Hasil untuk "Stratigraphy"

Yunpeng Sun, Wei Wang, Xianguo Lang et al.

Abstract The Tonian Period (1000–720 Ma) bore witness to the transition from a prokaryote-dominated marine ecosystem to one characterized by the proliferation of eukaryotes. This fundamental shift has generally been attributed to evolving marine redox states. Here, we present sedimentological and geochemical analyses of the early Tonian Huainan, Feishui, and Huaibei groups in the Xuhuai basin of the North China craton. Multiple redox proxies show consistent, water depth-dependent variations across the Xuhuai basin. Excess barium contents and Ba/Al ratios further highlight spatial variations in primary productivity which ultimately regulate basinal redox structures. We propose that a shallow-water oxygen minimum zone sandwiched between the oxic/suboxic mid-depth and surface layer water masses occur in the oligotrophic Xuhuai basin, which is analogous to, but much shallower than modern oxygen minimum zones. Such marine redox architectures may benefit the maintenance of a bioavailable nitrate reservoir in the ocean, foreboding the subsequent expansion of eukaryotes.

Jan Erik Rudjord, Mads Huuse

Abstract Oligo-Miocene strata in the northern North Sea comprise hundreds of enigmatic km-scale sand-cored mounds. We investigated these using a basin-scale 3D seismic dataset coupled with petrophysical logs and cuttings mineralogy for hundreds of wells. Here we document the discovery of ‘sinkites’, large-scale sand bodies that have sunk into and underpin low-density bio-silicious ooze rafts, violating the law of superposition. The stratigraphic inversion is attributed to buoyancy instabilities between km-scale rigid low density ooze rafts and liquefied, younger, denser, unconsolidated sand. The sand slurry dislodged the ooze as rafts, delimited by early-stage polygonal faults formed due to volumetric contraction of underlying ooze packages. Akin to load casts, but orders of magnitude bigger, ‘sinkites’ introduce a new large-scale gravitational process into geology. Their discovery and association to fractured low density ooze is important to stratigraphy and assessments of reservoir, seal and fluid flow in petroleum and CO2 storage projects and may have other implications.

Andrew D. Miall

Stefan Back, Sebastian Amberg, Victoria Sachse et al.

Abstract. Archimedes' principle states that the upward buoyant force exerted on a solid immersed in a fluid is equal to the weight of the fluid that the solid displaces. In this 3D salt-reconstruction study we treat Zechstein evaporites in the subsurface of the Netherlands, Central Europe, as a pseudo-fluid with a density of 2.2 g/cm3, overlain by a lighter and solid overburden. 3D sequential removal (backstripping) of a differential sediment load above the Zechstein evaporites is used to incrementally restore the top Zechstein surface. Assumption of a constant subsurface evaporite volume enables the stepwise reconstruction of base Zechstein and the approximation of 3D salt-thickness change and lateral salt re-distribution over time. The salt restoration presented is sensitive to any overburden thickness change irrespective if caused by tectonics, basin tilt or sedimentary process. Sequential analysis of lateral subsurface salt loss and gain through time based on Zechstein isopach difference maps provides new basin-scale insights into 3D subsurface salt flow and redistribution, supra-salt depocentre development, the rise and fall of salt structures, and external forces' impact on subsurface salt movement. The 3D reconstruction procedure described can serve as a template for analyzing other salt basins worldwide and provides a stepping stone to physically sound fluid-dynamic models of salt tectonic provinces.

Rustam F. Bulgakov

Vertical motions, especially in the active continental margins such as Kuril-Kamchatka transition zone, are still pure studied. One of the factors significantly affecting the amplitudes and directions of vertical motions is mantle convections. Estimates of the amplitudes of vertical motions in region have been obtained by means of numerical modeling of the mantle convection made by the method of finite elements. The values of emergences in the area of Sakhalin Island and the Kuril Ridge from 0–3 to 13 m were obtained with the accepted rates of mantle convection from 1 to 5 mm/year. The results obtained should be taken into account when reconstructing neotectonic history of the region and assessing the geodynamic situation in the region of the Sea of Okhotsk.

