles, LA 70609-3140, USA b Department of Physical Sciences, Nicholls State University, P.O. Box 2022, Thibodaux, LA 70310, USA Received 25 November 2002; received in revised form 20 January 2003; accepted 26 January 2003
Abstract Microscopic petrified grains were collected from a mafic–ultramafic pipe, NE of Dreikeesh, NW Syria. The grains were identified as anthersygynoecia in herbygrass flowers. Three of the grains showed evidence of magnetism, two slowly dissolved in concentrated HCl, and three microprobed grains showed a montmorillonitic composition. Iron originating from pyroxene was oxidized to magnetite. Released silica formed the mineral suite agate–chalcedony– opal. Warmycold paleoclimatic fluctuations, occurring during late Pliocene–Holocene, depended on water vapor, CO2 production, and cinders in the atmosphere. Most of these were associated with changing volcanicytectonic events. Fluctuations were controlled by heat reflected from the Earth’s surface being absorbed by water vapor and CO2, which both re-reflected the heat back to the surface, thus, raising the temperature. This cycle was repeated several times during late Pliocene–Holocene. 䊚 2003 Elsevier Science B.V. All rights reserved. Keywords: Paleoclimatic fluctuations; Pliocene; Holocene
1. Introduction The study area was located in the northeastern corner of the Mediterranean Sea, along the western slope of the N-trending Alawite mountain range between Turkey (north) and Lebanon. The area was a phytogeographical region having Mediterranean climate, surrounded in the east and north by the Irano-Turanian continental climate and in the south by the Saharo-Arabian desert w1x. The *Corresponding author. Tel.: q1-337-475-5755. E-mail address: [email protected] (R.F. Mahfoud).
upslope, in the study area, started from sea level and climbed eastward to a height of 700–800 m. The highest peak along the Alawite mountain range was over 1900 m. The studied location was approximately 550–600 m high. The slope exhibited deep narrow ravines carved by rainwater in thinly bedded, and heavily fractured, sheared, and faulted carbonates of Jurassic–Cretaceous age. Due to these discontinuities, springs were rare, despite the heavy seasonal precipitation (rain and snow) in winter. Summer is generally dry to humid, with occasional light rain. Annual precipitation may have reached over 1 m along the
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western slope of the mountain range with temperatures ranging between y5 and over 30 8C. Climate was clement most of the year, with circulation of fresh to cool landward breezes from the sea during daytime, and a seaward cold breeze from the mountains at night. In winter, the mountains were capped with snow for approximately 2–3 months. Commonly, very cold boreal winter wind masses moved southward and westward into the warm Mediterranean region, forcing the temperature to dip below 0 8C. This seasonally variable weather was in sharp contrast with the dry steppe-like climate along the eastern sides of the Alawite and Lebanese mountain ranges, and eastward, where xeric herbs were noticeably present. Dryness was probably due to the scarce rain during the wet season, and the wide difference between day and night temperatures. These weather conditions clearly reflected a steppe-like environment. Climatic studies in the Mediterranean area are based on palynology, foraminifera, anthracology, flora distribution, appearanceydisappearance of tree varieties and also based on the amount of moisture, seeds found in old civilizations, and charcoal 14C-dating w1–5x. These results were generally descriptive of the climatic changes from 3.5 Myr ago during late Pliocene–Holocene. Climatic fluctuations starting in the late Pliocene (;3.2 Myr ago) were found to vary: first, by successive dry and humid periods taking place up to the present; and second, the Mediterranean Pleistocene had two distinct climatic phases, an earlier warmer period, starting approximately 2.3 Myr ago (xeric phase), and a later period showing wide temperature fluctuations w4x. Climatic conditions of that period did not include an analysis of the presence of petrified anthers and gynoecia, nor did they mention the role played by CO2 w4x. Due to the lack of pollen, and foraminifera, it is suggested that paleovolcanic and paleotectonic events, in the Upper Tertiary and Quaternary, would shed light on the paleoclimatic evolution in the study area. Results could then be compared to previous eras, such as reported w2–5x. Historically, the Alawite and Lebanese mountains were folded during Tertiary, and mainly after the Red Sea was opened in the Miocene. These events were accom-
panied by successions of volcanic lava flows and pyroclastic extrusions during Miocene and late Pliocene. Later, lava flows covered a huge area, with plateau basalt and composite volcanoes, extending from Homs to Banias cities (Fig. 1). Along with intermittent lava flows, water, CO2, SO2, heat, and cinders were released into the atmosphere creating climatic fluctuations including hot, dry, humid, cold and arid environments. This scenario could be correlated to that stated by Ref. w4x, approximately 3.2 Myr ago (late Pliocene), when dry and humid periods occurred. During the Pleistocene, volcanic activity was followed by tectonic and hydrothermal events that led to faulting, rifting, fracturing, shearing, and alterationy chemical weathering w6,7x. Hydrothermal activity released heat and warmed the climate matching the earlier warmer