Depositional Environment

Grain-size analysis of beach sediments along Rosetta beach of the Nile delta coast has been carried out to reveal the depositional environment condition, energy and hydrodynamic conditions, as well as the mode of transportation along the study area. In total 56 beach samples were collected, distributed along 3 profiles parallel to the shoreline and covering the shoreline, semi-wet area, and the dry backshore area. The study showed the great sensitivity of the interrelationships of various grain size statistical parameters (mean size, sorting, skewness, and kurtosis) to the slight variations in the compositional formula of the sediment mixture. Distribution of the textural parameters revealed the dominance of unimodal pure sand sediments, mainly Nile sand sources. The fluctuation between moderately well-sorted to well-sorted sediments and from coarse skewed to fine skewed under leptokurtic to platykurtic nature was distinguished at different localities and relevant environmental implications. Different discrimination tools as bivariate cross plot of grain size parameters, Linear Discrimination Functions (LDF), skewness and kurtosis relationship as a non-dimensional  expression of sediment/energy simulation, Energy Process diagram, and mode of transportation (C-M diagram), indicates the marine signature followed the riverine input as a function of the sediments locality. Depositional processes were mainly hydraulically controlled through active energy processes of the marine environment. The fluvial nature of sediment demonstrated the graded suspension and saltation modes as the prime factors for transportation, influenced by marine and turbidity environment actions, within a shallow agitated marine environment.

The facies models are the most powerful method for the genetic interpretation of the stratigraphic record, acting as syntheses of the facies relationships. Nowadays, the facies relationship interpretation is fundamented either by the Walther's Law (or Facies Correlation Law) or by the application of geostatistic tests. On the other hand, the present stratigraphic basin analysis search for stratal discontinuities (actually bedding surfaces). It is the bedding surface hierarchization, according to its physical magnitude (scale), that have revealed a usefull way for the facies association diagnosis. In accordance to this practise, it is adopted the postulate of that facies contained between bedding surfaces of the same hierarchical order, in one stratigraphic succession, without the intervenience of a bedding surface of greater magnitute, are genetically related one to each other, and may be conceived in association. This postulate differs from the universalized facies diagnosis procedures for not making use of the magnitude of the stratal discontinuities as a physical argument of the facies relationship falsification (unconformities in the Walther's Law), but as the foundation of its interpretation; furthermore, it takes away the necessity of geostatistic tests as an argument to the relationship verification, which only determines the possible and probable relations.

This PhD thesis deals with the Tagus River in Portugal, the 12th largest river of Europe. One of the first times terrestrial and marine environments are integrated in one study. The results show that this river experienced enormous changes during the last 20,000 years. These changes range from erosion of a deep valley during the last ice age, through drowning of the valley and creation of an inland sea, to the dramatic effect of human impact during the last 1000 years.

Specimens of the trace fossil Gyrochorte from the Ordovician, Jurassic and Cretaceous of Utah, and the Pliocene of Spain are described. These ocurrences expand the stratigraphic range of the ichnogenus, and allow for a reexamination of this paleoenvironmentally sensitive and puzzling trace fossil. The recognition of the penetrative characteristic of the trace is essential for a correct identification, as some trace fossils have been erroneously ascribed to Gyrochorte in the past. The producer must have been a detritus-feeding worm-like animal, probably an annelid, that created a bilobed, vertically penetrating and sometimes plaited meandering trace. Gyrochorte typically occurs in sandy facies in moderately energetic nearshore and shallow marine paleoenvironments in association with other trace fossils, usually pascichnia and fodinichnia.

This study is focused on the sedimentary environments, facies distribution and sequence stratigraphy of the Santonian intervals (Ilam Formation of Bangestan Group) that host enormous hydrocarbon reserves in five giant and supergiant oilfields in the central and southern parts of the Dezful Embayment (SW Iran). This reservoir formation is investigated using detailed petrographic analysis assisted by microscopic image analyses to explain its depositional facies and sedimentary environment in the subsurface sections of this embayment. Petrographic studies led to the recognition of 18 microfacies that formed in four facies belts: inner ramp (including shoal facies and open to restricted lagoons), mid-ramp (including channels and patch reef talus facies), outer ramp and basin. To locate the approximate position of the studied wells in the conceptual depositional model, frequency analyses for facies associations are carried out. The studied intervals consist of two, thick shallowing-upward 3rd-order sequences. Facies variations of the Ilam Formation investigated throughout the studied oilfields using correlation in a sequence stratigraphic framework.

