Abundance Of Palynomorphs Research Articles

Distribution of palynomorphs from mangrove swamps in the Eagle Island section of the New Calabar River in the Niger Delta

Palynological results have been employed in interpreting the distribution of palynomorphs from mangrove swamps in the Eagle Island section of the New Calabar River, recent sediments from fifteen locations in the area were palynologically examined. The results record about forty per cent in abundance of palynomorphs, it shows that the pollen from mangroves was believed to have substantially increased to very high grains, and probably transported landward by wind with the presence of charred Poaceae cuticles and Podocarpus milanjianus which has accounted for the higher records of Poaceae in the study area. The abundant plants represented in the sediment source areas as revealed by the palynomorphs recovered are Poaceae, Elaeis guineensis, Acrostichum aureum, Pteris spp., Nephrolepis undulata, Cyclosorus afar and Verrucatosporites spp. Pollen of Rhizophora spp. and freshwater forest trees that are abundant in sediments have been reduced greatly and replaced by Poaceae and Elaeis guineensis pollen due to anthropogenic activities. Proximity to shore determines the abundance of pollen and spores, fungal spores Concentricytes. Protoperidinium spp. and other dinoflagellates with the lowest temperature and high salinity. Microforaminiferal wall linings were however recovered mostly in the proximal area, recovered diatoms show useful ecological trends. These results further confirm the usefulness of these palynomorphs and diatoms for paleoenvironmental and paleovegetational reconstruction. The degradation of ecosystems has undergone anthropological activities within the study area.

Biostratigraphic characteristics and correction of the boundary between Miocene and Oligocene sediments in the northern Malay - Tho Chu basin

Stratigraphic study in oil and gas wells is dependent on the research method and the characteristics of the collected samples, such as sample types and spaces between samples, that is why the stratigraphic boundary of the wells may fluctuate in a certain sedimentary range. Therefore, when re-evaluating the hydrocarbon potential or expanding the petroleum exploration targets of an area, we need to study additional evidence and geological events to correct the stratigraphic boundary of the well and correlate regional stratigraphy. These studies often use biostratigraphic and seismic stratigraphic methods.
 This paper provides evidence on biostratigraphy to correct the stratigraphic boundary between Miocene and Oligocene sediments in the northern Malay - Tho Chu basin and compares them with the general stratigraphy of the Malay basin. The research results determined that the top of the Oligocene sediment after correcting is higher than what was specified in the previous studies based on marker fossil findings in a palynomorph abundance cycle; and there are similar biostratigraphic characteristics between the studied area and the Malay basin.

Distribution of palynomorphs in recent bottom sediments offshore Niger delta: A preliminary study

A palynological and sedimentological study of recent bottom sediments from shallow proximal and distal locations offshore Niger Delta was carried out in order to assess the distribution of palynomorphs viz-a-viz the lithofacies in the study area. Fractions of the sediments were subjected to standard laboratory treatments to recover palynomorphs and to make deductions on their lithofacies types. The salinity and pH values of the sediments were also recorded. The most abundant palynomorphs recovered were those of Poaceae, Rhizophora, Elaeis guineensis, Alchornea cordifolia, and spores of fern species. Four lithofacies types were recognized across the locations. They are: Poorly sorted sands (I), Moderately sorted sands (II), Hard textured shale (III) and Sandy shale (IV). Shallow distal locations recorded higher proportions of palynomorphs than deeper proximal locations. Distal location A1 had the highest number of palynomorphs while proximal location B4 is devoid of palynomorphs. The result also revealed that sandy samples from proximal locations (B2,4,5,6) had paucity of palynomorphs; samples with mixture of sand and shale i.e., paralic (B1, 3 and A4) had moderately abundant palynomorphs while shaly samples in distal locations A1, 2, 3 had the highest number of palynomorphs. Seafloor morphology/topography made different areas to have different lithofacies at the same period, hence, low palynomorph recovery in sandy deposits may not always indicate dry paleoclimate condition of source area. Palynomorph abundance in the sediments studied seems to be guided primarily by lithofacies and salinity.

