BIOINDICATORS OF SEA-LEVEL FLUCTUATIONS IN SOUTHEASTERN BRAZIL: NEW DATA AND METHODOLOGICAL REVIEW

Radiocarbon ◽  
2021 ◽  
pp. 1-15
Author(s):  
Julia Caon Araujo ◽  
Kita Chaves Damasio Macario ◽  
Vinícius Nunes Moreira ◽  
Anderson dos Santos Passos ◽  
Perla Baptista de Jesus ◽  
...  
Keyword(s):  
Sea Level ◽  
Late Holocene ◽  
Data Interpretation ◽  
Progressive Increase ◽  
Southeastern Brazil ◽  
Recrystallization Process ◽  
Sea Level Changes ◽  
Sea Level Fluctuations ◽  
Data Gap ◽  
Current Zero

ABSTRACT The vermetidae fossils of Petaloconchus varians, formed by calcium carbonate, associated with their radiocarbon ages, are the most accurate indicators of paleo sea level due to their restricted occupation in the intertidal zone in the rocky shore. However, the recrystallization of minerals can affect these age calculations and, consequently, the interpretation of the data. The aim of this study is to present new indicators of paleo sea-level changes in Southeast Brazil for the last 6000 years contributing to fill the data gap for the late Holocene. The influence of the recrystallization process was successfully resolved using the CarDS protocol, enabling the separation of the original aragonite fraction by density, prior to radiocarbon dating. This avoids the rejuvenation of ages and ensures greater efficiency for data interpretation. Paleo sea-level indicators were able to show a progressive increase in sea level up to the transgressive maximum of 4.15 m in 3700 BP years, followed by a regression to the current zero. This regression seems to have in addition, here we reinforce the reliability of the use of fossil vermetids as indicators of sea-level fluctuations.

A multi-proxy evidence for the transition from estuarine mangroves to deltaic freshwater marshes, Southeastern Brazil, due to climatic and sea-level changes during the late Holocene

CATENA ◽  
2015 ◽  
Vol 128 ◽  
pp. 155-166 ◽  
Author(s):  
Marlon C. França ◽  
Igor Charles C. Alves ◽  
Darciléa F. Castro ◽  
Marcelo C.L. Cohen ◽  
Dilce F. Rossetti ◽  
...  
Keyword(s):  
Sea Level ◽  
Late Holocene ◽  
Southeastern Brazil ◽  
Sea Level Changes ◽  
Freshwater Marshes ◽  
And Sea Level

Palaeoclimatic and sea-level fluctuations from the last deglaciation to late Holocene from western India: evidence from multiproxy studies

2021 ◽  
pp. 104777
Author(s):  
Rachna Raj ◽  
Jayant K. Tripathi ◽  
Pankaj Kumar ◽  
Saurabh K. Singh ◽  
Binita Phartiyal ◽  
...  
Keyword(s):  
Sea Level ◽  
Late Holocene ◽  
Western India ◽  
Last Deglaciation ◽  
Sea Level Fluctuations ◽  
The Last Deglaciation ◽  
And Sea Level

Middle to late-Holocene decreased fluvial aggradation and widespread peat initiation in the Ishikari lowland (northern Japan)

The Holocene ◽  
2016 ◽  
Vol 26 (12) ◽  
pp. 1924-1938 ◽  
Author(s):  
Yuji Ishii ◽  
Kazuaki Hori ◽  
Arata Momohara ◽  
Toshimichi Nakanishi ◽  
Wan Hong
Keyword(s):  
Sea Level ◽  
Late Holocene ◽  
Climate Changes ◽  
Asian Summer Monsoon ◽  
Sedimentary Environment ◽  
New Approach ◽  
Sea Level Fluctuations ◽  
Asian Summer ◽  
Fluvial Sedimentation ◽  
Northern Japan

