scholarly journals Holocene Sea-Level Changes in Southern Brazil Based on High-Resolution Radar Stratigraphy

Geosciences ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 326
Author(s):  
Eduardo Guimarães Barboza ◽  
Sergio Rebello Dillenburg ◽  
Matias do Nascimento Ritter ◽  
Rodolfo José Angulo ◽  
Anderson Biancini da Silva ◽  
...  
Keyword(s):  
High Resolution ◽  
Sea Level ◽  
Maximum Level ◽  
Luminescence Dating ◽  
Brazilian Coast ◽  
Southern Brazil ◽  
Sea Level Changes ◽  
Aeolian Deposits ◽  
Coastal Deposits ◽  
Spatial Positioning

This paper focuses on high-resolution coastal stratigraphy data, which were revealed by the Ground Penetrating Radar (GPR) system. Surveys performed with GPR on the surface of prograded barriers reveal patterns of reflections that allow the interpretation of the geometry and stratigraphy of coastal deposits in a continuous mode. At the Curumim prograded barrier in southern Brazil (29°30′ S–49°53′ W), a two-dimensional transverse GPR survey revealed, with high precision, a serial of contacts between aeolian deposits of relict foredunes and relict beach deposits that have a strong correlation with sea level. In a 4 km GPR profile, a total of 24 of these contacts were identified. The high accurate spatial positioning of the contacts combined with Optical Stimulated Luminescence dating resulted in the first confident sea-level curve that tells the history of sea-level changes during the last 7 ka on the southernmost sector of the Brazilian coast. The curve shows that sea-level was still rising before 6 ka BP, with a maximum level of 1.9 m reached close to 5 ka BP; after that, sea-level started to falling slowly until around 4 ka BP when fall accelerated.

scholarly journals Quaternary Evolution of Coastal Plain in Response to Sea-Level Changes: Example from South-East Sicily (Southern Italy)

Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1524
Author(s):  
Salvatore Distefano ◽  
Fabiano Gamberi ◽  
Niccolò Baldassini ◽  
Agata Di Stefano
Keyword(s):  
High Resolution ◽  
Continental Shelf ◽  
Sea Level ◽  
Tectonic Activity ◽  
Research Approach ◽  
Coastal Environments ◽  
Sea Level Changes ◽  
Continental Shelves ◽  
Wide Range ◽  
Coastal Deposits

During a cycle of sea-level variation, coastal environments develop in different position of the continental shelf following seaward and landward shift of the coastline. They vary widely in character, reflecting the wide range of process-regimes that are brought about during the different stages of sea-level variations. Within this scenario, the morphology of continental shelves, mainly resulting from the combined effect of tectonic activity and eustatism, plays an important role in controlling the features and the preservation of coastal environments. Coastal deposits formed along continental shelves in the past, during different stages of sea-level changes, consist of discontinuous and thin depositional bodies, thus their reconstruction can be best carried out through the interpretation of high-resolution seismic data. Such a research approach is adopted in the present study to investigate a portion of the continental shelf of the southernmost sector of SE Sicily, in the offshore of Marzamemi village (Syracuse). The interpretation of high-resolution “Sparker” profiles allowed us to reconstruct the evolution of alluvial and lagoonal environments, established on a substratum of Pliocene or more ancient marine deposits, with the detection of several seismic units and unconformity surfaces, which have been related to alternating sedimentation and erosional processes, depicting the sea-level change framework of glacial-interglacial phases, from the late Pleistocene onward.

scholarly journals High-resolution isotope stratigraphy of the Lower Ordovician St. George Group of western Newfoundland, Canada: implications for global correlation

2009 ◽  
Vol 46 (6) ◽  
pp. 403-423 ◽  
Author(s):  
Karem Azmy ◽  
Denis Lavoie
Keyword(s):  
High Resolution ◽  
Sea Level ◽  
Sea Level Changes ◽  
Global Correlation ◽  
Lower Ordovician ◽  
Isotope Stratigraphy ◽  
Platform Carbonates ◽  
The Baltic ◽  
Marine Platform ◽  
Bottom To Top

