After the Storm: Fate and Leaching of Particulate Nitrogen (PN) in the Fluvial Network and the Influence of Watershed Sources and Moisture Conditions

Large storms can erode, transport, and deposit substantial amounts of particulate nitrogen (PN) in the fluvial network. The fate of this input and its consequence for water quality is poorly understood. This study investigated the transformation and leaching of PN using a 56-day incubation experiment with five PN sources: forest floor humus, upland mineral A horizon, stream bank, storm deposits, and stream bed. Experiments were subjected to two moisture regimes: continuously moist and dry–wet cycles. Sediment and porewater samples were collected through the incubation and analyzed for N and C species, as well as the quantification of nitrifying and denitrifying genes (amoA, nirS, nirK). C- and N-rich watershed sources experienced decomposition, mineralization, and nitrification and released large amounts of dissolved N, but the amount of N released varied depending on the PN source and moisture regime. Drying and rewetting stimulated nitrification and suppressed denitrification in most PN sources. Storm deposits released large amounts of porewater N regardless of the moisture conditions, indicating that they could readily act as N sources under a variety of conditions. The inputs, processing, and leaching of large, storm-driven PN inputs become increasingly important as the frequency and intensity of large storms is predicted to increase with global climate change.

The origins of marine and non-marine boulder deposits: a brief review

We identify 14 mechanisms, marine and non-marine, one man made, that result and could result in the formation of boulder deposits after reviewing issues associated with clast shape, size and classification. Four of these mechanisms: storm deposits; waterspouts; cliff collapse; and catastrophic flooding below sea level, may produce deposits stretching for significant distances along shorelines which could be confused with historical or prehistoric tsunami deposits. However, recent debate has more specifically focused on parameters that can be employed in the distinction between coarse-grained tsunami and storm deposits, both of which can occur in the same location. We argue that features such as size, areal distribution and clast shape are not uniquely characteristic of either deposit. Rather, a wide variety of parameters, which reflect the period and the frequency of the transporting waves, need to be taken into account. Such analyses may be aided by profiles which evaluate the variation in modeled flow velocities with distance from the shoreline. Finally, we compare and contrast characteristics of coarse grained tsunami deposits with those of northeast Atlantic storm deposits that may aid in the identification of the transporting wave.

Environmental DNA signatures distinguish between tsunami and storm deposition in overwash sand

Sandy onshore deposits from tsunamis are difficult to distinguish from storm deposits, which makes it difficult to assess coastal hazards from the geological record. Here we analyse environmental DNA from microbial communities preserved in known tsunami and storm-deposited sediments and intercalating soils and non-marine sediments near Cuddalore, India, and Phra Thong Island, Thailand. Both sites were impacted by the 2004 Indian Ocean Tsunami and a subsequent storm flooding event (2011 Cyclone Thane at Cuddalore and a 2007 storm at Phra Thong Island). We show that the microbial communities in the overwash deposits are significantly different from soil and sediments that are not derived by overwash processes at both locations. Our method also successfully discriminates between modern tsunami deposits and storm deposits. We suggest molecular techniques have the potential to accurately discriminate overwash deposits from catastrophic natural events.

Investigation of sedimentary records of Hurricane Irma in sinkholes, Big Pine Key, Florida

Few paleotempestological studies have focused on coastal sinkholes, a common feature in Florida, which can receive and preserve storm overwash sediments. The major goal of this research is to improve our understanding of the characteristic signatures of storm sediments in sinkholes thereby determining reliability of these environments as proxies for hurricanes. Hurricane Irma as a category 5 storm provides an excellent case study for characterizing storm deposits in sinkholes on Big Pine Key. We cored at four sinkholes along a 350 m transect normal to the shoreline. Core sediments were characterized using physical description, short-lived radioisotope dating, sediment grain size analysis, loss-on-ignition, microfossil analysis, and x-ray fluorescence elemental analysis. We found that Irma deposits had higher abundances of marine foraminifera, less total organic matter and elevated Si/Al and Ca/Ti ratios, compared to pre- or post-Irma sediments. In addition, there was a thinning of the storm sediments along the inland transect. Consequently, we propose that sinkholes, particularly those that are closer to the shoreline, can provide reliable sites for paleotempestology studies.

