Friday Field Photo #132: Microfaulted sedimentary rock

microfaulted sedimentary rock

This week’s Friday Field Photo is from Permian strata of the Karoo Basin in South Africa. This outcrop displays some spectacular micro-faulting. The alternating lighter and darker colored layers (sandier and muddier, respectively) highlights the very small offset normal faults.

This was part of a rather large chunk of strata (about size of a small car) that was clearly a block within a slide complex. It was encased in muddy debris flow deposits and joined by other, much smaller, chunks of similar looking rock. Essentially, the block slid down a slope in a submarine landslide event. This faulting must have been the result of the block very slightly deforming as it was transported.

Happy Friday!

What Rocks: The Week’s Best in the Geoblogosphere

Each Monday I pick five posts from the previous week in the geoscience blogosphere that caught my eye. I limit it to just five because I want those who are not already plugged into this community to get a manageable sampling of the awesome stuff out there.

Here is my list for November 8-14, 2010:

Enjoy!

* This digest is what catches my eye throughout the week. With scores of posts a week from geoscience blogs I’m sure to miss a lot. Don’t hesitate to let me know about other great posts in the geoblogosphere via Twitter, e-mail, or in the comment thread.

Image: from my Flickr page

Friday Field Photo #131: Trace of an ancient sea urchin preserved in the mountains of Spain

Scolicia trace fossil

This week’s Friday Field Photo is from some Eocene sedimentary rocks (~56-34 million years old) I visited in the Spanish Pyrenees a couple of weeks ago.

You are looking straight up at an overhanging ledge and the basal bedding plane of a sandstone bed. It is up on a cliff face about 10 meters and out of reach, hence no scale — the field of view is approximately 60-70 cm across.

If you haven’t noticed already, check out the sinuous, double-ridged feature in the center-top of the photo. This is a trace fossil known as Scolicia. Trace fossils are neither fossilized remnants of hard body parts nor are they perfect imprints of soft body parts. Rather, they are traces of burrowing, grazing, and other behavior preserved in the sediment. Dinosaur tracks are trace fossils. If your footprints in a muddy tidal flat were buried, preserved, and lithified they would be trace fossils.

Although trace fossils have their own names to help categorization it’s important to note that one trace can be made by multiple species and one species can make multiple traces. In the case of Scolicia, it is thought to be the trace of a type of echinoderm (e.g., sea urchins, sand dollars, etc.) plowing it’s way through the sand.

Happy Friday!

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Image: Scolicia trace fossil; from my Flickr collection

Investigating Nature’s Experiments

DSCF1422

I’m back from a month of traveling, which included spending a fair amount of time in the field looking at rocks in their natural habitat. I’m still sifting through the pile of things to do that accumulated while away, so it may take a few more days for me to get back into the swing of things here on the blog.

I was talking with some close colleagues about this trip and realized that it has been a while — at least a few years –since I’ve had a somewhat relaxed field experience. I’ve been in the field a couple times in the last few years but it was when I was taking a lead role in organizing and/or teaching. As much as I love leading trips, every once in a while it is nice to simply be a participant and let others worry about the logistics.  

This state of mind allowed me to reconnect with doing science in the field. Talk to almost any geologist for more than five minutes and you’ll find out that where they really want to be is in the field. There is something very special about being out where the relationships of nature are on full display.

Robert Frodeman captures this in his fantastic book Geo-Logic: Breaking Ground Between Philosophy and the Earth Sciences, a must-read for any scientist who spends time in the field:

Science in the field proceeds at a different rhythm. Outside, in the open air, the scientist is subject to the elements. Rather than the controlled experience of the lab, the field scientist is immersed in a constantly changing sensorium that expresses wonder and serendipity of experience. The conceptual and physical walls that isolated the lab scientist are gone; the field scientist passes through a shifting, frameless flow of events. In the lab, nature is constrained so that it will show itself in a regular fashion; in the field, the scientist must adjust herself to nature’s patterns, cultivating a disposition of alert repose and anticipating the moment whent he world reveals itself. The biologist may wait all day fo the chance appearance of a species, and the geologists devotes hours searching for the telling fossil, splitting bedding planes in a shale unit.