Palaeoenvironmental changes in Eocene Tibetan lake systems traced by geochemistry, sedimentology and palynofacies

• Late Eocene continental climate in Central Asia remains poorly understood. • Tibetan lake deposits preserve records of Eocene palaeoenvironmental changes. • Saline lakes in east-central Tibet existed in a cool and semi-arid desert-steppe. • Late Eocene aridification caused a palaeoenvironmental shift in Central Asia. • Tibetan palaeoclimate was primarily influenced by regional to global drivers. Ancient lake deposits preserve detailed records of Cenozoic environmental changes, providing information on past climate, vegetation, precipitation and lake chemistry. This study focuses on palaeoenvironmental changes recorded in Eocene limnic environments across what is today the modern Tibetan Plateau. We describe a section dated as late Eocene (~38–37 Ma) and integrate these findings within a regional context of similarly-aged Tibetan lake deposits across the plateau. These sedimentary archives of environmental change indicate a period of late Eocene aridification and cooling in the lead-up to the greenhouse-icehouse transition, which remains poorly understood in Central Asia. We show, based on geochemical, sedimentological, and palynofacies analyses, that a large saline lake existed within a semi-arid to arid steppe environment in the Nangqian Basin, east-central Tibet. The saline lake experienced cyclic drying intervals with shifts to a playa lake / mudflat system. Evidence of increased aridity is recorded in the upper part of the section, including a thinning of gypsum beds, decrease in palynomorph abundance, and concurrent increase in wood debris and amorphous organic matter. This is consistent with late Eocene aridity in Asia, drying of the playa lake, and an impoverished desert-steppe vegetation. Grain size data and geochemistry indicate a stable provenance of sedimentary material, suggesting that tectonic activity did not dominate sedimentation in east-central Tibet during deposition of these successions. Rather, palaeoenvironmental changes across the Tibetan region were most probably controlled by global climate oscillations and retreat of the proto-Paratethys Sea during the late Eocene: knowledge that is relevant for ecological interpretations through the Cenozoic, Quaternary and to the present.

Evaluation of the Hydrocarbon Potentials of Shale Exposures at Okpekpe in Edo North

This study evaluates the source rock characteristics of rock exposures along a newly exposed road cut in Okpekpe. An integrated technique of organic geochemical analysis and biostratigraphy evaluation were adopted to determine the source rock quality, Maturation index, kerogen types, depositional environment andsediment age.
 Results of organic geochemistry gave total organic carbon (TOC) value between 0.81 to 3.04 w.t% (2.08wt.% average) indicative of a good source potentials. The plot of Total Sulphur Content (TSC) against TOC suggests a transitional depositional environment for the samples while the plot of hydrogen index (HI) against oxygen index (OI) shows that the samples are capable of generating mixed type II/III kerogen.
 Palynological analysis revealed that the basal section of the exposure is characterized by the occurrences of typical and moderately rich Late Cretaceous – Early Tertiary palynomorphs. While the upper section is poorly rich in palynomorph abundance but with spot occurrences. The palynomophs asssemlages is of Late Maastrichtian - Early Paleocene and the outcrop is characterized by the presence of terrestrial pollens and spores indicating a continental to transitional depositional environment, typical of the Mamu Formation of the Anambra Basin.

Miospore biozonation of cenomanian - santonian succession in Famo-1 well, Gongola Sub Basin, Upper Benue Trough, Nigeria

The Early Cretaceous succession penetrated by Famo-1 well in Gongola sub Basin, Upper Benue Trough, Nigeria were analyzed for its palynological content. This investigation produced significant Pollen and Spore and the assemblage reveals the dominance of angiosperm Pollen grain and pteridophytes spore. Gymnosperm pollen was scarce and less varied. The studied interval penetrated a sequence of sandstone, sandy shale and mudstone occurring at different intervals in the studied section of the well. Established on the stratigraphic distribution of the palynomorphs recovered from Famo-1 well, three informal assemblage palynozones covering the Early Cretaceous were identified. The zones are: Assemblage Zones I & II (Cenomanian); Assemblage Zone III (Turonian - Santonian). The different zones signifies a time stratigraphic unit comparable to the identified lithostratigraphic units penetrated by the well. The age (Cenomanian - Santonian) determinations are based on the known stratigraphic ranges of pollen and spores and their relative stratigraphic positions. Data from the studied well revealed that there is relatively higher frequency of the land derived pollen and spores compared to marine palynomorph abundance, which suggests a paralic condition of continental to shallow marine environment. The shallow marginal marine environment is further sustained by the presence of foraminifera test linings at some depths which are indicative of marine palaeoenvironment (inner neritic environment). Interpretations from the spore and pollen assemblages reveal sediment deposition took place in a wet to arid climate condition in marginal marine to nearshore environment.Keywords: Palynology, Gongola sub Basin, Cretaceous, Famo-1 Well

