A Drowned Lagunar Channel in the Southern Brazilian Coast in Response to the 8.2-ka Event: Diatom and Seismic Stratigraphy

Santos-Fischer, Cristiane Bahi dos; Weschenfelder, Jair; Corrêa, Iran Carlos Stalliviere; Stone, Jeffery R.; Dehnhardt, Beatriz Appel; Bortolin, Eduardo Calixto

doi:10.1007/s12237-018-0373-z

Cited by 18 publications

(4 citation statements)

References 117 publications

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“…That process causes the exposure and erosion of lagoon deposits on the shoreface due to landward migration of barriers on top of those deposits, as recorded in sectors of the Holocene Barrier IV, including the northern RSCP (Tomazelli & Villwock, 1991;Dillenburg, 1996;Campos et al, 2021;Lopes et al, 2022). The change from lagoon to fully marine environments is indicated by mixed Holocene assemblages of estuarine and marine invertebrates in Mirim and Patos Lagoons (Santos-Fischer et al, 2018;Lopes et al, 2021Lopes et al, , 2022. The available data, however, do not permit to infer the degree of temporal mixing, the proportion of reworked specimens, or their respective absolute ages.…”

Section: Discussionmentioning

confidence: 98%

Paleoecological characterization of ostracods in beachrocks from the Northern sector of the Rio Grande do Sul Coastal Plain, Brazil

Bergue¹,

Lopes²,

Caron³

et al. 2022

Rev. bras. paleontol.

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A micropaleontological analysis on 15 beachrock samples from the Northern sector of Rio Grande do Sul Coastal Plain (RSCP ), southern Brazil , revealed a relatively diverse and well-preserved ostracod assemblage composed of 16 species , including Cyprideis multidentata Hartmann, Callistocythere nucleoperiscum Whatley et al., Cytheretta punctata Sanguinetti, Caudites ohmerti Coimbra & Ornellas , and Argenticytheretta levipunctata Sanguinetti et al. Eleven ostracod species are left in open nomenclature or tentatively identified . Besides ostracods , some foraminifers , echinoderm spines, and fish remains (teeth) were also recovered ; however , the scarcity of specimens or poor preservation precluded identification at species level. Based on the Ostracoda taxonomic composition it is proposed that the beachrocks characterize environmentally condensed assemblages . This preliminary study reveals the importance and potentiality of micropaleontology for understanding the processes involved in the formation of beachrocks. Keywords: Pelotas Basin, Quaternary, coastal environments, micropaleontology, taphonomy.

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Section: Discussionmentioning

confidence: 98%

Paleoecological characterization of ostracods in beachrocks from the Northern sector of the Rio Grande do Sul Coastal Plain, Brazil

Bergue¹,

Lopes²,

Caron³

et al. 2022

Rev. bras. paleontol.

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“…The high accumulation rates reported in these channels for mid-Holocene (Bortolin 2017 represent the drowning of these systems, caused by a marine ingression, attested by the predominantly marine diatom assemblages (Santos-Fischer et al 2016). This sedimentary drowning occurred relatively fast at rates of 1.8 cm/year (8,040 ± 120 cal yr BP to 7,820 ± 140 cal yr BP), possibly as a consequence of the 8.2 ky BP Melt Water Pulse event (Gornitz 2007, Smith et al 2011, Bortolin 2017, Santos-Fischer et al 2018.…”

Section: Transgressive System Tractmentioning

confidence: 92%

“…The rates of muddy estuarine deposition were very high in some packages of the TST, reaching 1.8 cm/year (8,040 ± 120 cal yr BP to 7,820 ± 140 cal yr BP) at some locations (Bortolin 2017. This may be associated with periods of rapid sea level rise (Melt Water Pulses -MWP; Gornitz 2007, Smith et al 2011, Bortolin 2017, Santos-Fischer et al 2018 and are recorded by C-14 dating (Figs. 2 and 3).…”

Section: Transgressive System Tractmentioning

confidence: 99%

Incised valley paleoenvironments interpreted by seismic stratigraphic approach in Patos Lagoon, Southern Brazil

