@Neotectonics and I flew over this fault on our way to El Paso a few weeks ago. It is an excellent exposure of a reverse fault in the Magdalena Formation, a mixed clastic-carbonate succession in the Franklin Mountains near El Paso, Texas (hint – its in the left-center of the image, just to the left of the larger arroyo). Coordinates are 31.9591601917, -106.517622624 if you want to copy-paste them into Google Earth. Pretty beautiful alluvial fan too!
I include a zoom-in to show the details – because the beds are steeply dipping to the right (and upside down in this view) and cutting across topography, there is apparent strike-slip offset of the beds. However, this appears to be a reverse fault, with the lefthand side as the hanging wall. This fault must have formed prior to the tilting of these beds during Laramide deformation. The exposure is kind of a mind-bender, so twist it around in Google Earth and see if you agree with me (I might be wrong!).
I include a very basic line drawing (remember, I am not a structural geologist) of the fault for you to critique. We are looking almost right down the fault plane in this view, so the fault looks fairly straight. Scroll down to see the map view of this fault to see how it is influenced by modern erosion and topography.
Below is a Google Earth screengrab with a line drawing below for good measure. What you see is that the fault plane must be dipping south due to the rule of V’s.
Finally, here is a geologic map, with the fault shown in the red circle. There is another fault, which can be seen in the image above (right at the bend in the arroyo), but is not as well exposed as the northern one. Good mapping by Harbour!
By the way, if you want to download this map or any other geologic map in the U.S., go to this fantastic USGS website!
With three new grad students recently accepted into the CoRE research group at Colorado School of Mines, I wanted to take them into the field to scope out thesis projects and just to show them some classic turbidite locales in California. Here is a very quick overview of that trip, and some pertinent references in case you are interested in exploring further.
We started in the Ventura Basin, looking at beautiful channelized outcrops of the Modelo and Towsley formations. My student James will be working here for his M.S. project, characterizing the submarine channel fill patterns. If you want to learn more about the Ventura Basin, start here (opens pdf).
Portrait of our field group, taken from a quadcopter (nicknamed the CoRECopter):
Next we drove south to look at the Mio-Pliocene Capistrano Formation at San Clemente State Beach, a famous turbidite channel locale (see fieldguide here). Here is a typical photo of the channel fill facies at San Clemente (Zoltan Sylvester for scale):
We continued our drive south to San Diego, where we spent a few days scoping a project for Rosie, who will be working on submarine lobe deposits of the Point Loma Formation. Relevant prior reading is here (opens a pdf). These are very photogenic outcrops!
While working in the Point Loma, we employed our ‘science boom’ (a telescoping pole with a camera on top) to take oblique photos of the outcrops for 3D model building. Here is a fun shot of us during science boom deployment:
Finally, we did a long beach walk from Torrey Pines State Beach to Scripps Pier in La Jolla to look at the upward-deepening succession interpreted to be shoreline-to-submarine canyon deposits. Lisa Stright did some really nice work here integrating the outcrops into forward seismic models – see the paper here.
Here is a photo of the shoreline deposits, in this case a tidal channel with a very nice erosional base:
As you walk south on the beach, this succession grades into a coarse-grained submarine canyon fill. This photo is of a ~20 m thick sandy channel-fill onlapping a grey mudstone taken from the CoRECopter (color enhanced):
Finally, this trip was also about getting new students out in the field to look at rocks. I think they enjoyed it!
I’ve decided to start posting again after a hiatus, and I will start it off by reviving an old series called “Geology on the Wing Wednesdays”. Generally, these are photos I have taken of various places while flying low and slow in search of a $100 hamburger.
This week’s GOTWW comes from near Anadarko, Oklahoma, where the beautiful Washita River, a tributary to the Red River, meanders across the plains. This river is interesting not only due to the complex meandering form, but also because the channel belt seems quite narrow, implying slow rates of lateral migration, or that this river is relatively ‘immature’ (that is to say, recently avulsed). The caveat to that interpretation is that the landscape is strongly anthropogenically modified, obscuring the true width of the channel belt.
