Cross-bedded Sandstone Facies Research Articles

Tidal-influenced shoreline interpretation of Miocene Tanjong Formation in Imbak Canyon, Sabah, Malaysia

The Tanjong Formation of Imbak Canyon, Sabah is the Early Miocene aged shallow marine unit that crops out in the Tongod district. Tanjong Formation has previously been interpreted to have been deposited in a shallow marine environment without tidal influence. This paper reinterpreted the depositional environment with emphasis on tidal deposits through newly logged sections encountered during 2019 Imbak Canyon Expedition. Proximity-driven strike orientation correlations were employed to interrelate the logged geological sections. The eight facies recognized are 1) Mudstone Facies (M), 2) Lenticular Facies (LF), 3) Wavy Facies (WF), 4) Flaser Facies (FF), 5) Hummocky Cross-Bedded Sandstone Facies (HCS), 6) Swaley Cross-Bedded Sandstone Facies (SCS), 7) Planar Cross-Bedded Sandstone Facies (PCS), and 8) Structureless Sandstone Facies (SS). Three interpreted facies associations deduced are 1) intertidal deposits, 2) middle to lower shoreface, and 3) offshore deposits. We conclude that Tanjong Formation was deposited in a macrotidal open coast setting with significant tidal imprint signatures. The identification of tidal influence within a wave-dominated system is an infrequent occurrence, yet it holds significant potential for enhancing the refinement of shallow marine models.

Evaluation of Presence of Quicklime (CaO) in Ohafia-Arochukwu Areas of Nsukka Formation, Afikpo Basin, Southeastern Nigeria

The co-ordinates of the area studied are within latitudes 5o29ˈ to 5o51ˈN and longitudes 7o29ˈ to 8o00ˈE. The Nsukka Formation in the studied area consists of two facies associations; limestone-shale and cross bedded sandstone. The Limestone-shale facies association consists of the following lithofacies; rippled clayey sandstone, carbonaceous shale, heterolithic sandstone-shale, laminated grey shale, fossiliferous limestone, Fine grained sandstone, Silty shale, Medium grained sandstone and carbonaceous sandstone. The cross bedded sandstone facies association consists of only cross bedded sandstone. Representative samples of these rocks from Ohafia area were collected and stored in a polythene bag for further investigations. XRF analyses were carried out on these rock samples. The XRF oxide content of elements in sample OHA 1 of original rock was found to be CaO (76.00), Fe₂O₃ (8.35), SiO₂ (7.13), Al₂O₃ (2.46), SO₃ (2.29) and MgO (1.81) with other oxides in minor quantities. The shale-limestone lithofacies of OHA 2 of the same rock showed CaO (85.90), SiO₂ (5.13), MgO (2.56), Al₂O₃ (1.80), SO₃ (1.71), Fe₂O₃ (1.20) and P₂O₅ (1.02) with other oxides in minor quantities. OHA 3 of cross-bedded sandstone lithofacies contains SiO₂ (52.70), Fe₂O₃ (14.10), Al₂O₃ (14.50), MgO (3.74), CaO (9.00), TiO₂ (2.54), K₂O (1.41) and Cl (0.12) with other oxides in minor quantities. For OHA 4 through the XRF indicates Chloride (Cl), CaO and SiO2 contains 79.60%, 0.58% and 3.52%. The samples showed that major component were SiO₂, Al₂O₃, Fe₂O₃, CaO, MgO and TiO₂. The presence of CaO was determined to be deposited on the surface of debris of rocks in the area. It was observed that the occurrence of CaO is amorphous in nature and not crystalline.

