The Granular Structure of Two Marine Carbonate Sediments

2018 ◽  
Author(s):  
Ryan D. Beemer ◽  
Alexandre N. Bandini-Maeder ◽  
Jeremy Shaw ◽  
Ulysse Lebrec ◽  
Mark J. Cassidy
Keyword(s):  
3D Models ◽  
Optical Microscope ◽  
Depositional Environments ◽  
Carbonate Sediments ◽  
Micro Computed Tomography ◽  
North West ◽  
The North ◽  
Geological Processes ◽  
Microscope Images ◽  
Hemipelagic Sediment

Calcareous sediments are prominent throughout the low-latitudinal offshore environment and have been known to be problematic for offshore foundation systems. These fascinating soils consist largely of the skeletal remains of single-celled marine organisms (plankton and zooplankton) and can be as geologically complex as their onshore siliceous counter parts. To enable an adequate understanding of their characteristics, in particular, their intra-granular micro-structure, it is important that geotechnical engineers do not forget about the multifaceted biological origins of these calcareous sediments and the different geological processes that created them. In this paper, the 3D models of soils grains generated from micro-computed tomography scans, scanning electeron microscope images, and optical microscope images of two calcareous sediments from two different depositional environments are presented and their geotechnical implications discussed. One is a coastal bioclastic sediment from Perth, Western Australia that is geologically similar to carbonate sediments typically used in micro-mechanics and particle crushing studies in the literature. The other is a hemipelagic sediment from a region of the North West Shelf of Australia that has historically been geotechnically problematic for engineers. The results show there is a marked difference between coastal bioclastic and hemipelagic sediments in terms of geological context and the associated particle micro-structures. This brings into question whether a coastal bioclastic calcareous sediment is a good micro-mechanical substitute for a hemipelagic one.

Depositional Environment Drive as Overpressure Generation: Study Case in “Gap” Field, North West Java Basin

2020 ◽  
Author(s):  
A., C. Prasetyo
Keyword(s):  
Clay Mineral ◽  
Depositional Environment ◽  
Mineral Content ◽  
Hydrocarbon Generation ◽  
Well Test ◽  
Burial History ◽  
The South ◽  
North West ◽  
The North ◽  
Geological Processes

Overpressure existence represents a geological hazard; therefore, an accurate pore pressure prediction is critical for well planning and drilling procedures, etc. Overpressure is a geological phenomenon usually generated by two mechanisms, loading (disequilibrium compaction) and unloading mechanisms (diagenesis and hydrocarbon generation) and they are all geological processes. This research was conducted based on analytical and descriptive methods integrated with well data including wireline log, laboratory test and well test data. This research was conducted based on quantitative estimate of pore pressures using the Eaton Method. The stages are determining shale intervals with GR logs, calculating vertical stress/overburden stress values, determining normal compaction trends, making cross plots of sonic logs against density logs, calculating geothermal gradients, analyzing hydrocarbon maturity, and calculating sedimentation rates with burial history. The research conducted an analysis method on the distribution of clay mineral composition to determine depositional environment and its relationship to overpressure. The wells include GAP-01, GAP-02, GAP-03, and GAP-04 which has an overpressure zone range at depth 8501-10988 ft. The pressure value within the 4 wells has a range between 4358-7451 Psi. Overpressure mechanism in the GAP field is caused by non-loading mechanism (clay mineral diagenesis and hydrocarbon maturation). Overpressure distribution is controlled by its stratigraphy. Therefore, it is possible overpressure is spread quite broadly, especially in the low morphology of the “GAP” Field. This relates to the delta depositional environment with thick shale. Based on clay minerals distribution, the northern part (GAP 02 & 03) has more clay mineral content compared to the south and this can be interpreted increasingly towards sea (low energy regime) and facies turned into pro-delta. Overpressure might be found shallower in the north than the south due to higher clay mineral content present to the north.

scholarly journals Morphology of <i>Emiliania huxleyi</i> coccoliths on the North West European shelf – is there an influence of carbonate chemistry?

