Marine Incursion Research Articles

Marine influence during deposition of the Kiliranjao Brown Shale, Central Sumatra, from palynology point of view

The Eocene to Oligocene succession of the Kiliranjao Brown Shale was deposited in a lacustrine environment. This study combines palynological analysis and XRD analysis technique to investigate the possibility of marine influence during deposition of Kiliranjao lacustrine shale. Two biostratigraphic zonations of Karbindo section are Middle to Late Eocene Proxapertites operculatus Zone and Oligocene Meyeripollis naharkotensis Zone. The marine flooding surface, as shown by the peak of the abundance of mangrove pollen, is used to delineate the section into five parasequences. The tripartite stratigraphic architecture of Karbindo section is consists of early rift deposit (TS1), syn-rift deposit (TS2), and syn-rift deposit (TS3). Middle to Late Eocene coal and limestone facies (parasequence I) represents the TS1. Late Eocene to Oligocene parasequence II to IV (below MFS) shows the TS2 (deepening-upward lacustrine succession), and the shallowing-upward lacustrine succession of Oligocene parasequence V (above MFS) indicate the TS3. The abundance of mangrove and back mangrove palynomorph assemblages and the high amount of carbonate mineral from XRD analysis are the evidence of marine influence to the deposition of Karbindo section Brown Shale. The marine incursion to the lacustrine environment occurred from the adjacent nearby open sea, that separated by shoal area, which can submerge below sea level during a marine transgressive event. Marine incursion events did contribute to the deposition of Kiliranjao Brown Shale though further work is still needed.

Early to middle Holocene rice cultivation in response to coastal environmental transitions along the South Hangzhou Bay of eastern China

South Hangzhou Bay (SHB) in eastern China is one of the regions where agriculture began in the early Holocene. To better understand how farming-based societies developed in this region, we examined pollen, charcoal, foraminifera and grain size information of a well-dated sediment core (YJ1503) in the Yaojiang Valley (YJV). Pollen assemblages show that before 8600 cal yr BP, Pinus, Quercus, Juglans and Pterocarya woodlands were dominant. During ca.8600–8400 cal yr BP, abundant foraminifera suggest a transient marine incursion. Although the former woodland species re-established during 8400–7600 cal yr BP, freshwater algae and dinoflagellates indicate a transition to brackish environments. Two peaks of charcoal at around 8200 and 7800 cal yr BP, are possible early signs of human occupation that pre-dated the Hemudu Culture. After 7600 cal yr BP, an increase of salt-tolerant herbs including Chenopodiaceae, Cyperaceae and Poaceae (<35 μm) and a decrease of dinoflagellate and foraminifera assemblages, imply a reduction in saline influence. Freshwater wetlands established around 6600 cal yr BP as indicated by increasing Typha and diminishing Chenopodiaceae pollen. This coincided with a sharp decline in Pinus pollen, marked increases of Poaceae pollen and a rise in charcoal suggesting more activity of human communities. Rice cultivation is confirmed by archaeological findings from this interval, with two distinctive periods at ca. 6600–6300 and 5500–5200 cal yr BP. The initial coastal land development started as early as 7800–7600 cal yr BP in the YJV, which was concurrent with that happened at the apex of SHB where the Kuahuqiao Culture originated, but rice farming trajectory at these two places differed. In the Kuahuqiao area, low salinity coastal settings developed, freshened by the discharge of the Qiantang River,and this area would have been especially suitable for agriculture. In contrast, in the YJV, early rice cultivation was possibly hampered by longer episodes of brackish intrusion during time of lower discharge of the Yaojiang River until a freshwater environment prevailed after ca. 7000 cal yr BP.

Holocene climate pulses and structural controls on the geomorphological estuarine evolution of the Iguape River, São Paulo, Brazil

The Iguape River estuary – located on the southern coast of São Paulo state (Brazil) – presents geomorphological records of the complex processes operating during the Late Holocene. Dating the top deposits of coastal (fluvial, transition and marine deposits) low terraces, contributes to the understanding of the erosive-depositional events resulting from autogenic and allogenic processes. Optically stimulated luminescence (OSL) dating, grain-size and morphostructural analysis were used to investigate the Late Holocene geomorphological evolution of the Iguape estuary. The results suggest that formation of the Iguape estuary is consistent with a marine incursion triggered by climate pulses by around 2.7 ka. However, the coastline displacement was controlled by base-level adjustments and fluvial incision phases probably induced by fault activity associated with the Guapiara Lineament. Finally, the results show that the estuarine systems in humid tropical regions are significantly sensitive to short time-scale climate events during the Holocene.

