The scientific endeavours of the Apollo Lunar missions provided two important, yet apparently contradictory, pieces of information. The lunar rock samples aged the Moon at 4.5Gy, whilst laser ranging measurements of present day lunar recession, facilitated by reflectors left on the Moon, imply an age of only 1.5Gy. It is evident that least one of these estimates must be wrong! We now know that Earth, because of its current continental configuration, has a very energetic tide. Because the dissipation of tidal energy act as a break on Earth’s rotation and thus forces the moon to recede, it is also a first order controller of lunar distance. Is it possible that the motion of continents has changed the tides enough on geological scales to facilitate a weaker tide that can reconcile the two age estimates of the moon? Here, I am hoping to answer this question by going on journey through Earth’s history and estimating the tidal energetics for a series of interesting time slices. I will also touch upon what the consequences may have been for other parts of the Earth system and for other planets.
Kathleen is a science team member for Mars 2020, This talk will give an overview of halite and gypsum on Mars and describe their potential to host microorganisms and organic compounds as solid inclusions and within fluid inclusions – as salt minerals on Earth do. The talk will place the search for life in salt minerals on Mars in context of the sample return plan for the Perseverance rover.
Join us as we explore the diverse world of Sedimentology. Drawing from a tranche of past BSRG talks and more, examples will be presented of sedimentary structures in ice and snow, the desert, the sky as well as more conventional settings. Prepare to be baffled by some real head scratchers and wowed by some of Earth’s largest ever structures, and finally head into space to speculate on the sedimentology of exoplanets.
During the webinar we shall report our recent studies to survey and sample the ultra-deep water hadal trenches that allow an unravelling the earthquake history of subduction zones and provide new insight into sediment mass and carbon transfer into the hadal trench – one of the least-explored sedimentary environments on our planet.
In the present day, Mars’ mid-to-high latitudes host abundant water ice within diverse and stunning glacial landscapes. In this talk, I will explore the recent history of glaciation and glacial meltwater on Mars, and discuss some of the morphological mysteries that remain.
The Cambrian Explosion marks the rise of diverse animal groups ca. 540 million years ago, but the triggers for this revolution remain poorly understood. The roots of the Cambrian Explosion are in to be found in the preceding Ediacaran, and we can now document a series of pulses of enhanced seawater oxygen stability over the Ediacaran to Cambrian interval. These coincide with pulses of diversification and increased body size in animals, and the biological control of carbonate production was driven by the rise of predation.
Strata may contain a signal that records the history of the tectonic and climatic forcing that controls how they form, and many conceptual models tie themselves in logical knots by assuming that these signals are always present in the strata. More interesting than assuming that a signal is present is testing what the signal might look like if it was present, and exploring how it can be extracted from the noise and autogenic patterns that may also be present. This presentation will show some results from numerical experiments using Lobyte3D, a simple stratigraphic forward model of a deep-water fan system, to investigate how an external signal is recorded, and how it can be distinguished, or not, from the autogenic patterns also present in the strata.
A Virtual Outcrop (VO) is a 3D photorealistic model of a cliff or quarry that captures the geological features. Most recently, model sharing across the web has become possible through generic sharing sites such as Sketchfab and purpose-built sites like V3Geo.com. In this presentation we review the history for virtual outcrops and briefly discuss how they are collected, processed and how to access data that is available for public usage. We will then take a short virtual fieldtrip to the Book Cliffs of Eastern Utah, primarily to illustrate some of our learnings on the topic. We will conclude with a short discussion on the mechanics of how to build a VFT using publicly available data in LIME.
Geology has traditionally been a descriptive science with a significant portion of the data coming from observations of features at a range of scales. Modern practices in the oil industry still rely in a large part on this legacy of observational data, for instance when rock facies are used to derive regional stratigraphic trends from core data, or as a building block for petrophysical classifications. However, a recent study has shown that even experienced carbonate sedimentologists will often classify the same facies using different textural names. This problem is compounded in industry by large teams often collaborating on a project, resulting in a heterogeneous attribution of facies to similar rocks despite the use of a common classification scheme. This problem reduces the reliability of descriptive data. In this presentation, I will talk about our research applying machine learning to automatic identification of carbonate facies using the Dunham classification scheme. We used high-resolution core images from the Integrated Ocean Discovery Program (IODP) Leg 194. Core images are used to train a model written in the Python programming language using the TensorFlow machine learning library. Specifically, we used Google’s Inception V3 network as a pre-trained Convolutional Neural Network (CNNs), and applied a method called ‘transfer learning’ to train Inception V3 to recognize carbonate core images. Results show that our CNN can achieve up to 90% accuracy for identification of Mudstone to Rudstone and Crystalline Dolomite. The main misclassifications were between matrix and grain supported facies, and fine and coarse-grained facies, textures also commonly misclassified by control tests with geologists. Interestingly, the bias observed in core description by the algorithm is very similar to human biases: a tendency to give a greater weight to grains as they stand out from the matrix, called ‘saliency’. But the CNNs were able to identify facies 60 times faster than humans, and with a much greater consistency. The results of our study demonstrate the potential of artificial neural networks to reliably interpret and quantify descriptive data for the oil and gas industry, in a fast, automated, high-resolution manner. Current and future work will focus on acquiring a larger dataset of core and thin section images, improving the training of the neural network, and coupling image recognition with logging and petrophysical data estimation.