Marine Palynomorphs Dominated by Heterotrophic Organism Remains in the Tropical Coastal Shallow-Water Sediment; the Case of Selangor Coast and the Estuary of the Manjung River in Malaysia

Abstract. We aimed to clarify and quantify the abundance of palynomorphs of tropical coastal marine shallow-water sediments collected from Oman, Malaysia, Okinawa and also the Sanriku region of Japan for making a comparison with temperate areas. Palynomorphs in these samples contained phototrophic and heterotrophic dinoflagellate cysts, acritarchs, resting cells of Prasinophyceae and Chrysophyceae, tintinnomorphs, microforaminiferal linings, testate amoebae and resting eggs and body fragments of copepods. The sediment samples from Malaysia, Oman, and Okinawa were characterized by dominance of heterotrophic marine palynomorphs, in particular microforaminiferal linings and heterotrophic dinoflagellate cysts, while the samples from Sanriku were different and dominated by phototrophic and heterotrophic dinoflagellate cysts. In addition subtropical-tropical assemblages were characterized by low cell/grain concentrations, especially phototrophic dinoflagellate cysts. These characteristics of marine palynomorphs...

Terrestrial and aquatic palynomorphs in Holocene sediments from the Chukchi–Alaskan margin, western Arctic Ocean: Implications for the history of marine circulation and climatic environments

Two sediment cores from the Chukchi Sea margin north of Alaska were analyzed for palynological composition including terrestrial and aquatic palynomorphs. Based on 13 radiocarbon ages, the investigated sedimentary record represents most of the Holocene with a century to multidecadal age resolution. Three palynological zones were discriminated based on the abundance of major palynomorph groups (terrestrial and freshwater palynomorphs and dinoflagellate cysts) and composition of spore and pollen assemblages. They are interpreted in terms of depositional and paleoclimatic changes including predominance of redeposition by meltwater or sea ice in the early-Holocene, a strong input of contemporaneous material related to Pacific water advection culminating after ca. 6000 yr BP, and more subtle changes in the late-Holocene. It is concluded that depositional environments, such as current transportation and mixing, have an overall major control on palynomorph distribution. The climatic factors may have also played an important role in palynomorph abundance and composition, especially in the middle- to late-Holocene, when circulation changes were less dramatic than during the flooding of the Bering Strait and the shallow Chukchi Sea shelf. Comprehending these linkages requires a better knowledge of the Holocene vegetation history in the coastal areas of Alaska and Chukchi Peninsula.

The palynology of the lower and middle Toarcian (Lower Jurassic) in the northern Lusitanian Basin, western Portugal

The lower and middle Toarcian (Lower Jurassic) successions of the northern Lusitanian Basin in western Portugal were examined for palynomorphs. Two localities, the Maria Pares and the Vale das Fontes sections, were sampled. The sections span the Dactylioceras polymorphum, Hildaites levisoni and Hildoceras bifrons ammonite biozones. The samples produced relatively low diversity dinoflagellate cyst floras which are typical of those from coeval European successions; the most abundant species is Luehndea spinosa. The other forms encountered were Mancodinium semitabulatum, Mendicodinium microscabratum, M. spinosum subsp. spinosum, Mendicodinium sp., Nannoceratopsis ambonis, N. gracilis and N. senex. Dinoflagellate cysts typically dominate throughout the Dactylioceras polymorphum ammonite biozone; their abundance significantly decreased in the overlying Hildaites levisoni and Hildoceras bifrons ammonite biozones. The low diversity Luehndea-Nannoceratopsis dinoflagellate cyst flora of the northern Lusitanian Basin is characteristic of the Sub-Boreal region of Europe. This is a transitional region, intercalated between the Boreal and Tethyan realms. The Toarcian Oceanic Anoxic Event (T-OAE) in the northern Lusitanian Basin is characterised by a sudden decline in palynomorph abundance and diversity, including the virtual absence of acritarchs and dinoflagellate cysts. Following the T-OAE, Mancodinium semitabulatum and Mendicodinium spp. were the only dinoflagellate cysts recorded. This ‘blackout’ of dinoflagellate cysts during the T-OAE, and their partial recovery following the event, shows that dinoflagellate populations were responding to a major palaeoenvironmental change.