Diagenetic alterations and deep high-quality reservoirs within deltaic distributary channel facies: a case study from the Permian Shihezi formation in the Hongde area, southwestern Ordos basin, China

Deep tight gas reservoirs are considered important hydrocarbon exploration targets. High-quality reservoir prediction is critical for successfully exploring and developing deeply buried tight sandstone gas. Previous research has found that the reservoir quality of deeply buried tight sandstones is controlled by diagenesis and sedimentary facies. However, the variation of diagenetic alterations in different facies is still poorly studied on deltaic tight gas sandstone. In this study, core analysis, wireline log data, and 3D seismic were studied for the characterization of diagenetic alterations and sedimentary facies. The tight sandstones were formed in braided river delta deposits. Gravel-bearing coarse-grained sandstone facies and cross-bedded sandstone facies developed in tight sandstones. The Gravel-bearing coarse-grained sandstone is formed in the mid-channel bar of deltaic distributary channels. The major diagenetic processes developed in the tight sandstone include compaction, cementation, and dissolution. Constructive diagenesis can generate secondary pores, mainly including dissolution and kaolinite metasomatism, which can effectively improve reservoir physical properties. Through the diagenesis alterations linked to different lithofacies in cored wells, there are obvious diagenesis variations in different lithofacies. Despite strong compaction, the reservoirs in coarse sandstone facies have developed internal dissolution. After compaction, cementation, and dissolution to increase porosity, the reservoir retains intergranular and secondary pores and forms relatively high-quality reservoirs. The fine sandstone facies with cross-bedding are strongly compacted, with internal ductile particles being compacted and deformed, and the particle orientation is clearly arranged. The reservoir is tight, and the development of dissolution in the reservoir is weak, resulting in poor reservoir quality. In addition, reservoirs located at the interface between sandstone and mudstone are often affected by diagenesis, resulting in the development of calcareous cementation, leading to poor reservoir quality. Therefore, high-quality reservoirs are mostly distributed in coarse sand lithofacies, mainly distributed in the mid-channel bar of distributary channel deposits. Sedimentary facies control the original physical properties of the reservoir with different content and texture; the quality of the original reservoir is subject to diagenetic alteration in different ways. The points in this study could offer insights better to predict deep tight reservoir quality in continental basins.

Facies association and Paleo depositional environment of the exposed Neogene succession in the Sitapahar Anticline of Rangamati Area, Chittagong Tripura Folded Belt (CTFB) region, Bengal Basin, Bangladesh

Neogene sedimentary rocks are exposed in the Chittagong Tripura Folded Belt (CTFB) Region in Bengal Basin. Sitapahar anticline is situated in the middle part of the CTFB Region. In this structure, eleven litho-facies have been identified in fluvial, overbank, shallow marine, deltaic, and deep marine depositional environments. Surma Group is composed of Bhuban and Boka Bil formation during Miocene time and was deposited in shallow marine, deltaic, and deep marine environments and characterized by the identification of interbedded shale facies (ShI), fine sandstone facies (SFs), lenticular laminated silty shale to shale facies (Zw), wavy bedded sandstone siltstone facies (Slsh), flaserbedded sandstone siltstone facies (Sxhs), ripple laminated sandstone facies (Sr), black Shale facies (Shb) and nodular shale facies (Zn). While, Pliocene Tipam group and Plio-Pleistocene Dupi Tila Formations were deposited in fluvial intervention and characterized by crossbedded sandstone facies (Sxbt), mudstone facies (Mf), interbedded mudstone and sandstone facies (MI).

Depositional environment and hydrocarbon exploration potential based on sedimentary facies and architectural analysis of the Upper Cretaceous Shendi Formation in Musawwarat-Naga area, Shendi-Atbara Basin, Sudan

This study examines both vertical and lateral facies changes as well as petrographic characteristics of the outcropping section of the Upper Cretaceous Shendi Formation in the Musawwarat-Naga area with a view of interpreting the depositional environment, provenance, and tectonic setting that prevailed during the deposition of the sediments. Field studies revealed the presence of eight different sedimentary lithofacies. The predominant is the trough cross-bedded sandstone facies (St), representing 75% of the total succession. Four architectural elements were recognized: sandy bedforms (SB), channel fill (CH), gravelly bars and bedforms (GB), and overbank fines (OF). Moreover, the mean value of paleocurrent directions was 285.3°, suggesting a southeasterly located source area. The majority of the sandstones were classified as quartz arenites with subordinate sublithic-arenites. Ternary plots of quartz-feldspar-lithic fragments (QFL) revealed that the tectonic setting is predominantly within the interior craton. It can be suggested that the sediments were sourced from the southeast region and associated with a braided, proximal, fluvial depositional environment. The results of this study provide outcrop analog data that might be useful in exploring hydrocarbons. Specifically, it can enhance the understanding and prediction of the proximal fluvial depositional styles in the subsurface deposits in the Shendi-Atbara Basin and similar rift basins in Sudan and Africa.