This study investigated the influence of sea-level and climate changes on the decreased fluvial aggradation and subsequent widespread peat initiation in the middle to late-Holocene in the Ishikari lowland, which is a coastal floodplain formed in response to the postglacial sea-level change. By introducing a new approach to separately evaluate the rates of organic and clastic sediment input, we demonstrated that the peat began to form when the fluvial sedimentation rate was significantly decreased (less than 0.6 mm/yr), while plant macrofossil analysis suggested that lowering of water level is also important to the peat initiation. Such changes in sedimentary environment may be associated with the abrupt abandonment of crevasse splays. The concentrated ages of the peat initiation around 5600–5000, 4600–4300, and 4100–3600 cal. BP suggest that an allogenic control promoted the abandonment of crevasse splays, and different onset ages can be explained by different fluvial responses of the Ishikari River and its tributaries. The abandonment of crevasse splays could result from sea-level fall or decreased precipitation. While submillennial sea-level fluctuations coincident with the peat initiation have not been reported in coastal lowlands of Japan, the close comparison of the onset ages and decreased precipitation recorded in a stalagmite from China, which represents the strength of the East Asian summer monsoon (EASM), suggests that decrease in precipitation led to the abandonment of crevasse splays. Our results may indicate that similar fluvial responses might be common in other coastal floodplains affected by the EASM.

Impacts of sea-level changes on mangroves from southeastern Brazil during the Holocene and Anthropocene using a multi-proxy approach

Geomorphology ◽  
2021 ◽  
pp. 107860
Author(s):  
Bettina S. Bozi ◽  
Beatriz L. Figueiredo ◽  
Erika Rodrigues ◽  
Marcelo C.L. Cohen ◽  
Luiz C.R. Pessenda ◽  
...  
Keyword(s):  
Sea Level ◽  
Southeastern Brazil ◽  
Sea Level Changes ◽  
The Holocene

scholarly journals Late Holocene relative sea level changes in SW Crete: evidence of an unusual earthquake cycle

1996 ◽  
Vol 39 (3) ◽  
Author(s):  
S. C. Stiros
Keyword(s):  
Sea Level ◽  
Late Holocene ◽  
Hanging Wall ◽  
Earthquake Cycle ◽  
Sea Level Changes ◽  
Land Uplift ◽  
Unusual Pattern ◽  
Wide Range ◽  
Coastal Changes ◽  
Seismic Deformation

Coastal challenges ill West Crete ill the last 4000 years can be described as a series of 11 relatively small (25 cm on the average) land subsidences alternating with short (150-250 year long) relatively still stands of the sea level. At 1500 B.P. an up to 9 m episodic relative land uplift and tilting of this part of the island occurred, but since then no significant coastal changes have been identified. There is strong evidence that these Late Holocene coastal changes are not a product of fluctuations of sea level, but reflect palaeoseismic events. The sequence of the latter is at variance with models of seismic deformation deduced from a wide range of observations in different tectonic environments, including coastal uplifts near major trenches: according to these models, strain buildup and release through earthquakes is described as a cyclic and rather uniform process, the earthquake cycle. In this process, the permanent seismic deformation accumulates after each earthquake to produce geological features, while the long-term deformation rate is approximately equal to the short term one. Obviously this is not the case with West Crete. The unusual pattern of seismic deformation in this island has been observed in other cases as well, but its explanation is not easy. The juxtaposition of different earthquake cycles, variations in the source and rate of stress or internal deformation of the uplifted hanging wall of a thrust in the pre-seismic period are some possible explanations for this unusual pattern of earthquake cycle in Greece.

Late Holocene sea-level changes and isostasy in western Denmark

2006 ◽  
Vol 66 (2) ◽  
pp. 288-302 ◽  
Author(s):  
W. Roland Gehrels ◽  
Katie Szkornik ◽  
Jesper Bartholdy ◽  
Jason R. Kirby ◽  
Sarah L. Bradley ◽  
...  
Keyword(s):  
Salt Marsh ◽  
Sea Level ◽  
Salt Marshes ◽  
Late Holocene ◽  
Glacial Isostatic Adjustment ◽  
Sea Level Changes ◽  
Relative Sea Level ◽  
Isostatic Adjustment ◽  
Tidal Embayment ◽  
Made In

AbstractCores and exposed cliff sections in salt marshes around Ho Bugt, a tidal embayment in the northernmost part of the Danish Wadden Sea, were subjected to 14C dating and litho- and biostratigraphical analyses to reconstruct paleoenvironmental changes and to establish a late Holocene relative sea-level history. Four stages in the late Holocene development of Ho Bugt can be identified: (1) groundwater-table rise and growth of basal peat (from at least 2300 BC to AD 0); (2) salt-marsh formation (0 to AD 250); (3) a freshening phase (AD 250 to AD 1600?), culminating in the drying out of the marshes and producing a distinct black horizon followed by an aeolian phase with sand deposition; and (4) renewed salt-marsh deposition (AD 1600? to present). From 16 calibrated AMS radiocarbon ages on fossil plant fragments and 4 calibrated conventional radiocarbon ages on peat, we reconstructed a local relative sea-level history that shows a steady sea-level rise of 4 m since 4000 cal yr BP. Contrary to suggestions made in the literature, the relative sea-level record of Ho Bugt does not contain a late Holocene highstand. Relative sea-level changes at Ho Bugt are controlled by glacio-isostatic subsidence and can be duplicated by a glacial isostatic adjustment model in which no water is added to the world's oceans after ca. 5000 cal yr BP.