Pleistocene, followed by successive faulting, rifting, shearing, and fracturing events leading to wide temperature fluctuations w4 x . In southern Syria, cycles of volcanic eruptions during late Pliocene, early Pleistocene, approximately 4000–5000 years ago, have taken place, expelling water vapor, CO2, SO2 and other gases, aiding in the warmycold paleoclimatic fluctuations. Those climatic changes clearly affected the spreading of vegetation approximately the eastern Mediterranean coast w2,3,8,9x. The scope of this work was first, to understand the chemistry and origin of the petrifying compounds; second, to describe the effects of paleovolcanic activities, from late Pliocene to Holocene, on paleoclimatic fluctuations in Syria; and third, to discuss the effect of CO2 depletion on local and surrounding climate (NW Syria). These effects will be discussed based on the presence of petrified anthers, gynoecia originating from herbyflowers not currently present in the study area. Processes caused by CO2 in the paleoclimatic fluctuations are explained. 2. Experimental 2.1. Field setting The surface of 21 g of brecciated, and sheared dark-gray kimberlite–pyrope peridotite–basanite
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1). Similar grains were not found in pulverized igneous rocks, indicating that these grains were not minerals, but petrified flower organs as suggested by their likeness to identified organs, roundness, surface apertures and inclusions. 2.2. Description of petrified specimens
Fig. 1. Index map of the study area.
rock sample, belonging to the diatreme facies of a mafic–ultramafic pipe w6,10x (Fig. 2), yielded over 50 loose rounded grains of different sizes and shapes. The crater facies of the pipe (yellow soil) and the Upper Jurassic–Cretaceous carbonate cover were eroded by rain along a westward sloping mountain (700–800 m high), approximately 15 km NE of the town of Dreikeesh, NW Syria, near the eastern shore of the Mediterranean Sea (Fig.
Twenty-nine identified fossils ranged in size from 0.25 to 1.0 mm (Fig. 3). Pollens sizes are known to range between 4.5 and 200 mm w11,12x, while those for spores, even smaller w11x. Their shapes correlated with anthers (male organs) and gynoecia (female organs) in herbs and grass flowers. Fig. 3 shows the wide variety of patterns, indicating that more than one type of organ was petrified. Sketches numbered 6, 7, 8, 9, 14, 21, 22, 24, 26, 27, 28 (Fig. 3) were spherical (anthers) with one or more large apertures, and smaller globular inclusions that may be fossilized gramineae pollens w11x. Tentative measurements showed a range of diameters (22.72–45.45 mm) for those inclusions; and the largest aperture, approximately 136 mm. Other anther-like elongated patterns included sketches 2, 4, 10, 13, 16, 18, 23, 25. The
Fig. 2. The white patch across the middle part of the picture represents the exposed diatreme facies of the mafic–ultramafic pipe.
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Fig. 3. Sketches of the 29 microscopic petrified anthers and gynoecia.
remaining ten organs 1, 3, 5, 11, 12, 15, 17, 19, 20, 29 (Fig. 3) showed no apertures, but a variety of rounded shapes, with or without miniscule inclusions that could be fossilized ovules inside gynoecia. The shape variations probably represent-
ed different species and genera. Sketch 1 in Fig. 3 could be a Malvaceaa w12x. Sketch 5 (Fig. 3) has the appearance of a gynoecium with stigma on top and a row of fossilized ovules, or seeds, inside, similar to a small pod of legume. Sketch 20 looked
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like a Cruciferae (b, in Fig. 54.1, in Ref. w13x). Sketch 15, with a spiral structure, resembled a female flower struggling for space due to stacking in the packed original inflorescence, or a stamen in stacked stamens in floral buds w12x. The absence of inclusions, in the latter sketch could mean that either the flower was too young during the fossilization process, or the ovary was already fertilized and had changed to seed w14x. Sketch 17 exhibited a long gynoecium with ovules, whereas number 29 could possibly be a fossilized female organ in a coniflower w15x. The absence of fossilized pollens, and other original features erased by petrification, rendered the positive identification of the 29 samples very difficult w16x. In addition, their age is ambiguous and difficult to ascertain. Were they petrified in place from recent flowers, or did they belong to Upper Cretaceous and transported to their actual location from the carbonate cover, or were they post-Pliocene in age petrified by Pleistocene or Holocene chemical weathering activities? Late Pliocene was determined to be the age of the youngest basanite present in the pipe w6x. The 29 fossils were hyalin, colorless, and transparentytranslucent, with a waxy to pearly luster. A few were yellowish; and three were attracted to a magnetized needle, suggesting the presence of tiny amount of magnetite (Fe3O4), or remnants of pyrrhotite (FeS) inclusions. Iron, sulfur, and other elements detected by microprobing some minerals, probably resulted from hydrothermal alterationy weathering of mafic–ultramafic rocks present in the pipe w6x. A hydrothermally formed pyrite (FeS2) was also found along a horizontal thin carbonate band across a Cretaceous limestone cliff overlying the pipe (Fig. 2). It is important to note that an absence of foraminifera fossils, among the 29 specimens, eliminated the cooperation of limestone cover in the petrification process.