2014 ◽  
Vol 11 (3) ◽  
pp. 4531-4561 ◽  
Author(s):  
J. R. Young ◽  
A. J. Poulton ◽  
T. Tyrrell
Keyword(s):  
Environmental Samples ◽  
Significant Variation ◽  
Emiliania Huxleyi ◽  
Morphometric Study ◽  
Saturation State ◽  
North West ◽  
The North ◽  
Microscope Images ◽  
Calcite Saturation ◽  
The Uk

Abstract. Within the context of the UK Ocean Acidification project, Emiliania huxleyi (type A) coccolith morphology was examined from samples collected during cruise D366. In particular, a morphometric study of coccolith size and degree of calcification was made on scanning electron microscope images of samples from shipboard CO2 perturbation experiments and from a set of environmental samples with significant variation in calcite saturation state (Ωcalcite). One bioassay in particular (E4 from the southern North Sea) yielded unambiguous results – in this bioassay exponential growth from a low level occurred with no artificial stimulation and coccosphere numbers increased ten-fold during the experiment. The samples with elevated CO2 saw significantly reduced coccolithophore growth. However, coccolithophore morphology was not significantly affected by the changing CO2 conditions even under the highest levels of perturbation (1000 μatm). Environmental samples similarly showed no correlation of coccolithophore morphology with calcite saturation state. Some variation in coccolith size and degree of calcification does occur but this seems to be predominantly due to genotypic differentiation between populations on the shelf and in the open ocean.

Preservation potential assessment of central Atlantic biogenic carbonate deposits using X-ray micro-computed tomography (XMCT)

2020 ◽  
Author(s):  
Stergios Zarkogiannis ◽  
George Kontakiotis ◽  
Assimina Antonarakou
Keyword(s):  
Planktonic Foraminifera ◽  
Carbonate Sediments ◽  
Ct Scanner ◽  
Micro Computed Tomography ◽  
The North ◽  
Preservation Potential ◽  
Globorotalia Truncatulinoides ◽  
Mid Atlantic Ridge ◽  
Average Water ◽  
Central Atlantic

&lt;p&gt;Dissolution of foraminiferal calcite above the lysocline can occur within the water column, at the sediment-water interface, and/or within the sediment column as a result of low in-situ carbonate ion concentrations. The dissolution of foraminiferal shells, which are widely used for paleoceanographic studies, has the potential to influence the weight and the chemical composition of the whole test. Their partial dissolution has been suggested to significantly bias their &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O and &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C signals, while the trace element ratios decrease as dissolution progresses. Despite the significant Atlantic importance on the climate system, and that of the carbonate system on atmospheric CO&lt;sub&gt;2&lt;/sub&gt; concentration, there have been only a few studies examining carbonate preservation along depth transects in the North and South Atlantic, and mostly by indirect means.&lt;/p&gt;&lt;p&gt;In order to assess the preservation potential of the central Atlantic basins, a set of 16 Atlantic surface sediment (core-top) samples along the mid-Atlantic Ridge was deployed. The samples span from approximately 30&amp;#176;N to 30&amp;#176;S and are situated along the mid-Atlantic Ridge from an average water depth of 3700 m, well above the 4200 m modern lysocline, with roughly equal bottom water &amp;#916;CO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;2&amp;#8722;&lt;/sup&gt; values (23 &amp;#177;4 &amp;#956;mol/kg). Typically 15 pre-weighed shells of three different planktonic foraminifera species, widely used in paleoceanographic research, were picked from each sample (300-355 &amp;#956;m) and scanned using a GE vtomex s high-resolution micro-CT scanner. The species under consideration, namely &lt;em&gt;Globigerinoides ruber&lt;/em&gt; s.s. (white), &lt;em&gt;Trilobatus trilobus&lt;/em&gt; and &lt;em&gt;Globorotalia truncatulinoides&lt;/em&gt;, inhabit different water depths and are known to have different geochemistries and thus preservation potentials. The preliminary analysis of the tomographs suggests that although carbonate sediments from the eastern basins below from the south equatorial upwelling zone are more corroded their initial geochemistry is not greatly altered by dissolution.&lt;/p&gt;

FLATTENED TIME SLICES—A STRATIGRAPHIC APPROACH TO 3D SEISMIC INTERPRETATION ON THE NORTH WEST SHELF OF AUSTRALIA

2003 ◽  
Vol 43 (1) ◽  
pp. 255
Author(s):  
K. Martens
Keyword(s):  
Vertical Section ◽  
Depositional Environments ◽  
Time Slice ◽  
North West ◽  
The North ◽  
Exploration Tool ◽  
Depositional Systems ◽  
Complex Channel ◽  
Structural Volume ◽  
Depositional Elements