Ages and stratigraphical architecture of late Miocene deposits in the Lorca Basin (Betics, SE Spain): New insights for the salinity crisis in marginal basins

Unlike most Neogene basins of the Betic Cordillera where the Salinity Crisis is dated to the Messinian, a contradictory Tortonian dating was proposed for evaporites of the Lorca Basin. As a consequence, complex structural models have been proposed in the literature to explain this discrepancy in the timing of evaporites. In order to integrate the Lorca Basin into the geological context of the western Mediterranean domain during the Late Miocene, new sedimentological and stratigraphical studies coupled with new dating were performed, which allow us to propose a Messinian age for both diatomite-bearing deposits and evaporites of the Lorca Basin. These new ages challenge the idea of a Tortonian salinity crisis in the Lorca Basin. Three main events of base-level drop were evidenced during the Messinian. Each event is correlated with successive steps of basin restriction. Shallow salina evaporites were deposited after a base-level fall during the Messinian before a final base-level drop, which led to the entire exposure of the basin. This last exposure is interpreted as coeval with the deposition of first evaporites and halite in the deep Mediterranean basins. The reflooding which allowed the deposition of brackish deposits and a short-lived marine incursion occurred at the end of the Messinian. Base-level drops occurred during eustatic falls amplified by the gradual uplift of the Betic Cordillera. The exhumation of the Tercia ridge along the strike-slip Alhama de Murcia fault system during the Messinian probably favoured the gradual restriction of the basin. A discussion on correlations of main unconformities between several Neogene basins of the Betics is proposed, suggesting a similar structural evolution at the regional scale.

A geochemical approach for identifying marine incursions: Implications for tsunami geology on the Pacific coast of northeast Japan

Potential tsunami inundation areas can be predicted by the distribution of paleo tsunami deposits on land, which are mainly composed of marine-derived sands and muds. These exotic sandy and muddy layers have been identified by multiple approaches. However, there still remain uncertainties regarding the sources and weathering trends over the long term, and other useful proxies need to be investigated to identify of tsunami deposits. We examined the geochemical signatures of modern tsunami deposits from the Pacific coast of northeast Japan (2011 Tohoku tsunami) and those paleo tsunami deposits taken from the Tohoku District (Jogan, ~1080 calibrated ages before present [cal BP] and Yayoi, ca. 2000 cal BP). A geochemical ternary diagram (Seawater-Rock-(As + Metals)) showed the weathering trends of tsunami deposits over approximately 2000 years in the Sendai plain in the Tohoku. In the tsunami layers from the Tohoku, the Na/Ti atomic ratios markedly increased to 23.4 with an average value of 19.3 ± 3.0 (Jogan and Yayoi tsunami deposits), which was clearly higher than those of other layers (soil deposits, 10.3 ± 3.5 on average). These results show that Na/Ti ratios and other geochemical proxies are useful indicators of marine incursions in our case, and may contribute to the detection of muddy tsunami deposits close to the limit of inundation.

Using multiple environmental proxies and hydrodynamic modeling to investigate Late Holocene climate and coastal change within a large Gulf of Mexico estuarine system (Mobile Bay, Alabama, USA)