Dryland vegetation from the Middle Pennsylvanian of Indiana (Illinois Basin): the dryland biome in glacioeustatic, paleobiogeographic, and paleoecologic context

AbstractA macrofloral assemblage dominated by elements of the Euramerican dryland biome is described from the Brazil Formation in Clay County, Indiana (Illinois Basin). Fossils were recovered from a thin heterolithic unit between a shallow-marine bed and the paleosol beneath the Minshall Coal, a Middle Pennsylvanian succession deposited near the Atokan-Desmoinesian and Bolsovian-Asturian boundaries. Sedimentological indicators imply accumulation under a seasonal climate, including interbedded siltstone and sandstone deposited during flashfloods, intraclasts eroded from local sources, and charcoal produced by wildfires. The macrofloral assemblage is consistent with a dryland setting, being dominated by large, coriaceous gymnosperm leaves with mesic to xeric traits, includingCordaitesspp. indet.,Lesleyasp. indet., andTaeniopterissp. cf.T. multinervia. Sphenopsids and ferns typical of the wetland biome are rare. In contrast, the microfloral assemblage is dominated by fern spores, with lesser lycopsid spores and cordaitalean pollen. The succession indicates that the dryland biome predominated during late regression, prior to the onset of perhumid conditions that resulted in peat accumulation at late lowstand. However, the abundance of palynomorphs from wetland vegetation implies gradual fragmentation of the prevailing dryland flora and replacement by the wetland biome in the transition to glacial maximum. The taphonomic and paleobiogeographic context confirms that floras adapted to seasonal moisture deficit periodically dispersed into tropical lowlands, rather than being transported from ‘extrabasinal’ or ‘upland’ environments. The precocious occurrence ofTaeniopteris, more typical of Late Pennsylvanian and Permian floras, may be the earliest record of the fossil-genus, and exemplifies the association of derived plant taxa with dryland habitats. The predominance of broad-leaved gymnosperms with mesic to xeric characters suggests that dryland communities contained more slow-growing and long-lived plants than contemporaneous wetland floras.

The terrestrial end-Permian mass extinction in South China

The end-Permian mass extinction reflects the most severe life crisis during the Phanerozoic and was associated with major global environmental changes. However, the consistency of the time and pattern of the terrestrial and marine extinctions remains controversial. In this paper, we presented detailed analyses of the high-resolution biostratigraphical and geochemical data from terrestrial sections in South China. Our analyses show that the transitional Kayitou Formation actually recorded the process of terrestrial mass extinction as evidenced by the mass disappearance of the Gigantopteris megaflora in the lower part, the dramatic reduction in abundance of palynomorphs in the middle, and the last occurrences of plant remains and abundant charcoal fossils in the uppermost part. It is associated with a distinct negative shift of δ13Corg, beginning in the middle part of the formation, which is correlative with that in the top of Bed 26 at the marine Meishan section. In addition, the Kayitou Formation is characterized by a distinct shift of lithofacies of fresh lake-swamp or river flat environment from olive/grey/black mudstone, siltstone, fine to coarse sandstone in the lower part to gradually increasing maroon rocks, to purely maroon mudrocks with poorly-sorted breccia, calcic palaeosols and calcareous nodules in the lowest part of the Dongchuan Formation, which indicates a dramatic collapse of soil system associated with rapid deforestation and climatic warming and drying. In the coastal area, the Kayitou Formation contains marine beds with the typical Permian–Triassic mixed faunas and floras which are correlative with the latest Changhsingian marine mixed fauna 1 at Meishan. The Kayitou Formation also recorded a distinct transgression that began in the latest Changhsingian. All above phenomena suggest that the Kayitou Formation is actually the witness of the terrestrial end-Permian mass extinction; and it is mostly or entirely of latest Changhsingian (Permian), rather than Triassic age.

