Calcium and clumped isotopes are affected by carbonate recrystallization in fundamentally different ways, and are affected by different factors. Here, they are used to study an evolving carbonate margin (Present day western Bahamian slope), in order to quantify the rate of recrystallization and the degree of fluid flow into the margin. Results show that, with the onset of drift deposits in the Straits of Florida, fluid flow into the margin increased a great deal, demonstrating the importance of larger platform structure in governing the nature of diagenetic reactions.
Meteorite impacts have long been debated as a cause of mass extinction on Earth. When they hit, meteorite impacts load the atmosphere with dust and cover the Earth’s surface with debris. This is thought to trigger ‘Impact Winter’, whereby sunlight is blocked from reaching the earth’s surface leading to catastrophic ecosystem collapse. The bigger the hit, the more severe the effects. But does it really work like that? In this talk I’ll show you that there is actually no correlation between size of impact and extinction intensity over 600 Myrs of multicellular life. Instead, it is the mineralogy of the target rocks that dictates extinction intensity, in particular their K-feldspar content. Weird. To find out how this benign mineral triggers mass extinctions, you’ll have to come along to the seminar!
In this talk I will provide an overview of recent work that has focused on quantifying how ecological changes have altered rates of carbonate production on modern coral reefs and the impacts for reef growth potential under sea-level rise. The talk will also review the options and challenges that exist in quantifying associated rates of reef sediment generation – a sedimentary component of reefs that contributes not only to reef-building, but also to proximal beaches and islands.
The ability to build very steep slopes is a characteristics of carbonate platforms. Microbially mediated fusing of grains and subsequent prismatic early cementation construct the margins of these edifices that are often obstacles for ocean currents along continental margins. Rock fall, margin collapse, slope canyons and slope failures are common features of carbonate slopes but cascading density currents as well as bottom and surface currents also shape the sediment distribution on the slope and in the adjacent basin. Depositional slope models largely ignore the current-related deposition. The talk will illustrate the extreme height of carbonate escarpments and the related processes using the carbonate platforms in the Florida Bahamas region.
Svalbard is a paradise for geologists, with high Arctic vegetation-free outcrops offering insights into the geological evolution of the archipelago. The short field season and remote outcrops, however, require a different approach than traditional fieldwork. The emergence of cost-efficient consumer UAVs and structure-from-motion photogrammetry has allowed us to digitize a growing number of Svalbard’s outcrops and openly share these through the Svalbox database. The available digital models are presented in the context of regional geoscientific data, including terrain models, geological maps and subsurface data. As such, Svalbox brings the Svalbard geological paradise also to geoscientists living in the lower latitudes.
Microbial carbonates dominated in the Phanerozoic during times of skeletal biota crises and environmental perturbations. High-relief platforms with steep slopes and margins with microbial boundstone reefs are non actualistic examples of highly productive carbonate systems largely representative of the late Palaeozoic, Triassic and Jurassic depositional record. This review explores the controls on facies character, depositional geometry and architecture of several examples of high-relief carbonate platforms evaluating the responses of the microbial carbonate factory, stratal geometry and platform growth to changes in accommodation.
The absence of known prehistoric underwater cultural heritage (UCH) sites on the inner continental shelf of Australia stands in stark contrast to the thousands of sites revealed elsewhere in the world. Two recent claims – Dortch et al. (D2019) and Benjamin et al. (B2020) – put forward the first in situ (i.e., primary context) marine UCH sites in the shallow waters of the Dampier Archipelago, NW Australia. Each paper argued that the stone artefact scatters are at least 7000 years old and are submerged (D2020) or intertidal (D2019) because of post-glacial sea-level rise. Huge international publicity resulted.
From the data published in D2019 and B2020, we use oceanography, sedimentary processes and geological logic to assess the explicit and implicit assumptions and uncertainties of these claims. We include results of new hydrodynamic modelling, data on coastal erosion and bathymetric data of northern Flying Foam Passage, which together help contribute to a reinterpretation of the sites’ sedimentary settings and the archaeology.
These and similar sites in the region (and elsewhere) would benefit from a thorough appraisal of past and present coastal processes to produce a sedimentologically defensible understanding of site formation processes. Even if the artefacts are not in original position, if investigated appropriately and dated effectively, they would still inform our understanding of process and change and might then inform us about past cultures.
The ongoing global Climate Crisis has sparked a strong interest in climate reconstructions and models of geological periods with high atmospheric CO2 concentrations.
But how much do we really now about the dynamics of Earth’s past climate and coastal ecosystems on the human timescale?
Now that concern is rapidly rising about the catastrophic effect of extreme weather events and seasonality, especially to our sensitive and economically important coastal areas, biogenic carbonate producers like mollusks (clams and snails) rise to the occasion as ideal archives for environmental and ecosystem change at the timescale that matters: days to decades.
In this talk, I will try to answer the question: What can these beautifully preserved shells teach us about the occurrence of extreme weather and seasonality under various climate states?
Tropical climates, such as SE Asia, can lead to poor exposure and heavily weathered outcrops. Whilst fieldwork can give an important insight into the underlying geology, detailed detrital analysis is essential to fill in the gaps. Here, a combination of light minerals, heavy minerals, and detrital grain ages from around SE Asia are used to try to reconstruct palaeogeographies in an area of complex tectonics.