A high degree of uncertainty exists for understanding and predicting coastal estuarine response to changing climate, land-use, and sea-level conditions, leaving geologic records as a best-proxy for constraining potential outcomes. With the majority of the world's population focused in coastal regions, understanding how local systems respond to global, regional, and even local pressures is key in developing mitigation, adaptation, and management plans. The geomorphology of Mobile Bay in southeast Alabama (USA) has evolved considerably (e.g., bayhead delta back-stepping) over the late Holocene in response to global and regional sea-level and climate change. Smaller-scale geomorphic changes (e.g., spit and beach ridge development) have also had a significant influence on the evolution of the estuary. Organic matter characteristics, inorganic sediment geochemistry, benthic microfossils, and pollen in a ~ 3500 cal yr BP sediment sequence recovered in a gravity core (20GC) from Bon Secour Bay, a small sub-bay in the southeast corner of Mobile Bay, record time-varying marine influence. Increases in marine influence during ~3500 to 2300 cal yr BP and 1930 to 1160 cal yr BP are defined as zones with high-density and pre-dominantly calcareous foraminiferal species, abundant sand (>10%) and more marine-like geochemical signatures, which contrast the low-density and pre-dominantly agglutinated foraminiferal and more terrestrially influenced estuarine muds observed in other intervals of the sedimentary record (2300–1930 and 1160–400 cal yr BP) and the modern bay. Hydrodynamic models constrained by geomorphic boundary conditions for the time ~ 3500 cal yr BP, consistent with the most prominent marine-influenced sediment, provide insight to potential coastal configuration that might have permitted such marine water intrusion into the bay. Of several scenarios evaluated, a breach in Morgan Peninsula produces tidal circulation within the basin supportive of persistent marine incursions in the bay between ~3500 to 2300 cal yr BP. The findings show that slight variations in coastal configuration can have broad-scale effects on bays and estuaries with consequences that may relate to water quality, vertebrate and invertebrate habitat, and coastal vulnerability to episodic events like (extra)tropical storms.

Saline Waters in Miocene Western Amazonia – An Alternative View

Before the onset of the modern Amazon River system, north-western South America was shaped by an extensive wetland during the Miocene. This ‘Pebas mega-wetland’ kept a well renowned endemic mollusk and ostracod fauna, which initiated a persisting debate about marine ingressions reaching the center of Amazonia at that time. Due to high endemism, uniformitarian principles are hardly applicable to this biota but also other paleontological, sedimentological and geochemical information led to ambiguous palaeoenvironmental interpretations. Here, we investigate the ostracod and foraminifer assemblages and the O/C-stable isotopy of their biogenic calcite from an outcrop at the cutbank of the Amazon River (NE-Peru, ~55 km S of Iquitos). While ostracods (e.g., Cyprideis) are able to calcify their carapaces along the entire salinity range, at least low saline conditions are a prerequisite for the biomineralization of calcareous foraminiferan tests. Hence, the finding of calcareous foraminifers (Ammonia, Elphidium), associated mainly with brackish water ostracods, indicates the presence of saline waters. In contrast, δ18O- and δ13C-analyses performed on co-occurring ostracod valves and foraminiferan tests yielded constantly very light ratios. Such values refer to a pure freshwater environment and are incompatible with the interference of isotopically heavier, marine waters or an evaporative stable isotope enrichment. Based on these opposing data, we hypothesize that the Pebas mega-wetland was episodically influenced by mineralized but isotopically light groundwater discharge. Possibly, the resulting specific hydrochemistry contributed not only to the evolution of the endemic Pebasian fauna but also facilitated the sporadic settlement of euryhaline foraminifers, which mimics short-lived marine incursions.

Basin-scale stratigraphic correlation of late Pleistocene-Holocene (MIS 5e-MIS 1) strata across the rapidly subsiding Po Basin (northern Italy)

Eight stratigraphic transects, 40–140 km long reveal, for the first time on a regional scale, a comprehensive picture of facies architecture of the highly preserved Late Pleistocene-Holocene sedimentary succession from the rapidly subsiding Po Basin. Facies analysis and pollen-based correlation, supported by radiocarbon, electron-spin resonance and optically stimulated luminescence dates, enabled the attribution of distinct stratigraphic intervals to Marine Isotope Stages (MIS) 6 to 1.Basin-scale facies changes appear to have been driven mostly by glacio-eustatic oscillations falling in the Milankovitch band (∼100 ky). The MIS 5e coastal wedge was tracked continuously beneath the modern shoreline, for over 110 km along strike. Along-dip (west-east) stratigraphic correlation over 140 km revealed the characteristic landward transition from shallow-marine and coastal facies to lagoonal, swamp, and floodplain deposits.The MIS 5d-MIS 2 stratigraphic succession, up to 95-m-thick, records the stepped, basinward shift of facies related to the post-MIS 5e sea-level fall. In particular, lagoon and swamp facies mark minor transgressions (Substages 5c and 5a), whereas thick floodplain deposits and laterally extensive (>40 km) fluvial channel-belts, up to 30 m thick, characterized the glacial periods (MIS 4 and MIS 2).The Holocene (MIS 1) coastal wedge shares many similarities in terms of facies architecture and geometry with its MIS 5e counterpart, though maximum landward marine incursion during the MIS 5e transgression was 10 km farther inland (36 km inland of modern shoreline). Organic-rich (freshwater swamp) environments developed > 100 km landwards of the present-day coastline.The MIS 5e-MIS 1 succession of the Po Basin displays an exceptional thickness, up to 130 m. Minimum values (∼20 m) are recorded close to the Apennine margin and above the buried actively growing anticlines. The spatial distribution and geometry of the MIS 5e-MIS 1 strata, as well as rapidly varying subsidence rates (from 0.2 to 1.0 mm/y) reflect the strong influence of the structural setting (location of major thrust fronts) over the creation/destruction of accommodation.