Jae-Hyuk Lee, Jae-Ho Lee, Seok-Hoon Yoon et al.

This study focuses on revisiting the tectostratigraphic framework of the Ulleung Basin and conceptualizing neotectonics around the western East Sea margin. Based on the analysis of 2D and 3D multi-channel seismic reflection data and offshore drill wells, we divided the entire sedimentary successions of the Ulleung Basin into four tectostratigraphic sequences, named TS1 (c. 23–16 Ma), TS2 (c. 16–9 Ma), TS3 (c. 9–4 Ma), and TS4 (c. 4 Ma–present), in ascending order. The results show that each sequence has been deformed once or multiple times in different periods by juxtaposing two major compressional structures named the Dolgorae Thrust-Fold Belt and the Gorae Anticline. Interpretation of the stratal deformation and termination patterns of the syn- and post-deformational sequences of each structures suggests that the thrusting and folding of the Dolgorae Thrust-Fold Belt was active from c. 16 Ma to c. 9 Ma under the NNW–SSE compressional stress regime (Stage-2), whereas the Gorae Anticline was active from 4 Ma to the present under the ENE–WSW compressional stress regime (Stage-4). Between these two compressional events, there was an intervening period of regional slow subsidence driven by thermal contraction of the back-arc lithosphere and isostatic sedimentary loading (Stage-3). Based on the stratigraphic and structural reconstruction, we propose a 4-stage tectonic model: Stage-1) back-arc opening stage associated with the southward drift of the Japanese islands (c. 23–16 Ma), Stage-2) tectonic-inversion stage in association with the reorganization of the Pacific and Philippine Sea plates and clockwise rotation of SW Japan (c. 16–9 Ma), Stage-3) post-inversion stage with regional thermal and isostatic subsidence (c. 9–4 Ma), and Stage-4) neotectonic stage in which embryonic subduction is nucleating on the East Sea margins under the E–W compressional stress regime (c. 4 Ma–present).

Leonidas Moforis, George Kontakiotis, Hammad Tariq Janjuhah et al.

Field investigation, biostratigraphic, paleoecological, and sedimentary microfacies analyses, as well as diagenetic processes characterization, were carried out in the Epirus region (Western Ionian Basin) to define the depositional environments and further decipher the diagenetic history of the Late Cretaceous–Early Paleocene carbonate succession in western continental Greece. Planktonic foraminiferal biostratigraphy of the studied carbonates revealed that the investigated part of the Gardiki section covers the Cretaceous–Paleogene (K-Pg) transition, partly reflecting the Senonian limestone and calciturbidites formations of the Ionian zone stratigraphy. Litho-and bio-facies analyses allowed for the recognition of three distinct depositional facies: (a) the latest Maastrichtian pelagic biomicrite mudstone with in situ planktonic foraminifera, radiolarians, and filaments, (b) a pelagic biomicrite packstone with abundant planktonic foraminifera at the K-Pg boundary, and (c) an early Paleocene pelagic biomicrite wackestone with veins, micritized radiolarians, and mixed planktonic fauna in terms of in situ and reworked (aberrant or broken) planktonic foraminifera. The documented sedimentary facies characterize a relatively low to medium energy deep environment, representing the transition from the deep basin to the deep shelf and the toe of the slope crossing the K-Pg boundary. Micropaleontological and paleoecological analyses of the samples demonstrate that primary productivity collapse is a key proximate cause of this extinction event. Additional petrographic analyses showed that the petrophysical behavior and reservoir characteristics of the study deposits are controlled by the depositional environment (marine, meteoric, and burial diagenetic) and further influenced by diagenetic processes such as micritization, compaction, cementation, dissolution, and fracturing.

