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.

Rembang Zone Petroleum Play, Stratigraphic and Petrographic Analysis of Ngrayong Formation as Reservoir, Jamprong Area, Tuban, East Java

The following research took place in the Jamprong area, Tuban Regency, East Java Province within a study area of 2 km2. Physiographically, the study area is situated in the anticlinorium of the Rembang Zone. This research aims to define the reservoir potential of outcrop samples from the Ngrayong Formation as an analogue for the subsurface. In addition, the depositional environment and the age of the rock in the research area was determined. The Ngrayong Formation is regarded as a potential reservoir in the North East Java Basin. The accumulated data consists of stratigraphy, petrographic analysisand paleontological analysis of rock samples, and geological mapping has been carried out to determine the distribution of rocks. Facies were determined based on outcrop observations and comprise predominantly arkose sandstone facies with fine – coarse grained, moderately sorted and with cross-bedding, herringbone, and lamination, and another facies namely massive carbonate grainstone. Based on these facies, the interpreted depositional environment is the transition of tidal flat to shallow marine carbonate platform with relative biostratigraphic age of Middle Miocene, Langhian to Serravallian (M6-M8 planktonic foraminiferal biozones). Rocks in the study area have porosity >20% or very good and permeability >130 or fair based on petrographic observations, and this supports the interpretation of the Ngrayong Formations as a potential reservoir of hydrocarbons.

Tidal Flat Depositional System of the Cretaceous Yolde Formation of the Gongola Sub-basin Northern Benue trough N. E. Nigeria: Implication for Macro-Tidal Coastline

This research aims to evaluate the facies and facies association of the Yolde Formation at Kware stream in the Gongola Sub-basin of the Northern Benue Trough with objective of characterizing its paleodepositional environment. Six lithofacies consisting of 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) defining its stratal packages were skewed into distinctive assemblages of flaser, wavy and lenticular bedding. This present a fining upward signature with facies association typical of tidal flat system. This is evident of a coastal progradation with sequences reflecting migration of a supra-tidal mudflat over intertidal mixed-flat zone which progressively superposed subtidal sandflats. This is indicative of a coastal shoreline with a relatively progradational phase within the net transgressive regional framework of the Cretaceous Yolde 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.

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

Facies evaluation carried out on the Yolde Formation at Gabukka locality in the Gongola Sub-basin of the Northern Benue Trough was aimed at enacting its paleo-depositional environment. The formation at this locality revealed an intercalated succession of massive bedded sandstone facies (Sm), planar crossbedded sandstone facies (Sp), ripple laminated sandstone facies (Sr), parallel laminated sandstone facies (Sl) and mudstone facies (Fm). These successions developed a thinning and thickening stratigraphic profile depicting periodic rhythmic signatures indicating deposits of tidal rhythmites. Thickening rhythmic packages are reflective of a spring tide whereas thinning phases are indicative of neap tide. These depositional sequences are genetic to intense tides conditions, thus an indexing a tide dominated oceanographic within the course of development of the Cretaceous Yolde Formation.

Speleothems in quartz-sandstone caves of Ponta Grossa municipality, Campos Gerais region, Paraná state, southern Brazil