Microfacies and environmental analysis of Khurmala Formation (Paleocene-Lower Eocene) was studied in the Zenta area, near Zenta village, Aqra district-Kurdistan region Northern Iraq. The formation is composed of 71 m thick bedded grey dolomitic limestone, partially bituminous with chert nodules and rare chert lenses and medium to thick bedded yellow limestone, interbedded with thin beds of marl and mudstone. The petrographic study showed the majority of the limestones are carbonate mud (micrite). The skeletal grains consist principally of benthonic foraminifera, calcareous green algae, ostracods, gastropods, pelycepods, and rare larvae echinoids. Non skeletal grains include peloids only. Three main microfacies were distinguished in the limestones of the studied section and two different lithological units were recognized, based on field evidence and petrographic study. They are in ascending order: thick bedded dolomitic limestone unit and bedded limestone with marl unit. Evidence derived from petrographic study, facies and textural analyses suggest that the Khurmala Formation was deposited in a shallow marine environment of shelf lagoon with circulation, under quiet and semi restricted conditions. ‫السحى‬ ‫تحليل‬ ‫بث‬ ‫الذقيق‬ ‫خ‬ ‫لتكويه‬ ‫الترسيبيت‬ ‫والبيئت‬ ‫ت‬ ‫(ببليوسيه‬ ‫رمبلت‬-‫االسفل)‬ ‫ايوسيه‬ ‫زوطت،‬ ‫قريت‬ ‫في‬ ‫العرا‬ ‫كردستبن،‬ ‫اقليم‬ ‫عقرة،‬ ‫قضبء‬ ‫ق‬ ‫ببلكي‬ ‫الذيه‬ ‫محي‬ ‫سردار‬ ‫و‬ ‫اسعذ‬ ‫شعببن‬ ‫عرفبن‬ ‫المستخلص‬ ‫دراست‬ ‫حًج‬ ‫ان‬ ‫سحُب‬ ‫(ببنٍىسٍٍ‬ ‫خريبنت‬ ‫نخكىٌٍ‬ ‫انخرسٍبٍت‬ ‫وانبٍئت‬ ‫انذلٍمت‬ ‫ث‬-‫فً‬ ‫انىالعت‬ ‫زَطت‬ ‫لرٌت‬ ‫فً‬ ‫االسفم)‬ ‫اٌىسٍٍ‬ ‫لضبء‬ ‫كردسخبٌ‬ ‫الهٍى‬ ‫فً‬ ‫عمرة‬-‫شً‬ ‫خ‬ ‫حكىٌٍ‬ ‫صخبرٌت‬ ‫حخأنف‬ ‫انعراق.‬ ‫بل‬ ‫يٍ‬ ‫انًخخبر‬ ‫يمطع‬ ‫فً‬ ‫ريبنت‬ 17 ‫طبمبث‬ ‫يٍ‬ ‫يخر‬ ‫انجٍر‬ ‫حجر‬ ‫يٍ‬ ‫سًٍكت‬ ‫جسئٍب‬ ‫انحبوي‬ ‫انرصبصً‬ ‫انًذنًج‬ ‫ي‬ ‫انمٍر‬ ‫عهى‬ ‫ودرَبث‬ ‫انصىاٌ‬ ‫وعذسبث‬ ‫انسفهً‬ ‫جسئه‬ ‫فً‬ ‫ا‬ ‫انسًك‬ ‫يخىسطت‬ ‫وطبمبث‬ ‫االصفر‬ ‫انجٍري‬ ‫حجر‬ ‫يٍ‬ ‫انسًٍكت‬ ‫نى‬ ‫انعهىي.‬ ‫جسئه‬ ‫فً‬ ‫انطًٍُ‬ ‫وحجر‬ ‫انًبرل‬ ‫يع‬ ‫انًخذاخم‬ ‫أظهرث‬ ‫انذراست‬ ‫ن‬ ‫انبخروغرافٍت‬ ‫ـ‬ 23 ‫اٌ‬ ‫رلٍمت‬ ‫شرٌحت‬ ‫صخىر‬ ‫يعظى‬ ‫انحجر‬ ‫انجٍري‬ ‫حخكىٌ‬ ‫يٍ‬ ‫انىحم‬ ‫انجٍري‬. ‫حضًُج‬ ‫انهٍكهٍت‬ ‫انحبٍببث‬ ‫انفىر‬ ‫يٍ‬ ‫كم‬ ‫وصذفٍبث‬ ‫خضراء‬ ‫وطحبنب‬ ‫انمبعٍت‬ ‫ايٍُفٍرا‬ ‫وبطٍُ‬ ‫و‬ ‫انمذو‬ ‫بث‬ ‫فضال‬ ‫انمذو‬ ‫فأسٍبث‬ ‫عٍ‬. ‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬

The aim of the present study is to provide additional information about the properties and depositional environment of the Kipra lignite seam, which was deposited during the regressive stage of development of the Maritza-West basin. Petrographical and mineralogical data, along with ash yields and sulphur contents of 24 samples from a seam profile, have been used to study the vertical variation of the depositional settings during peat accumulation and subsequent coalification.The Kipra lignite is characterized by high ash yields and sulphur contents. It formed in a rheotrophic, low-lying mire with alkaline pH value. Vegetation with low preservation potential dominated within the palaeomire. During peat formation, frequent changes of the water level controlled the depositional environment. During the deposition of units 1 and 2, high water energy caused the transportation of high amounts of inorganic material into the mire, resulting in the formation of weakly gelified mineral-rich lignite. The organic matter from units 3 and 4 is characterized by enhanced gelification, which probably reflects the decreasing energy of the system. Good positive correlation between sulphur contents and the GI values was established in units 4, indicating that the gelification of the tissues was probably mainly controlled by the bacterial activity. In contrast, the gelification of the samples from unit 3 of the Kipra seam was probably governed by the redox conditions. The organic matter deposited under relatively wet conditions, in which the thermal and oxidative destruction of the tissues, was limited.A variety of major, minor and accessory minerals are present in Maritza-West lignite. The mineral composition is dominated mainly by pyrite, gypsum and calcite, and to a lesser extent limonite, quartz, kaolinite, montmorillonite, illite, chlorite and plagioclase. Jarosite, hematite, halloysite, mica, K-feldspar, aragonite, siderite, and dolomite were also determined in very low concentrations. These minerals formed syngenetically and epigenetically. The syngenetic stage is characterized mainly by the formation of pyrite, carbonates, silicates and sulphates, whereas the Fe-oxyhydroxides, partially the carbonates and almost all silicates are of detrital origin. During the epigenetic stage, carbonates, sulphates, clay minerals, pyrite, and Fe-oxyhydroxides were formed. Alteration products like gypsum, jarosite, limonite, chlorite, kaolinite, illite, mica, and calcite were generated due to the transformation of detrital and authigenic minerals.

Subsurface mass-transport deposits (MTDs) commonly have a chaotic seismic-reflection response. Synthetic seismic-reflection profiles, created from a precise lithological model, are used to interpret reflection character and depositional geometries at multiple frequencies. The lithological model was created from an outcrop of deep-water lithofacies where sandstone deposition was influenced by mass-transport deposit topography. The influence of MTD topography on sandstone distribution should be considered in reservoir characterization and modeling when MTDs underlie the reservoir, especially if the reservoir is thin relative to the scale of the topography. MTD topography up to several tens of meters in both the horizontal and vertical dimensions (relative to local elevation) compartmentalizes significant quantities of sandstone and is not resolved at lower seismic-reflection frequencies. The resolvability of thick (up to 70 m) sandstone packages is hindered when they are encased in MTDs of at least equivalent thickness. Lateral and vertical changes in seismic-reflection character (e.g., amplitude, polarity, geometry) of sandstone packages in the synthetic profiles are due to lithology changes, tuning effects, resolution limits, and depositional geometries, which are corroborated by the lithological model. Similar reflection-character changes are observed in an actual seismic-reflection profile, of comparable scale to the synthetic profiles, from the Gulf of Mexico, which demonstrates similar lithofacies distributions. Synthetic profiles, when constrained by a precise lithological model, are particularly useful analogues for interpretation of lithofacies relationships, and depositional geometries, in complicated depositional environments, such as deep-water slope deposits.