The Lower Ordovician St. George Group of western Newfoundland consists mainly of shallow-marine-platform carbonates (∼500 m thick). It is formed, from bottom to top, of the Watts Bight, Boat Harbour, Catoche, and Aguathuna formations. The top boundary of the group is marked by the regional St. George Unconformity. Outcrops and a few cores from western Newfoundland were sampled at high resolution and the extracted micritic materials were investigated for their petrographic and geochemical criteria to evaluate their degree of preservation. The δ13C and δ18O values of well-preserved micrite microsamples range from –4.2‰ to 0‰ (VPDB) and from –11.3‰ to –2.9‰ (VPDB), respectively. The δ13Ccarb profile of the St. George Group carbonates reveals several negative shifts, which vary between ∼2‰ and 3‰ and are generally associated with unconformities–disconformities or thin shale interbeds, thus reflecting the effect of or link with significant sea-level changes. The St. George Unconformity is associated with a negative δ13Ccarb shift (∼2‰) on the profile and correlated with major lowstand (around the end of Arenig) on the local sea-level reconstruction and also on those from the Baltic region and central Australia, thus suggesting that the St. George Group Unconformity might have likely had an eustatic component that contributed to the development–enhancement of the paleomargin. Other similar δ13Ccarb shifts have been recorded on the St. George profile, but it is hard to evaluate their global extension due to the low resolution of the documented global Lower Ordovician (Tremadoc – middle Arenig) δ13Ccarb profile.

Insights in beachrock formation mechanism using multiproxy experimental data: Case study of Diolkos, Corinth, Greece

2021 ◽  
Author(s):  
Giannis Saitis ◽  
‪Konstantinos Tsanakas ◽  
Anna Karkani ◽  
Satoru Kawasaki ◽  
Niki Evelpidou
Keyword(s):  
Sea Level ◽  
Formation Mechanism ◽  
Analytical Data ◽  
Mean Value ◽  
Luminescence Dating ◽  
Sea Level Changes ◽  
Needle Penetration ◽  
Beach Sediments ◽  
Needle Penetration Test ◽  
Ureolytic Bacteria

<p>Many studies have been published concerning the occurrence and formation mechanism of beachrocks around the world. However, there are only few quantified data on the precipitation mechanism and the parameters affecting it. The formation mechanism of beachrocks is directly related to their palaeoenvironmental significance, as it provides insights into sea level evolution and palaeogeographic evolution. In this study we corelate analytical data of natural and artificial beachrocks, which were created by the microbially induced carbonate precipitation (MICP) technique using sediments and ureolytic bacteria from the coastal zone of Diolkos, Corinth, Greece.</p><p>A multiproxy analysis was accomplished which included the mineralogical and geochemical analysis of both natural and artificial beachrocks, and the sedimentological and mechanical properties analysis of the artificial ones. This study focuses on four parameters that concern the cementation processes of artificial beachrocks: (a) sediment granulometry, (b) CaCO<sub>3 </sub>content, (c) bacteria type and (d) cement type. Diolkos, due to its location and history, presents great palaeo-geographic and geoarchaeological interest; for this reason, luminescence dating was accomplished on selected beachrock samples, in order to elucidate the relative sea level changes (RSL) and palaeogeographic evolution of the site.</p><p>For the artificial beachrocks formation, we conducted solidification test using ureolytic bacteria <em>Micrococcus yunnanensis sp.</em> and <em>Virgibacillus sp. </em>isolated from local sand samples. In order to determine the solidification of the beach sediments we estimated the unconfined compressive strength (UCS) by using needle penetration test on the surface of each sample. Furthermore, the precipitated CaCO<sub>3</sub> cement of the artificial beachrock samples, was calculated using HCl rinsing method. The artificial beachrocks were examined under SEM-EDS, XRD and XRF for their mineralogical and chemical composition accordingly.</p><p>Microscopy studies (optical and SEM-EDS) revealed that the cement of the artificial beachrock consists of calcite, in form of acicular sediment coating forming fans and multilayer concentrations. The cement in many cases was amorphous calcite crystals or microcrystalline, with thickness varying between 5 μm and 40 μm. The analysis from the artificial beachrock was correlated with the natural beachrock of Diolkos area. Our results revealed that the artificial beachrocks had different type of cement with microstratigraphy of an early digenesis. Moreover, amongst the artificial beachrocks, the sample with very well sorting (in terms of granulometry) has shown high values of CaCO<sub>3</sub> content, which corresponds to cement, a mean value of UCS 11 MPa and the best cement precipitation.</p>