The primary depositional structures of the Upper Bima Member from Fufore and environs, Yola Arm of the Upper Benue Trough, Northeastern Nigeria: implications for paleoenvironment

Primary depositional structures are important parameters that can provide the means of unraveling the processes and process responses in sedimentary depositional settings. This paper is aimed at determining the paleoenvironment of the Upper Bima Member in Fufore and environs using the primary depositional structures. This research was carried out in two phases which involved fieldwork that dealt with logging the outcrops sections and desk work whereby the logged sections and other field data are digitized, remodeled and analyzed using relevant computer programs. The result of the study shows that the Upper Bima Member is composed of five lithofacies succession; trough cross-bedded sandstone facies (St), planar cross-bedded sandstone facies (Sp), horizontal bedded sandstone facies (Sh), ripple cross-laminated sandstone facies (Sr), and mudstone facies (Fm). These lithofacies gave rise to two facies associations; sand dominated and fine-grained facies dominated facies association. The cross-stratified facies show an overall paleocurrent trend in the NW direction. These facies succession represent both shallow perennial and ephemeral sand-bed in a braided river depositional environment.

Sedimentologic and Petrographic Study of Outcrops of Ajali Sandstone in Okigwe, Uturu and Isiukwuato, Anambra Basin Southeastern Nigeria

The Ajali Formation outcrops at Okigwe, Ihube, Onyekaba mine, Uturu and Isiukwuato in the Anambra Basin southeastern Nigeria were evaluated for an integrated field, sedimentologic and petrograpic methods. The study was aimed at presenting a better understanding of the depositional processes and provenance. Five lithofacies were altogether described namely: planar Cross bedded sandstone facies A, Massive sandstone facies B, Ferruginized sandstone facies C, herringbone cross bedded sandstone facies D, and Bioturbated sandstone facies E. The facies were deposited in a fluvially influenced shallow marine environment. The overall grain size interpretation shows that sediments from the study area are fine to coarse grained with values ranging from 0.2 to 2.0Φ, poorly sorted to very well sorted with range value of 0.28 to 1.2Φ, nearly symmetrical to strongly fine skewed with values of -0.04 to 0.59Φ and platykurtic to very leptokurtic with values of 0.79 to 2.46Φ. An inspection of the cumulative frequency curves of the studied samples shows that the sediment population is dominated by saltation population. Texturally, the sandstone sediments are sub-mature containing grains that are moderately to poorly sorted and not well rounded. The Mineral Maturity Index of the sandstone in the study area ranges from 24-49 which falls within the mature to super mature class. The high quartz content and insignificant amount of feldspar and rock fragments further support this assertion. The study suggest the sandstones must have been subjected to substantial high degree of reworking that resulted in the removal of the ferromagnesian minerals and feldspar typical of recycled sediments.

Lithofacies, particle size analysis and paleodepositional environment of the Eze-Aku Group (Cenomanian–Turonian) in the Itigidi-Ediba area, Afikpo Synclinorium, southeastern Nigeria

Field, lithofacies and particle size analysis of sediments of the Eze-Aku Group in the Itigidi-Ediba localities, Afikpo Synclinorium, were carried out to describe the textural attributes of the sediments and reconstruct the paleodepositional environment of the study area. Field studies show that the geology is characterized by a succession of marine shales and shaly-limestone overlain by elongate sandstone ridges that trend in a northeast–southwest direction. In certain cases, the sandstone ridges alternate with shales. These deposits are characterized by wave and tide generated sedimentary structures with trace fossil assemblages consisting mainly of Ophiomorpha, Skolithos, and Cruziana ichnofacies that are suggestive of a moderately disturbed environment. Lithofacies studies of the sedimentary succession indicates five facies associations: conglomeritic consolidated sandstone, laminated sandstone, bioturbated sandstone, laminated shaly-limestone and cross-bedded sandstone facies associations suggesting deposition in proximal sub-marine, shelf edge/sub-marine fan, distal sub-marine fan/distal shelf, shallow/deep marine, and shoreface/foreshore sub-environments, respectively indicating a tidal shallow shelf to deep marine environment. Analysis of the grain size spectrum in some selected outcrops shows sediments that are moderate to poorly sorted, generally positively and very positively skewed and mesokurtic, platykurtic to leptokurtic, deposited in a shallow marine environment under moderate to high energy conditions, with fluvial influence.