J. J. Y. He, P. W. Reiners, P. W. Reiners

<p>Accurate corrections for the effects of alpha ejection (the loss of daughter <span class="inline-formula">He</span> near grain or crystal surfaces due to long alpha stopping distances) are central to <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M3" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mo>(</mo><mi mathvariant="normal">U</mi><mo>-</mo><mi mathvariant="normal">Th</mi><mo>)</mo><mo>/</mo><mi mathvariant="normal">He</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="58pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="26d53101b6c836ab0b6ef325d9bca65f"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-4-629-2022-ie00003.svg" width="58pt" height="14pt" src="gchron-4-629-2022-ie00003.png"/></svg:svg></span></span> thermochronometry. In the case of apatite <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M4" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mo>(</mo><mi mathvariant="normal">U</mi><mo>-</mo><mi mathvariant="normal">Th</mi><mo>)</mo><mo>/</mo><mi mathvariant="normal">He</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="58pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="c9cf0718e10396f6e2182a01dacbca3e"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-4-629-2022-ie00004.svg" width="58pt" height="14pt" src="gchron-4-629-2022-ie00004.png"/></svg:svg></span></span> dating, alpha-ejection correction is complicated by the fact that crystals are often broken perpendicular to the <span class="inline-formula"><i>c</i></span> axis. In such cases, the correction should account for the fact that only some parts of the crystal are affected by alpha ejection. A common current practice to account for such broken crystals is to modify measured lengths of broken crystals missing one termination by a factor of 1.5, and those missing both terminations by a factor of 2. This alpha-ejection “correction correction” systematically overestimates the actual fraction of helium lost to alpha ejection, and thus overcorrects the measured date relative to that determined for an otherwise equivalent unbroken crystal. The ratio of the alpha-ejection-affected surface area to the volume of a fragmented crystal is equivalent to the surface-area-to-volume ratio of an unbroken crystal that is either twice as long (for fragments with one termination) or infinitely long (for fragments with no termination). We suggest that it is appropriate to revise the fragmentation correction to multiply the lengths of crystals missing one <span class="inline-formula"><i>c</i></span>-axis termination by 2, and those missing both <span class="inline-formula"><i>c</i></span>-axis terminations by some large number <span class="inline-formula">≳20</span>. We examine the effect of this revised correction and demonstrate the accuracy of the new method using synthetic datasets. Taking into account alpha ejection, the rounding of the <span class="inline-formula">He</span> concentration profile due to diffusive loss, and the accumulation of radiation damage over a range of thermal histories, we show that the revised fragmentation alpha-ejection correction proposed here accurately approximates the corrected date of an unbroken crystal (“true” date) to within <span class="inline-formula">&lt;0.7</span> % on average (<span class="inline-formula">±4.2</span> %, 1<span class="inline-formula"><i>σ</i></span>), whereas the former method overcorrects dates to be <span class="inline-formula">∼3</span> % older than the “true” date on average. For individual grains, the former method can result in dates that are older by a few percent in most cases, and by as much as 12 % for grains with aspect ratios of up to <span class="inline-formula">1:1</span>. The revised alpha-ejection correction proposed here is both more accurate and more precise than the previous correction, and does not introduce any significant systematic bias into the apparent dates from a sample.</p>

S. Nachtergaele, J. De Grave

<p>A new method for automatic counting of etched fission tracks in minerals is described and presented in this article. Artificial intelligence techniques such as deep neural networks and computer vision were trained to detect fission surface semi-tracks on images. The deep neural networks can be used in an open-source computer program for semi-automated fission track dating called “AI-Track-tive”. Our custom-trained deep neural networks use the YOLOv3 object detection algorithm, which is currently one of the most powerful and fastest object recognition algorithms. The developed program successfully finds most of the fission tracks in the microscope images; however, the user still needs to supervise the automatic counting. The presented deep neural networks have high precision for apatite (97 %) and mica (98 %). Recall values are lower for apatite (86 %) than for mica (91 %). The application can be used online at <span class="uri">https://ai-track-tive.ugent.be</span> (last access: 29 June 2021), or it can be downloaded as an offline application for Windows.</p>