Depositional Environment of the Upper Triassic Baluti Formation in Gara Anticline, Kurdistan Region, North Iraq: Insight from Microfacies and Biomarker Characteristics

The studied section is located in the core of the Gara Anticline, about 12 km southeast of Amedi Town. The Baluti Formation is generally composed of grey and green shale, calcareous, dolostone with intercalations of thinly bedded dolostones, dolomitic limestones, and silicified limestones which are occasionally brecciated. The petrographic study shows five main microfacies in the Baluti Formation namely; finely laminated dolomudstone, fossil-barren and lime mudstone, fenestral mudstone/packstone, peloids and ooids wackestone, and lithoclasts (intraclasts) grainstones. The mudstones facies with no fauna and radial-fibrous ooids can point to a protected and low energy environment. Moreover, fenestral structures are reliable criteria for identifying a tidal flat environment. The presence of the lithoclasts (intraclasts) with radial ooids and a few terrestrial fragments may represent a quiet environment, albeit one affected by infrequent storm deposits. As a supplementary to microfacies, the biomarker characterizations were used to deduce the depositional environment of the Baluti Formation. Biomarker parameters show that the Baluti Formation could be deposited in anoxic to suboxic environment, and organic matter input is more likely characterized by land plant organic matter. This study showed that the most likely paleoenvironments for the Baluti Formation were supratidal, intertidal, subtidal, and sand shoals setting. However, the lack and/or very low diversity of skeletal fauna, and the lack of subaerial exposure may indicate that some parts of the formation seem to be deposited in low energy and restricted environment (Lagoon).

Hutchison Medallist 1. Wave-Dominated to Tide-Dominated Coastal Systems: A Unifying Model for Tidal Shorefaces and Refinement of the Coastal- Environments Classification Scheme

Coastal depositional systems are normally classified based on the relative input of wave, tide, and river processes. While wave- through to river-dominated environments are well characterized, environments along the wave-to-tide continuum are relatively poorly understood and this limits the reliability and utility of coastal classification schemes. Two tidal shoreface models, open-coast tidal flats (OCTF) and tidally modulated shorefaces (TMS), have been introduced for mixed wave-tide coastal settings. Following nearly two decades of research on tidal shorefaces, a number of significant insights have been derived, and these data are used here to develop a unified model for such systems. First, OCTFs are components of larger depositional environments, and in multiple published examples, OCTFs overlie offshore to lower shoreface successions that are similar to TMS. Consequently, we combine OCTFs and TMSs into a single tidal shoreface model where TMS (as originally described) and TMS-OCTF successions are considered as variants along the wave-tide continuum. Second, tidal shoreface successions are preferentially preserved in low- to moderate-wave energy environments and in progradational to aggradational systems. It is probably difficult to distinguish tidal shorefaces from their storm-dominated counterparts. Third, tidal shorefaces, including both TMSs and OCTFs, should exhibit tidally modulated storm deposits, reflecting variation in storm-wave energy at the sea floor resulting from the rising and falling tide. They may also exhibit interbedding of tidally generated structures (e.g. double mud drapes or bidirectional current ripples), deposited under fairweather conditions, and storm deposits (e.g. hummocky cross-stratification) through the lower shoreface and possibly into the upper shoreface.The development of the tidal shoreface model sheds light on the limitations of the presently accepted wave-tide-river classification scheme of coastal environments and a revised scheme is presented. In particular, tidal flats are components of larger depositional systems and can be identified in the rock record only in settings where intertidal and supratidal deposits are preserved; consequently, they should not represent the tide-dominated end-member of coastal systems. Instead, we suggest that tide-dominated embayments should occupy this apex. Tide-dominated embayments exhibit limited wave and river influence and include a wide range of geomorphological features typically associated with tidal processes, including tidal channels, bars and flats.

Tracing the late Holocene storminess at the Polish Baltic Sea coast – regional survey and local in depth research.

<p>Within the Baltic Sea basin, the frequency and intensity of coastal flooding caused by storms is influenced by wind direction and exposure of the coast. Strong (north)westerly winds associated with the North Atlantic Oscillation hit large parts of the Polish coast, while (north)easterly winds affect Puck Bay. Following from that, the research on the frequency and magnitude of past storminess within the Baltic Sea sheds light onto regional climatic conditions indicating changes in wind-field directions and storminess in north-western and northern Europe. Despite the fact that the Baltic Sea basin area bears potentially vast amount of information on the past storminess and climatic conditions on the regional scale, no systematic, basin-wide research on storm deposits and analysis of frequency and intensity of storminess is available.</p><p> </p><p>The spatially variable occurrence of sedimentary evidence for coastal flooding caused by storms indicates necessity for multisite investigations in order to develop reliable records of past storm frequency and intensity. As the historical written sources and instrumental records are insufficient to draw informative conclusion on the past storminess, the survey in search for the depositional evidence of catastrophic coastal flooding has been undertaken along the Polish coast, from the Puck Bay to Wolin Island. Following from that, detailed research on the storm deposits has been undertaken in 4 key locations (one is presented here, Mechelinki).</p><p>The survey allowed to create the list of features common for the locations where sedimentary evidence for coastal flooding is preserved. These include flat, inundational character of the coast, prevailing organic deposition in lowlands close to the shore and non-tidal character of adjacent marine basin.</p><p>Mechelinki peatland (Puck Bay) is separated by a N-S extending sand barrier from the open sea and exposed to (north)easterly winds. Investigated sedimentary succession comprises ca. 450 cm of peat interdigitated with few centimetres thick layers of sand. The origin of sand has been established based on multiproxy investigation including: particle size, shape (automated MorphologyG3, thin sections), diatom, XRF and heavy mineral analyses. Geochronology has been established based on <sup>14</sup>C and <sup>210</sup>Pb/<sup>137</sup>Cs measurements. In the Mechelinki research site, the evidence for about 20 coastal flooding events which took place during the last 5000 years has been discovered. The results prove, there is no universal method to differentiate the storm deposits from the sediments of other origin and only the combination of multiproxy analyses bears unambiguous results.</p><p>The research project CatFlood is funded by National Science Centre, Poland, OPUS grant nr: 2018/29/B/ST10/00042</p>