Conventional time slices are a powerful method of integrating horizon picks and fault picks into a unified interpretation and are a handy way of viewing structures, especially in faulted areas. The limitation is that time slices are seldom useful in viewing the morphology of a horizon. A 3D cube is the present day structural volume; it retains any structure imparted on the geology after deposition. When a time slice is defined, the structural dip limits the area of the integral depositional elements that can be imaged. For example, a depositional surface developed as part of a fluvial-deltaic system is seldom one event and it cannot be easily identified and picked in a vertical section. Flattened time slices take out the regional dip and allow a complete depositional surface to be viewed.The North West Shelf of Australia and especially the Barrow Sub-basin is a particularly suitable place to apply this exploration technique. The entire sedimentary package, laid down in a variety of depositional environments, has been tilted to the northwest by an average of 3°. This strong post-depositional tilt limits the uses of conventional time slices to imaging only the diprelated features of an area. Whereas conventional time slices only make apparent the dip of the section, flattened time slices can reveal subtle and intricate stratigraphic architecture.This paper describes the seismic features of a number of depositional systems from the Barrow Sub-basin and outlines how complex channel systems can be determined by the use of the flattened time slice approach. Given the importance of stratigraphic plays in the Barrow Subbasin, the technique outlined in this paper is considered to be an important exploration tool.

LITHOSTRATIGRAPHY OF THE LOWER EROMANGA BASIN SEQUENCE IN SOUTH WEST QUEENSLAND

1987 ◽  
Vol 27 (1) ◽  
pp. 196
Author(s):  
B.H. John ◽  
C.S. Almond
Keyword(s):  
High Energy ◽  
Depositional Environments ◽  
Oil Fields ◽  
North West ◽  
The North ◽  
Investigation Area ◽  
South West ◽  
Basin Surface ◽  
Petroleum Wells ◽  
Eromanga Basin

Five fully-cored and wire-line logged stratigraphic bores have been drilled by the Queensland Department of Mines, relatively close to producing oil fields in the Eromanga Basin, south-west Queensland. Correlations between the stratigraphic bores and petroleum wells have established lithologic control in an area where lithostratigraphy is interpreted mainly from wire-line logs. The Eromanga Basin sequence below the Wallumbilla Formation has been investigated, and a uniform lithostratigraphic nomenclature has been applied; in the past, an inconsistent nomenclature system was applied in different petroleum wells.Accumulation of the Eromanga Basin sequence was initiated in the early Jurassic by major epeirogenic downwarping; in the investigation area the pre-Eromanga Basin surface consists mainly of rocks comprising the Thargomindah Shelf and the Cooper Basin. The lower Eromanga Basin sequence in the area onlaps the Thargomindah Shelf and thickens relatively uniformly to the north-west. The sequence comprises mainly Jurassic/Cretaceous terrestrial units in which vertical and lateral distribution is predominantly facies-controlled. These are uniformly overlain by the mainly paralic Cadna-owie Formation, signalling the initiation of a major Cretaceous transgression over the basin.The terrestrial sequence over most of the area comprises alternating coarser and finer-grained sedimentary rocks, reflecting major cyclical changes in the energy of the depositional environment. The Hutton Sandstone, Adori Sandstone and 'Namur Sandstone Member' of the Hooray Sandstone comprise mainly sandstone, and reflect high energy fluvial depositional environments. Lower energy fluvial and lacustrine conditions are reflected by the finer-grained sandstone, siltstone and mudstone of the Birkhead and Westbourne Formations, and 'Murta Member' of the Hooray Sandstone. Similar minor cycles are represented in the 'basal Jurassic' unit. The Algebuckina Sandstone, recognised only in the far south-west of the investigation area, comprises mainly fluvial sandstones.

scholarly journals On the Late Pliocene stone tools of the Quranwala Zone, north-west sub-Himalayas, India

Antiquity ◽  
2017 ◽  
Vol 91 (357) ◽  
Author(s):  
Vidwan Singh Soni ◽  
Anujot Singh Soni
Keyword(s):  
Stone Tools ◽  
Fossil Bone ◽  
Question Mark ◽  
North West ◽  
Cut Marks ◽  
The North ◽  
Geological Processes ◽  
Animal Bones ◽  
Fossil Bones