The present communication characterizes and discusses the genesis of cave speleothems developed in Furnas Formation (Silurian-Devonian) and Vila Velha sub-unit (Campo Mourão Formation, Upper Carboniferous) quartz-sandstones, in southern Brazil. The research, which involved stratigraphic and petrographic studies, was conducted to identify the faciological context of occurrence of these features, and to determine, through different analytical methods, their mineralogical composition and porosity, and also the action of microbial markers on the genesis of these secondary mineral deposits. The speleothems were classified into six types based on form, composition and genesis: (1) arborescent (coral), (2) mushroom-shaped, (3) stalactitic, (4) stalagmitic, (5) columnar with horizontal/ascending growth, and (6) fibrous. In response to substrate permoporosity, speleothems develop on all sandstone facies of the study area, mainly in sites controlled by bedding, stratification and fracturing planes. They are less frequent, however, in conglomerate and silty-clayey layers of the Furnas Formation, being composed mainly of silica (opal-A and cryptocrystalline silica) and kaolinite, with lesser contribution of gypsum and amorphous iron oxides associated with goethite and hematite. Detritic minerals such as quartz and muscovite also take part in the composition of these features. Plant and invertebrate fragments were identified, including biosignatures and microorganisms capable of favoring precipitation of silica (possibly cyanobacteria and diatom) and iron oxide (possibly Gallionella ferruginea). Such biosignatures and extracellular polymeric substances (biofilms) associated with speleothems are evidence of organomineralization, also known as biologically induced mineralization. The results, which indicate biological action on the genesis of speleothems, raise further discussion on the influence of microorganisms on the dissolution and precipitation of silica and kaolinite in the region.

Proposed depositional scenarios of the Nise Formation on the Mid-Norwegian Continental Shelf, with focus on the Halten Terrace.

<p>The Late Cretaceous Nise Formation is located on the Mid-Norwegian Continental Shelf. On the Halten Terrace, the formation is generally described as a mudstone interbedded with thin sandstones and carbonate stringers. The spatial distribution, connectivity, sediment source and depositional processes of the sandstones are uncertain. </p><p>Six cores and associated thin sections of the Nise Formation on the Mid-Norwegian Continental Shelf have been described. Three of the cores are from the Halten Terrace area, and one core each are from the Vestfjorden Basin, Nyk High and the Møre/Vøring Basin transition respectively. The main focus has been on the Halten Terrace while the cores from the other areas (tens to hundreds of kilometres away from Halten) are included to compare facies, depositional environment, source of sediment, grade of bioturbation and other characteristics with those of the Halten Terrace.</p><p>An isochore map of the Nise Formation in the central part of the Halten Terrace has been constructed based on interpretation of wireline logs from approximately 280 well penetrations. The map reveals a distinct thickness increase in the central parts of the Halten Terrace, suggesting the infilling of a former sub-basin. Additionally, the map supports an eastern and/or northern sediment source, which might exclude the Greenlandic landmasses as a provenance area. The cores from the Halten Terrace, supported by additional wireline well logs, indicate that the upper parts of the formation contain a greater amount of sandstone facies compared to the lower parts. These sandstones are interpreted as densely bioturbated distal turbidites. The comparison of facies development in the cores from the different areas indicates variability in depositional systems between the areas at the time of deposition.</p><p>Different depositional scenarios of the Nise Formation on the Mid-Norwegian Continental Shelf are being developed in order to increase the understanding of the Nise Formation on the Halten Terrace. The proposed scenarios include various sediment input models and alternative depositional environments in the different areas. The scenarios mainly display marine, isolated systems. </p>

Depositionally-Induced Magnetic Frequency Variations of a Sandstone Facies from the Copper Harbor Conglomerate of the North American, Mid-Continent Rift at Union Bay, Michigan

Precambrian sandstones were investigated to determine whether deep-time, fluvial red-beds can maintain magnetic variations related to deposition. Using an easily accessible site on Earth, it is possible to define methods that benefit future studies related to magnetic variations as linked to conditions of formation. The study utilized environmental magnetism and cyclostratigraphic techniques to determine magnetic characteristics and susceptibility variation frequencies. Magnetite and hematite were inferred from laboratory measurements and the magnetic fabric agreed with previous paleocurrent observations, suggestive that susceptibility correlates with deposition. Hematite concentration controlled susceptibility: high-susceptibility corresponded with large grain-sizes and cross-bedding, while low-susceptibility was attributed to small grain-sizes and erosional or color boundaries. A statistically-significant, cyclic, susceptibility signal was observed from the stratigraphy, suggesting that susceptibility variations may arise from climatically-induced variations in depositional or post-depositional processes. The observed frequency also supports the capacity for fluvial red-bed deposits to maintain depositional characteristics original to formational processes.