A Visual Basic program to plot sediment grain-size data on ternary diagrams

This paper is not subject to U.S. copyright. The definitive version was published in Computers & Geosciences 34 (2008): 561-565, doi:10.1016/j.cageo.2007.03.019.Sedimentologic datasets are typically large and compiled into tables or databases, but pure numerical information can be difficult to understand and interpret. Thus, scientists commonly use graphical representations to reduce complexities, recognize trends and patterns in the data, and develop hypotheses. Of the graphical techniques, one of the most common methods used by sedimentologists is to plot the basic gravel, sand, silt, and clay percentages on equilateral triangular diagrams. This means of presenting data is simple and facilitates rapid classification of sediments and comparison of samples

Geochemistry and Mineralogy of Clastic Sediments of Tukau Formation: Implications on Provenance and Tectonic Setting

A study is proposed on the clastic sedimentary rocks of the Tukau Formation in the North-West Borneo using combined methods (i.e. geochemistry and petrography) to infer the provenance, tectonic setting and paleoweathering. Generally, Tukau sandstones are classified into quartz arenites , sublitharenites, litharenites, wacke and shale. Source rock is derived from the sedimentary to meta-sedimentary rocks dominated source with minor contribution from granitoids and ultramafic rocks. Tectonically, the Tukau Formation sedimentary rocks were deposited in a passive margin with minor extent towards active margin boundary

GEOCHEMICAL CHARACTERIZATION OF THE BONE SPRING FORMATION, DELAWARE BASIN, USING CHEMOSTRATIGRAPHY AND INTEGRATED PETROPHYSICS

The Delaware Basin forms part of West Texas\u27s and New Mexico’s famous petroleum-generating Permian Basin. The Bone Spring Formation is a prolific hydrocarbon producer within this basin, creating one of the world’s richest oil shales. This formation has lithological sequences that are characterized by repeating carbonate and siliciclastic intervals of a third-order cycle which can largely be correlated to highstand and lowstand systems tracts, respectively. Lithological complexity and facies change are manifested by debris flows, turbidites, and slumps. In addition to glacio-eustasy, both tectonism and broader Milankovitch cycles have influenced the depositional history. Previous investigations have utilized cores and wireline logs to provide high-resolution chemo-facies segregation, which can be correlated with reservoir and rock properties; however,core and wireline logs are sporadically collected, whereas drill cuttings are available from most wells. For this study, XRF elemental data derived from drill cuttings collected at 30 – 60ft (9 – 18m) intervals have been compared to wireline well logs. XRF measurements were categorized using hierarchical cluster and principal component analysis based on chemical facies. Chemostratigraphic units and packages were applied to generate cross-sections and facies maps to understand depositional cyclicity, terrigenous influence, grain size, ii mineralogy, organic content and rock property distribution. These data sets can be used to high-grade acreage for resource identification and storage to optimize drilling performance, completion designs and as a geosteering input

Development of algebra algorithms for automated generation of grain-size distribution maps

The grain-size distribution of sediments is a fundamental characteristic in understanding the earth’s surface environments and an essential tool in classifying sedimentary environments. Grain-size data provide important information on the energy and dynamics of depositional environments and aid our understanding of sediment transport. Ternary diagrams (TD) are useful and conventional tools to classify sediments on the basis of relative grain-size (i.e., gravel, sand, mud or sand, silt, clay). The development of spatial modelling in a Geographical Information System (GIS) can assist in treating, computing and displaying sedimentological data, such as grain-sizes. The grain-size distribution of sediments is a fundamental characteristic in understanding the earth’s surface environments and an essential tool in classifying sedimentary environments. Grain-size data provide important information on the energy and dynamics of depositional environments and aid our understanding of sediment transport. Ternary diagrams (TD) are useful and conventional tools to classify sediments on the basis of relative grain-size (i.e., gravel, sand, mud or sand, silt, clay). The development of spatial modelling in a Geographical Information System (GIS) can assist in treating, computing and displaying sedimentological data, such as grain-sizes

Sedimentary, geochemical and geophysical study of the Ecca group, Karoo supergroup and its hydrocarbon potential in the Eastern Cape Province, South Africa