The AAPG meeting in Houston next spring (April 2-5) is the centennial meeting, and should be a good one. In recent years, AAPG has organized the technical program into broad ‘themes’ rather than allowing specific session proposals, and then just grouped the submissions into sessions after the deadline. People have generally rebelled against this and just organized sessions with their colleagues in order to have coherent sessions. These are only sent out via email, however, and are hard to find. I wanted to collect all the emails I have been getting about different sessions, so here it is. If you have one to add, please make a comment below, and I will add it to the list.
If you want to submit an abstract to one of these ‘sessions’, just write your abstract in such a way that it incorporates the ideas in the proposal, and submit it to the theme listed (seems more complicated than it needs to be, doesn’t it?).
The abstract submission site is here. (DEADLINE IS SEPTEMBER 22)
Stratigraphic Architecture of Deepwater Systems: Subsurface, Outcrop, and Modern Analogs (Submit to Theme 5).
Primary Convener: Zane Jobe (Colorado School of Mines), Steve Hubbard (Univ. Calgary), and Brian Romans (Virginia Tech)
Session description: Submarine depositional systems are large and persistent features on the Earth’s surface, and their deposits form significant reservoirs for hydrocarbons. Knowledge of the stratigraphic architecture of these systems enables prediction of reservoir quality and connectivity. We welcome contributions that document and examine the stratigraphic architecture of deepwater depositional systems, particularly those with applications to hydrocarbon reservoir prediction. Contributions utilizing modern (seafloor) and ancient (outcrop, subsurface) data as well as numerical and experimental models are encouraged.
Mixed Siliciclastic-Carbonate Systems (Submit to Theme 5).
Primary Convener: Jake Covault, UT/BEG
Session description: Mixed depositional systems are increasingly important deepwater exploration targets near the Atlantic continental margins and have been extensively studied in the Permian basin of West Texas and Southern New Mexico. Recent seafloor and shallow subsurface observations show that siliciclastic and carbonate deepwater depositional systems exhibit remarkably similar three-dimensional stratigraphic architectures associated with mass-transport, channel, levee, and lobe elements. However, questions remain regarding the long-term depositional processes and accumulation patterns of mixed systems. In particular, how do siliciclastic and carbonate systems interact to form stratigraphy in petroliferous sedimentary basins? We solicit contributions using outcrop, seafloor, and/or subsurface data to study the dynamics and controls of mixed deepwater systems.
Deep-marine sediment gravity flow deposits: new insights relevant to deep-water exploration and production (Submit to Theme 5).
Primary Conveners: Anna Pontén (Statoil) and Ian Kane (Univ. Manchester)
Session description: Sediment gravity flows are responsible for the transport and sorting of sediment from terrestrial and shallow marine environments to deep-marine basins. The resulting sedimentary accumulations are amongst the largest sedimentary bodies on earth, submarine fans. Owing to their size and large volumes of sand grade sediment within them, submarine fans represent significant, yet challenging, exploration targets. These potential reservoirs present challenges during exploration, owing to their often deep burial depth and deep-water setting resulting in poor seismic imaging and limited core calibration, and at the development and production stages owing to their complex internal heterogeneity distribution. Developing an understanding of the range of flow behavior, such as runout length, grain fractionation, erosion and flow transformation, and the subsequent character of their deposits enables prediction of lithofacies and likely reservoir qualities and stratigraphic compartmentalisation. In addition, the effects of burial diagenesis on the different facies types is non-uniform, and this may be considered in addition to the primary depositional reservoir property distribution. This session therefore seeks presentations that address the theme of relating flow processes to reservoir quality and to the sealing potential and distribution of stratigraphic baffles and barriers in deep-water settings.
Integrated Source to Sink Sedimentary Systems and Basin Scale Stratigraphy (Submit to Theme 5 or Theme 1).