A recent study of the Quranwala Zone (QZ) of the north-west sub-Himalayas, India, presents evidence for anthropic activity during the Pliocene that includes a number of stone tools found in association with fossil animal bones with cut marks. Based on the date of the Pliocene rock outcrop, the tools and bones are suggested to date from 2.6 Ma (Gaillard et al. 2016). There is, however, a question mark over the context of these tools within an outcrop of Pliocene rocks and, hence, over the date of these tools and the fossil bones. The trench from which they were excavated at Masol 2 (Gaillard et al.2016: fig. 3) lies in a depression at the bottom of a slope; the description provided in section 2 of the paper by Gaillard et al. (2016) suggests that the stone tools may not have been in situ within the Pliocene levels, but had accumulated there and were mixed with the fragments of fossil bone due to geological processes. Moreover, many of the stone tools, such as the ‘simple choppers’ found in association with the fossil animal bones (Gaillard et al.2016: figs 6, 8, 9), are usually found on much more recent sites and are therefore unlikely to date from 2.6 Ma.

scholarly journals MODELING THE DECAY IN AN HBIM STARTING FROM 3D POINT CLOUDS. A FOLLOWED APPROACH FOR CULTURAL HERITAGE KNOWLEDGE

2017 ◽  
Vol XLII-2/W5 ◽  
pp. 605-612 ◽  
Author(s):  
F. Chiabrando ◽  
M. Lo Turco ◽  
F. Rinaudo
Keyword(s):  
Laser Scanner ◽  
Point Clouds ◽  
3D Models ◽  
Historical Building ◽  
North West ◽  
Survey Techniques ◽  
The North ◽  
3D Point Clouds ◽  
Subsequent Conversion ◽  
3D Information

The recent trends in architectural data management imply the scientific and professional collaborations of several disciplines involved in the design, restoration and maintenance. It seems an achieved concept that, in the next future, all the information connected to new interventions or conservation activities on historical buildings will be managed by using a BIM platform. Nowadays the actual range or image based metric survey techniques (mainly produced by using Terrestrial Laser Scanner or photogrammetric platform today more based on projective geometry) allow to generate 3D point clouds, 3D models, orthophotos and other outputs with assessed accuracy. The subsequent conversion of 3D information into parametric components, especially in an historical environment, is not easy and has a lot of open issues. According to the actual BIM commercial software and to the embedded tools or plugin, the paper deals with the methodology followed for the realization of two parametric 3D models (Palazzo Sarmatoris and Smistamento RoundHouse, two historical building in the north-west part of Italy). The paper describes the proposed workflow according to the employed plug-in for automatic reconstruction and to the solution adopted for the well-known problems connected to the modeling phase such as the vaults realization or the 3D irregular surfaces modeling. Finally, the studied strategy for mapping the decay in a BIM environment and the connected results with the conclusions and future perspectives are critically discussed.

scholarly journals ROLE OF 2D AND 3D MODELS IN JONSDAP '76

1978 ◽  
Vol 1 (16) ◽  
pp. 63
Author(s):  
A.M. Davies
Keyword(s):  
North Sea ◽  
Three Dimensional ◽  
3D Models ◽  
Three Dimensional Model ◽  
North West ◽  
The North ◽  
Dimensional Distribution ◽  
The North Sea ◽  
2D And 3D

This paper describes how a two-dimensional numerical model of the North Sea was used to determine optimum positions for the deployment of off-shore tide gauges during the JONSDAP '76 oceanographic exercise. A three-dimensional model of the North West European Shelf is also described. Using this model the three-dimensional distribution of the M2 tidal current over the shelf has been computed. This model has also been used to compute the wind induced circulation of the North Sea for the INOUT period of JONSDAP '76.

Mechanical Response of Two Carbonate Sediments From Australia’s North West Shelf

2014 ◽  
Author(s):  
Barry M. Lehane ◽  
J. Antonio H. Carraro ◽  
Nathalie Boukpeti ◽  
Sarah Elkhatib
Keyword(s):  
Water Content ◽  
Simple Shear ◽  
Void Ratio ◽  
Mechanical Response ◽  
Carbonate Sediments ◽  
Fines Content ◽  
North West ◽  
The North ◽  
Undrained Strength

The carbonate sediments found offshore on the North West Shelf of Australia can generally be described as silts with varying proportions of clay-sized and sand-sized carbonate particles. This paper investigates the undrained shearing response (as measured under simple shear and triaxial conditions) of two sediments with different grading curves. The importance of the fines content in controlling the density and hence dilatancy and undrained strength of the materials is demonstrated. The paper discusses the importance of fabric to the behavior of these soils and provides guidance on how undrained strengths of soils of this nature may be assessed with a knowledge of a material’s in-situ water content (or void ratio) and composition.

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