scopic spherical shell pieces. Water and diluted HCl gave negative results when applied to test the solubility of fossils, however, two specimens dissolved gradually when treated with concentrated HCl. Therefore, suggesting that the fossilizing material was neither silica (SiO2), nor calcite (CaCO3). Specimens 11, 18, 28 (Figs. 3 and 4) were microprobed by FEI Company of Hillsboro, Oregon. Results showed the same petrifying chemical composition (O, Si, Mg, Al, Zn, Ca and C) (Fig. 5), i.e. montmorillonite—wMgAl2Si4 O10 (OH)2ØnH2Ox mixed with some CaCO3 w17x.
3. Analytical methods and scope
The warmycold paleoclimatic fluctuations from late Pliocene to Holocene was based on varying CO2 concentrations, and the duration and concentration of cinders in the atmosphere that covered NW Syria in particular, and Syria in general. Water vapor and CO2 are recognized as being the best heat absorbers among all gases present in the air
The Pasco Scientific binocular microscope was used to collect more than 50 specimens; however, only 29 remain because others were lost during their treatment with diluted HCl and water. During the rock crushing process some broke into micro-
4. Mineralogy The composition of the fossilizing material resulted from chemical weathering of Ca-bearing pyroxene and Ca-rich-plagioclase, the two most important minerals in basanite. Zinc present in pyroxene is an impurity in the montmorillonite w18x. Leached iron (from pyroxene) was probably oxidized to form magnetiteyhematite. A trace of magnetite was detected in three specimens, and Na from plagioclase, nepheline, and pyroxene could have formed Na bicarbonate and then transported away by water. In addition, some silica gel was released through the process of desilicification by rainwater acidified by atmospheric CO2, Agate, chalcedony, and opal were found among the weathering products. Carbon dioxide from the atmosphere was needed to form carbonic acid necessary for chemical weathering of silicates. This continuous desilicification process would certainly lead to depletion of atmospheric CO2 w19x. These authors described the importance of CO2 in chemical weathering of silicates; however, did not mention the role of CO2 in controlling climatic fluctuations in the atmosphere. 5. Discussion
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Fig. 4. Three electronic micrographs representing the sketches 11, 28 and 18. The smaller figure associated with 18 belongs to sketch 15. Note the petrified pollens inside 18 and 28. Top left is sketch 11.
w20x. They suggested that heat-waves reflected from the Earth’s surface toward the lower part of the troposphere (i.e. the Albado), would be absorbed by water vapor and CO2, followed by the re-reflection of heat back to the surface. This would increase the temperature causing a Pliocene green house effect. It is obvious that increasing CO2 andyor H2O(v) would lead to warmer climates and decreasing CO2 to colder climates. The presence of cinders in the atmosphere would also
prevent solar heat from reaching the Earth’s surface, also causing colder climates. The study area is close to the Mediterranean Sea that continuously supplies water vapor, in addition to that emanated by volcanoes. The major CO2 supplier, however, from late Pliocene to Holocene was volcanic activity. During old civilizations and continuously to the present time burning of wood and fossil fuels also generated additional atmospheric CO2. Chemically, rainwater is neutral
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Fig. 5. Three microprobe spectrographs for sketches 11, 28 and 18, exhibiting the same montmorillonitic composition.
or slightly acidic (pH 5.5–7); and has little effect on chemical weathering. However, its loss would lower the humidity in the air and, consequently, the temperature on the surface. The effectiveness of rainwater to cause weathering would increase when associated with CO2 causing increases of carbonic acid in rainwater. At high concentrations even this weak acid will dissolve carbonates, and react with and dissociate silicates w6x.