Subsurface geological imaging of northeastern Tunisia during the middle to the upper Eocene: Insights from integrated geophysical interpretation

2021 ◽  
pp. 1-64
Author(s):  
Oussama Abidi ◽  
Kawthar Sebei ◽  
Adnen Amiri ◽  
Haifa Boussiga ◽  
Imen Hamdi Nasr ◽  
...  
Keyword(s):  
Sea Level ◽  
Regional Scale ◽  
Upper Eocene ◽  
Sea Level Changes ◽  
Seismic Profiles ◽  
Borehole Data ◽  
Third Order ◽  
Good Correspondence ◽  
Basin Inversion ◽  
Sea Level Fluctuations

The Middle to Upper Eocene series are characterized by multiple hiatuses related to erosion, non-deposition or condensed series in the Cap Bon and Gulf of Hammamet provinces. We performed an integrated study taking advantage from surface and subsurface geology, faunal content, borehole logs, electrical well logs, vertical seismic profiles and surface seismic sections. Calibrated seismic profiles together with borehole data analysis reveal unconformities with deep erosion, pinchouts, normal faulting and basin inversion which are dated Campanian, intra-Lutetian and Priabonian compressive phases; these events were also described at the regional scale in Tunisia. Tectonics, sea level fluctuations and climate changes closely controlled the depositional process during the Middle to Upper Eocene time. The depositional environment ranges from internal to outer platform separated by an inherited paleo-high. We determine eight third order sequences characterizing the interaction between tectonic pulsations, sea level changes and the developed accommodation space within the Middle to Upper Eocene interval. We correlate the obtained results of the Cap Bon-Gulf of Hammamet provinces with the published global charts of sea-level changes and we find a good correspondence across third order cycles. Model-based 3D inversion proved to be a solution to model the lateral and vertical lithological distribution of the Middle to Upper Eocene series.

scholarly journals Aquifer-eustasy as the main driver of short-term sea-level fluctuations during Cretaceous hothouse climate phases

2019 ◽  
Vol 498 (1) ◽  
pp. 9-38 ◽  
Author(s):  
Benjamin Sames ◽  
M. Wagreich ◽  
C. P. Conrad ◽  
S. Iqbal
Keyword(s):  
Sea Level ◽  
Phase Relationship ◽  
Sea Level Changes ◽  
Short Term ◽  
Groundwater Levels ◽  
Sequence Stratigraphic ◽  
Sea Level Fluctuations ◽  
Minimum Estimate ◽  
Underlying Mechanisms ◽  
Continental Ice Sheets

AbstractA review of short-term (<3 myr: c. 100 kyr to 2.4 myr) Cretaceous sea-level fluctuations of several tens of metres indicates recent fundamental progress in understanding the underlying mechanisms for eustasy, both in timing and in correlation. Cretaceous third- and fourth-order hothouse sea-level changes, the sequence-stratigraphic framework, are linked to Milankovitch-type climate cycles, especially the longer-period sequence-building bands of 405 kyr and 1.2 myr. In the absence of continental ice sheets during Cretaceous hothouse phases (e.g. Cenomanian–Turonian), growing evidence indicates groundwater-related sea-level cycles: (1) the existence of Milankovitch-type humid-arid climate oscillations, proven via intense humid weathering records during times of regression and sea-level lowstands; (2) missing or inverse relationships of sea-level and the marine δ18O archives, i.e. the lack of a pronounced positive excursion, cooling signal during sea-level lowstands; and (3) the anti-phase relationship of sea and lake levels, attesting to high groundwater levels and charged continental aquifers during sea-level lowstands. This substantiates the aquifer-eustasy hypothesis. Rates of aquifer-eustatic sea-level change remain hard to decipher; however, reconstructions range from a very conservative minimum estimate of 0.04 mm a−1 (longer time intervals) to 0.7 mm a−1 (shorter, probably asymmetric cycles). Remarkably, aquifer-eustasy is recognized as a significant component for the Anthropocene sea-level budget.

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