Primary Conveners: Tor O. Sømme (Statoil), Lorena Moscardelli (Statoil), Vanessa Kertznus (Shell)
Session description: We welcome contributions that cover wide spatial and temporal scales of source-to-sink systems, using modern analogues, outcrops, subsurface data or modeling experiments. Source-to-sink analysis investigates relationships between sediment production, transport and deposition in the onshore and offshore domains of sediment routing systems. Understanding the stratigraphic record in these areas relies on an integrated understanding of how these sediment routing systems respond to allogenic forcing and autogenic processes at various spatial and temporal scales. Similarly, analysis of the stratigraphic record can reveal how ancient landscapes and sediment routing have changed through time in response to tectonic forcing and climate change. The recent interest in interdisciplinary source-to-sink studies have partly been driven by higher quantity and quality of seismic data, global cover of high resolution remote sensing data, as well as better geochronological tools, allowing higher resolution studies to be conducted both in modern and in deep-time settings. Being able to predict stratigraphic variability in source-to-sink systems is crucial for the hydrocarbon industry in order to define the distribution of reservoirs, sources and seals in the subsurface
Gulf of Mexico Regional Depositional and Structural Studies: Key to Deep-water Exploration (Submit to Theme 5)
Primary Conveners: John Snedden (UT Austin) and Paul Mann (Univ. Houston)
Session description: Regional studies in the greater Gulf of Mexico Basin have and continue to illuminate the complex depositional and tectonic history of this prolific hydrocarbon basin. Advances in our understanding of sedimentary processes from onshore to deep-water realms, the interplay of salt tectonics and deposition, and the transport pathways from mountain source to basin sink will be covered in this technical session. We expect presentations ranging from Mesozoic to Pleistocene, subsalt to Pleistocene fans, case studies of successes and insights from play tests that have extended the life of this remarkable habitat for oil and gas exploration. Papers about regional studies from the US, Mexico, and Cuba are welcome.
Modeling of Deepwater Systems: Understanding Reservoir Architecture and Predicting Reservoir Presence (Submit to Theme 5)
Primary Conveners: Anjali M. Fernandes (U-Conn), Peter Burgess (Univ. Liverpool), Zoltan Sylvester (Chevron)
Session description: The gradual shift in deepwater exploration and production to tackle reservoirs that display more challenging porosities and permeabilities requires a more realistic characterization of reservoir geometries and permeability heterogeneities. In this session, we will welcome abstracts that address this characterization problem across a range of spatial and temporal scales, from the dynamic construction and distribution of sand-rich reservoirs on continental margins, to the distribution and properties of individual architectural elements, to the details of grain size partitioning- and/or facies distribution. We solicit submissions that combine process analysis, measurement, and prediction, including but not limited to experimental, numerical, reduced complexity, or geostatistical modelling methods. We especially encourage submissions that bridge the gap between observations and models to better understand the impact of stratigraphic architecture on fluid flow through reservoirs.
Recent developments in sequence stratigraphic concepts and their application to deepwater deposits (Submit to Theme 5)
Primary Conveners: David Hodgson (Univ. Leeds), Cristian Carvajal (MBARI)
Session description: The widely applied sequence stratigraphic framework for deep-water deposits related cyclic change in shelf accommodation (due to relative sea level variations) to repeated changes in the character of the lithology and stacking of depositional elements. However, the stratigraphic record of deep-water systems results from the interplay of many autocyclic and allocyclic controls. Therefore, caution is needed in the simple translation of sequence stratigraphic terminology and principles that have been defined for shallow-water systems. Recent developments include: 1) the importance of source to sink configurations and the timing of waxing and waning sediment supply cycles and the development of highstand fans, 2) the documentation of exhumed deep-water systems over large areas, 3) the availability of high resolution seismic reflection datasets with well control, 4) the time transgressive nature of key surfaces in deep-water, and 5) the introduction of stacking-pattern analysis to investigate relationships between architecture, and relative base level changes and sediment supply. This proposed session is an opportunity to review and discuss recent advances in the refinement and application of sequence stratigraphy in deep-marine systems using modern, subsurface, ancient and modelled systems.
Non-turbidite deepwater units as reservoirs, seals, and trap elements: Towards a paradigm shift (Submit to Theme 5, co-sponsored by S4SLIDE)
Primary Conveners: Rachel Brackenridge (Shell, UK), F. Javier Hernández-Molina (RHUL, UK) & Derek Sawyer (Ohio State Univ., USA)
Session description: This session aims to address recent findings and case studies of non-turbidite deepwater deposits including contourites and Mass-Transport Deposits (MTDs), in siliciclastic and carbonate systems and their roles as reservoirs, seals, and trap elements. Deepwater sand deposits are frequently interpreted as turbidites and have been the single most commonly interpreted facies in the rock record. However, are all of these sands truly turbidites? In addition, there is an increasing catalogue of reservoirs worldwide with anomalous reservoir qualities, and mixed (turbidity-contourite) systems are more common on continental margins than previously thought. MTDs can exhibit variable and complex physical properties owing to their deformational history and composition and can act as reservoirs or seals. Contourites and other along-slope systems are often neglected in classical models, mainly due to many unknowns regarding mixed-drift systems. This can lead to significant differences between reservoir models and core information. Accordingly, conceptual models for mixed-drift systems need to be defined and the potential for enhanced turbidite play exploration considered.