Two types of currents dominate sediment transport and deposition on continental slopes: sediment gravity flows that travel down the slope through submarine canyons, channels, and gullies; and bottom currents that are part of the ocean circulation and commonly flow along the slope. Continental slope morphologies reported from mixed sediment gravity flow – bottom current systems across the planet reflect various degrees of interaction between sediment gravity flows and bottom currents. Unfortunately, two communities of researchers have historically specialized in either gravity driven sediment transport or bottom current sediment transport. Consequently, the processes governing sediment transport and deposition in mixed systems are not clearly established and interpretations of mixed-system deposits in literature remain hypothetical and sometimes appear contradictory. In this seminar we will present the first measurements of combined contour-current and turbidity-current flows, which were obtained in laboratory experiments. The measurements demonstrate that contour currents flowing at 10 % of the turbidity current speed can pervasively deflect the turbidity current flow and prove for the first time that hybrid bottom-turbidity currents can be at the origin of asymmetric channel-levee systems. These first experiments are the starting point for discussions on the themes that need to be addressed by the deep water community to achieve an integrated understanding of sediment deposition in deep water environments by contour currents and turbidity currents.
Carbonate sedimentary rocks form through the accumulation of organisms and chemically precipitated calcium carbonate, usually on the sea floor. They preserve fragments of marine organisms, which are sensitive to temperature, salinity and seawater chemistry during their growth, and they therefore provide an exceptional record of evolutionary and climatic change through Earth’s history. Carbonate sediments are also highly reactive, dissolving and precipitating in surface water. For these reasons, despite their simple mineralogy, they have a reputation for being difficult to understand and many clastic sedimentologists approach them with caution! Nevertheless, carbonate sedimentary rocks are important for many reasons. They have been exploited for millenia for their minerals, water resources and, more recently, for cement, roadstone and hydrocarbon. Now, as we face the effects of climate change, we can use carbonate strata to understand how Earth responds to environmental stress and use this knowledge to better predict the effect of climate change on modern ecosystems. There is also growing interest in how carbonate sedimentary rocks can be used to good effect for carbon storage and geothermal heat production. This talk will provide an introduction to ‘novices’ of carbonate sedimentology to the principle processes that govern their formation and modification during lithification. It will illustrate their importance to our modern landscape and heritage and demonstrate how ancient carbonate systems can hold warnings, and solutions, to the effects of anthropogenic environmental impact.
The threat posed by plastic pollution to ecosystems and human health is under increasing scrutiny and the amount of mismanaged plastic waste entering the environment is growing at a staggering rate. In particular microplastics (plastic particles <1 mm in size) have been discovered in every sedimentary system on the planet and thus became a new type of sediment particle. As such, sedimentology represents an important and powerful tool to understand and predict the transport, dispersal, and ultimate fate of microplastics in different environments. However, due to the complex shapes and low densities the transport and sedimentation behavior of this new sediment particle may differ significantly from those of natural sediments. The presence of microplastics in the environments poses new challenges for the field of sedimentology, but may also provide opportunities to better understand the dynamics of sedimentary systems. In this talk I will provide an overview on global plastic-pollution, microplastic as a new and unique sediment particle, and on microplastics in seafloor sediments.
Based on a recent review of the literature a data base of absolute values of short term (<3my) Cretaceous sea level rises and falls has been created. This shows an overall amplitude range of 5 to >65m, organised in four broad trends. The potential of aquifer eustasy has been investigated using climate modelling which showed a maximum impact of 5 to 10 meters. This leaves Glacio-eustasy as the key driver for short term high magnitude sea level changes in the Cretaceous.
The Halimeda algal bioherms of the Great Barrier Reef, Australia represent the largest living, actively accumulating Halimeda deposits worldwide. Following the Holocene post-glacial marine transgression, these bioherms kicked off the outer-shelf carbonate factory some 2000 years earlier than the nearby coral reefs. Recent multi-disciplinary work has revealed new insights into their surface geomorphology, subsurface architecture and depositional environment that may be of interest to those working on their fossil counterparts.