SilicatesqH2OqCO2™Clays qNa–Ca-carbonatesqSilica gel qFe-oxihydroxides The mentioned silicates include olivine, pyroxenes, pyrope (garnet), Ca-rich plagioclase, and nepheline, all present in the kimberlite–pyrope peridotite–basanite mixture present in the pipe. Clays were mostly montmorillonites; and the silica,
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was mainly agate, chalcedony, and opal. Iron hydroxides were found in the yellow soil as goethite and limonite. The effect of carbonic acid production was the depletion of CO2 in the atmosphere. These fluctuations have occurred since the orogenic movement that generated the Alawite and Lebanese mountains in the late Pliocene (age of basanite). Microprobing of three petrified flower organs (11, 18 and 28) revealed that the petrifying material was montmorillonite, probably derived from chemical weathering of pyroxenes (augite and diopside) Ca-rich plagioclase, and nepheline (all present in the peridotite and basanite). Iron in the pyroxenes and Ca–Na in plagioclase and nepheline probably dissolved and was then transported by water. Remnants of oxidized iron (Fe3O4) were detected in three specimens. Montmorillonite was the clay mineral found in petrified flower organs, suggesting that the process of fossilization took place at the same time, and under the same conditions. Erosion of the westward sloping land along the Alawite and Lebanese mountains controlled desilicification, because acidified rainwater always found fresh silicates to chemical weather due to erosion, resulting in CO2 depletion, aiding the climatic fluctuations. 6. Conclusions It can be concluded that first, no daily sharp changes can be delineated from warmydry to coldy humid climates along the Syrian coast; second, the daily climatic variations have no major effects on vegetation spreading; and third, CO2 and water vapor, in the atmosphere, would influence climatic fluctuations only when their concentrations changed drastically for relatively long periods of time. Their concentrations in air greatly depended on volcanic and tectonic activities in NW and southern Syria from late Pliocene to Holocene. The amount of chemical weathering of silicates in the diatreme facies of the pipe reflected the consumption depth, and importance, of CO2 and H2O
in climatic fluctuations. Thus, increasing CO2 in air results in higher temperatures and favorable conditions for chemical weathering, followed by periods of cooling when CO2 decreases. References w1x K. Neumann, Actualites ´ Botaniques 139 (1992) 421–440. w2x W. Van Zeist, J.A.H. Bakker-Heeres, Palaeohistorica 27 (1982) 316–347. w3x W. Van Zeist, S. Botterna, in: J.L. Bintcliff, W. Van Zeist (Eds.), Vegetational history of the eastern Mediterranean and the near East during the last 20,000 years, BAR Int. Ser., 133 (1982) 277–322. w4x J.P. Suc, Nature 307 (1984) 429–432. w5x J.P. Suc, Cahiers Micropaleontologie ` 7 (12) (1992) 165–186. w6x R.F. Mahfoud, Research in progress. w7x R.F. Mahfoud, J.N. Beck, J. Geodynam. 17 (1993) 57–76. w8x N. Liphshitz, in: T. Hachens, A.V. Munaut, C. Till (Eds.), Bois et Archeologie. Actes du Sympos. Europ. Louvain-la-Neuve, October 1987, PACT, 22 (1988) 133–146. w9x N. Miller, in: W.K. Van Zeist, W.K. Wasylikova, K.E. Behre (Eds.), Progress in Old World Palaeoethnobotany, Rotterdam, 1991, pp. 133–160. w10x R.F. Mahfoud, Microchem. J. (2002) 1–8. w11x R.P. Wodehouse, Pollen Grains, Hafner Publ. Co., Inc, 1965, p. 574. w12x P.K. Endress, Diversity and Evolutionary Biology of Tropical Flowers, Cambridge University Press, NY, 1994, p. 511. w13x I. Figueiral, G. Willcox, in: T.P. Jones, R.P. Rowe (Eds.), Archaeobotany: Collecting and Analytical Techniques for Sub-Fossils, Geol. Soc, London, 1999, pp. 290–294. w14x B. Bager, Nature as Designer: a Botanical Art Study, Van Nostrand Reinhold Co, NY, 1996, p. 176. w15x G. Erdtman, Handbook of Palynology, Hafner Publ. Co, NY, 1969, p. 486. w16x P.D. Moore, J.A. Webb, An Illustrated Guide to Pollen Analysis, Wiley, NY, 1978, p. 33. w17x R.L. Bates, in: J.A. Jackson (Ed.), Glossary of Geology, Amer. Geol. Inst, Falls Church, VA, 1980, p. 7l5. w18x R.F. Mahfoud, J.N. Beck, Int. Geol. Rev. 37 (1995) 448–470. w19x M.E. Raymo, W.F. Ruddiman, Nature 359 (1992) 117–122. w20x F.K. Lutgens, E.J. Tarbuck, Foundations of Earth Science, Prentice Hall, New Jersey, 1999, p. 454.