Distinguishing Late Holocene Storm Deposit From Shore-normal Beach Sediments From the Gulf of Thailand

Grain size, as one of sedimentological proxies, coupled with a detailed description of the sedimentary structures and luminescence dating were used to unveil the sediment sources and transport process of the Holocene ancient coastal storm events recorded in the beach ridge plain, wet swale and muddy environments at Prachuap Khiri Khan, in the Southern Peninsula of Thailand. In this study, a total of 141 sand samples were collected from the shore-normal ridge-swale topography and analyzed for layers of candidate storm deposits, revealing at least 21 candidate coastal storm events. The grain size distribution of beach sediments was, in general, unimodal, while the candidate storm sediments revealed a mixed combination of multimodal, bimodal and unimodal distributions. Plots of mean grain size against skewness and kurtosis and of skewness against kurtosis could differentiate storm deposits from shore-normal beach sediments. Sedimentary structures preserved in the ancient coastal storm deposits included parallel and inclined landward laminations, mud rip-up clasts, layers of shell fragments, a pebble grain, normal and reverse grading and sharp lower and upper contacts. Candidate storm layers overlain on a dry beach ridge intervened with mud in a swale showed a finer and thinner landward deposit. Marine shell fragments, smaller foraminifers, ostracod and scaphopod (tusk shell), were well preserved. Based on optically stimulated luminescence dating and a correlated accelerator mass spectrometry age, multiple layers of sand derived from different frequencies of coastal storms were deposited over the middle to late Holocene.

Paleoenvironmental significance of microbial mat-related structures and ichnofaunas in an Ordovician mixed-energy estuary, Áspero Formation of Santa Victoria Group, northwestern Argentina

ABSTRACT The study on a unique set of outstandingly preserved sedimentary surface textures (SSTs) found in the late Tremadocian Áspero Formation of northwestern Argentina, coupled with the sedimentological and ichnological analysis, indicate that they were formed in the intertidal to supratidal setting of a mixed-energy estuary recording storm and tide sedimentation. We recognize seven types of SSTs: probably biotic microbial mat-related SSTs (Kinneyia, elephant skin, exfoliating sandy laminae), abiotic SSTs (elliptical scours and convex parallel ridges type I “wrinkle marks” sensuAllen 1985), and problematic (convex parallel ridges type II and dot matrix texture). Elliptical scours and convex parallel ridges type I show features which indicate reworking of a cohesive sandy substrate in an intertidal or supratidal setting. Abundance of biotic SSTs with specific associated trace fossils reflect matground development and mat-grazing ichnofaunas, indicating the suppression of intense, penetrative bioturbation due to intense physicochemical stress. The “dot matrix” texture, described here for the first time, consists of a regular horizontal network of millimeter-scale pits; it appears associated with exfoliating sandy laminae, probably reflecting a mat-related origin. Three facies associations are defined through paleoenvironmental analysis. Facies association 1 is dominated by high-energy sandy and bioclastic storm deposits with tidal flat facies, and corresponds to the outer bay of a mixed-energy estuary; highly impoverished Cruziana assemblages and distal expressions of the Skolithos Ichnofacies reflect high energy and sedimentation rate. Facies association 2 shows tidal-channel and tidal-flat facies with subordinated storm deposits, representing the middle bay; impoverished Cruziana assemblages dominated by simple facies-crossing structures, with high-density monogeneric opportunistic suites, evidence physicochemical stress associated with subaerial exposure, frequent episodic deposition, high water turbidity, and/or brackish water conditions in these relatively sheltered tidal flats. Facies association 3 is formed by interdistributary-bay deposits with intercalation of channel-fill deposits in the upper part, and represents the river-dominated bay-head delta; low degrees of bioturbation in fine-grained facies indicate brackish- to fresh-water conditions. SSTs are found in tidal flat facies of facies association 2; they indicate an intertidal to supratidal environment subject to localized conditions of intense physicochemical stress. The paleoenvironmental interpretation of SSTs converges with the one performed through sedimentological and ichnological analysis, producing a robust and more detailed paleoenvironmental model for the Áspero Formation. Our study highlights the use of SSTs as a tool for supporting and refining paleoenvironmental analysis.