Early to middle Miocene vegetation history of Antarctica supports eccentricity-paced warming intervals during the Antarctic icehouse phase

Recent palynological evidence from the upper section (<664mbsf) of the Miocene ANDRILL 2A (AND-2A) core in the Ross Sea indicated a brief warm period during the Mid Miocene Climatic Optimum (MMCO), during Antarctica's icehouse phase. The nature of other Miocene climate fluctuations in Antarctica remains poorly resolved. Here, we present new palynological data from the lower section of the AND-2A core (>664mbsf) that reveal additional intervals of increased palynomorph abundance and diversity during the Antarctic early to middle Miocene. This evidence is consistent with a relatively dynamic early Miocene Antarctic icehouse climate with intervals of increased temperature and moisture, prior to the MMCO. Comparison with previous AND-2A studies indicates that periods of increased palynomorph abundance in the lower stratigraphic section largely coincide with ice sheet minima, distal ice conditions, and the presence of freshwater (i.e. increased precipitation, meltwater run-off, and freshwater ponds). Decreases in plant productivity mostly coincide with increased glaciation, decreased freshwater, and ice-proximal conditions during the Antarctic Miocene. Comparing the palynological data with other AND-2A data and global climate proxies (e.g., pCO2, δ18O, relative sea level, Milankovitch cycles) helps to resolve questions regarding the driving forces behind climate and vegetation change. We found that palynomorph assemblages reflecting generally warmer conditions are largely associated with 400-kyr eccentricity maxima, while assemblages indicative of colder conditions coincide with 400-kyr eccentricity minima. These data are consistent with other findings that indicate the early to middle Miocene climate was eccentricity-paced.

Principal Component and Cluster Analyses of Palynodebris from Aj-X Well, Offshore Dahomey Basin and their Environmental Significance

The palynofacies study carried out on offshore ditch cuttings from AJ-X well in Dahomey basin revealed different types of palynodebris. To assess the pattern of distribution of the palynofacies types, their abundances were submitted to Cluster analysis and Principal component analysis. The PCA diagram consists of four curves, PC1, PC2, PC3 and PC4 with a cumulative variance of 45.8% showing fluctuations in PC curves supporting the response of the palynodebris to changing environments. The cluster for the well revealed two super clusters based on the abundance and composition of the kerogen groups. These are informally designated as: super cluster X, which is subdivided into X1, X2 and X3, and super cluster Y, subdivided into Y1 and Y2. X1 is composed mostly of phytoclasts and a moderate abundance of the AOM group (Phy/AOM); X2 of high abundances of phytoclasts combined with moderate to high abundances of palynomorphs (Phy/Pal); and X3 is composed of very high abundances of phytoclasts (Phy). The high abundances of the AOM group occur in super cluster Y. Y1 is characterized by very high abundances of the AOM group. In Y2 this group occurs with phytoclasts and, in particular with the palynomorph group (AOM/Pal). The major break that occurred between clusters X and Y is strongly related to the abundance of the phytoclasts group. The size, shape and texture of all the components were integrated with sedimentological features and palynomorphs to recognize distal suboxic-anoxic shallow neritic shelf environment.

Palynology and biostratigraphy of the Maastrichtian Coal Measures in the Anambra Basin, Southeastern Nigeria.

A total of sixty-eight (68) core samples retrieved from eleven wells penetrating the Mamu Formation in the Anambra Basin, Southeastern Nigeria were studied for their palynomorph content in order to determine the age and paleoenvironment of deposition of the Mamu Formation. The wells are characterized by intercalation of laminated fine grained sand and light-dark grey fissile shale with interbeds of coal seams. The lower part with dark grey shale is characterized by the maximum development of Longapertites marginatus Acme Zone, dated Middle Maastrichtian. The upper part defined by intercalation of sand and shale with coal seam layers interbedding belong to Spinizonocolpites baculatus Assemblage Zone. This zone is characterized by the occurrence of Spinizonocolpites baculatus, S.echinatus, Gemmazonocolpites sp, Constructipollenites ineffectus, Syncolporites marginatus, Periretisyncolpites gigantus, Zlivisporites blanensis, Retidiporites magdalenensis, Distaverrusporites simplex, Foveotriletes margaritae, L.vaneendenburgi, Proxapertites cursus, Proteacidites sp, Buttina andreevi, Periretisyncolpites sp and Monocolpites marginatus. All these forms characterize Upper Maastrichtian age on the basis of the recognized diagnostic forms in the wells. The palynomorph abundance and diversity peaks and fossil assemblage of Mamu Formation show similarity with South American forms characterized by colder and warmer climate. These are directly related to eustatic change in sea level resulting to transgression and regression phases. The marine incursion resulted in Mid-Maastrichtian leading to the deposition of basal shale sequence of Mamu Formation while the coal seams were deposited during the regressive phases in the Late Maastrichtian.