Application of organic facies and biomarkers in characterization of paleoenvironmental conditions and maturity of sediments from the Codó Formation in the west-central part of the São Luís Basin, Brazil

Paleoenvironmental conditions of the sediments of the Cretaceous Codó Formation in Brazil are still being debated. The main point of controversy is whether they were deposited in a strictly marine environment or under lacustrine conditions of varying salinity. In this study, organic facies and biomarker analyses were performed on samples from the Codó Formation in the São Luís Basin, northwest Brazil, to reconstruct the paleoenvironmental conditions, the origin, and the thermal maturity of the organic matter. Four types of palynofacies associations (PI – amorphous organic matter, PII – amorphous organic matter+sporomorphs, PIII – phytoclasts, and IV – marine palynomorphs) were identified. The total organic carbon (TOC) content exhibits a strong correlation (ρ = 0.75, p < .05) with amorphous organic matter (AOM) content suggesting that AOM is the main factor controlling TOC in the stratigraphic section, and that increases in the AOM contribution were associated with an increase in the water column and expansion of reducing conditions that favored organic matter preservation. The TOC and total sulfur (TS) plots suggest that there were salinity variations in the depositional environment. The identification of marine palynomorphs (Subtilisphaera genus) are indicative of several local marine incursions. The n-alkane distribution (unimodal and bimodal) confirmed the presence of strong input of higher plant components (phytoclast-dominated Palynofacies III) and the bacterially-reworked organic material (Palynofacies I/II). The aquatic terrestrial (ATR), terrigenous/aquatic (TAR), and proxy for aquatic macrophytes (Paq) ratios suggest autochthonous (Palynofacies I and II) and allochthonous (Palynofacies III) organic matter, and eutrophic and submerged-floating plants. Based on palynofacies associations and biomarkers we conclude that the depositional environment ranged from an anoxic/reducing to dysoxic/oxic within a closed-lacustrine system having a stratified water column. High evaporation rates favored a decrease in the water column and an increase in salinity, allowing the precipitation of salt by evaporation (CaCO3 > 80%). The thermal maturity indicators including vitrinite reflectance (%Ro), spore color index (SCI), Ts/(Ts + Tm) ratios, and C29 20S/(20S + 20R) and C29 ββ/(αα + ββ) indicate that the organic matter is immature to marginally mature.

Tectonic controls on the Maastrichtian-Danian transgression in the Magallanes-Austral foreland basin (Chile): Implications for the growth of the Southern Patagonian Andes