While the lab narrows and controls the flow of information, the field’s perceptual and conceptual kaleidoscope exceeds our capacities to sort, test, and categorize it. Field scientists develop intuitive skills for parsing knowledge in implicit, nonpropositional ways. Walk an outcrop with a field geologist. Years in the field have taught him how to sift through the superabundance of information and identify the significant anomaly — an odd dip in the strata, an unusual color along the bottom layer. Field scientists do not operate in objective geographical space conceptualized by Cartesian geometry. Rather, they move through the world of implied meaning constituted by the acting and perceiving body as it interacts with its environment.

Most of what I do in the field is aimed at reconstructing and understanding the processes and relationships of an ancient sedimentary system. My goal is to visualize the depositional landscape that once existed through the present-day erosional landscape within which the rocks are now displayed. In some cases, quirks of the geomorphology and how the landscape is weathered and eroded offer clues. In other cases, I need to ‘look though’ the complex history of nature’s processes.

Tanqua Karoo

But that’s just me — other Earth scientists might go to the exact same outcrop and focus on the features that I essentially ignored. This is what I love about the field. There is a long and complex history of natural processes that are on display. The Earth is constantly conducting ‘experiments’ and when we go out in the field we are observing the results. Regardless of how sophisticated and (seemingly) realistic the results of numerical and physical experiments of Earth systems are we must continue to characterize the results of nature’s experiments

I’m already looking forward to the next trip.  

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Images: (1) Swartberg Range, Cape Fold Belt; from my Flickr collection, (2) Tanqua Karoo; from my Flickr collection

Friday Field Photo #130: Faulted turbidite strata on the California coast

small fault
This week’s Friday Field Photo shows some Paleocene turbidite deposits of the Gualala Block along the northern California coast. Sedimentary rocks, especially those with distinct alternation of rock types like this, are great for seeing structural deformation. It’s unclear how big the offset is on the fault in this photograph — my guess is that it’s not very big but we couldn’t confidently correlate across given the beach cliff exposure we had.

Happy Friday!

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Image: from my Flickr collection

Sand: The Neverending Story — A Q&A with author Michael Welland

Note: I’m traveling right now (looking at rocks) so I’ve scheduled a few posts from my archives. Below is an edited version of a review and Q&A about the book “Sand”. If you’re a new reader, enjoy! If you’re a long-time reader, enjoy again!

I have to admit that when I found out there was a popular science book devoted to sand I got really excited. Not only am I geologist, but I am a sedimentary geologist … and not only am I a sedimentary geologist, but I specialize in clastic sediments — a lot of which is sand. So, perhaps it’s not a big surprise that I’m a fan of book all about sand. But, at the same time, because I’m a sand-lover (or an ‘arenophile’ as Welland calls us) I read this book not only for the enjoyment of the narrative but also for additional insights and specific facts about my field of study.

However, this book is not just for the specialist. The subtitle for the edition I have is ‘The Neverending Story’* and the clever narrative that Welland employs throughout much of the book is the journey a grain of sand takes from birth through transport, deposition and burial, and, if the geologic situation is right, lithification of those grains into sandstone, and potentially the breakdown of that sandstone back to sand again.

… sand is one of our planet’s most ubiquitous and fundamental materials and is both a medium and a tool for nature’s gigantic and ever-changing sculptures.

This narrative is woven into a book that’s filled with fascinating facts and stories about the role sand has played in both natural and human history. Thus, ‘Sand’ is a great read for anyone interested in the story of one of nature’s most important geologic agents.

I enjoyed Welland’s writing style — some passages almost approach a rhythmic, even poetic style, but the writing manages to stay within a enjoyable and accessible style typical of non-fiction books:

When sand moves under a gathering desert wind, it seems to take on a life of its own, to become a different form of matter — like a gas, like liquid nitrogen spilling and spreading, following the ground surface. Spraying off the crest of a dune, shimmering in the light, veils of sand race and ripple, spread and vanish, their place continually taken by the next gossamer sheet, dancing, playing, celebrating. Are these jinns, the spirits of the desert? The sight is beautiful and hypnotizing in the evening sun, but if the wind gathers speed, beauty rapidly vanishes as the violence and menace of a sandstorm grows. Suddenly, it seems as if the entire mass of desert sand has sprung from the ground to hurtle with the wind. On the surface, everything is moving, even the largest grains, rolling, tumbling, kicking smaller grains into the rushing current. The sky disappears, and the howl of the wind seems amplified by its cargo of sand. The air is filled with flying sand, unbreathable.