FLUVIO-DELTAIC DEPOSITIONAL COMPLEX OF THE CAMPANO-MAASTRICHTIAN GOMBE FORMATION OF THE GONGOLA SUB-BASIN, NORTHERN BENUE TROUGH, N.E. NIGERIA

Evaluation of the stratigraphic architecture of the Gombe Formation of the Gongola Sub-basin in the Northern Benue Trough indicated a build-up from six facies assemblage that consist of trough crossbedded sandstone, planar crossbedded sandstone, massive bedded sandstone, ripple laminated sandstone, parallel laminated sandstone and mudstones. These units were packaged into three facies association that constitutes of bedded sandstone facies association (FAgI), interbedded sandstone and mudstone facies association (FAgII) and amalgamated trough crossbedded sandstone facies association (FAgIII). These reflects mouth-bars, pro-delta and delta slope deposits and upper delta plain respectively. This deltaic prism is characterized by unidirectional current system devoid of signatures of tide and waves hydrodynamics in the subaqueous delta regions, thus indicating that the delta system of the Gombe Formation is a fluvial dominated delta.

SYN-RIFT FLUVIO-LACUSTRINE DEPOSITIONAL SYSTEM OF THE CRETACEOUS BIMA FORMATION IN THE GONGOLA SUB – BASIN, NORTHERN BENUE TROUGH, NE, NIGERIA

The facies analysis of the syn-rift sequences Bima I Formation in the Gongola Sub-basin of the Northern Benue Trough displayed assemblages of trough crossbedded sandstones facies, planar crossbedded sandstone facies, massive bedded sandstone facies, ripple laminated sandstone facies, parallel bedded sandstone facies and mudstones facies. These arrays of facies form two suites of facies association that consist of the lacustrine-delta complex depicting coarsening upward cycles and fluvial complexes showcasing fining upwards cycle the former accounts for a scenario where the incremental accommodation is lower than the sediment discharge, whereas the latter is reflective of a case where improved subsidence rate induces high accommodation rate that outruns sediment supply. The stratigraphic architecture of the syn-rift Bima I Formation indicated that the lacustrine-delta are restricted to the lower stratigraphic horizons whereas the fluvial complexes essentially defines the upper stratigraphic zones of this formation.

Incised Valley Depositional System of the Cretaceous Yolde Formation of the Gongola Sub-basin Northern Benue Trough N.E. Nigeria

This research was carried out in the Gongola Sub-basin of the Northern Benue Trough aimed at deciphering of the paleo-depositional environment of the Yolde Formation based on facies on facies analysis. Six lithofacies were identified to include trough crossbedded sandstone facies (St), massive bedded sandstone facies (Sm), planar crossbedded sandstone facies (Sp), ripple laminated sandstone facies (Sr), parallel sandstone facies (Sl) and mudstone facies (Fm). These build into two facies association of fluvial channel and tidally influenced fluvial channel facies associations. The fluvial successions typical characterizes the lower stratigraphic horizons and their contained dominances of trough crossbedded sandstone facies with high channel to overbank facies and contained mud-clast reflecting deep, high energy braided river system. The submergences of these channels by surging sea level rise generated the tidally influenced fluvial facies association and this package characteristically defines the upper interval stratigraphic architecture of this formation, displaying occasional bi-directional current system and abundant marine ichnogenera. This architectural symmetry is reflective of an incised valley fills, developing as a consequence of Cenomanian transgressive phase induced by the mid-Cretaceous global marine transgression.