An earliest Givetian “Lilliput Effect” in the Paraná Basin, and the collapse of the Malvinokaffric shelly fauna

An earliest Givetian ''Lilliput Effect'' at So´tio Wolff and Sao Bento in the ParanaBasin occurred after an extinction event, possibly related to the latest Eifelian KAC y AK Event. The Malvinokaffric fauna was reduced from 65 genera before the extinction event to eight genera after the event. However, the abundance of the individual taxa is high. The size reduction of the surviving taxa was up to 90%. The palynomorphs during the extinction and post-extinction (''Lilliput Effect'') events are scarce. Nor- mal palynomorph abundance and diversity is restored later in the early Givetian immediately after the post-extinction event. The relictual fauna in the beds with the ''Lilliput Effect'' at So´tio Wolff and Sao Bento constitute the last survivors of the classical Malvinokaffric shelly fauna in the ParanaBasin, and are at these sites mixed with immigrants and alien elements (e.g. orthoconic nautiloids).

PREDICTION OF ATMOSPHERIC 13CO2 USING PLANT CUTICLE ISOLATED FROM FLUVIAL SEDIMENT: TESTS ACROSS A GRADIENT IN SALT CONTENT

Abstract In order to test the assertion that the carbon-isotopic composition of the ancient atmosphere (δ13CO2) can be reconstructed from the carbon-isotopic composition of fossil terrestrial plant tissues across a variety of environments, the δ13C value of land-plant tissues isolated from modern fluvial sediments was compared to that of today's atmosphere. Plant stem and leaf fragments were isolated from organic carbon-rich sediments of the Black River in Jamaica, which drains a basin containing only C3 ecosystems. Sediment was sampled at 12 sites along a dissolved salt-content gradient, from the coastal plain to near its mouth, which allowed evaluation of the effect of salt influence on the organic carbon-isotope signature. Many properties of the sediment varied systematically with salt content (e.g., mass-percent carbonate, abundance of palynomorphs, δ13C and δ18O values of carbonate), confirming a significant and increasing marine influence closer to the mouth of the river. The δ13C value of total org...

Pollen analysis of a soil sample associated with a Greek cult statue as a guide to provenance

A Classical Greek cult statue of a Goddess, “Aphrodite”, currently on display in the J. Paul Getty Museum has recently been reclaimed by the Italian government. The statue is thought to have been sculpted between 425 and 400 B.C. in southern Italy or Sicily, but its provenance is obscure. Soil incorporated into the true right arm socket of the acrolithic statue at the time of burial was pollen analyzed to provide information on its geographic origin. Since palynomorphs are often not well preserved in soils, a preliminary study was undertaken to investigate preservation and abundance of palynomorphs to determine the potential benefits of undertaking further analyses. Although concentration was low, the soil contained sufficient pollen and spores to determine the environment in the vicinity of the burial site of the statue. The landscape had been cleared of natural arboreal vegetation and intensively cultivated. Juglans regia and cereals were cultivated, and pastoralism may have been practiced. A specific geographic location could not be inferred without comparative soil analyses.

