Surface Elevation Changes Estimation Underneath Mangrove Canopy Using SNERL Filtering Algorithm and DoD Technique on UAV-Derived DSM Data

Estimating surface elevation changes in mangrove forests requires a technique to filter the mangrove canopy and quantify the changes underneath. Hence, this study estimates surface elevation changes underneath the mangrove canopy through vegetation filtering and Difference of DEM (DoD) techniques using two epochs of unmanned aerial vehicle (UAV) data carried out during 2016 and 2017. A novel filtering algorithm named Surface estimation from Nearest Elevation and Repetitive Lowering (SNERL) is used to estimate the elevation height underneath the mangrove canopy. Consequently, DoD technique is used to quantify the elevation change rates at the ground surface, which comprise erosion, accretion, and sedimentation. The significant findings showed that region of interest (ROI) 5 experienced the highest volumetric accretion (surface raising) at 0.566 cm3. The most increased erosion (surface lowering) was identified at ROI 8 at −2.469 cm3. In contrast, for vertical change average rates, ROI 6 experienced the highest vertical accretion (surface raising) at 1.281 m. In comparison, the most increased vertical erosion (surface lowering) was spotted at ROI 3 at −0.568 m. The change detection map and the rates of surface elevation changes at Kilim River enabled authorities to understand the situation thoroughly and indicate the future situation, including its interaction with sea-level rise impacts.

The Origin and 3D Architecture of a Km-Scale Deep-Water Scour-Fill: Example From the Skoorsteenberg Fm, Karoo Basin, South Africa

Scours, and scour fields, are common features on the modern seafloor of deep-marine systems, particularly downstream of submarine channels, and in channel-lobe-transition-zones. High-resolution images of the seafloor have improved the documentation of the large scale, coalescence, and distribution of these scours in deep-marine systems. However, their scale and high aspect ratio mean they can be challenging to identify in outcrop. Here, we document a large-scale, composite erosion surface from the exhumed deep-marine stratigraphy of Unit 5 from the Permian Karoo Basin succession in South Africa, which is interpreted to be present at the end of a submarine channel. This study utilizes 24 sedimentary logs, 2 cored boreholes, and extensive palaeocurrent and thickness data across a 126 km2 study area. Sedimentary facies analysis, thickness variations and correlation panels allowed identification of a lower heterolithic-dominated part (up to 70 m thick) and an upper sandstone-dominated part (10–40 m thick) separated by an extensive erosion surface. The lower part comprises heterolithics with abundant current and sinusoidal ripples, which due to palaeocurrents, thickness trends and adjacent depositional environments is interpreted as the aggradational lobe complex fringes. The base of the upper part comprises 2-3 medium-bedded sandstone beds interpreted as precursor lobes cut by a 3–4 km wide, 1–2 km long, and up to 28 m deep, high aspect ratio (1:100) composite scour surface. The abrupt change from heterolithics to thick-bedded sandstones marks the establishment of a new sediment delivery system, which may have been triggered by an updip channel avulsion. The composite scour and subsequent sandstone fill support a change from erosion- and bypass-dominated flows to depositional flows, which might reflect increasingly sand-rich flows as a new sediment route matured. This study provides a unique outcrop example with 3D stratigraphic control of the record of a new sediment conduit, and development and fill of a large-scale composite scour surface at a channel mouth transition zone, providing a rare insight into how scours imaged on seafloor data can be filled and preserved in the rock record.

The Río Grío–Pancrudo Fault Zone (central Iberian Chain, Spain): recent extensional activity revealed by drainage reversal

The NNW–SSE-trending extensional Río Grío–Pancrudo Fault Zone is a large-scale structure that obliquely cuts the Neogene NW–SE Calatayud Basin. Its negative inversion during the Neogene–Quaternary extension gave rise to structural and geomorphological rearrangement of the basin margin. Geological mapping has allowed two right-relayed fault segments to be distinguished, whose recent extensional activity has been mainly characterized using a deformed planation surface (Fundamental Erosion Surface (FES) 3; 3.5 Ma) as a geomorphic marker. Normal slip along the Río Grío–Lanzuela Fault Segment has induced hanging-wall tilting, subsequent drainage reversal at the Güeimil valley after the Pliocene–Pleistocene transition, as well as morphological scarps and surficial ruptures in Pleistocene materials. In this sector, an offset of FES3 indicates a total throw of c. 240 m, resulting in a slip rate of 0.07 mm a–1, while retrodeformation of hanging-wall tilting affecting a younger piedmont surface allows the calculation of a minimum throw in the range of 140–220 m after the Pliocene–Pleistocene transition, with a minimum slip rate of 0.07–0.11 mm a–1. For the late Pleistocene period, vertical displacement of c. 20 m of a sedimentary level dated to 66.6 ± 6.5 ka yields a slip rate approaching 0.30–0.36 mm a–1. At the Cucalón–Pancrudo Fault Segment, the offset of FES3 allows the calculation of a maximum vertical slip of 300 m for the last 3.5 Ma, and hence a net slip rate close to 0.09 mm a–1. Totalling c. 88 km in length, the Río Grío–Pancrudo Fault Zone could be the largest recent macrostructure in the Iberian Chain, probably active, with the corresponding undeniable seismogenic potential.