Incised Valley Depositional System of the Cretaceous Yolde Formation of the Gongola Sub-basin Northern Benue Trough N.E. Nigeria

This research was carried out in the Gongola Sub-basin of the Northern Benue Trough aimed at deciphering of the paleo-depositional environment of the Yolde Formation based on facies on facies analysis. Six lithofacies were identified to include trough crossbedded sandstone facies (St), massive bedded sandstone facies (Sm), planar crossbedded sandstone facies (Sp), ripple laminated sandstone facies (Sr), parallel sandstone facies (Sl) and mudstone facies (Fm). These build into two facies association of fluvial channel and tidally influenced fluvial channel facies associations. The fluvial successions typical characterizes the lower stratigraphic horizons and their contained dominances of trough crossbedded sandstone facies with high channel to overbank facies and contained mud-clast reflecting deep, high energy braided river system. The submergences of these channels by surging sea level rise generated the tidally influenced fluvial facies association and this package characteristically defines the upper interval stratigraphic architecture of this formation, displaying occasional bi-directional current system and abundant marine ichnogenera. This architectural symmetry is reflective of an incised valley fills, developing as a consequence of Cenomanian transgressive phase induced by the mid-Cretaceous global marine transgression.

Granulometry analysis of Ngrayong sandstone, Tempuran Area, Rembang Zone, North East Java Basin

The study area is located near Tempuran Village, Rembang Zone, North-East Java. Ngrayong sandstone is a famous reservoir in north-east Java, mainly composed of sandstones which are exposed along east-west trending along the southern flank of Pakel Anticline. Eighteen samples from four different facies from eight outcrops conducted for granulometry analysis. The objective of this paper is to predict the reservoir potential base on granulometry analysis especially grain size and sorting. The study area is still needs to confirm about reservoir quality. Ngrayong Formation consists of laminated to thin bedded sandstone facies, thick bedded to massive sandstone facies, calcareous sandstone facies and cross-bedded sandstone facies. According to the analytical results, sandstone facies are composed of very fine to fine, poorly sorted to very well sorted sandstones. Base on the results of analyzed samples, Ngrayong sandstone have good porosity and permeability, thus Tempuran area can be considered as a prospective reservoir.

Storm and tide influenced depositional architecture of the Pliocene–Pleistocene Chad Formation, Chad Basin (Bornu Sub–basin) NE Nigeria: A mixed fluvial, deltaic, shoreface and lacustrine complex

Lithofacies analyses of the upper part of the Chad Formation (Bama Ridge Complex) in the Bornu Sub–basin of the Chad Basin indicated four facies associations; fluvial, deltaic, shoreface and lacustrine sequences. The fluvial sequences are composed of fining upward cycles with successive occurrence of planar crossbedded sandstone facies displaying unimodal paleocurrent system and rare mudstone facies typical of braided river system. The deltaic succession consists of both fining and coarsening upwards cycles with the former depicting fluvial setting of an upper delta plain while the later suggestive of mouth–bar sequences. The setting displays a polymodal current system of fluvial, waves, storms and tides that were primarily induced by complex interactions of seiches and lunar tides. Similar current systems devoid of fluvial patterns were reflected in the coarsening upward packages of the shoreface sequences. Lacustrine succession composed of thick bioturbated mudstone facies generally defines the base of these coarsening upward profiles, giving a fluvio–lacustrine geomorphic relief where complex interaction developed the deltaic and shoreface facies along its shorelines. Clay mineral fractions of the formation are dominantly kaolinitic, indicating a predominantly humid tropical–subtropical climatic condition during their deposition. This climatic regime falls within the African humid period of the early–mid Holocene that led to the third lacustrine transgression of the Lake Mega-Chad, whereas the subordinate smectite mineralization points to aridification that characterizes most of the post humid period to recent.

Composition, provenance and tectonic setting of Eze-Aku Sandstone facies in the Afikpo Synclinorium, Southern Benue Trough, Nigeria

Field study, petrographic and major element geochemical composition of the Eze-Aku Sandstone facies outcropping in the Afikpo Synclinorium, southeastern Nigeria, were utilized in this study. The aim is to interpret the provenance and tectonic setting for sandstones in the sedimentary basin. Field observation shows alternating sequence of parallel sandstone ridges trending NE-SW and shales which represent the low-lying plains in the area. Four major sandstone facies were identified: massive conglomeritic sandstone facies, laminated sandstone facies, bioturbated sandstone facies and cross-bedded sandstone facies. Ternary plots for framework elements (quartz, feldspar and rock fragments) from petrography of the sandstones indicate the sandstones as arkosic and subarkosic arenites. Tectonic setting discrimination diagrams plotted based on major element oxides revealed continental block provenance dominantly in a passive continental margin. Petrographic and geochemical results indicate large amounts of detritus were derived principally from plutonic igneous rocks with minor contribution from metamorphic source region, probably from Obudu Plateau, Oban and Cameroon Massifs.

