rock formations
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2021 ◽  
Author(s):  
Justin Tweet ◽  
Holley Flora ◽  
Summer Weeks ◽  
Eathan McIntyre ◽  
Vincent Santucci

Grand Canyon-Parashant National Monument (PARA) in northwestern Arizona has significant paleontological resources, which are recognized in the establishing presidential proclamation. Because of the challenges of working in this remote area, there has been little documentation of these resources over the years. PARA also has an unusual management situation which complicates resource management. The majority of PARA is administered by the Bureau of Land Management (BLM; this land is described here as PARA-BLM), while about 20% of the monument is administered by the National Park Service (NPS; this land is described here as PARA-NPS) in conjunction with Lake Mead National Recreation Area (LAKE). Parcels of state and private land are scattered throughout the monument. Reports of fossils within what is now PARA go back to at least 1914. Geologic and paleontologic reports have been sporadic over the past century. Much of what was known of the paleontology before the 2020 field inventory was documented by geologists focused on nearby Grand Canyon National Park (GRCA) and LAKE, or by students working on graduate projects; in either case, paleontology was a secondary topic of interest. The historical record of fossil discoveries in PARA is dominated by Edwin McKee, who reported fossils from localities in PARA-NPS and PARA-BLM as part of larger regional projects published from the 1930s to the 1980s. The U.S. Geological Survey (USGS) has mapped the geology of PARA in a series of publications since the early 1980s. Unpublished reports by researchers from regional institutions have documented paleontological resources in Quaternary caves and rock shelters. From September to December 2020, a field inventory was conducted to better understand the scope and distribution of paleontological resources at PARA. Thirty-eight localities distributed across the monument and throughout its numerous geologic units were documented extensively, including more than 420 GPS points and 1,300 photos, and a small number of fossil specimens were collected and catalogued under 38 numbers. In addition, interviews were conducted with staff to document the status of paleontology at PARA, and potential directions for future management, research, protection, and interpretation. In geologic terms, PARA is located on the boundary of the Colorado Plateau and the Basin and Range provinces. Before the uplift of the Colorado Plateau near the end of the Cretaceous 66 million years ago, this area was much lower in elevation and subject to flooding by shallow continental seas. This led to prolonged episodes of marine deposition as well as complex stratigraphic intervals of alternating terrestrial and marine strata. Most of the rock formations that are exposed in the monument belong to the Paleozoic part of the Grand Canyon section, deposited between approximately 510 and 270 million years ago in mostly shallow marine settings. These rocks have abundant fossils of marine invertebrates such as sponges, corals, bryozoans, brachiopods, bivalves, gastropods, crinoids, and echinoids. The Cambrian–Devonian portion of the Grand Canyon Paleozoic section is represented in only a few areas of PARA. The bulk of the Paleozoic rocks at PARA are Mississippian to Permian in age, approximately 360 to 270 million years old, and belong to the Redwall Limestone through the Kaibab Formation. While the Grand Canyon section has only small remnants of younger Mesozoic rocks, several Mesozoic formations are exposed within PARA, mostly ranging in age from the Early Triassic to the Early Jurassic (approximately 252 to 175 million years ago), as well as some middle Cretaceous rocks deposited approximately 100 million years ago. Mesozoic fossils in PARA include marine fossils in the Moenkopi Formation and petrified wood and invertebrate trace fossils in the Chinle Formation and undivided Moenave and Kayenta Formations.