There are many sections of ‘Sand’ that are able to communicate how dynamic and beautiful nature’s processes are. Another theme that is apparent throughout Welland’s writing is the concept of scale — both spatial and temporal — and how sand is so intimately connected with considerations of deep time and countless numbers.

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Below is a Q&A I did with author Michael Welland about ‘Sand’ (was originally posted in January 2010).

Brian Romans (BR): How did the idea for ‘Sand’ develop? Is this something you’ve wanted to write for a long time or did it come to you in an “ah ha!” moment?

Michael Welland (MW): Several years ago (I just realized that, astonishingly, it was 2004), I had an idea for a book that would be a guide to looking at landscapes. Working on bits and pieces of that, I started writing the story of a sand grain’s journey down a river, and, the more I worked on it, the more the idea struck me that here was the basis for a different book in its own right – and the rest, as they say, is history. So it was a kind of “ah ha!” moment, and the “ah has” rapidly escalated as I thought through the scope of topics that a book on sand needed to cover – all the journeys that a sand grain could take us on.

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BR: My favorite chapters were the ones that tracked the journey a grain of sand might take in a sedimentary system. These pages artfully discussed what I think is a fascinating area of research in sedimentary geology that attempts to integrate observations and measurements from an entire sediment-routing system — that is, from source areas to terminal depositional basins and everywhere in between. How did you come to use the Susquehanna River and associated offshore areas of eastern North America as the setting for telling that story?

MW: I wanted to use an essentially wild river, one as close to its natural state as possible, free from dams and other manmade influences that would impede the sand grain’s journey. Since I had been writing about a sand grain’s birth in the tepuis, the incredible flat-topped mountains of Venezuela’s Canaima National Park, I assumed that I could just continue from there – about as remote a place as you can get, home of Conan Doyle’s The Lost World, wild and romantic landscapes. It turned out that this was a very naive assumption – the rivers flowing out of the park and, ultimately, into the Orinoco, are, today, some of the most disrupted in the world – gold mining and gigantic hydroelectric power projects the culprits.

So I embarked on a review of the literature of the world’s rivers and our influence on them. What emerged was the startling fact that, in order to find a truly wild river, you have to go to the Arctic of Canada and Russia. But what I wanted was a river that would be familiar to the reader, a setting that would resonate – and lead the narrative on to a coast that would do the same. It turns out that, relatively speaking, the Susquehanna is as close to a wild river in a familiar setting as you can get. It also had the advantage of linking strands on the Appalachians, the ice ages, and the importance of rivers in culture and history – plus it leads to the Chesapeake Bay, the Outer Banks, barrier islands, and a dramatic coastal system, all wonderful grist for my mill, so to speak.

I agree that the whole topic of sediment-routing systems is fascinating – as much for what we don’t know as what we do. Measurements are not only tricky, but generic, different instantaneous cargoes of dissolved, suspended, and bed load sediment measured at particular times in particular places. Individual frames in a movie much of which we can’t watch, characters on journeys that we can’t follow. I found the reports of the Grand Canyon sediment flushing experiments fascinating since this is one of the few examples of tracking a specific cargo in real time.

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BR: Which part of the book turned out to be the most challenging to research and/or write? Why?

MW: Without doubt, the section on the strange behaviors of granular materials – I had no idea what I was getting into! But I found it absolutely fascinating and compelling, a dramatic example of the apparently simple presenting physicists with something complex and baffling. I knew about Per Bak’s work on sand piles, self-organizing criticality, and so on, but that was only the beginning. The first challenge was understanding some of these phenomena myself and the second finding a way of explaining them clearly (I hope), and communicating the excitement of the science. I was fortunate in that many of the researchers not only happily provided me with permission to use the images, but gave me a lot of help with understanding what was going on – together with the mysteries. And this topic I continue to find fascinating – it continues to crop up in science news and, as I’m sure you’ve noticed, I blog about the wonders of granular materials quite frequently. I recently had great fun giving a talk where there was no provision for the crutch of powerpoint illustrations, so I spent the whole time doing table-top experiments – “magic tricks” – with sand.

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BR: What was the most surprising bit of scientific or historical information you came across during your research for ‘Sand’?

MW: I was astonished to discover the microscopic ecological diversity of life between grains of sand – Rachel Carson’s “Underground City.” I’m no biologist, and so the world of meiofauna and extremophiles was a revelation.