The Maastrichtian-Danian transgression was one of the most extensive Atlantic-derived marine incursions in Patagonia. This study examines its stratigraphic record and origin in the Magallanes-Austral Basin, revealing an interplay of sedimentation, tectonism, and base-level changes, which contribute to our understanding of foreland basin dynamics. We present a multidisciplinary approach from a relatively poorly documented sector (51°38′-53°50′S) of the basin. This approach includes facies and provenance analysis, palynology, sequence stratigraphy, and U-Pb geochronology. These techniques enable us to evaluate the role of climate, tectonics, and eustasy on the transgression, as well as providing insight into the growth of the Southern Patagonian Andes. A first shallowing-upward cycle (late Campanian to late Maastrichtian) is represented by the transition from outer shelf and upper slope deposits (Fuentes and Tres Pasos formations) to shoreface and deltaic environments (Rocallosa and Dorotea formations), favoured by high erosion rates in the fold-thrust belt and eustatic sea-level drop. A subsequent deepening-upward cycle (late Maastrichtian to Paleocene) records the Atlantic transgression, manifested by estuarine deposits in an incised valley (uppermost Dorotea Formation) and deep-water turbidites (Chorrillo Chico Formation and Cabo Naríz beds). Palynological results suggest a temperate palaeoclimate (~6–17 °C) during the Maastrichtian-Danian, which agrees with significant cooling of the South Atlantic Ocean at this time. Therefore, relative climatic optima are not a driver of marine ingression. The stratigraphic and tectonic evolution of the succession studied suggests that flexural and dynamic subsidence promoted marine incursion into the Magallanes-Austral Basin. Provenance data indicate sediment input to the basin from the Southern Patagonian Batholith, Rocas Verdes Basin remnants, Tobífera Formation, and metamorphic terranes exposed in the hinterland of the Southern Patagonian Andes during the early Maastrichtian. However, by the Paleocene, sediments derived from the hinterland had been structurally dammed during basinward propagation of the fold-thrust belt.

Age of the earliest transgressive event in the Krishna-Godavari Basin, India: evidence from dinoflagellate cysts and planktonic foraminifera biostratigraphy

A combined biostratigraphic study of dinoflagellate cysts and foraminifera was carried out on Early Cretaceous subsurface well cutting sediments from well A (DNG) (2800–2746 m depth) from the Krishna-Godavari Basin, India. The last appearance datum of marker species of dinoflagellate cysts and planktonic foraminifera was considered for the construction of the biostratigraphic framework. The study shows dominance of Early Cretaceous marker dinoflagellate cysts Cassiculosphaeridia magna, Cribroperidinium perforans, Hystrichodinium voigtii, Kleithriasphaeridium eoinodes, and planktonic foraminifera Hedbergella aptiana, Hedbergella mitra, Hedbergella praelippa, Hedbergella tardita, Microhedbergella miniglobularis and Hedbergella mitra species. In addition to this, the dinoflagellate cyst data were compared with the dinoflagellate biozones of Austral and Tethyan provinces. Based on earlier micropalaeontological records from the Krishna-Godavari Basin and the present study, a latest Barremian-early Aptian age has been determined for the earliest marine transgression in the Krishna-Godavari Basin. The early marine incursion during late Barremian-earliest Aptian in the Krishna-Godavari Basin compared to Albian age in Cauvery Basin suggests the opening of east coast from north to south.

Systematic Review Shows That Work Done by Storm Waves Can Be Misinterpreted as Tsunami-Related Because Commonly Used Hydrodynamic Equations Are Flawed

Coastal boulder deposits (CBD), transported by waves at elevations above sea level and substantial distances inland, are markers for marine incursions. Whether they are tsunami or storm deposits can be difficult to determine, but this is of critical importance because of the role that CBD play in coastal hazard analysis. Equations from seminal work by Nott (1997), here referred to as the Nott Approach, are commonly employed to calculate nominal wave heights from boulder masses as a means to discriminate between emplacement mechanisms. Systematic review shows that this approach is based on assumptions that are not securely founded and that direct relationships cannot be established between boulder measurements and wave heights. A test using an unprecedented dataset of boulders moved by storm waves (with associated sea-state data) shows a lack of agreement between calculations and actual wave heights. The equations return unrealistically large heights, many of which greatly exceed sea states occurring during the boulder-moving storms. This underscores the finding that Nott-Approach wave-height calculations are unreliable. The result is general, because although the field data come from one region (the Aran Islands, Ireland), they represent a wide range of boulder masses and topographic settings and present a valid test of hydrodynamic equations. This analysis demonstrates that Nott Approach equations are incapable of distinguishing storm waves from tsunami transport and that wave heights hindcast from boulder masses are not meaningful. Current hydrodynamic understanding does not permit reliable computation of wave height from boulder measurements. A combination of field, numerical, and experimental approaches is required to quantify relationships between wave power and mass transport onshore. Many CBD interpreted as tsunami deposits based on Nott-Approach analysis may in fact have been emplaced during storms and should therefore be re-evaluated. This is especially important for CBD that have been incorporated into long-term coastal risk assessments, which are compromised if the CBD are misinterpreted. CBD dynamics can be better determined from a combination of detailed field measurements, modeling, and experiments. A clearer understanding of emplacement mechanisms will result in more reliable hazard analysis.