High-resolution Stratigraphy of Holocene Lagoon Terraces of Southern Brazil

2015 ◽  
Vol 83 (1) ◽  
pp. 52-65 ◽  
Author(s):  
Natália B. dos Santos ◽  
Ernesto L.C. Lavina ◽  
Paulo S.G. Paim
Keyword(s):  
High Resolution ◽  
Sea Level ◽  
Radiometric Dating ◽  
Sea Level Changes ◽  
Relative Sea Level ◽  
Base Level ◽  
Depositional Processes ◽  
Close Relationship ◽  
Northern Portion ◽  
Depositional Architecture

AbstractThe northern portion of the coastal plain of the Rio Grande do Sul State (southernmost Brazil) comprises an outer sandy barrier that protects a complex lagoon system formed during the Holocene. The terraces of three different lagoons (Gentil, Malvas and Pinguela) formed along their margins record the depositional processes and the relative base level changes over the past 5000 yr. Therefore, our main objective was to characterize and quantify base level fluctuations from the study of these terraces, to correlate them to sea-level changes and to describe the depositional architecture related to the distinct sea-level stages (high-resolution sequence stratigraphy). Satellite images, topographic and GPR profiles, auger holes and radiometric dating were used. The main results indicate a close relationship between relative base level and relative sea-level changes, a stillstand period just after the last transgressive maximum (4840–4650 cal yr BP) and a subsequent overall relative sea-level fall of about 3 m. Both a normal (highstand systems tract) and a forced regression (falling-stage systems tract) controlled the geological record preserved in the terraces. The highstand (older terrace) is characterized by agradational bedding, whereas the falling stage comprises three progradational sets (terraces) bounded by erosive surfaces related to smaller-scale sea-level drops.

The Silurian Mulde Event and a scenario for secundo–secundo events

2002 ◽  
Vol 93 (2) ◽  
pp. 135-154 ◽  
Author(s):  
Lennart Jeppsson ◽  
Mikael Calner
Keyword(s):  
High Resolution ◽  
Sea Level ◽  
Greenhouse Effect ◽  
Sedimentary Facies ◽  
Sea Level Changes ◽  
Secondary Result ◽  
Sedimentary Succession ◽  
Detailed Record ◽  
Quaternary Glaciations ◽  
Oceanic Model

ABSTRACTGraphic correlation using graptolites and conodonts provides a high-resolution timescale for correlating from coastal to deep oceanic sections and, thereby, also a detailed record of the sequence of changes during the Mulde Secundo-Secundo Event. That interval includes sedimentary facies otherwise unknown in older Wenlock to early Ludlow strata on Gotland. The identified sequence of changes includes a detailed record of, in order: two extinctions (Datum points 1 and 1·5); widespread deposition of carbon-rich sediments extensive enough to cause a δ13C increase of c. 4.8‰, the onset, maximum and end of a sea-level fall and rise of at least 16 m during 30 kyr; a third extinction (Datum 2); a disaster fauna; and a slow faunal recovery. Thus, a secondary result of the event was a weakened greenhouse effect triggering a glaciation: the Gannarve Glaciation (new term). The order of changes proves that regression did not cause the extinctions. Faunal and sea-level changes, as well as the sedimentary succession, fit well with predictions based on an oceanic model. Extinctions were primarily caused by a severe drop in primary planktonic productivity, causing starvation among planktonic larvae in non-coastal settings. The Grötlingbo Bentonite (new term), the thickest in the Wenlock of Gotland, was deposited across the basin shortly after Datum 2. Temporal resolution is high enough to permit some comparison with Quaternary glaciations.

scholarly journals River response to climate and sea level changes during the Late Saalian/Early Eemian in northern Poland – a case study of meandering river deposits in the Chłapowo cliff section

Geologos ◽  
2016 ◽  
Vol 22 (1) ◽  
pp. 1-14
Author(s):  
Damian Moskalewicz ◽  
Robert J. Sokołowski ◽  
Stanisław Fedorowicz
Keyword(s):  
Sea Level ◽  
River Sediments ◽  
Luminescence Dating ◽  
Heavy Minerals ◽  
Sea Level Changes ◽  
Point Bar ◽  
Meandering River ◽  
Base Level ◽  
River Deposits ◽  
And Sea Level