Michael Andrew Anderson

The last decade of advances in Image-Based Modeling (IBM) data acquisition based on Structure from Motion (SfM) have made it possible as never before to record excavated archaeological deposits, historical architectural remains, artifacts, and geographical surroundings in the field. Armed only with digital cameras and low-cost or open-source software, researchers can now produce accurate point clouds of millions of points, capturing archaeological information in high-resolution detail. But what changes will IBM really bring to the standards, requirements, and expectations of practical field methodology for projects operating on shoe-string budgets? Since 2010, the Via Consolare Project, a small archaeological research project from a State level University, has employed an entirely open-source and “free for academic use” IBM pipeline to record a variety of archaeological features in Insula VII 6 and the “Villa delle Colonne a mosaico” in Pompeii. Ranging from surviving architecture, to rubble fill layers, to the interiors of inaccessible cisterns and drains, this work has been carried out in preparation for the eventual coordination of these data into a 3D GIS of all recorded stratigraphy. Rarely were sufficient resources available for dedicated equipment or personnel to be devoted to this task. While practical implementation, even in a low-budget excavation environment, has confirmed that this technology can indeed augment archaeological field documentation and provide investigation opportunities that would otherwise be impossible, it failed to replace traditional handdrafted recording techniques and was found to present significant challenges and a number of hidden costs. This emphasizes a need for appropriate and cautious planning in implementation, especially in projects with limited means.

J. Henninges, E. Martuganova, E. Martuganova et al.

<p>We performed so-far-unprecedented deep wireline vertical seismic profiling at the Groß Schönebeck site with the novel method of distributed acoustic sensing (DAS) to gain more detailed information on the structural setting and geometry of the geothermal reservoir, which is comprised of volcanic rocks and sediments of Lower Permian age. During the survey of 4 d only, we acquired data for 61 source positions using hybrid wireline fiber-optic sensor cables deployed in two 4.3 km deep, already existing wells. While most of the recorded data have a very good signal-to-noise ratio, individual sections of the profiles are affected by characteristic coherent noise patterns. This ringing noise results from incomplete coupling of the sensor cable to the borehole wall, and it can be suppressed to a large extent using suitable filtering methods. After conversion to strain rate, the DAS data exhibit a high similarity to the vertical component data of a conventional borehole geophone. We derived accurate time–depth relationships, interval velocities, and corridor stacks from the recorded data. Based on integration with other well data and geological information, we show that the top of a porous and permeable sandstone interval of the geothermal reservoir can be identified by a positive reflection event. Overall, the sequence of reflection events shows a different character for both wells explained by lateral changes in lithology. The top of the volcanic rocks has a somewhat different seismic response in both wells, and no clear reflection event is obvious at the postulated base of the volcanic rocks, so that their thickness cannot be inferred from individual reflection events in the seismic data alone. The DAS method enabled measurements at elevated temperatures up to 150 <span class="inline-formula">^∘</span>C over extended periods and led to significant time and cost savings compared to deployment of a conventional borehole geophone string. This wireline approach finally suggests significant implications for observation options in old wells for a variety of purposes.</p>

Raz Muhammad H. Karim, Samira Muhamad Salh

In this study, the Tobit Model as a statistical regression model was used to study factors affecting blood pressure (BP) in patients with renal failure. The data have been collected from (300) patients in Shar Hospital in Sulaimani city. Those records contain BP rates per person in patients with renal failure as a response variable (Y) which is measured in units of millimeters of mercury (mmHg), and explanatory variables (Age [year], blood urea measured in milligram per deciliter [mg/dl], body mass index [BMI] expressed in units of kg/m2 [kilogram meter square], and Waist circumference measured by the Centimeter [cm]). The two levels of BP; high and low were taken from the patients. The mean arterial pressure (MAP) was used to find the average of both levels (high and low BP). The average BP rate of those patients equal to or >93.33 mmHg only remained in the dataset. The 93.33 mmHg is a normal range of MAP equal to 12/8 mmHg normal range of BP. The others have been censored as zero value, i.e., left censored. Furthermore, the same data were truncated from below. Then, in the truncated samples, only those cases under risk of BP (greater than or equal to BP 93.33mmHg) are recorded. The others were omitted from the dataset. Then, the Tobit Model applied on censored and truncated data using a statistical program (R program) version 3.6.1. The data censored and truncated from the left side at a point equal to zero. The result shows that factors age and blood urea have significant effects on BP, while BMI and Waist circumference factors have not to affect the dependent variable(y). Furthermore, a multiple regression model was found through ordinary least Square (OLS) analysis from the same data using the Stratigraphy program version 11. The result of (OLS) shows that multiple regression analysis is not a suitable model when we have censored and truncated data, whereas the Tobit model is a proficient technique to indicate the relationship between an explanatory variable, and truncated, or censored dependent variable.