Depositional style changes during the Permo‐Carboniferous–Early Jurassic evolution of the Central Kalahari Karoo Sub‐basin, Botswana

The Permo‐Carboniferous–Lower Jurassic Karoo succession in the Central Kalahari Karoo Sub‐basin of Botswana is largely confined to the subsurface, and contains coal, coalbed methane and groundwater resources, similar to other Karoo strata throughout southern Africa. Characterization of the stratigraphic architecture (i.e., spatiotemporal stacking character of sedimentary facies) is essential for various aspects of subsurface resource prediction (e.g., resource parameters; reservoir architecture; mining feasibility). This study uses sedimentary facies analysis on borehole cores from central Botswana and sequence stratigraphic principles to resolve large‐scale depositional style changes during the evolution of the greater Kalahari Karoo Basin in southwestern Gondwana. The results show that changes in the Karoo stratigraphic architecture define two, large‐scale overall fining‐upward depositional sequences (i.e., Lower and Upper Karoo) that are marked by regional subaerial unconformities. These regionally mappable depositional sequences contain pairs of high‐ to low‐amalgamation units, which are typified by stacked, multistorey sandstone bodies, succeeded by finer grained units that are sometimes rich in coal (e.g., the Dukwi‐Makoro‐Kamotaka vs. the Morupule‐Serowe‐Tlhabala formations in the Lower Karoo; the lower versus upper Mosolotsane‐Ntane formations in the Upper Karoo). The large‐scale depositional style changes, reflecting base‐level fluctuations and variation in the balance between accommodation and sediment supply, resulted from climatic changes (e.g., Permo‐Carboniferous deglaciation), tectonic events (e.g., regional pre‐Mosolotsane uplift event), and marine incursions. The latter is documented, for the first time, via the marine‐influenced ichnofauna in the uppermost Ecca Group. Further refining this initial sequence stratigraphic framework for the Botswanan Karoo will require acquisition of radioisotopic dates (e.g., U–Pb zircon ages) and modern seismic reflection data.

The predominantly fresh history of Lake Alexandrina, South Australia, and its implications for the Murray–Darling Basin Plan: a comment on Gell (2020)

The pre-European settlement state of Lake Alexandrina, a lake system at the mouth of the River Murray has been the subject of some debate. Fluin et al. (2007) concluded on the basis of diatom evidence from sediment cores that ‘Marine water indicators were never dominant in Lake Alexandrina’. In a report to the South Australian Government, Fluin et al. (2009) stated, consistent with the earlier research, that ‘There is no evidence in the 7000 year record of substantial marine incursions into Lake Alexandrina’. Gell (2020) has argued both that Fluin et al. (2009) is in error and claims that it, and Sim and Muller’s (2004) book that describes early European settler accounts of the lake being fresh, underpin water provisions for Lake Alexandrina under the Murray–Darling Basin Plan. This response demonstrates that all these claims are untrue. Of the three diatom species suggested by Gell (2020) to be indicators of marine waters, Thalassiosira lacustris grows in the freshwater River Murray today, Cyclotella striata was never more than a minor component of the diatom flora and Paralia sulcata has not been detected in the lake in over 3000 years. Water provisions for Lake Alexandrina under The Basin Plan are founded on contemporary environmental water requirements and achievement of agreed socio-ecological-economic objectives, rather than the history of the lake. Nevertheless, the aim to maintain the lake as a freshwater ecosystem under The Murray–Darling Basin Plan is consistent with its history.