The Ecca Group of Karoo Supergroup is a sedimentary rock sequence that deposited between the Late Carboniferous (Dwyka Group) and the Late Permian-Middle Triassic (Beaufort Group). The Ecca Group investigated in this study is situated in the Eastern Cape Province of South Africa and it comprises mainly of shales, mudstones, siltstones and sandstones. The Ecca Group sequence contains considerable carbon content and suitable thickness to make it an ideal target for shale gas exploration. Previous studies put more emphasis on the geology and stratigraphy of the Ecca Group, this study revised the stratigraphy, and put new insight on the petrography, depositional processes, sedimentary facies, provenance, paleoweathering, tectonic setting, subsidence rates and history, electrical resistivity, source rock characteristics and diagenesis of the potentially feasible sandstone and mudrock reservoir rocks of the Ecca Group. Based on the lithological features, sedimentary structures and facies characteristics, the stratigraphy of the Prince Albert, Whitehill, Collingham and Fort Brown Formations of the Ecca Group is now subdivided into two informal members each, i.e. Lower Member and Upper Member. Furthermore, the Ripon Formation is now subdivided into three informal members. Each member has been asigned a lithological name. The grain size parameters show that most of the Ecca Group sandstones are very fine to fine grained, poorly to moderately well sorted, mostly near-symmetrical and mesokurtic in grain-size distribution. The linear discriminant function analysis is dominantly indicative of turbidity current deposits under deep marine environment for Prince Albert, Whitehill and Collingham Formations, shallow marine environment for Ripon Formation, while the Fort Brown Formation is lacustrine-deltaic deposits. Modal composition analysis and petrography studies revealed that the detrital components of the sandstones are dominated by monocrystalline quartz, feldspar and lithic fragments. The sandstones are compositionally and texturally immature and can be classified as feldspathic wacke and lithic wacke. The provenance analysis revealed plutonic and metamorphic terrains as the main source rocks with minor debris derived from recycled sedimentary rocks. The detrital modal compositions of these sandstones are related to back arc to island and continental margin of tectonic setting. Based on the detailed sedimentological analyses of outcrop and borehole data, fourteen lithofacies were identified and seven facies associations (FAs) were recognised. The facies associations are: FA 1: Shale and mudstones intercalated with siltstones, FA 2: Carbonaceous shale, mudstone with subordinate chert and sandstone, FA 3: Mudstones rhythmite with thin bedded mudstone and lenticular siltstone, FA 4: Greyish medium bedded sandstone intercalated with laminated mudstone, FA 5: Dark-grey medium to thick bedded mudstone and siltstone, FA 6: Thin to medium bedded sandstone alternated with thin bedded carbonaceous mudstone, and FA 7: Varved mudstone rhythmite intercalated with siltstone and minor sandstone. Sedimentological characteristics of the identified facies associations indicate four deposition environments, namely, deep marine basin, turbidite, shallow marine and lacustrine environments, which constitute a gradually regression sequence as a result of sea-level dropping and shallowing of the basin during the developmental processes. Geochemical analysis of the Ecca mudrocks and sandstones revealed that the rocks are of quartzose sedimentary provenance, suggesting that they were derived from a cratonic interior or recycled orogen. The petrography and geochemistry of the sandstones indicated that the source areas are composed of plutonic and metamorphic rocks with a minor component from sedimentary rocks. The geochemical diagrams and indices of weathering suggested that the granitic source rocks underwent moderate to high degree of chemical weathering. The tectonic setting discrimination diagrams support passive continental margin setting of the provenance

Characterization of DIVA09 : a gravity core from the Minho shelf

Project NATURA MIÑO-MINHO "Valorización de los recursos de la cuenca hidrográfica del MIÑO-MINHO

Chromite Crystal Structure and Chemistry applied as an Exploration Tool

The spinel group minerals have long been of interest to the geosciences due to their use as indicator minerals. Unit cell is a structural measure controlled by composition but is also affected by pressure and temperature relations through order-disorder. This study attempted to look at the applications of unit cell in exploration. The implementation of µXRD for this purpose required the creation the Slice Integration Technique to improve signal over background. Compositions of binary spinels can be approximated through their correlation with unit cell. Possible applications include gemology and curatorial studies, where the nondestructive nature of µXRD is highly advantageous and kimberlite vs non-kimberlite discrimination. The analysis of an indicator mineral was conducted using a field portable XRD and could determine isostructural grains in a field setting or unit cell could be used in the field in conjunction with other new field-portable technologies