Submarine landslides are gravity-driven mass movements that occur in underwater slope settings worldwide. Despite their potential to damage expensive seafloor infrastructure such as pipelines or telecommunication cables and to generate hazardous tsunamis, many aspects of submarine landslide formation remain poorly understood. Many studies have proposed that the formation of submarine landslides on seemingly stable slopes may be explained by weak layers within the slope stratigraphy. Our understanding of weak layers, especially their compositional and structural characteristics, however, is restricted due to often limited data availability and resolution. This talk will focus on the integration of datasets at different scales and resolution in order to both qualitatively and quantitatively investigate the role of sediment structure and composition on weak layer and submarine landslide formation.
Investigations in living microbialites are providing significant data that are critical to disentangle the role of the various biotic and abiotic processes contributing to their development. Despite these efforts separating the impact and magnitude of these processes remain a difficult task.
Field and laboratory studies in modern lacustrine environments from the Andes to the Alps show that extrinsic – environmental – factors might have a changeable impact over short periods of time switching mineral precipitation from biotic to abiotic and vice-versa. Such switch may or may not be distinguishable in fossilized microbialites.
Global marine archives from the early Pleistocene suggest that glacial-interglacial cycles, and their corresponding sea-level cycles, have predominantly a periodicity of ~ 41 kyrs driven by Earth’s obliquity. However, in Taiwan, clastic shallow-marine strata from the early Pleistocene challenge the idea of a “41-kyr world”. The studied strata revealed precession-dominated sea-level fluctuations during the early Pleistocene, independent of a global ice-volume proxy. Preservation of this signal is possible due to the high-accommodation creation and high-sedimentation rate in the basin, enhancing the completeness of the stratigraphic record.
Macrofossils have the potential to provide significant sedimentological data, from aiding the interpretation of depositional settings, understanding the processes operating to concentrate fossils, palaeocurrent interpretation, to diagenetic analysis and much more. Join us to learn more about how to leverage your lamellibranchs, exploit your echinoids and generally put your palaeo to work.
Investigations of tsunami sedimentology has expanded dramatically in recent years following the devasting ‘Boxing Day’ Indian Ocean Tsunami in 2004. Tsunamis cause significant coastal erosion and can deposit sand sheets on coastal plains. In this talk we demonstrate the potential to trace tsunami sands and associated erosional scours in the shallow subsurface using ground-penetrating radar (GPR). We will include examples form the 2004 Indian Ocean Tsunami in Thailand and Indonesia as well as the Storegga tsunamis in Scotland and the Shetland Islands.
Seds Online Student Webinar (SOSW 4): Exploring sediment transport dynamics from source to sink
Presenters: Nikhil Sharma (University of Geneva), Octria Prasojo (University of Glasgow) Jing Lyu (University of Bremen) Maximilian Droellner (Curtin University)
The carbonate factories model, as defined at the beginning of this century, provides a subdivision of marine carbonate sediment production-systems based on the style of carbonate precipitation. The main factors controlling marine carbonate precipitation are light, water temperature, nutrients, salinity, substrate and carbonate saturation. Site-specific controls influencing the systems comprise ocean currents, upwelling and non-upwelling systems, ocean-atmosphere systems, atmospheric systems, shallow-water dynamics, and terrestrial sediment and water input.
The sequence stratigraphic patterns differ for the individual factories. The Tropical factory being light dependent is characterized by higher sediment production when the platform tops are flooded (highstand shedding). It displays decoupled sediment wedges with the partial infill of accommodation in the shallow-water realm and major sediment export towards the slopes and surrounding basins. The Cold-Water Coral factory is marked by in situ production and deposition with limited sediment export forming single cold-water coral spots or sediment accumulation ridges. The Cool-Water factory has a siliciclastic equivalent style of sediment distribution with lowstand-dominated, shelf edge wedges and a shaved-off shelf during sea-level highstands. Slope shedding marks the Microbial factory in which sediment production occurs within the upper slope realm of the flat-topped platforms both during highstands and lowstands in sea-level. This allows for fairly continuous sediment production exhibiting minor impact of sea-level changes, but with progradation, aggradation, and retrogradation of the system being only limited by local environmental changes. Planktic factory sediment production may vary in accordance with variations in sea-level providing time lines, systems tracts boundaries, in the pelagic realm.
In summary, each factory is branded by an individual set of features, e.g. production window, sediment production and export, morphologies and slopes. It is this unique set of variables marking each factory that determines the factory-dependent response to small-scale and large-scale environmental changes through space and time as shown in the sequence stratigraphic development.
Humans are becoming increasingly active and increasingly recognized as geomorphic agents, and a key value of Earth surface processes research is its relevance to society. As 21st century landscapes evolve at unprecedented rates, knowledge of human-landscape interactions is needed to design effective management strategies for sedimentary basins. In this talk, I present findings from sediment dating and archaeological investigations in the Mississippi Delta, USA, a delta that has experienced rapid land loss over the past century. I use these results to describe the relationship of prehistoric settlement patterns to delta evolution and offer insights into prehistoric, contemporary, and future human-landscape interactions in the Mississippi Delta and other coastal sedimentary basins.
Brine, with salinities reaching six times that of seawater, occurs as groundwater throughout the subsurface of the McMurdo Dry Valleys and the Victoria Land Basin, Antarctica. This brine, derived from seawater freezing, is responsible for widespread precipitation of calcite, dolomite and aragonite cement and alteration of skeletal grains in Cenozoic glaciomarine strata. Relationships among depth, sediment age, and cement precipitation temperature suggest that cement—and brine—likely formed during discrete periods of cooling and ice sheet expansion.