2021 ◽  
Vol 15 ◽  
pp. 11-43
Author(s):  
Jacek Kolbuszewski

The study uses a variant of the geocritical methodology combined with humanistic mining studies. It was pointed out that in Dante’s poem there were numerous references to the realities of real space (the Alps and the Apennines, which, appearing as a separate part of the mountain world, in the poem at the same time constitute a kind of props room of mountain motifs, used in the construction of Purgatory Mountain). Also, the journeys of the heroes, Dante and his guide Virgil, can be perceived realistically as an actual journey, made in a difficult mountain terrain. It was specified in the realities of Hell, Purgatory Mountain, and Paradise. In this way, using specific Earth realities, Dante created a powerful vision largely made of mountain realities. Mount Purgatory, the target of Dante’s ascent, created when Lucifer, thrown from the heavens, struck the depths of the Earth deep into its center, which changed the hemisphere and pushed up the land masses, throwing them over the surface of the ocean covering the southern hemisphere. Locating the Mount of Purgatory in the center of the southern hemisphere, and at the antipodes of Jerusalem, as a mountain rising on a small island from the vastness of the seas covering this part of the world, Dante used elements of the Muslim tradition (perhaps known to him) with its notions of a lofty, pyramidal shape, which is considered to be the holy Mount of Adam (2243 m) in Ceylon (Sri Lanka). The poet, however, never once described the Purgatory Mountain as a whole, creating a vision of its enormity seen from under its steep walls, but he introduced into the poem numerous details about the surface of this mountain and how to climb it. He filled his abstract vision with real details. From the very first songs of Purgatory, the narrative runs in the order of the characters’ ascent towards the summit Paradise. The work hypothesized that the famous poet Bismantova became the prototype of the Dante Mountain of Purgatory, such a judgment is almost universally approved. That Dante saw this mountain is certain: he was in Lunigiano and Casentino (Bismantova rises right next to it) in 1306, and certainly before 1315, at the time when Divine Comedy was being written. For the accuracy of this hypothesis, the shape of this vast rock mass (culmination in 1047), rising above the level of the surrounding valleys by about 400 m in height with almost vertical rock walls, is of great importance for the accuracy of this hypothesis. The peak landscape largely corresponds to the ideas of an ancient idyllic grove. These realities of the mountain landscape meant that the thought about them found literary expression in the pages of Dante’s poem, which prompts me to share my opinion that the sight of the boatswain and his presence in it gave Dante a vision of the Purgatory Mountain as a “hybrid” creation, partially a description of a real landscape and in part a fantastic, syncretic vision based on elements of ancient literary tradition. The description of climbing this mountain leads us through a narrow chimney, overhang, and other rock formations, forming terraces in the structure of the mountain. The conclusion of the work are the words of Italian literary researcher Filippo Zolezzi, who wrote that “Mount Purgatory appears as an absolute ideal of a mountain, because on its top there is an earthly Paradise — a space of direct contact with the divine, hence even the most beautiful earthly mountains are merely a copy of them. However, the very fact that a poet — a man — to reach this summit, has to climb, climb, makes it an ideal prototype for mountain climbing”.


Minerals ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 3
Author(s):  
Yongqian Wang ◽  
Xuan Wang ◽  
Jiasheng Zhang ◽  
Xiaobin Chen ◽  
Wujun Zhu ◽  
...  

Sinking and horizontal movements are necessary parameters for assessing the potential impacts of surface subsidence in mining activities. Based on similarity criteria, the surface subsidence mechanism was studied using a physical model composed of similar materials such as sand, cement, and gypsum. With constant field geological parameters maintained in two angles of a coal seam, models of roof subsidence of composite rock were compared for different mining configurations. In accordance with observations from the physical model, it was concluded that subsidence and horizontal movement of strata near to and far from the coal seams were different and divided into five zones. The zone above a mined-out area underwent greater total subsidence compared to unexploited regions on both sides. Correlations between a subsidence curve and the height of a caving zone and the mining dip angle were obtained and verified from numerical model results. According to the roof’s position relative to the goaf, the area above the goaf of the composite rock layer was divided into three regions: a curving zone, a water-conducting fracture zone, and a falling zone, to which the subsidence and movement characteristics of each area could be proposed. Compared with the subsidence and movement characteristics observed from the physical and numerical model, the acquisition of subsidence characteristics and parameters in different areas can provide an idea for improvement, innovation or proposal of a theoretical formula for subsidence prediction of composite rock formations.


2021 ◽  
Vol 54 (2) ◽  
pp. 120-153
Author(s):  
Pedro Bastos de Macêdo Carneiro ◽  
Antônio Rodrigues Ximenes Neto ◽  
Caroline Vieira Feitosa ◽  
Cristiane Xerez Barroso ◽  
Helena Matthews-Cascon ◽  
...  