Shenghua LAI, Pu BAI, Chao YE et al.

The method of using seismic information to study the planar distribution characteristics of sedimentary system is illustrated using the lower part of the second member of the Lower Permian Shanxi Formation in the Gaojiahe 3D area of the Ordos Basin as an example. Firstly, based on rock physical properties, time-frequency scanning technology was used to study the seismic reflection characteristics of coal seams in a 90° phase seismic data volume. Secondly, by designing specific filters, seismic waves were filtered to suppress the influence of coal seams on seismic reflection characteristics. A fine (high-frequency) isochronous stratigraphic framework in the 3D seismic data volume was created by combining high-precision sequence stratigraphy with seismic sedimentology. Finally, combining geological features, logging responses and seismic facies analysis, provided the sedimentary analysis of isochronous stratigraphic slices with different frequencies. Mixed frequency display technology was applied to study the spatial distribution characteristics of sedimentary facies. The distributary channels in the lower delta plain sub-facies of the second member of Shanxi Formation in the Gaojiahe 3D area are mainly represented by three trends: (1) Some show north-south, east-west, and then north-south trends, along S229, S228, S232, S208, Y124 well edge. In these distributary channels, a meandering beach with a certain scale may develop near well S231. (2) Some show a northwest-southeast trend, mainly distributed along wells S212, Y127, and S209; (3) Some show a nearly west trend. A large-scale lateral river migration zone develops along wells S210 and S226.

Z. Zhang, S. Kruschwitz, S. Kruschwitz et al.

<p>We investigate the pore space of rock samples with respect to different petrophysical parameters using various methods, which provide data on pore size distributions, including micro computed tomography (<i>μ</i>-CT), mercury intrusion porosimetry (MIP), nuclear magnetic resonance (NMR), and spectral-induced polarization (SIP). The resulting cumulative distributions of pore volume as a function of pore size are compared. Considering that the methods differ with regard to their limits of resolution, a multiple-length-scale characterization of the pore space is proposed, that is based on a combination of the results from all of these methods. The approach is demonstrated using samples of Bentheimer and Röttbacher sandstone. Additionally, we compare the potential of SIP to provide a pore size distribution with other commonly used methods (MIP, NMR). The limits of resolution of SIP depend on the usable frequency range (between 0.002 and 100&thinsp;Hz). The methods with similar resolution show a similar behavior of the cumulative pore volume distribution in the overlapping pore size range. We assume that <i>μ</i>-CT and NMR provide the pore body size while MIP and SIP characterize the pore throat size. Our study shows that a good agreement between the pore radius distributions can only be achieved if the curves are adjusted considering the resolution and pore volume in the relevant range of pore radii. The MIP curve with the widest range in resolution should be used as reference.</p>

CARLO SPANO

The megafauna recovered from the Lower Pliocene sequence at Capo S. Marco (Sinis Peninsula) are analysed; detailed studies concern taxonomy, stratigraphy and paleoecology.

Radivojević Dejan N.