Channel incision into a submarine landslide: an exhumed Carboniferous example from the Paganzo Basin, San Juan, Argentina

Emplacement of submarine landslides, or mass transport deposits, can radically reshape the physiography of continental margins, and strongly influence subsequent sedimentary processes and dispersal patterns. The irregular relief they generate creates obstacles that force reorganisation of sediment transport systems. Subsurface and seabed examples show that channels can incise directly into submarine landslides. Here, we use high-resolution sedimentological analysis, geological mapping and photogrammetric modelling to document the evolution of two adjacent, and partially contemporaneous, sandstone-rich submarine channel-fills (NSB and SSB) that incised deeply (>75 m) with steep lateral margins (up to 70°) into a 200 m thick debrite. The stepped erosion surface mantled by clasts, ranging from gravels to cobbles, points to a period of downcutting and sediment bypass. A change to aggradation is marked by laterally-migrating sandstone-rich channel bodies that is coincident with prominent steps in the large-scale erosion surface. Two types of depositional terrace are documented on these steps: one overlying an entrenchment surface, and another located in a bend cut-off. Above a younger erosion surface, mapped in both NSB and SSB, is an abrupt change to partially-confined tabular sandstones with graded caps, interpreted as confined lobes. The lobes are characterised by a lack of compensational stacking and increasingly thick hybrid bed deposits, suggesting progradation of a lobe complex confined by the main erosion surface. The incision of adjacent and partially coeval channels into a thick submarine landslide, and sand-rich infill including development of partially confined lobes, reflects the complicated relationships between evolving relief and changes in sediment gravity flow character, which can only be investigated at outcrop. The absence of channel-fills in bounding strata, and the abrupt and temporary presence of coarse sediment infilling the channels, indicates that the submarine landslide emplacement reshaped sediment transport systems, and established conditions that effectively separated sand- from mud-dominated deposits.

The origin and 3D architecture of a km-scale deep-water scour-fill: example from the Skoorsteenberg Fm., Karoo Basin, South Africa

Scours, and scour fields, are common features on the modern seafloor of deep-marine systems, particularly downstream of submarine channels, and in channel-lobe-transitions-zones. High-resolution images of the seafloor have improved the documentation of the large scale, coalescence, and distribution of these scours in deep-marine systems. However, their scale and high aspect ratio mean they can be challenging to identify in outcrop. Here, we document a large-scale, composite erosion surface from the exhumed deep-marine stratigraphy of Unit 5 from the Permian Karoo Basin succession in South Africa, which is interpreted to be present at the end of a submarine channel.This study utilizes 24 sedimentary logs, 2 cored boreholes, and extensive palaeocurrent and thickness data across a 126 km2 study area. Sedimentary facies analysis, thickness variations and correlation panels allowed identification of a lower heterolithic-dominated part (up to 70 m thick) and an upper sandstone-dominated part (10-40 m thick) separated by an extensive erosion surface. The lower part comprises heterolithics with abundant current and sinusoidal ripples, which due to palaeocurrents, thickness trends and adjacent depositional environments is interpreted as the aggradational lobe complex fringes. The base of the upper part comprises 2-3 medium-bedded sandstone beds interpreted as precursor lobes cut by a 3-4 km wide, 1-2 km long, and up to 28 m deep, high aspect ratio (1:100) composite scour surface. The abrupt change from heterolithics to thick-bedded sandstones marks the establishment of a new sediment delivery system, which may have been triggered by an updip channel avulsion. The composite scour and subsequent sandstone fill support a change from erosion- and bypass-dominated flows to depositional flows, which might reflect increasingly sand-rich flows as a new sediment route matured. This study provides a unique outcrop example with 3D stratigraphic control of the record of a new sediment conduit, and development and fill of a large-scale composite scour surface at the channel mouth, providing a rare insight into how scours imaged on seafloor data can be preserved in the rock record.

New onshore/offshore evidence of the Messinian Erosion Surface from key areas: the Ibiza-Balearic Promontory and the Orosei-Eastern Sardinian margin

<p>As the Messinian sea-level drawdown associated with the Messinian Salinity Crisis is still questioned, we propose to show that the widely spread erosion surface affecting the Mediterranean margins is indeed linked to an exondation demonstrated from offshore and onshore data.</p><p>Our study presents for the first time a comprehensive onshore to offshore correlation of the Messinian erosional surface, and it is focused on small drainage systems or interfluve areas, outside of evaporite basins or incised canyons, where the Messinian erosion had not yet been studied previously: around Ibiza on the Balearic Promontory and around Orosei on the Eastern Sardinian margin, Tyrrhenian Basin, both areas where new offshore data were recently acquired. We show that the late Messinian erosion formed in subaerial settings, as testified by evidence of continentalization events, and attests for a regression phase that was correlated from the offshore continental slopes to the onshore paleo-platforms in both areas. Characteristics of this erosion in both study areas strengthen the scenario with at least one important low-stand sea-level for the Messinian Salinity Crisis with evaporites subbasins lying at different depths and possibly disconnected.</p>

New onshore/offshore evidence of the Messinian Erosion Surface from key areas: The Ibiza-Balearic Promontory and the Orosei-Eastern Sardinian margin

As the Messinian sea-level draw down associated with the Messinian Salinity Crisis is still questioned, we propose to show that the widely spread erosion surface affecting the Mediterranean margins is indeed linked to an exondation demonstrated from offshore and onshore data. Our study presents a comprehensive onshore to offshore correlation of the Messinian erosional surface. It is focused on small drainage systems or interfluve areas, outside of evaporite basins or incised canyons, where the Messinian erosion had not yet been studied previously: around Ibiza on the Balearic Promontory and around Orosei on the Eastern Sardinian margin, Tyrrhenian Basin, both areas where new offshore data were recently acquired. We show that the late Messinian erosion formed in subaerial settings, as testified by evidence of continentalization events, and attests for a regression phase that was correlated from the offshore continental slopes to the onshore paleo-platforms in both areas. Characteristics of this erosion in both study areas strengthen the scenario with at least one important low-stand sea-level for the Messinian Salinity Crisis with evaporites subbasins lying at different depths and possibly disconnected.