This paper is a literature review on marine hardbottom environments (MHE) that emerge in coastal regions in the Brazilian state of Ceará. This stretch of the Brazilian coast houses several rock formations, which are widely distributed in the intertidal zone. These formations have various origins and composition, ranging from crystalline rocks to biogenic structures, but most are composed by sandstones. These substrates support biodiverse ecosystems that produce valuable environmental goods and services, which have historical and socioeconomic relevance for the state. Despite their importance, they are currently threatened by various types of local and global stressors, and a consistent government effort to protect them is still lacking. There are many knowledge gaps regarding these formations and new studies are needed to support conservation actions involving these ecosystems. Keywords: reef, beachrock, sandstone, intertidal zone, benthos


Geographies ◽  
2021 ◽  
Vol 1 (3) ◽  
pp. 362-380
Author(s):  
Vladyslav Zakharovskyi ◽  
Károly Németh

The assessment of geodiversity is a relatively new field of research connecting abiotic aspects of nature to the wider environment. The study of geodiversity is still in development, so a uniform and complete paradigm remains to be defined. Therefore, an assessment of geodiversity may be highly dependent on the nature of the territory subject to study, available databases, and the researchers’ field of specialization. The main quantitative method for the assessment of geodiversity was proposed to the scientific world only few years ago and may only be relevant to some places in the world, rather than all, which would be desirable. However, while similarities in research methods may be apparent, the directions, scales, and data utilized are clearly different. This article demonstrates a quantitative-qualitative method for an assessment of geodiversity, based on a five-point evaluation system and the utilization of widely available standard databases such as geological maps, SRTM models, and satellite images. Western Samoa Islands (Savai’i and Upolu Islands) were selected for assessment, as a typical example of basaltic ocean island volcanism generating relatively homogenous rock formations and subject to gradual geomorphology (e.g., shield volcano). While initially appearing as a region of simple geology and morphology, complexity is added by considering rock ages, the position and type of eruptive centres, and the coastal geoenvironment. By considering these factors, the assessment becomes specifically tailoring for geodiversity assessment of the islands of Samoa. In conclusion, it has been demonstrated a simple methodology of general assessment of geodiversity with additional improvements to take account of variability in other abiotic factors.


2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Long Cheng ◽  
Hui Wang ◽  
Xu Chang ◽  
Yewei Chen ◽  
Feilu Xu ◽  
...  

Weak and hard inhomogeneous rock formations are typically encountered during tunnel excavations. The physical and mechanical properties and geological conditions of these rock formations vary significantly; thus, it is crucial to investigate the mechanical characteristics of deep bedded composite rock formations. Three-dimensional (3D) scanning and 3D printing were used to prepare composite rock specimens to simulate natural rock laminae. Triaxial compression tests were conducted to determine the influence of the bedding angle, rock composition, and confining pressure on the mechanical properties of the composite rock specimens. The anisotropic strength characteristics and the damage patterns of the composite rock specimens were analyzed under different confining pressures, and the failure mechanism during triaxial loading was revealed. The results show that the damage of the composite rock specimens with a bedding structure depends on the bedding dip angle and the rock formation. The stress-strain curves and peak strengths of the composite rock specimens have anisotropic characteristics corresponding to their failure modes. As the bedding dip angle increases, the peak strength of the three groups of specimens first decreases and then increases under different confining pressure levels. The compressive strength has a nonlinear relationship with the confining pressure, and the difference between the compressive strengths of specimens with different inclination angles decreases as the confining pressure increases. The Hoek–Brown strength criterion is a good predictor of the nonlinear increase in peak strength of the composite rock specimens under different confining pressures. The specimen with a β  = 60°dip angle shows the most significant increase in the strength difference with increasing confining pressure. The results can be used as a reference for testing and analyzing the anisotropic mechanical properties of bedded rock masses.


2021 ◽  
Author(s):  
Weikai LIU ◽  
Yanbin ZHAO ◽  
Mei YANG ◽  
Yueqing XU ◽  
Guangming LI

Abstract Based on research on the response mechanism of rock formations and reservoirs to logging curves, 12 logging curves selected by combining the depth characteristics of formations are proposed to identify rock formations and reservoirs using four algorithms: logistic regression (LR), support vector machine (SVM), random forest (RF) and XGBoost. Out of 60 wells in the study block, 57 wells were selected for training and learning, and the remaining 3 wells were used as prediction samples for testing the algorithm. The recognition of rock formations and reservoirs is performed by each of these four machine learning algorithms, and predictive knowledge is obtained separately. It was found that the accuracy of the 4 algorithms for rock formation and reservoir layer identification reached over 90%, but the XGBoost algorithm was found to be the best in terms of the 4 scoring criteria of F1-score, precision, recall and accuracy. The accuracy of rock formation identification could reach over 95%, and the correlation analysis between the logging curve and rock formation could be performed on this basis. The results show that the RMN, RLLD and RLLS have the most obvious responses to the sandstone layer, off-surface reservoir and effective thickness layer, and the CAL has the least effect on the formation and reservoir identification, which can provide an effective reference for the selection and dimensionality reduction of the subsequent logging curves.