And, in a completely different way, the sand bottles of Andrew Clemens (first encountered by my wife, my trusty research assistant) were a complete surprise, an awe-inspiring example of human creativity and tenacity.

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BR: A book like this requires a lot of research and I’m sure a great deal of interesting material ended up being trimmed or even completely cut out of the final version. Could you share a few facts or anecdotes you uncovered during your research that didn’t make it into the book?

MW: It’s still surprising, for a book about such an apparently mundane material as sand, howmuch stuff I had to leave out. This was one of the motivations for starting the blog – which I’ll return to in a later response.

There were a lot more examples of sand in art and literature that I would have liked to include, but permissions costs as well as space sent them to the cutting room floor. Bob Dylan, Salvador Dali, Andy Goldsworthy….

One noticeable omission, that I’m very conscious of and resulted from the fact that I used a river that ends in an estuary, is anything much about deltas which are, after all, some of the planet’s greatest piles of sand. And there are, of course, endless great tales from Earth’s history that sand can tell and I didn’t have the space to.

One of the fascinating and fertile areas of research was the imagery of sand in myths and sayings, cross-culturally and around the world. The stories of ropes of sand, for example, or sayings such as the definition of a one-horse town, “just a spit in the sand in the middle of nowhere,” or, from Japan, “Getting money is like digging with a needle. Spending it is like water soaking into the sand.” The Danes observe that “Many grains of sand will sink a ship” and, from India, the highly dubious and politically incorrect observation that “A woman without a man is like a spit in the sand – she dries up.” I think I’ll leave it at that……

A somewhat related point of interest is the challenge of the infamous Chapter 9 – sand in our daily lives. People either love it or hate it and I know that you’ve commented on it in your review as coming over too much like an encyclopedia. Fair enough – it does, but I have to admit that I was at a complete loss as to how to spin a story, a narrative through the staggering diversity of topics – any alternatives that I came up with seemed contrived. Hafnium and Fred Astaire? Aerogels and golf courses? Vines and quicksand? I’ll come up with something better for the movie!

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BR: What’s next for you as an author? Was ‘Sand’ the one-off book you’ve always wanted to write or do you have plans to write another popular book about Earth science? What other scientific (or non-scientific) topics are you interested in enough to learn about and maybe write about someday?

MW: No, it’s certainly not a one-off (I hope). I enjoyed the process (well, most of it) so much that I intend to continue (the blog is a great outlet). Of course one of the challenges is that writing a book does not generate proper income (unless it’s Harry Potter) and certainly no-one should embark on the process with that as an aspiration. What I enjoy, and which is evident, I hope, inSand, are connections and the inter-relationships between science, particularly geology, and our daily lives, global issues, art and literature; I have in mind a couple of topics for another book that would continue this kind of exploration, but I’d prefer to keep them to myself for the moment – sorry!

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BR: Since this is a blog, I’ve got a few blog-related questions for you. I’ve noticed that your blog, Through the Sandglass, contains some material that is in ‘Sand’, but it also has some other material that I don’t remember being in the book. Have some of the topics that didn’t make it into ‘Sand’ found a home on your blog? Do you consider the primary purpose of your blog as a way to promote the book? Do you use it as a way to brainstorm topics you want to write about? Many of my readers are also science bloggers and would be interested to hear your thoughts on the connection of blog writing with book writing.

MW: I started the blog at the encouragement of the University of California Press as support and continuation of the book. I’d had nothing to do with the blogosphere before that, and I’ll readily admit that I suffered from sone of the common prejudices (“the self-absorbed ramblings and rants of adolescents of all ages. Political and social tirades from grinders of the well-honed axes of zealotry. Mindless and breathless accounts of minor celebrities and nonentities” etc.).  But I rapidly came to appreciate how wrong I was and how powerful the blogosphere can be as a communication tool. I’m now, obviously I hope, a dedicated and enthusiastic member of the community and have derived immense pleasure from all the contacts that I would never otherwise have made, and all the stuff I’ve learned.