Role of water vapor and CO2 in the paleoclimatic fluctuations along northwestern and southern Syria, and the adjacent Mediterranean Sea Robert F. Mahfouda,*, James N. Beckb a
PhysicsyGeology Department, McNeese State University, P.O. Box 93140, Lake Charles, LA 70609-3140, USA b Department of Physical Sciences, Nicholls State University, P.O. Box 2022, Thibodaux, LA 70310, USA Received 25 November 2002; received in revised form 20 January 2003; accepted 26 January 2003
Abstract Microscopic petrified grains were collected from a mafic–ultramafic pipe, NE of Dreikeesh, NW Syria. The grains were identified as anthersygynoecia in herbygrass flowers. Three of the grains showed evidence of magnetism, two slowly dissolved in concentrated HCl, and three microprobed grains showed a montmorillonitic composition. Iron originating from pyroxene was oxidized to magnetite. Released silica formed the mineral suite agate–chalcedony– opal. Warmycold paleoclimatic fluctuations, occurring during late Pliocene–Holocene, depended on water vapor, CO2 production, and cinders in the atmosphere. Most of these were associated with changing volcanicytectonic events. Fluctuations were controlled by heat reflected from the Earth’s surface being absorbed by water vapor and CO2, which both re-reflected the heat back to the surface, thus, raising the temperature. This cycle was repeated several times during late Pliocene–Holocene. 䊚 2003 Elsevier Science B.V. All rights reserved. Keywords: Paleoclimatic fluctuations; Pliocene; Holocene
1. Introduction The study area was located in the northeastern corner of the Mediterranean Sea, along the western slope of the N-trending Alawite mountain range between Turkey (north) and Lebanon. The area was a phytogeographical region having Mediterranean climate, surrounded in the east and north by the Irano-Turanian continental climate and in the south by the Saharo-Arabian desert w1x. The *Corresponding author. Tel.: q1-337-475-5755. E-mail address: [email protected] (R.F. Mahfoud).
upslope, in the study area, started from sea level and climbed eastward to a height of 700–800 m. The highest peak along the Alawite mountain range was over 1900 m. The studied location was approximately 550–600 m high. The slope exhibited deep narrow ravines carved by rainwater in thinly bedded, and heavily fractured, sheared, and faulted carbonates of Jurassic–Cretaceous age. Due to these discontinuities, springs were rare, despite the heavy seasonal precipitation (rain and snow) in winter. Summer is generally dry to humid, with occasional light rain. Annual precipitation may have reached over 1 m along the
0026-265X/03/$ - see front matter 䊚 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0026-265X(03)00029-8
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western slope of the mountain range with temperatures ranging between y5 and over 30 8C. Climate was clement most of the year, with circulation of fresh to cool landward breezes from the sea during daytime, and a seaward cold breeze from the mountains at night. In winter, the mountains were capped with snow for approximately 2–3 months. Commonly, very cold boreal winter wind masses moved southward and westward into the warm Mediterranean region, forcing the temperature to dip below 0 8C. This seasonally variable weather was in sharp contrast with the dry steppe-like climate along the eastern sides of the Alawite and Lebanese mountain ranges, and eastward, where xeric herbs were noticeably present. Dryness was probably due to the scarce rain during the wet season, and the wide difference between day and night temperatures. These weather conditions clearly reflected a steppe-like environment. Climatic studies in the Mediterranean area are based on palynology, foraminifera, anthracology, flora distribution, appearanceydisappearance of tree varieties and also based on the amount of moisture, seeds found in old civilizations, and charcoal 14C-dating w1–5x. These results were generally descriptive of the climatic changes from 3.5 Myr ago during late Pliocene–Holocene. Climatic fluctuations starting in the late Pliocene (;3.2 Myr ago) were found to vary: first, by successive dry and humid periods taking place up to the present; and second, the Mediterranean Pleistocene had two distinct climatic phases, an earlier warmer period, starting approximately 2.3 Myr ago (xeric phase), and a later period showing wide temperature fluctuations w4x. Climatic conditions of that period did not include an analysis of the presence of petrified anthers and gynoecia, nor did they mention the role played by CO2 w4x. Due to the lack of pollen, and foraminifera, it is suggested that paleovolcanic and paleotectonic events, in the Upper Tertiary and Quaternary, would shed light on the paleoclimatic evolution in the study area. Results could then be compared to previous eras, such as reported w2–5x. Historically, the Alawite and Lebanese mountains were folded during Tertiary, and mainly after the Red Sea was opened in the Miocene. These events were accom-