Water ◽  
2021 ◽  
Vol 13 (24) ◽  
pp. 3523
Author(s):  
Bo Wang ◽  
Xiaocheng Zhou ◽  
Yongsheng Zhou ◽  
Yucong Yan ◽  
Ying Li ◽  
...  

Analyzing the hydrochemical composition in thermal springs is an advantageous method for studying the coupling mechanism of the deep and shallow fluids in active fault zones. Here we conducted sampling in 30 thermal springs near fault zones in Fujian Province, and the major elements, trace elements, silica, stable isotopes (δD and δ18O) and strontium isotopes were tested in the laboratory. The results show that (1) the thermal springs in the study area can be divided into six types according to the content of the major elements: HCO3-Na, HCO3·SO4-Na, Cl·HCO3-Na, Cl-Na, Cl-Na·Ca and HCO3·SO4-Ca; (2) hydrogen and oxygen isotopes indicate that precipitation is the main source of recharge for thermal springs in the study area, and the recharge height is between 258 m and 1859 m; (3) the content of SiO2 in the thermal spring varies from 18.1 mg/L to 59.3 mg/L. The geothermal reservoir temperature calculated is 90~226 °C, and the circulation depth is 2.9~5.4 km, except for the W10 thermal spring, whose circulation depth is 8.4 km; and (4) the 87Sr/86Sr of the thermal springs in southwestern Fujian and eastern Fujian has obviously different characteristics, indicating the influence of different rock formations on the groundwater cycle process. Additionally, a continuous measurement of the main anions and cations was performed in five thermal springs every three days since January 2020. There were obvious abnormal changes in the hydrochemical compositions, chlorine in four of the five springs, sodium at three springs, and four ions at one spring, which all showed abnormal high-value changes by 15% to 80%, and which occurred 85~168 days prior to the M6.1 earthquake in Hualien, Taiwan. An inspiration could be provided for obtaining effective earthquake precursor anomalies by monitoring the change in ion concentration in thermal springs.


2021 ◽  
Author(s):  
Anders Kallhovd ◽  
Neil R Kelsall ◽  
Erik Haaland ◽  
Jon Haugestaul ◽  
Erik Akutsu ◽  
...  

Abstract The southern part of the North Sea continental shelf is known for large intervals of hard, compact, cretaceous chalk formations that historically have proven to be challenging to drill through in one run. In recent years technology has been developed to drill specifically through these types of sedimentary successions as effectively as possible to be durable and competitive in similarly challenging drilling settings. Formations that previously would require multiple bit runs are now being drilled in one. The exploration well 2/9-6 S Eidsvoll, operated by MOL Norge AS, was drilled in this area of the North Sea continental shelf, with this specific type of chalk being drilled in the 12 ¼-in. section. Because the 12 ¼-in. section consisted of several different lithologies, it was vital to design the bottom hole assembly (BHA) to handle the diversity of rock formations to be drilled. Lithologies ranging from soft, swelling clay to hard compact chalk with an Unconfined Compressive Strength (UCS) as great as 20,000 psi were expected. In addition to managing the challenging drilling environment, determining the casing setting depth was of the highest priority because a pressure ramp was expected near the planned setting depth. This pressure ramp is located in the Base Cretaceous Unconformity (BCU), which is a well-known seismic reflector in the area. The top of this reflector had an uncertainty of ±75 m, which is not ideal following a decision to set the 9 ⅞-in. casing as near as possible to the reservoir. Seismic-while-drilling technology was applied to reduce this uncertainty and better tie-in the acoustic velocities to the pre-drilling seismic model. In addition, a geomechanics team was tasked with creating and updating the prognosed pore pressure estimation model. This information was important in making the mud-weight decision when drilling the 8 ½-in. section.


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