Abstract Fluvial sediments in the Chłapowo cliff section were studied in order to reconstruct their palaeoflow conditions and stratigraphical position. Lithofacies, textural and palaeohydraulic analyses as well as luminescence dating were performed so as to achieve the aim of study. Sedimentary successions were identified as a record of point bar cycles. The fluvial environment probably functioned during the latest Saalian, shortly after the retreat of the Scandinavian Ice Sheet. Discharge outflow was directed to the northwest. The river used the older fluvioglacial valley and probably was directly connected to the Eem Sea. Good preservation and strong aggradation of point-bar cycles were related to a rapid relative base level rise. The meandering river sediments recognised showed responses to climate and sea level changes as illustrated by stratigraphical, morphological and sedimentological features of the strata described. The present study also revealed several insights into proper interpretation of meandering fluvial successions, in which the most important were: specific lithofacies assemblage of GSt (St, Sp) → Sl → SFrc → Fm (SFr) and related architectural elements: channel/sandy bedforms CH/SB → lateral accretion deposits LA → floodplain fines with crevasse splays FF (CS); upward-fining grain size and decreasing content of denser heavy minerals; estimated low-energy flow regime with a mean depth of 1.6–3.3 m, a Froude number of 0.2–0.4 and a sinuosity of 1.5.

scholarly journals New Geomorphological and Historical Elements on Morpho-Evolutive Trends and Relative Sea-Level Changes of Naples Coast in the Last 6000 Years

Water ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2651 ◽  
Author(s):  
Gaia Mattei ◽  
Pietro Aucelli ◽  
Claudia Caporizzo ◽  
Angela Rizzo ◽  
Gerardo Pappone
Keyword(s):  
High Resolution ◽  
Sea Level ◽  
Digital Terrain Model ◽  
Optical Data ◽  
Sea Level Changes ◽  
Historical Sources ◽  
Relative Sea Level ◽  
Terrain Model ◽  
Digital Terrain ◽  
Geomorphological Map

This research aims to present new data regarding the relative sea-level variations and related morpho-evolutive trends of Naples coast since the mid-Holocene, by interpreting several geomorphological and historical elements. The geomorphological analysis, which was applied to the emerged and submerged sector between Chiaia plain and Pizzofalcone promontory, took into account a dataset that is mainly composed of: measurements from direct surveys; bibliographic data from geological studies; historical sources; ancient pictures and maps; high-resolution digital terrain model (DTM) from Lidar; and, geo-acoustic and optical data from marine surveys off Castel dell’ Ovo carried out by using an USV (Unmanned Surface Vehicle). The GIS analysis of those data combined with iconographic researches allowed for reconstructing the high-resolution geomorphological map and three new palaeoenvironmental scenarios of the study area during the Holocene, deriving from the evaluation of the relative sea-level changes and vertical ground movements of volcano-tectonic origin affecting the coastal sector in the same period. In particular, three different relative sea-level stands were identified, dated around 6.5, 4.5, and 2.0 ky BP, respectively at +7, −5, and −3 m MSL, due to the precise mapping of several paleo-shore platforms that were ordered based on the altimetry and dated thanks to archaeological and geological interpretations.

Influence of the "Hypsithermal Age" and "Neoglaciation" climatic conditions on the Brazilian coast.

2001 ◽  
Vol 28 (2) ◽  
pp. 213 ◽  
Author(s):  
KENITIRO SUGUIO
Keyword(s):  
United States ◽  
Gulf Of Mexico ◽  
Sea Level ◽  
Southeastern United States ◽  
Climatic Conditions ◽  
Brazilian Coast ◽  
Sea Level Changes ◽  
Relative Sea Level ◽  
Sea Levels ◽  
The Past

Meanwhile the highest relative sea-level is the present one in southeastern United States (Gulf of Mexico) or in Netherlands coast, most of the Brazilian coast exhibited Holocene sea-levels higher than the present in the past. The Brazilian curves, representing the relative sea-level changes during last 7.000 years, are outlined using sedimentological, biological and prehistorical past sea-level records. This paper shows that these relative sea-level records, during the Holocene, can be suitably used to demonstrate the influence of the worldwide known paleoclimatic events, like the “Hypsithermal Age” and “Neoglaciation” on the Brazilian coast.

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