2018

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The Rio Grande do Sul (RS) coastal plain area (33,000 km 2) had its physiography modified several times through the Quaternary, responding to allogenic and autogenic forcings. The Patos Lagoon covers a significant area of RS coastal plain (10,000 km 2), where incised valleys were identified in previous works. About 1,000 km of high resolution (3.5 kHz) seismic profiles, radiocarbon datings, Standard Penetration Test (SPT) and gravity cores were analyzed to interpret the paleoenvironmental evolution as preserved in incised valley infills. Seismic facies were recognized by seismic parameters. The sediment cores were used to ground-truth the seismic interpretations and help in the paleoenvironmental identification. Key surfaces were established to detail the stratigraphical framework, and seismic facies were grouped into four seismic units, which one classified in respective system tracts within three depositional sequences. The oldest preserved deposits are predominantly fluvial and estuarine facies, representing the falling stage and lowstand system tracts. The Holocene transgressive records are dominated by muddy material, mainly represented by estuarine facies with local variations. The transgression culminated in Late Holocene deposits of Patos Lagoon, representing the highstand system tract. The depositional pattern of the vertical succession was controlled by eustatic variations, while the autogenic forcing (paleogeography and sediment supply) modulated the local facies variation.

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“…Such a centennial cold event has been regarded as a global climatic reversal during the early Holocene (Mayewski et al, 2004;Wanner et al, 2011); it was not restricted to Greenland (Alley and Agustsdottir, 2005) and other high-latitude northern hemisphere regions (Daley et al, 2011;Eddudóttir et al, 2018), but also occurred in many low-to mid-latitude regions (Wu et al, 2012;Dixit et al, 2014;Schemmel et al, 2016;Peckover et al, 2019), and even in some areas of the southern hemisphere (Sallun et al, 2012;dos Santos-Fischer et al, 2018;Voarintsoa et al, 2019). This global 8.2 ka event has been the focus of considerable research and has been well-documented in all research associated with cold events that occurred during the early Holocene.…”

Section: Introductionmentioning

confidence: 99%

Phytolith records of flourishing early Holocene Pooideae linked to an 8.2 ka cold event in subtropical China

Zuo

Lü

et al. 2020

Elem Sci Anth

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The grass subfamily Pooideae originated in a temperate niche during the late Cretaceous; it is the largest Poaceae subfamily, consisting of almost 4,000 species, which are distributed worldwide. Pooideae responses to climate changes at different time scales, and different ecological zones are thus important in understanding Poaceae evolutionary processes and their relationship with climate change. In the study described in this article, we reconstructed Pooideae variability during the early Holocene, as inferred by a phytolith sequence from the Lower Yangtze in subtropical China. The phytolith assemblage was marked by three increases in Pooideae phytoliths, dated to ca 8.4–8.0, 7.8–7.6, and 7.4–7.2 ka BP (before present, 1950 AD), with each representing pronounced increases in Pooideae extent and distribution. All these increases were within age ranges that agreed well with the timing of weak Asian Monsoon events, at 8.2, 7.7, and 7.3 ka BP. The first Pooideae flourishing period in subtropical China was the most significant, lasting for approximately four centuries and being characterized by a double peak, which equated with an event at 8.2 ka. This suggested that cold and/or dry conditions—which occurred over a period of several hundred years and were linked to weakening of the Asian monsoon—probably caused Pooideae to flourish in the Lower Yangtze region. Comparison of two diagnostic trapezoid phytolith types—namely wavy and wavy narrow—which showed different changes between ca 8.4 and 8.0 ka BP, suggested that they responded differently to the climate change represented by the 8.2 ka event. Our phytolith records have provided not only new data clarifying the detailed Pooideae response to the 8.2 ka event but also a reliable index for past cold climates in subtropical China.

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A Drowned Lagunar Channel in the Southern Brazilian Coast in Response to the 8.2-ka Event: Diatom and Seismic Stratigraphy

Cited by 18 publications

References 117 publications

Paleoecological characterization of ostracods in beachrocks from the Northern sector of the Rio Grande do Sul Coastal Plain, Brazil

Paleoecological characterization of ostracods in beachrocks from the Northern sector of the Rio Grande do Sul Coastal Plain, Brazil

Incised valley paleoenvironments interpreted by seismic stratigraphic approach in Patos Lagoon, Southern Brazil

Phytolith records of flourishing early Holocene Pooideae linked to an 8.2 ka cold event in subtropical China

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