Shoreface to estuarine sedimentation in the late Paleocene Matanomadh Formation, Kachchh, western India

Late Paleocene sedimentation in the pericratonic Kachchh Basin marks the initial marine transgression during the Cenozoic era. A 17m thick sandstone-dominated succession, known as the clastic member (CM) of the Matanomadh Formation (MF), is exposed sporadically in the basin. Three facies associations are reconstructed in the succession in three different sections. Facies association-1 contains matrix-supported pebbly conglomerate facies, horizontally-laminated sandstone-mudstone alternation facies, hummocky- and swaley cross-bedded sandstone facies, wave-rippled sandstone facies and climbing ripple cross-laminated sandstone facies. This facies association developed between shoreface and foreshore zone under the influence of storms on a barrier ridge. Facies association-2 contains sigmoidal cross-bedded sandstone facies, sandstone-mudstone alternation facies, flaser-bedded sandstone facies, herringbone cross-bedded sandstone facies and tangential cross-bedded sandstone facies. This facies association possessing tidal bundles and herringbone cross-beds developed on a tidal flat with strong tidal influence. Facies association-3 comprises pebbly sandstone facies, horizontally-bedded sandstone facies, tangential cross-bedded sandstone facies exhibiting reactivation surfaces and tabular cross-bedded sandstone facies. This facies association represents sedimentation in a river-dominated estuary and reactivation surfaces and herringbone cross-beds indicating tidal influence. The bipolar paleocurrent pattern changes to unipolar up-section because of the change in the depositional currents from tidal to fluvial. The sedimentation took place in an open coast similar to the Korean coast. The presence of neap-spring tidal rhythmites further suggests that a semidiurnal system similar to the modern day Indian Ocean was responsible for the sedimentation. Here, the overall sequence developed during the transgressive phase where barrier ridge succession is succeeded by the tidal flat succession and the latter, in turn, is succeeded by the estuarine succession. This study resolves the most debated issue of initial marine transgression in the Kachchh Basin during the Cenozoic.

Field and lithostratigraphic studies of the Eze-Aku Group in the Afikpo Synclinorium, southern Benue Trough, Nigeria

Field and lithostratigraphic studies of sediments of Eze-Aku Group in the Afikpo Synclinorium were carried out to define the lithostratigraphic status of the Amasiri Sandstone unit of the group. The study involved field mapping, description of outcrops and lithofacies analysis. Lithostratigraphic study shows that the group comprises marine shales and limestones overlain by succession of dominant sandstones alternating with shales. Five major lithofacies associations deposited in tidal shallow shelf to deep water depositional setting were revealed in this study: massive, conglomeritic sandstone, laminated sandstone, bioturbated sandstone, laminated shale and cross bedded sandstone facies associations. Two component formations were identified for the Eze-Aku Group in the basin: the late Cenomanian-early Turonian Eze-Aku Shale (transgressive phase) and the middle-late Turonian Amasiri Sandstone (regressive phase). The Eze-Aku Shale and Amasiri Sandstone represent lower boundary and unit stratotypes respectively. The cross bedded sandstones represent the uppermost part of the formation. Results of field studies also show that the Eze-Aku Group in Afikpo Synclinorium is bounded above and below by Santonian unconformity and late Albian – middle Cenomanian unconformity respectively.