The Lamja Sandstone conformably overlies the Numanha Shale. The exposures of the formation occur on the eastern and southern fringes of the Tertiary Lunguda Basalt Plateau. The Lamja Sandstone consists of shale, coal, siltstone, sandstone, sandy limsestone and carbonaceous sandstone. The dominant sedimentary structures are parallel lamination, cross bedding, cross lamination, cross stratification, planar bedding and bedding planes. Petrographic studies show that the sandstone is poorly-moderately sorted, very fine-fine grained and sub-angular-sub-rounded. Granolumetric data show a graphic mean size of 2.82ø (fine grained sandstone), mean standard deviation of 1.62 (poorly sorted) while the skewness values are positively fine skewed, and kurtosis; showing an average value of 0.860 (mesokurtic). Bivariate plots standard deviation versus skewness, standard deviation versus mean; and standard deviation versus first percentile for sample studied cluster within the river environment. The cumulative probability curves plotted, showed that most of the samples are characteristics of fluvial.

The Maastrichtian Mamu and Nsukka Formations in the Anambra Basin (SE Nigeria) consists of a cyclic succession of coals, carbonaceous shales, silty shales and siltstones interpreted as deltaic deposits. The Anambra Basin was formed at the NW of the anticlinorium and the Afikpo syncline at the SE part of the anticlinorium, making both basins a depocenter during the Campanian to Maastrichian. Clay fractions of shale samples obtained from the Cretaceous Mamu and Nsukka Formations in the Afikpo Basin, south eastern Nigeria through the process of sedimentation technique were air – dried and analyzed using the empyrean diffractometer manufactured by Panalytical to determine the paleoclimate and depositional environments of the shales. The result shows that the bulk mineral composition of the shales comprises of quartz, clay minerals, carbonates and iron rich minerals, while the dominant clay mineral is kaolinite (70 – 80%) with minor amounts of illite (4 – 7 %) and smectite (10 – 20). This shows that both Formations were deposited under warm and humid conditions (typical of tropical to sub – tropical climate), while the depositional environment with evidence from biostratigraphy is suggested to be a near shore estuarine environment.

The Pliocene sedimentary filling of the Baix Ebre basin includes both a transgressive and a regressive sequence. During the transgressive period, buildups and bioerosion surfaces were developed on the most isolated areas of the paleorelief with low or no terrigenous sedimentation. Other nearshore areas were occupied by pebbly-sandy beaches including typically littoral trace fossils (Gastrochaenolites, Entobia, Skolithos) which change laterally and vertically to shallow bay sands and clays deposited in a rather restricted environment with low bioturbation dominated by J-burrows. The blue clays which underlie those deposits correspond to the maximum of the transgression, and they are fully bioturbated. During the regression, the marine deposits were sands and clays including different facies and ichnoassociations which correspond to bay deposits (Sinusichnus and Teichichnus-Fugichnia assemblages), sand bars (Skolithos assemblage) and restricted proximal environments (Teichichnus assemblage). The continental units, lacustrine and alluvial culminate the regressive sequence.

In the south-western Anti-Atlas of Morocco (Dra Plain), a continuous exposure of Lower Devonian sedimentary successions more than 400 km long provides an example of mixed siliciclastic-carbonate shelf sequences. The carbonates were deposited adjacent and down-dip to large lobes of storm-dominated deltaic complexes during sea-level lowstands, and subsequently transgressed over the 200 m thick prograding siliciclastic wedges during sea-level rise, depositing limestone units between 5 and 20 m thick. The deltaic lobes switched through time and caused alternating siliciclastic supply along the shoreline oblique–parallel transect. Condensed limestone successions formed in clastic sediment starved areas due to delta-complex abandonment.Down-gradient, in outer ramp environments, the direct juxtaposition of carbonate and siliciclastic lithofacies associations comprising rhythmic lime mudstones/marls and massive shelf sandstones, provides the opportunity for mutual interpretation of their mode of deposition and bathymetry. This lateral relationship suggests that significant amalgamation took place in falling stage systems tracts to produce laterally extensive shelf sandstone-sheets on the outer ramp.Two types of stacking patterns are observed in prograding siliciclastic wedges. A normal progradational shoreline pattern with well developed parasequence sets in the proximal ramp, and an abrupt-regressive succession in which the amalgamated shelf sandstones rest more or less directly on offshore siltstones in the distal ramp. In the latter case, the falling stage systems tract sandstones are overlain by a relatively thick cyclic alternation with brachiopod-rich storm-beds below a marked transgressive surface at the base of the capping transgressive limestones. The cyclic alternation is interpreted as lowstand systems tract deposits. Marked flooding surfaces on parasequence sets are Fe-enriched and contain abundant articulated brachiopods, indicating breaks in sedimentation and an overall deepening-upward facies from the underlying maximum regression and sequence boundary. These aggradational to retrogradational stacked lowstand systems tracts are thus rather ‘transgressive’, not regressive in character, as is commonly described in sequence stratigraphic ramp models.