panied by successions of volcanic lava flows and pyroclastic extrusions during Miocene and late Pliocene. Later, lava flows covered a huge area, with plateau basalt and composite volcanoes, extending from Homs to Banias cities (Fig. 1). Along with intermittent lava flows, water, CO2, SO2, heat, and cinders were released into the atmosphere creating climatic fluctuations including hot, dry, humid, cold and arid environments. This scenario could be correlated to that stated by Ref. w4x, approximately 3.2 Myr ago (late Pliocene), when dry and humid periods occurred. During the Pleistocene, volcanic activity was followed by tectonic and hydrothermal events that led to faulting, rifting, fracturing, shearing, and alterationy chemical weathering w6,7x. Hydrothermal activity released heat and warmed the climate matching the earlier warmer Pleistocene, followed by successive faulting, rifting, shearing, and fracturing events leading to wide temperature fluctuations w4 x . In southern Syria, cycles of volcanic eruptions during late Pliocene, early Pleistocene, approximately 4000–5000 years ago, have taken place, expelling water vapor, CO2, SO2 and other gases, aiding in the warmycold paleoclimatic fluctuations. Those climatic changes clearly affected the spreading of vegetation approximately the eastern Mediterranean coast w2,3,8,9x. The scope of this work was first, to understand the chemistry and origin of the petrifying compounds; second, to describe the effects of paleovolcanic activities, from late Pliocene to Holocene, on paleoclimatic fluctuations in Syria; and third, to discuss the effect of CO2 depletion on local and surrounding climate (NW Syria). These effects will be discussed based on the presence of petrified anthers, gynoecia originating from herbyflowers not currently present in the study area. Processes caused by CO2 in the paleoclimatic fluctuations are explained. 2. Experimental 2.1. Field setting The surface of 21 g of brecciated, and sheared dark-gray kimberlite–pyrope peridotite–basanite
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1). Similar grains were not found in pulverized igneous rocks, indicating that these grains were not minerals, but petrified flower organs as suggested by their likeness to identified organs, roundness, surface apertures and inclusions. 2.2. Description of petrified specimens
Fig. 1. Index map of the study area.
rock sample, belonging to the diatreme facies of a mafic–ultramafic pipe w6,10x (Fig. 2), yielded over 50 loose rounded grains of different sizes and shapes. The crater facies of the pipe (yellow soil) and the Upper Jurassic–Cretaceous carbonate cover were eroded by rain along a westward sloping mountain (700–800 m high), approximately 15 km NE of the town of Dreikeesh, NW Syria, near the eastern shore of the Mediterranean Sea (Fig.
Twenty-nine identified fossils ranged in size from 0.25 to 1.0 mm (Fig. 3). Pollens sizes are known to range between 4.5 and 200 mm w11,12x, while those for spores, even smaller w11x. Their shapes correlated with anthers (male organs) and gynoecia (female organs) in herbs and grass flowers. Fig. 3 shows the wide variety of patterns, indicating that more than one type of organ was petrified. Sketches numbered 6, 7, 8, 9, 14, 21, 22, 24, 26, 27, 28 (Fig. 3) were spherical (anthers) with one or more large apertures, and smaller globular inclusions that may be fossilized gramineae pollens w11x. Tentative measurements showed a range of diameters (22.72–45.45 mm) for those inclusions; and the largest aperture, approximately 136 mm. Other anther-like elongated patterns included sketches 2, 4, 10, 13, 16, 18, 23, 25. The
Fig. 2. The white patch across the middle part of the picture represents the exposed diatreme facies of the mafic–ultramafic pipe.
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Fig. 3. Sketches of the 29 microscopic petrified anthers and gynoecia.
remaining ten organs 1, 3, 5, 11, 12, 15, 17, 19, 20, 29 (Fig. 3) showed no apertures, but a variety of rounded shapes, with or without miniscule inclusions that could be fossilized ovules inside gynoecia. The shape variations probably represent-
ed different species and genera. Sketch 1 in Fig. 3 could be a Malvaceaa w12x. Sketch 5 (Fig. 3) has the appearance of a gynoecium with stigma on top and a row of fossilized ovules, or seeds, inside, similar to a small pod of legume. Sketch 20 looked
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like a Cruciferae (b, in Fig. 54.1, in Ref. w13x). Sketch 15, with a spiral structure, resembled a female flower struggling for space due to stacking in the packed original inflorescence, or a stamen in stacked stamens in floral buds w12x. The absence of inclusions, in the latter sketch could mean that either the flower was too young during the fossilization process, or the ovary was already fertilized and had changed to seed w14x. Sketch 17 exhibited a long gynoecium with ovules, whereas number 29 could possibly be a fossilized female organ in a coniflower w15x. The absence of fossilized pollens, and other original features erased by petrification, rendered the positive identification of the 29 samples very difficult w16x. In addition, their age is ambiguous and difficult to ascertain. Were they petrified in place from recent flowers, or did they belong to Upper Cretaceous and transported to their actual location from the carbonate cover, or were they post-Pliocene in age petrified by Pleistocene or Holocene chemical weathering activities? Late Pliocene was determined to be the age of the youngest basanite present in the pipe w6x. The 29 fossils were hyalin, colorless, and transparentytranslucent, with a waxy to pearly luster. A few were yellowish; and three were attracted to a magnetized needle, suggesting the presence of tiny amount of magnetite (Fe3O4), or remnants of pyrrhotite (FeS) inclusions. Iron, sulfur, and other elements detected by microprobing some minerals, probably resulted from hydrothermal alterationy weathering of mafic–ultramafic rocks present in the pipe w6x. A hydrothermally formed pyrite (FeS2) was also found along a horizontal thin carbonate band across a Cretaceous limestone cliff overlying the pipe (Fig. 2). It is important to note that an absence of foraminifera fossils, among the 29 specimens, eliminated the cooperation of limestone cover in the petrification process.