This paper presents two basic approaches in seismic stratigraphy interpretation. The first one as starting point have seismic sections, whose interpretation in the later stage correlates with well data. The second one in initial phase analyze the data obtain by deep well drilling which are later correlated with the seismic sections. The chronological order and seismic stratigraphy procedure are explained for both approaches. Those interpretation approaches enabled oil companies a detailed and more precise insight into geological features, reduction of exploration risk and more rational design of development wells.

P. E. Olsen, J. W. Geissman, D. V. Kent et al.

<p>Phase 1 of the Colorado Plateau Coring Project (CPCP-I) recovered a total of over 850&thinsp;m of stratigraphically overlapping core from three coreholes at two sites in the Early to Middle and Late Triassic age largely fluvial Moenkopi and Chinle formations in Petrified Forest National Park (PFNP), northeastern Arizona, USA. Coring took place during November and December of 2013 and the project is now in its post-drilling science phase. The CPCP cores have abundant detrital zircon-producing layers (with survey LA-ICP-MS dates selectively resampled for CA-ID-TIMS U-Pb ages ranging in age from at least 210 to 241&thinsp;Ma), which together with their magnetic polarity stratigraphy demonstrate that a globally exportable timescale can be produced from these continental sequences and in the process show that a prominent gap in the calibrated Phanerozoic record can be filled. The portion of core CPCP-PFNP13-1A for which the polarity stratigraphy has been completed thus far spans  ∼ 215 to 209&thinsp;Ma of the Late Triassic age, and strongly validates the longer Newark-Hartford Astrochronostratigraphic-calibrated magnetic Polarity Time-Scale (APTS) based on cores recovered in the 1990s during the Newark Basin Coring Project (NBCP).</p><p>Core recovery was  ∼ 100&thinsp;% in all holes (Table 1). The coreholes were inclined  ∼ 60–75° approximately to the south to ensure azimuthal orientation in the nearly flat-lying bedding, critical to the interpretation of paleomagentic polarity stratigraphy. The two longest of the cores (CPCP-PFNP13-1A and 2B) were CT-scanned in their entirety at the University of Texas High Resolution X-ray CT Facility in Austin, TX, and subsequently along with 2A, all cores were split and processed at the CSDCO/LacCore Facility, in Minneapolis, MN, where they were scanned for physical property logs and imaging. While remaining the property of the Federal Government, the archive half of each core is curated at the NSF-sponsored LacCore Core Repository and the working half is stored at the Rutgers University Core Repository in Piscataway, NJ, where the initial sampling party was held in 2015 with several additional sampling events following. Additional planned study will recover the rest of the polarity stratigraphy of the cores as additional zircon ages, sedimentary structure and paleosol facies analysis, stable isotope geochemistry, and calibrated XRF core scanning are accomplished. Together with strategic outcrop studies in Petrified Forest National Park and environs, these cores will allow the vast amount of surface paleontological and paleoenvironmental information recorded in the continental Triassic of western North America to be confidently placed in a secure context along with important events such as the giant Manicouagan impact at  ∼ 215.5&thinsp;Ma (Ramezani et al., 2005) and long wavelength astronomical cycles pacing global environmental change and trends in atmospheric gas composition during the dawn of the dinosaurs.</p>

ROBERTO BARTOLE

An old high-penetration seismic survey of the Tuscany-Latium continental shelf furnished use­ful information on Neogene stratigraphy, structural setting and paleogeography. The seismically penetrated stratigraphic column is composed of five seismic units which may be correlated with the tectonic and strati­graphic units of the inner Apennine belt, described in the literature. Three tectonically superposed units consti­tute the deformed substratum, transgressively overlain by two postorogenic sedimentary cycles. From the last diastrophic phases onward, the area underwent a very diversified tectono-sedimentary evolution, which gave origin to different structural landscapes. During the Upper Tortonian (?)-Middle Plio­cene time interval the Elba-Argentario sector was subject to remarkable extensional tectonics, accompanied by important strike-slip components of mostly anti-apennine trend. Analogies with the geodynamic processes that gave rise to the inner belt Neogene basins, lead to inter­pret this sector of the shelf as the penetration path of the Tyrrhenian rifting within the continental area.