Quaternary sequence stratigraphy of onshore Abu Dhabi Emirate

Glacially driven eustatic sea-level fluctuations have left a clear signature only along the coastal regions and barrier islands of the Abu Dhabi Emirate. Four marine sequences are identifiable although others are known to exist offshore. The stratigraphy is complicated by aeolian processes associated especially with the Shamal winds which have blown from the northwest to create dune fields that dominate the Quaternary sedimentation. Whilst aeolian facies can clearly be identified separating marine incursions along the coastal regions, aeolian deflation has complicated the stratigraphy by recycling sediment partly in response to loss of windward sediment sources during marine transgressions and partly in response to glacially driven climatic changes. Unravelling the sequence stratigraphy of the desert dunes inland, especially beyond the coastal sabkhas, is therefore extremely difficult. The late Quaternary aeolian dunes and their veneer of mobile aeolian sands are grouped into a single poorly defined formation which spans the entire timescale of the sequences identified along the coast.

Impacts of Holocene and modern sea‐level changes on estuarine mangroves from northeastern Brazil

AbstractProjections of the impacts of modern Relative Sea Level (RSL) rise on estuarine mangroves should be supported by coastal topographic data and records of mangrove dynamics under past RSL change. This work identified inland and seaward mangrove migrations along the Jucuruçu River (Bahia, Northeastern Brazil), during the Holocene based on sedimentary features, palynological and geochemical (δ13C, δ15N, C/N) data integrated with digital elevation models. During the Middle Holocene, in response to RSL rise, the estuary saw mangrove forest establish up to ~37 km inland. RSL stood between ‐1.4 (+0.36/‐2.2 m) and +1 (2.19/0.2 m) around 7400 cal yr BP, and rose to a highest position of +3.25 (4.22/2.45 m) reached around 5350 cal yr BP. That marine incursion caused the inland replacement of freshwater vegetation by mangroves on tidal flats. Since then, the estuary experienced RSL fall, reducing inland tidal water salinity towards the Late Holocene, making that the mangroves were replaced by freshwater floodplain vegetation. Today, in the seaward part of the estuary near its mouth, mangroves occupy an area of ~10 km2 along tidal channels. Considering a RSL rise of 98 cm up to the end of the 21st century, at a rate significantly higher than that of Middle Holocene RSL rise (1.5 mm/yr) and fall (0.6 mm/yr), the current mangrove substrates are expected to drown and/or eroded near the coast, while new mangroves may establish inland, at topographically higher tidal flats in nowadays freshwater‐tidal zones. Mangrove area could expand over 13 km2 of coastal and flood plain. Following the same interaction between RSL/climate changes and Holocene mangrove dynamics, such upstream mangrove migration may be attenuated or intensified by changes in fluvial discharge. © 2019 John Wiley &amp; Sons, Ltd.

Clay minerals from the Lameta Formation of Pandhari area, districts Amravati, Maharashtra and Betul, Madhya Pradesh: Its paleoclimatological implications

This report highlights the record of clay minerals from the Lameta Formation of a new locality of central India. A 9-m thick argillaceous column represented by various shades of grayish-greenish-brownish-yellowish coloured clay to silty-clay has been investigated. The clay has been separated from the host sediment by pipette method which has been further subjected to XRD analysis. The peaks identified are of palygorskite, sepiolite, illite, montmorillonite and kaolinite. The assemblage is interpreted to be a product of arid to semi-arid climatic condition due to weathering of pre-existing rocks. The depositional site also shows the possibility of short term marine incursion.

Age of the Berlin moraine complex, New Hampshire, USA, and implications for ice sheet dynamics and climate during Termination 1

AbstractAt its late Pleistocene maximum, the Laurentide Ice Sheet was the largest ice mass on Earth and a key player in the modulation of global climate and sea level. At the same time, this temperate ice sheet was itself sensitive to climate, and high-magnitude fluctuations in ice extent, reconstructed from relict glacial deposits, reflect past changes in atmospheric temperature. Here, we present a cosmogenic 10Be surface-exposure chronology for the Berlin moraines in the White Mountains of northern New Hampshire, USA, which supports the model that deglaciation of New England was interrupted by a pronounced advance of ice during the Bølling-Allerød. Together with recalculated 10Be ages from the southern New England coast, the expanded White Mountains moraine chronology also brackets the timing of ice sheet retreat in this sector of the Laurentide. In conjunction with existing chronological data, the moraine ages presented here suggest that deglaciation was widespread during Heinrich Stadial 1 event (~18–14.7 ka) despite apparently cold marine conditions in the adjacent North Atlantic. As part of the White Mountains moraine system, the Berlin chronology also places a new terrestrial constraint on the former glacial configuration during the marine incursion of the St. Lawrence River valley north of the White Mountains.