Depositional Environments and Petrographic Characteristics of Bida Formation around Share-Pategi, Northern Bida Basin, Nigeria

The Campanian Bida Formation is the oldest stratigraphic unit in the northern Bida Basin, central Nigeria. Facies analysis of the investigated sections indicates three main facies which include conglomerate, sandstone and claystone. The poorly sorted, matrix and grain supported conglomeratic facies which overly unconformably the weathered schists and granites is interpreted as gravity induced debris flow deposit. The massive to crossbedded sandstone facies with unidirectional paleo-flow dominantly to the NNE were deposited in braided fluvial channels. The sequence grades into claystone facies which probably was formed in localized non-marine floodplains. Results of grain size analysis; standard deviation and skewness which range from 0.65 to 1.69 and -0.02 to 0.96 (average values of 1.29 and 0.11f) respectively suggest that the sandstones are predominantly texturally immature and, thus, imply fluvial origin. Average mean sizes of 0.79f suggest predominance of coarse sands and this suggest that saltation is the most prevalent mode of transportation. Pebble morphology study also indicates mainly fluvial processes for the clasts from the conglomerates and conglomeratic sandstones. Few individual clasts with sphericity and Oblate – Prolate (OP) index values less than 0.66 and -1.5 respectively, however, provide evidence of recycling of some of the clasts from older sediments. Petrographic study reveals that quartz is the dominant framework grain ranging from 66.3 to 88.5%. Feldspar dominated by plagioclase type constitutes between 10 to 27.7%. The plotted QFR diagrams suggest subarkosic sandstones derived from rifted and uplifted continental basement rocks in a warm humid paleoclimatic setting.

Depositional environment as Interpreted from facies analysis of Injana Formation in Kand fold North Iraq

Facies analysis of sandstone in the injana formation of kand anticline indicated the presence of : intraformational conglomerate facies (Gm), trough cross –bedded sandstone facies (st), planar cross-bedded sandstone facies (sp), horizontal bedded sandstone facies (sh). Massive bedded sandstone facies(sm), horizontal laminated sandstone facies (fl), ripple cross –laminated siltstone facies (sr) and massive mudstone facies (fsm). Facies association in the lower part of the succession has affinity to river – dominated delta sequences characterize by small - scale coarsening – upward cycles , while the upper part shows diagnostic thick fining upward sequences of meandering river. Paleocurrent analysis indicates a unidirectional south – south west trend.

Sedimentology and Fractal-Based Analysis of Permeability Data, John Henry Member, Straight Cliffs Formation (Upper Cretaceous), Utah, U.S.A.

Interpretation of depositional environments combined with field measurement of permeability for a portion of the Upper Cretaceous Straight Cliffs Formation near Escalante, Utah, provides new results for understanding and modeling facies-dependent perme- ability variations. Offshore, transition-lower shoreface, upper shore- face, and foreshore environments are interpreted for part of the John Henry Member on the basis of outcrop investigation. Using a newly designed drillhole minipermeameter probe, permeability was measured for two of the facies within this unit: lower-shoreface bioturbated sand- stone and upper-shoreface cross-bedded sandstone. Approximately 500 permeability measurements at a sample spacing of 15 cm were made along four vertical profiles and three horizontal transects o na6m 3 21 m outcrop. Permeability ranges from 41 to 1,675 millidarcies (md) in the bio- turbated sandstone facies, which is massive-bedded, moderately to well-sorted, and very fine- to fine-grained. In contrast, permeability ranges from 336 to 5,531 md in the moderately to moderately well sorted, fine- to medium-grained, cross-bedded sandstone facies. A high degree of variability in permeability of the cross-bedded facies is caused by small-scale variations in grain size and structure related to depositional processes. The geometric mean permeability in the bio- turbated sandstone is 253 md, compared with 1,395 md in the cross- bedded facies. While the facies-dependent differences in permeability (k) are ap- parent and related to depositional and biological processes, fractal- based statistical analysis of the horizontal ln( k) increments yields near- ly identical results for the bioturbated facies and the cross-bedded fa- cies, possibly suggesting an underlying statistical commonality in the formation of both facies. Increment distributions from both facies ap- pear similar with peaking around the mean. Ln(k) increments from the smaller vertical data set appear similar also, but with a variance approximately 3.7 times larger than the horizontal value. Variance scaling analyses of horizontal and vertical data both yield a Hurst co- efficient near 0.26, which is characteristic of negative spatial correla- tion of the increments. The methodology developed herein offers a po- tential high-resolution alternative to existing methods for understand- ing and characterizing subsurface properties.