scholarly journals The origin of upper Precambrian diamictites, northern Norway: a case study applicable to diamictites in general

Geologos ◽  
2017 ◽  
Vol 23 (3) ◽  
pp. 163-181 ◽  
Author(s):  
Mats O. Molén
Keyword(s):  
Quartz Sand ◽  
Laboratory Data ◽  
Gravity Flow ◽  
Geological Data ◽  
Submarine Fan ◽  
Northern Norway ◽  
Gravity Flows ◽  
Material Evidence ◽  
Geological Context

AbstractUpper Precambrian diamictites in Varangerfjorden (northern Norway) have been examined for evidence of origin, whether glaciogenic, gravity flow or polygenetic. Studies of geomorphology, sedimentology and surface microtextures on quartz sand grains are integrated to provide multiple pieces of evidence for the geological agents responsible for the origin of the diamictites. The documented sedimentary and erosional structures, formerly interpreted in a glaciogenic context (e.g., diamict structure, pavements and striations) have been reanalysed. Field and laboratory data demonstrate that, contrary to conclusions reached in many earlier studies, the diamictites and adjacent deposits did not originate from glaciogenic processes. Evidence from macrostructures may occasionally be equivocal or can be interpreted as representing reworked, glacially derived material. Evidence from surface microtextures, from outcrops which are believed to exhibit the most unequivocal signs for glaciation, display no imprint at all of glaciogenic processes, and a multicyclical origin of the deposits can be demonstrated. The geological context implies (and no geological data contradict this) an origin by gravity flows, possibly in a submarine fan environment. This reinterpretation of the diamictites in northern Norway may imply that the palaeoclimatological hypothesis of a deep frozen earth during parts of the Neoproterozoic has to be revised.

scholarly journals The gravity flow dynamics of submarine fan sedimentation in the Magura Basin of the Western Carpathians (Magura Nappe, Slovakia)

2010 ◽  
Vol 61 (3) ◽  
pp. 201-209 ◽  
Author(s):  
František Teťák
Keyword(s):  
Deep Water ◽  
Flow Dynamics ◽  
Western Carpathians ◽  
Gravity Flow ◽  
Submarine Fan ◽  
Sedimentary Structures ◽  
Gravity Flows ◽  
Bed Thickness ◽  
Change Position ◽  
Current Arrangement

The gravity flow dynamics of submarine fan sedimentation in the Magura Basin of the Western Carpathians (Magura Nappe, Slovakia)This article deals with the dynamics of the deep-water gravity flows sedimentation within the Magura Formation. This investigation is based on analysis of the Magura sandstone sedimentary structures studied on the outcrops. The final comparison of the sedimentary structures and cycles with the paleocurrent directions provided an interpretation of the gravity flows dynamics and helped to restore the migration of the sandy lobes in space and time. Three modes of sedimentation are recorded: regular cyclic sedimentation from the lobe, irregular sedimentation from the immature lobe and pelitic sedimentation on the basin plane without the lobe influence. We compared the occurrence of some sedimentary structures with the changes of the current directions and bed thickness. The following interpretations of gravity flow fan dynamics are results of this comparision: the fan consists of one or several lobes, the lobe branches out into branches with the radial current arrangement, the lobes laterally change position and the lobes suddenly die out.

DETERMINING THE DENSITY OF MULTIPLE LAYERS USING GAMMA SPECTROSCOPY

2021 ◽  
Author(s):  
Mayir Mamtimin ◽  
◽  
Jeffrey Crawford ◽  
Keyword(s):  
Gamma Spectroscopy ◽  
Laboratory Data ◽  
Hole Density ◽  
Radial Density ◽  
New Approach ◽  
Simulation Tools ◽  
Radial Density Profile ◽  
Gamma Density ◽  
Open Hole

Due to the volumetric nature of the physics and the measurement, traditional gamma-gamma density tools measure an average bulk density of the formation. However, a bulk measurement is not adequate for certain applications where a more detailed resolution of a radial density profile is necessary. In this paper, a new approach of gamma spectral analysis is introduced focusing on the main Compton scattering angles. Several energy windows are linked to the unique radial layers based on scattering angles and location of interaction. As a result, the density of multiple layers can be calculated. The paper first outlines the main principles and analytical structures to formulate two methods to measure layer densities. Then computer simulation tools are used to simulate realistic tool configuration and measurement response to validate and benchmark efficacies of the outlined methods. Finally, a case study is presented to demonstrate the applicability of these methods using laboratory data. The paper is concluded with a list of other possible applications such as open-hole density and behind-pipe evaluation where layer density can provide more details for the analysis.