Early Jurassic palaeoenvironments in the Surat Basin, Australia – marine incursion into eastern Gondwana

AbstractInterpretations of palaeodepositional environments are important for reconstructing Earth history. Only a few maps showing the Jurassic depositional environments in eastern Australia currently exist. Consequently, a detailed understanding of the setting of Australia in Gondwana is lacking. Core, wireline logs, two‐dimensional and three‐dimensional seismic from the Precipice Sandstone and Evergreen Formation in the Surat Basin have been used to construct maps showing the evolution of depositional environments through the Early Jurassic. The results indicate the succession consists of three third‐order sequences (Sequence 1 to Sequence 3) that were controlled by eustatic sea level. The lowstand systems tract in Sequence 1 comprises braidplain deposits, confined to a fairway that parallels the basin centre. The strata were initially deposited in two sub‐basins, with rivers flowing in different orientations in each sub‐basin. The transgressive systems tract of Sequence 1 to lowstand systems tract of Sequence 3 is dominated by fluvio–deltaic systems infilling a single merged basin centre. Finally, the transgressive and highstand systems tracts of Sequence 3 show nearshore environments depositing sediment into a shallow marine basin. In the youngest part of this interval, ironstone shoals are the most conspicuous facies, the thickness and number of which increase towards the north and east. This study interprets a corridor to the open ocean through the Clarence–Moreton Basin, or the Carpentaria and Papuan basins, evidence of which has been eroded. These results challenge a commonly held view that eastern Australia was not influenced by eustasy, and propose a more dynamic palaeogeographic setting comprising a mixture of fluvial, deltaic and shallow marine sedimentary environments. This work can be used to unravel the stratigraphic relationships between Mesozoic eastern Australian basins, or in other basins globally as an analogue for understanding the complex interplay of paralic depositional systems in data poor areas.

Lacustrine environmental evolution and implications on source rock deposition in the Upper Cretaceous-Paleocene of the South Yellow Sea Basin, offshore eastern China

Lacustrine source rocks are well developed within the Upper Cretaceous-Paleocene in the South Yellow Sea Basin (SYSB) in offshore eastern China. Understanding the deposition of these source rocks could provide critical information for hydrocarbon exploration in the SYSB, as well as reveal the paleoenvironment across the Cretaceous/Paleogene boundary in eastern China. This study investigates the lacustrine environmental evolution during the Upper Cretaceous Taizhou Formation (K2t) to Paleocene Funing Formation (E1f) within the SYSB and its implications on source rock deposition based on core observation combined with organic geochemical indicators. Multiple maturity parameters (vitrinite reflectance, Tmax and biomarker isomerization ratios) reveal that the organic matter (OM) has reached early oil window maturity. The OM of source rocks is dominated by kerogen Type II-III (liptinite and vitrinite). Anoxic, saline-brackish deep to semi-deep lacustrine environments prevailed during the deposition of K2t2 (second member of the K2t), E1f2 (second member of the E1f) and E1f4L (lower unit of fourth member of the E1f). The deposition of three intervals was influenced by marine incursion, as evidenced by geochemical and paleontological results. Low to moderate TOC contents (avg. 0.78 wt% to 1.91 wt%), which corresponds to low to moderate terrestrial OM input, are observed through three intervals. Abundant freshwater, together with high terrestrial OM flowed into the lacustrine environments during the deposition of E1f4U (upper unit of fourth member of the E1f), leading to dysoxic-oxic and freshwater conditions. High terrestrial OM input is probably the major controlling factor for relatively high TOC contents (avg. 2.49%) in the E1f4U. An evolution from balanced-fill to overfilled lake-type is observed in the Upper Cretaceous-Paleocene of SYSB, consistent with an evolution from semi-arid to humid paleoclimate conditions. The E1f4U and E1f2 source rocks exhibit fair to good potential, whereas poor to fair potential is present in the E1f4L and K2t2 source rocks. Compared with the Paleogene source rocks in onshore eastern China, the Upper Cretaceous-Paleocene source rocks in the SYSB probably hold good potential for generating commercial quantity of oil, although further study on hydrocarbon generation kinetics of source rocks and overall basin history are needed.