Palynological assemblages of non-marine rocks at the Permian–Triassic boundary, western Guizhou and eastern Yunnan, South China

Marine and non-marine facies of the Permian–Triassic boundary stratigraphic set (PTBST) are well developed in South China. Palynological assemblages enable subdivision and correlation of the Permian–Triassic boundary (PTB) rocks. Three palynological assemblages are recognized across the PTBST in two terrestrial PTB sections in western Guizhou and eastern Yunnan, South China. Assemblage 1 (Xuanwei Formation) is a Late Permian palynological assemblage dominated by ferns and pteridosperms, with minor gymnosperms. Most taxa are typical long-ranging Paleozoic forms, but the appearance of Lueckisporites confirms a Late Permian age for this assemblage. Assemblage 2 (PTBST) is marked by an abrupt decrease in palynomorph abundance and diversity, and thriving fungal/algal(?) spores. Assemblage 2 is still dominated by ferns and pteridosperms, with a few gymnosperms, but is characterized by a mixed palynoflora containing both Late Permian and Early Triassic elements. Most taxa are typical Late Permian ones also found in Assemblage 1, however, some taxa of Early Triassic aspect, e.g. Lundbladispora and Taeniaesporites, appeared for the first time. In Assemblage 3 (top Xuanwei Formation and Kayitou Formation), the proportion of gymnosperm pollen increases rapidly, exceeding that of ferns and pteridosperms, but the abundance of palynomorphs is still low. Typical Early Triassic taxa (such as Lundbladispora, Aratrisporites and Taeniaesporites) are present in greater abundance and confirms an Early Triassic age for this assemblage.

Contribution of quantitative ecological methods to the interpretation of stratigraphically homogeneous pre‐quaternary sediments: A palynological example from the oligocene of Venezuela

This paper deals with an Oligocene section that is stratigraphically homogeneous from both a lithological and palynological point of view. It has been impossible to subdivide it into discrete units, using either taxon‐range analysis or assemblage‐zone approach based on the relative abundance of palynomorphs. Furthermore, the common multivariate numerical methods used so far with success in the region (Cluster Analysis, Principal Components Analysis, etc.) gave no useful results in this case. The search for cyclicity using palynocycles and ecologs has been also unsuccessful. Instead of considering the section of low interest, an alternative, high‐resolution ecological approach was attempted to extract the information contained in these sediments. Paleoecologi‐cal trends were deduced from statistical methods commonly used in modern and Quaternary ecology, mainly TWINSPAN and gradient analysis, combined with diversity analysis. As a result, the fine‐scale stratigraphic variability of the data could be successfully explained in terms of paleoecological succession taking place in upper delta environments, characterised by a complex mosaic vegetation including morichales, herbaceous fern swamps, and gallery forests. The succession could be reconstructed in detail, and would be of indirect stratigraphic value for high‐resolution correlation. This is an example of how the search for narrow or biased objectives can hidden significant information. It is more fruitful to have a wider perspective, and to be open to any information that sediments can provide us, without a priori limitations.

CONTRIBUTION OF QUANTITATIVE ECOLOGICAL METHODS TO THE INTERPRETATION OF STRATIGRAPHICALLY HOMOGENEOUS PRE-QUATERNARY SEDIMENTS: A PALYNOLOGICAL EXAMPLE FROM THE OLIGOCENE OF VENEZUELA

This paper deals with an Oligocene section that is stratigraphically homogeneous from both a lithological and palynological point of view. It has been impossible to subdivide it into discrete units, using either taxon-range analysis or assemblage-zone approach based on the relative abundance of palynomorphs. Furthermore, the common multivariate numerical methods used so far with success in the region (Cluster Analysis, Principal Components Analysis, etc.) gave no useful results in this case. The search for cyclicity using palynocycles and ecologs has been also unsuccessful. Instead of considering the section of low interest, an alternative, high-resolution ecological approach was attempted to extract the information contained in these sediments. Paleoecological trends were deduced from statistical methods commonly used in modern and Quaternary ecology, mainly TWINSPAN and gradient analysis, combined with diversity analysis. As a result, the fine-scale stratigraphic variability of the data could be successfully explained in terms of paleoecological succession taking place in upper delta environments, characterised by a complex mosaic vegetation including morichales , herbaceous fern swamps, and gallery forests. The succession could be reconstructed in detail, and would be of indirect stratigraphic value for high-resolution correlation. This is an example of how the search for narrow or biased objectives can hidden significant information. It is more fruitful to have a wider perspective, and to be open to any information that sediments can provide us, without a priori limitations.