scopic spherical shell pieces. Water and diluted HCl gave negative results when applied to test the solubility of fossils, however, two specimens dissolved gradually when treated with concentrated HCl. Therefore, suggesting that the fossilizing material was neither silica (SiO2), nor calcite (CaCO3). Specimens 11, 18, 28 (Figs. 3 and 4) were microprobed by FEI Company of Hillsboro, Oregon. Results showed the same petrifying chemical composition (O, Si, Mg, Al, Zn, Ca and C) (Fig. 5), i.e. montmorillonite—wMgAl2Si4 O10 (OH)2ØnH2Ox mixed with some CaCO3 w17x.
3. Analytical methods and scope
The warmycold paleoclimatic fluctuations from late Pliocene to Holocene was based on varying CO2 concentrations, and the duration and concentration of cinders in the atmosphere that covered NW Syria in particular, and Syria in general. Water vapor and CO2 are recognized as being the best heat absorbers among all gases present in the air
The Pasco Scientific binocular microscope was used to collect more than 50 specimens; however, only 29 remain because others were lost during their treatment with diluted HCl and water. During the rock crushing process some broke into micro-
4. Mineralogy The composition of the fossilizing material resulted from chemical weathering of Ca-bearing pyroxene and Ca-rich-plagioclase, the two most important minerals in basanite. Zinc present in pyroxene is an impurity in the montmorillonite w18x. Leached iron (from pyroxene) was probably oxidized to form magnetiteyhematite. A trace of magnetite was detected in three specimens, and Na from plagioclase, nepheline, and pyroxene could have formed Na bicarbonate and then transported away by water. In addition, some silica gel was released through the process of desilicification by rainwater acidified by atmospheric CO2, Agate, chalcedony, and opal were found among the weathering products. Carbon dioxide from the atmosphere was needed to form carbonic acid necessary for chemical weathering of silicates. This continuous desilicification process would certainly lead to depletion of atmospheric CO2 w19x. These authors described the importance of CO2 in chemical weathering of silicates; however, did not mention the role of CO2 in controlling climatic fluctuations in the atmosphere. 5. Discussion
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Fig. 4. Three electronic micrographs representing the sketches 11, 28 and 18. The smaller figure associated with 18 belongs to sketch 15. Note the petrified pollens inside 18 and 28. Top left is sketch 11.
w20x. They suggested that heat-waves reflected from the Earth’s surface toward the lower part of the troposphere (i.e. the Albado), would be absorbed by water vapor and CO2, followed by the re-reflection of heat back to the surface. This would increase the temperature causing a Pliocene green house effect. It is obvious that increasing CO2 andyor H2O(v) would lead to warmer climates and decreasing CO2 to colder climates. The presence of cinders in the atmosphere would also
prevent solar heat from reaching the Earth’s surface, also causing colder climates. The study area is close to the Mediterranean Sea that continuously supplies water vapor, in addition to that emanated by volcanoes. The major CO2 supplier, however, from late Pliocene to Holocene was volcanic activity. During old civilizations and continuously to the present time burning of wood and fossil fuels also generated additional atmospheric CO2. Chemically, rainwater is neutral
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Fig. 5. Three microprobe spectrographs for sketches 11, 28 and 18, exhibiting the same montmorillonitic composition.
or slightly acidic (pH 5.5–7); and has little effect on chemical weathering. However, its loss would lower the humidity in the air and, consequently, the temperature on the surface. The effectiveness of rainwater to cause weathering would increase when associated with CO2 causing increases of carbonic acid in rainwater. At high concentrations even this weak acid will dissolve carbonates, and react with and dissociate silicates w6x.