Most parsimonious areagrams versus fossils: the case of Nothofagus (Nothofagaceae)

2001 ◽  
Vol 49 (3) ◽  
pp. 367 ◽  
Author(s):  
Ulf Swenson ◽  
Robert S. Hill
Keyword(s):  
Software Component ◽  
Historical Biogeography ◽  
Geological Data ◽  
Biogeographic Patterns ◽  
Vicariance Biogeography ◽  
Dispersal Events ◽  
Geological Context

Vicariance biogeography uses most parsimonious areagrams in order to explain biogeographic patterns. One notion is that areagrams convey biogeographic information to the extent that alternative palaeogeographic hypotheses are suggested. However, extinctions may distort biogeographic information, leading to areagrams showing area relationships not supported by geological data, and plausible dispersal events might also be overlooked. By the use of the software COMPONENT 2.0, Nothofagus phylogeny was reconciled with the most parsimonious areagrams. Well-preserved fossils, identified to subgenera, were optimised to the reconciled tree. Not all past distributions were predicted by the analysis, and Nothofagus has clearly been present in areas where it cannot have been if strict vicariance is followed. It can therefore be demonstrated that the biogeographic signal in Nothofagus areagrams is incomplete, and that most parsimonious areagrams can be flawed. Areagrams can be a useful tool in historical biogeography, but must be scrutinised within a known geological context and not accepted uncritically as alternative palaeogeographical hypotheses.

Introduction

2017 ◽  
Author(s):  
Oliver H. Creighton ◽  
Duncan W. Wright ◽  
Michael Fradley ◽  
Steven Trick
Keyword(s):  
Civil War ◽  
Material Culture ◽  
Evidence Base ◽  
Final Part ◽  
Documentary History ◽  
Siege Warfare ◽  
Material Evidence ◽  
The Church

This introductory chapter outlines the historiography of the reign of King Stephen (1135–54), highlighting how study has been dominated by documentary history while archaeological and other material evidence has played a marginal role. It identifies landmark studies of the period, summarises the principal chroniclers that cover Stephen’s reign and discusses charters as another cornerstone of the evidence base. A major debate has centred on whether or not the period should continue to be styled as ‘the Anarchy’, with scholars taking maximalist and minimalist views of the violence and disturbances of the period. The final part of the chapter explains the approach and structure of the volume: after a chronological outline of the civil war (Chapter 2), the book covers conflict landscapes and siege warfare (Chapter 3), castles (Chapter 4), artefacts and material culture (Chapter 5), weaponry and armour (Chapter 6), the church (Chapter 7), settlements and landscape (Chapter 8), and a detailed case study of the fenland campaigns (Chapter 9), while Chapter 10 presents a self-contained concluding essay that reflects on what the material evidence can and cannot us about the conflict and its consequences.

scholarly journals The Agency of the Displaced? Roman Expansion, Environmental Forces, and the Occupation of Marginal Landscapes in Ancient Italy

Humanities ◽  
2018 ◽  
Vol 7 (4) ◽  
pp. 116 ◽  
Author(s):  
Elisa Perego ◽  
Rafael Scopacasa
Keyword(s):  
Social Groups ◽  
Environmental Context ◽  
Key Players ◽  
Displaced People ◽  
The Mediterranean ◽  
Material Evidence

This article approaches the agency of displaced people through material evidence from the distant past. It seeks to construct a narrative of displacement where the key players include human as well as non-human agents—namely, the environment into which people move, and the socio-political and environmental context of displacement. Our case-study from ancient Italy involves potentially marginalized people who moved into agriculturally challenging lands in Daunia (one of the most drought-prone areas of the Mediterranean) during the Roman conquest (late fourth-early second centuries BCE). We discuss how the interplay between socio-political and environmental forces may have shaped the agency of subaltern social groups on the move, and the outcomes of this process. Ultimately, this analysis can contribute towards a framework for the archaeological study of marginality and mobility/displacement—while addressing potential limitations in evidence and methods.

Sign in / Sign up

Export Citation Format

Share Document