دراسة الخصائص النسيجية وتوزع الرسوبيات الساحلية في القطاع الشمالي من الرصيف القاري السوري

Detailed textural study of the Northern section of the Syrian Continental shelf (N35.92991 E35.91785: N35.35752 E35.91542) has been carried out in order to determine the sediment nature and distribution. The sediments are mainly coarse to very fine-grained particles, moderately sorted, negatively skewed to fine skewed and leptokurtic to mesokurtic in nature. Interrelationship of various parameters shows bimodal nature of sediments having dominance of mainly medium to coarse sand. The major part of the sediment fall in coarse to very fine grained category (sand, silt and clay). Based on the CM (Coarser one percentile and Median size values in micron) pattern, the sediment fall in rolling and suspension field. These factors indicate that the sediments discharged from the rivers mixes with offshore sediments and with the sediments eroded from a source rock. Moreover, the wave energy conditions were high enough to disperse the sediments along the shelf and passing it to the open ocean and later dispersing them by littoral currents. أجريت دراسة ترسيبية مفصلة للقطاع الشمالي من الرصيف القاري السوري (N35.92991 E35.91785: N35.35752 E35.91542) بغية تحديد طبيعة، وتوزع وخصائص الرسوبيات البحرية الموزعة على كامل هذا القطاع. أظهرت الدراسة أن الرسوبيات تتراوح بين الخشنة والناعمة جداً، معتدلة الفرز، ذات ميل سلبي إلى متماثل وأخيراً مفرطحه إلى متوسطة التفرطح. أظهرت علاقات الارتباط المختلفة لعدة بارامترات الطبيعة ثنائية الترسيب لرسوبيات المنطقة حيث يغلب الرمل على كافة العينات مع وجود كل من السلت والغضار ولكن بنسب مختلفة. بالاعتماد على مخطط CM، فإن أغلب الرسوبيات قد ترسبت إما عن طريق الدحرجة على القاع أو بشكل مباشر من المعلقات. تشير هذه العوامل إلى أن الرسوبيات قد تم تفريغها من الأنهار ومن ثم اختلطت مع الرسوبيات العميقة والرسوبيات المجواة من الصخور الأم. علاوة على ذلك، كانت طاقة الأمواج عالية بما فيه الكفاية لتشتيت هذه الرواسب على طول الرصيف القاري السوري ومن ثم نقلها إلى الأعماق المفتوحة ليتم تفريقهم بعد ذلك من قبل التيارات الساحلية

Tracking Icebergs and Sea Ice in the Mid-Pleistocene Bering Sea Suggests Sea Ice Affects Ice Sheet Growth

Ice sheets are losing volume and regions of sea ice cover are shifting; these changes in Arctic and sub-Arctic regions amplify climate change through positive feedback mechanisms. A history of sea ice cover and iceberg activity in high latitude seas would help to predict climate change. Sea ice and icebergs entrain and dump sediment into the oceans; both transport sand, but glacial ice is much more likely to entrain gravel (\u3e2 mm) than sea ice. This study uses siliciclastics \u3e63 μm from Bering Sea Site U1343 to track icebergs and sea ice during the Mid-Pleistocene, a period of change in global climate cycles. Fine sand (63\u3c\u3c250 μm) averages 10% of the bulk sediment at U1343 from 910 to 860 ka. A new method uses a ratio (fine sand/gravel count) to indicate the more likely presence of sea ice. Icebergs are likely present during Marine Isotope Stage (MIS) 23 and in the latter part of MIS 22 when four pulses of gravel-size ice rafted debris come before the deglaciation. A period of low ice rafted debris in MIS 22 when the sea level is decreasing rapidly is interpreted as a time of more open water. Sea ice is suggested at the coldest time in MIS 22 and at the start of the deglaciation, consistent with the Sea Ice Switch (Gildor and Tziperman 2000) hypothesis for the Mid-Pleistocene climate transition. Abundant fine sand in MIS 21 suggests the presence of sea ice in the early interglacial