So yes, the blog started out as a way of writing about the book material that ended up on the cutting room floor, and as a means of publicizing the book (this “virtual book tour” is an example) but it’s become much more than that. By far the majority of the material in the blog is new (not from the book) and it seems that every day the backlog of topics I want to write about grows longer. I continue to be amazed at how the theme crops up on a daily basis in such a variety of contexts – I write about what intrigues and surprises me and I’m never at a loss. I often think that now, after fourteen months of blogging, I’ve actually written another book; but I haven’t – what I’ve done is write a series of articles, connected by a theme, yes, but it’s as much as anything a form of journalism. So yes, there can be a connection between blog-writing and book-writing, but I suspect that a blog emerges more naturally from a book than the other way round. I found the results of the recent geoblogosphere survey by Lutz Geissler, Robert Huber, and Callan Bentley really resonated with me. The equally top-ranked responses to the question “why do you blog?” were “to inform”, “to share knowledge”, and “to popularise the geosciences” – followed closely by “to have fun”. Absolutely!

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^ Make sure to check out Michael’s blog Through the Sandglass to read more fascinating stories about sand — some of which are included in the book, but many that are not.

Michael Welland explains why there are two editions of ‘Sand’ with different subtitles on his blog here.

Seafloor Sunday #76: Iceberg Gouges in the Ross Sea

Note: This is a scheduled post. I’m traveling right now and won’t respond to any comments for a couple of weeks.

This week’s Seafloor Sunday is a multibeam bathymetric image from the Ross Sea, Antarctica, showing grooves on the ocean floor. Combine large icebergs with relatively shallow water and you get a situation where the keels of icebergs can plow into the sediment leaving these marks. Image is approximately 25 km across.

Here is a regional map showing the location of the Ross Sea.

Images: (1) Marine Geoscience Data System (image created in GeoMapApp); (2) Wikipedia

Friday Field Photo #129: The Na Pali Coast

Na Pali coast

Note: I’m traveling right now (looking at rocks) so I probably won’t respond to any comments for a couple weeks.

This week’s Friday Field Photo is of the rugged Na Pali Coast on the island of Kaua’i. Earlier this year my wife and I eroded our savings and took a trip to Hawai’i. I had never been before and it was totally worth it. We spent five days on Kaua’i, the oldest (~5 million years) of the main Hawaiian islands.

The lava flows on Kaua’i are weathered to a beautiful reddish-brown color and dissected by canyons and gullies. Combine that with the bright green vegetation and the scenery is simply spectacular.

The Na Pali Coast is on the west-northwest side of the island and accessible only by foot. This photo was taken from a half-day cruise we did where we also saw this.

breaching whale

Happy Friday!

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Images: Both from my photos on Flickr tagged with ‘Kauai’

Climate Cycles Recorded in Martian Sediments?

Note: I’m traveling right now (looking at rocks) so I’ve scheduled a few posts from my archives. If you’re a new reader, enjoy! If you’re a long-time reader, enjoy again!

A study led by researchers from Caltech used high-resolution images of the surface of Mars (from HiRISE) to document and analyze ancient sedimentary layering exposed at the surface of the red planet. Before discussing the study and the paper, I just want to make a quick comment about the title of the press release. Here it is for this study:

Caltech Researchers Find Ancient Climate Cycles Recorded in Mars Rocks

And here’s the title of the paper:

Quasi-Periodic Bedding in the Sedimentary Rock Record of Mars

See the difference? The title for the actual paper directly fits the results of their study — what they found with the data they collected and analyzed. The press release title jumps immediately to an interpretation and implications of those results. Maybe you think I’m splitting hairs and being unnecessarily cranky, but there is a difference. Here is a statement in the abstract about the rhythmic bedding:

This repetition likely points to cyclicity in environmental conditions, possibly as a result of astronomical forcing.

The repetition in the bedding is what the study documents, a reasonable interpretation of the repetition is that it’s a function of cyclicity in the controls on bedding — and, finally a statement about the possibility of that cyclicity being forced by changes in orbital geometry (e.g., Milankovitch cycles). This is what you do in a paper like this — report your results and then discuss interpretations. This is in contrast to the statement from the press release that jumps directly to the potential implications. Words matter.

Okay, enough of that … for now. This paper, published in Science by Lewis et al. in December 2008, is very cool. You can find the paper here, or read the press release here.

The study area for this work is an area on Mars called Arabia Terra where layered sedimentary rocks are beautifully preserved within craters. The image above, from the Mars Reconnaissance Orbiter (MRO) website, shows the nature of these exposures in Becquerel Crater.