This is a tentative to illustrate the tectonic-sedimentary evolution of Brazilian sedimentary basins during the geological time. This pannel was presented and distributed as a CD-ROM during the 46° Congresso Brasileiro de Geologia occurred in Santos city, São Paulo from Sep, 30th to Oct, 5th.

This work examines ichnological attributes and variability of core samples from four wells (1-4) within the Coastal Swamp and shallow Offshore depobelts in the Niger Delta basin. The cores consist of facies interpreted as mainly shoreface deposits. These deposits are in successions and well-developed. The shoreface successions are divided up into a lower, middle and upper shoreface. The lower shoreface lies within fair weather wave base. The ichnofossils assemblages characteristically represent a diverse and abundant Cruziana ichnofacies. The middle shoreface contains swaly and lesser hummocky cross-stratified sandstones with an ichnofossil assemblage dominated by the Skolithos ichnofacies. The upper shoreface is dominated by planar and trough cross-beddings. Ichnofossils are fairly abundant and consist of deeply penetrating structures of the Skolithos ichnofacies. These facies reveal a wide range of variability, mostly limited to the lower and middle shoreface intervals. This variability appears to be determined by relative storm dominance and the episodic character of associated storm bed deposition. The successions are grouped into three: (1) high energy shorefaces consist entirely of stacked storm beds with moderate bioturbation, (2) moderate energy shorefaces comprises stacked laminated to burrowed intervals, recording recurrent erosive storm bed emplacement, followed by opportunistic colonization, and normally overprinted by resident fair-weather burrowing, and (3) low energy shorefaces ordinarily exhibit intense bioturbation with low preservation of storm beds. Discrimination between lower and middle shoreface deposits is mainly based on the resident fair-weather ichnofossil assemblage; under increased energy settings. In addition, based on storm intensity, relative water depth, storm frequency and shoreline character, the nature of coexistent lower and middle shoreface facies can differ significantly along strike. In some cases, the lower and middle shoreface differentiation was difficult.

Abstract
The Eocene transgressive deposits of the Acıgöl, Burdur and Isparta basins are the best exposed of the SW Turkey and shed light on one of the outstanding problems of the tectono- sedimentary evolution during paleotectonic and neotectonic period. In the present paper we describe a tectonic model of the
progressive foreland migration of the allochthonous units such as Lycian and Antalya nappes, initial
emplacement onto stable carbonate platform in the Early Oligocene, carrying piggy-back basins and
incorporating from alluvial fan to deep-marine deposits recognized in these terrigenous successions.
In general, the facies and structural observations on the overall Mid-Late Eocene clastic sequences,
outcropping in behind the Lycian nappes, indicate: i) the alluvial fan to shallow marine settings of the
Başçeşme Fm in Acıgöl, ii) the Varsakyayla Fm in Burdur and iii) proximal to distal flysch facies
trend of the Kayıköy Fm in Isparta. The collected data allow us to hypothesize that the Mid-Late Eocene tectono-sedimentary history was characterized by a terrigenous clastics, probably lying on the constructing tectonic edifice and then deformed and covered by a piggy-back like sequence. The
tectono-sedimentary evolution of the Eocene transgressive in SW Turkey has been probably developed through a progressive migration towards the foreland basin.

A well-preserved, low-diversity assemblage of fossil echinoderms from the early Middle Volgian in the Slottsmøya Member (Agardhfjellet Formation) has been discovered at Janusfjellet, Sassenfjorden area, central Spitsbergen. Five species are recognised: the isocrinid Chariocrinus sp., the pedinoid Hemipedina sp., the forcipulate asteroid Asteriidae sp., the ophiacanthid Ophiacanthidae sp. and the ophiurid Ophiurinae sp. A depositional environment model reconciling autecologic, taphonomic and sedimentary evidence is presented. The Janusfjellet Lagerstätte was formed by a single, rapid burial event during a storm, entombing together autochthonous asteroids and ophiurids, and allochthonous crinoids and echinoidson a dysoxic muddy sea-floor. Comparable echinoderm material from the Boreal Late Jurassic-Early Cretaceous is scarce, outdated and usually poorly described and illustrated. The scarcity of reported occurrences probably results from a collector bias for rare complete specimens and doesnot reflect the true echinoderm composition of Mesozoic high-latitude communities.