SilicatesqH2OqCO2™Clays qNa–Ca-carbonatesqSilica gel qFe-oxihydroxides The mentioned silicates include olivine, pyroxenes, pyrope (garnet), Ca-rich plagioclase, and nepheline, all present in the kimberlite–pyrope peridotite–basanite mixture present in the pipe. Clays were mostly montmorillonites; and the silica,
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was mainly agate, chalcedony, and opal. Iron hydroxides were found in the yellow soil as goethite and limonite. The effect of carbonic acid production was the depletion of CO2 in the atmosphere. These fluctuations have occurred since the orogenic movement that generated the Alawite and Lebanese mountains in the late Pliocene (age of basanite). Microprobing of three petrified flower organs (11, 18 and 28) revealed that the petrifying material was montmorillonite, probably derived from chemical weathering of pyroxenes (augite and diopside) Ca-rich plagioclase, and nepheline (all present in the peridotite and basanite). Iron in the pyroxenes and Ca–Na in plagioclase and nepheline probably dissolved and was then transported by water. Remnants of oxidized iron (Fe3O4) were detected in three specimens. Montmorillonite was the clay mineral found in petrified flower organs, suggesting that the process of fossilization took place at the same time, and under the same conditions. Erosion of the westward sloping land along the Alawite and Lebanese mountains controlled desilicification, because acidified rainwater always found fresh silicates to chemical weather due to erosion, resulting in CO2 depletion, aiding the climatic fluctuations. 6. Conclusions It can be concluded that first, no daily sharp changes can be delineated from warmydry to coldy humid climates along the Syrian coast; second, the daily climatic variations have no major effects on vegetation spreading; and third, CO2 and water vapor, in the atmosphere, would influence climatic fluctuations only when their concentrations changed drastically for relatively long periods of time. Their concentrations in air greatly depended on volcanic and tectonic activities in NW and southern Syria from late Pliocene to Holocene. The amount of chemical weathering of silicates in the diatreme facies of the pipe reflected the consumption depth, and importance, of CO2 and H2O
in climatic fluctuations. Thus, increasing CO2 in air results in higher temperatures and favorable conditions for chemical weathering, followed by periods of cooling when CO2 decreases. References w1x K. Neumann, Actualites ´ Botaniques 139 (1992) 421–440. w2x W. Van Zeist, J.A.H. Bakker-Heeres, Palaeohistorica 27 (1982) 316–347. w3x W. Van Zeist, S. Botterna, in: J.L. Bintcliff, W. Van Zeist (Eds.), Vegetational history of the eastern Mediterranean and the near East during the last 20,000 years, BAR Int. Ser., 133 (1982) 277–322. w4x J.P. Suc, Nature 307 (1984) 429–432. w5x J.P. Suc, Cahiers Micropaleontologie ` 7 (12) (1992) 165–186. w6x R.F. Mahfoud, Research in progress. w7x R.F. Mahfoud, J.N. Beck, J. Geodynam. 17 (1993) 57–76. w8x N. Liphshitz, in: T. Hachens, A.V. Munaut, C. Till (Eds.), Bois et Archeologie. Actes du Sympos. Europ. Louvain-la-Neuve, October 1987, PACT, 22 (1988) 133–146. w9x N. Miller, in: W.K. Van Zeist, W.K. Wasylikova, K.E. Behre (Eds.), Progress in Old World Palaeoethnobotany, Rotterdam, 1991, pp. 133–160. w10x R.F. Mahfoud, Microchem. J. (2002) 1–8. w11x R.P. Wodehouse, Pollen Grains, Hafner Publ. Co., Inc, 1965, p. 574. w12x P.K. Endress, Diversity and Evolutionary Biology of Tropical Flowers, Cambridge University Press, NY, 1994, p. 511. w13x I. Figueiral, G. Willcox, in: T.P. Jones, R.P. Rowe (Eds.), Archaeobotany: Collecting and Analytical Techniques for Sub-Fossils, Geol. Soc, London, 1999, pp. 290–294. w14x B. Bager, Nature as Designer: a Botanical Art Study, Van Nostrand Reinhold Co, NY, 1996, p. 176. w15x G. Erdtman, Handbook of Palynology, Hafner Publ. Co, NY, 1969, p. 486. w16x P.D. Moore, J.A. Webb, An Illustrated Guide to Pollen Analysis, Wiley, NY, 1978, p. 33. w17x R.L. Bates, in: J.A. Jackson (Ed.), Glossary of Geology, Amer. Geol. Inst, Falls Church, VA, 1980, p. 7l5. w18x R.F. Mahfoud, J.N. Beck, Int. Geol. Rev. 37 (1995) 448–470. w19x M.E. Raymo, W.F. Ruddiman, Nature 359 (1992) 117–122. w20x F.K. Lutgens, E.J. Tarbuck, Foundations of Earth Science, Prentice Hall, New Jersey, 1999, p. 454.