The authors of the study used 1 m-resolution stereo images from the HiRISE equipment onboard the MRO to analyze the bedding. The images were integrated with a digital terrain model (DTM), which allowed correcting for structural dip. Spectral analyses* of both thickness and color (i.e., image grayscale/brightness values) revealed statistically significant quasi-periodicity of the layering. Their analysis also revealed multiple orders of layering — beds (meter scale) and ‘bundles’ of beds (10s of meters scale).

The observation of rhythmic layering on Mars at multiple locations across the Arabia region constitutes evidence of cyclic variation in ancient surface conditions.

The biggest question on my mind while reading this paper is what the depositional environment was for these sediments. Johnson et al. address this question directly when they state:

The nature of the sedimentation process that deposited the Arabia layers remains uncertain. However, the observation of regularly cyclic bedding rules out processes that occur in a purely stochastic manner, including volcanism and impact cratering. … the size-frequency distributions of many stochastic depositional processes are skewed toward smaller events and can be described in many cases by a power law. Such processes include turbidites, flood events, landslides, volcanic eruptions, and impacts …

If I had to provide an educated guess — I would say that these strata represent chemical sedimentation processes of some kind (e.g., precipitation out of solution). To get such rhythmically-bedded deposits that are so consistently thick across a large area usually requires relatively “quiet” conditions (i.e., not a lot of highly energetic processes like waves and currents moving sediment around). Perhaps in the interior of a large lake or similar body of water. But, this is just a hunch — it would be fun to chat with the authors to hear their speculation.

The paper then discusses the intriguing implication of these rhythmic deposits — that they were caused by climate cycles. If the observed cyclicity is not a function of stochastic depositional processes or internal dynamics (sometimes referred to as autogenic cycles) then external forcings are at play. In this case, the authors draw upon research that has been done on Earth regarding the signature of Milankovitch cycles in strata.

Based on a pattern of layers within layers measured at … Becquerel crater the scientists propose that each layer was formed over a period of about 100,000 years and that these layers were produced by the same cyclical climate changes [link].

How cool is that!? This is an intriguing study because if we can find more areas on Mars where this method can be applied then we’ll have a better chance at unraveling the planet’s climate history (at geological time scales), which will help us better understand the planet’s overall geological history. This is why these orbiters, landers, and rovers are so important — they are collecting so much information that researchers can do science with.

Reading this paper and writing this post got me thinking about planetary science in general. An interesting area of research is investigating and testing various remote sensing tools and methods here on Earth where researchers can “ground truth” the results and comparing that with results from Mars (or other bodies). Obviously, there will always be specific aspects of other planetary bodies that are different from Earth — tests like that may not always return valuable results, especially for very specific questions. But I think it is valuable to do such studies to get a general sense of which methods work in different situations and why.

Within the context of the Lewis et al. study, it would be interesting to see if something like this has been done for a location on Earth — where rhythmic bedding was analyzed quantitatively by remote sensing methods and from direct measurement on the ground. How might they compare? How significant would the measurement error be between the methods? Etc.

It’s very exciting to see how methods of sedimentary research that have been utilized on Earth are influencing the investigation of sediments and sedimentary rocks on other planets.

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K. W. Lewis, O. Aharonson, J. P. Grotzinger, R. L. Kirk, A. S. McEwen, T.-A. Suer (2008). Quasi-Periodic Bedding in the Sedimentary Rock Record of Mars Science, 322 (5907), 1532-1535 DOI: 10.1126/science.1161870

* See this post from the climate science blog Open Mind for some general information about how researchers use statistical methods to extract information about cycles.

Images: (1) NASA/JPL-Caltech/University of Arizona [link] (2) HiRISE Images, NASA/JPL/University of Arizona [link]

Seafloor Sunday #75: Deformation along the Kimmeridge Coast

Note: This is a scheduled post, I’m traveling right now. If you leave a comment I might not be able to respond for another week or so.

This week’s Seafloor Sunday is from the southern coast of England and nicely shows folding of the Jurassic (200-145 million years old) Kimmeridge Clay offshore. This plunging fold shows up so well as a result of the well-banded character of the clay unit, which forms ridges. In some cases, high-resolution bathymetric data like this can reveal structural deformation not recognizable onshore because of erosion. This image reminds me of a similar image showing the geology offshore of Half Moon Bay just south of San Francisco.

This image and many more can be found on this great site by Ian West about the geology of Wessex Coast. Here’s a map from Google Earth zooms out to show the regional context.

Images: (1) Geology of the Wessex Coast of Southern England, by Ian West / link (2) Google Earth