Adopting new perspectives involving non-turbidite deepwater deposits would enhance understanding of the variability in deepwater deposits and aid in developing accurate deepwater petroleum play and reservoirs models. This understanding has great implications for identifying new hydrocarbon reservoirs in the future and re-assessing existing reservoirs.
Other sessions (that I don’t have all the information for):
How Seismic and Sequence Stratigraphy Have Advanced: 40 Years after AAPG Memoir 26 and 30 Years after SEPM Special Publication 42 (co-sponsored with Themes 5 and 12)
Innovative Techniques and Workflows for Characterizing Sedimentary Systems (co-sponsored with Theme 9)
Continental to Shallow Marine Depositional Systems and Sediments
Clastic Diagenesis, Reservoir Quality and Geochemistry
Impact of Structure on Sedimentary Systems and Reservoir Properties
Challenging Basins – Mixed Systems, Seismically-Challenged, etc. (co-sponsored with Themes 2 and 5)
New Insights From the Sediments of Mexico and Eastern North America
Contributions from Physical, Numerical and Forward Models (co-sponsored with Theme 5)
Sea-level, Climatic, and autogenic Controls on Coastal and Marine Stratigraphy: A Session Honoring the Career of John B. Anderson
I tweeted an image that got a lot of attention the other day and wanted to follow it up with a quick post describing the deposit. The back story is this: Lesli Wood, a submarine landslide expert, showed an image at a recent conference that is a spectacular example of a mass transport deposit (MTD), or more simply, a submarine landslide deposit. Landslides occur on land (example video), causing plenty of infrastructure damage and other problems. While they are difficult to view and visualize, landslides also occur on the seafloor, causing massive reorganization of the seafloor that can generate tsunamis. In fact, the Storegga slide that occurred offshore Norway about 6000 B.C. likely killed many Europeans.
Due to their volume and size, submarine landslides are usually characterized best with seismic reflection data – the map and cross section below from this paper by T.M. Alves. The map shows large blocks of rock that have been broken apart and transported downslope (from left to right) and the cross section shows what the internal character of those blocks are. Note the discordant nature of the blocks, very similar to the image above of the outcrop, with rocks in all directions.
Outcrops usually are too small or not well enough exposed to view these types of features, but the outcrops created by road making on the Boso Peninsula in Japan are definitely good enough. This paper by Yamamoto et al (download the paper here)describing these outcrops has a very nicely drawn diagram that demonstrates the deposit. There are probably two landslide deposits that are stacked here, with a turbidite separating them (grey layer in the middle of the diagram).
Here is another nice photo from a field symposium website showing a closeup of the deposit.
Callan Bentley over at Mountain Beltway just posted about Aden Crater, and I though i would share a few photos from Kilbourne Hole, a nearby maar volcanic crater. It’s only about 15 miles from my childhood home, and I went there quite a bit in high school, both for geology and just to get out into the desert (mainly to drink beer).
Geologically speaking, it is the crater that resulted from a magmato-phreatic explosion, or when, as Wikipedia says:
rising magma super-heats water-saturated earth, far enough below the surface that a high pressure can be contained. At some point, the pressure is too much, and a steam explosion occurs, throwing the earth out in a catastrophic event. Country rocks are fragmented and expelled in the atmosphere (together with fragments of the magma), eventually creating a deep crater, the bottom of which sits below the pre-eruptive ground surface.
For some nice images of other maars in action, go here. The main reason I like these features so much is that the ash cloud that the eruption produces (called a base surge) is a sediment gravity flow (just like a snow avalanche and a turbidity current). So, these are just really hot turbidity currents on land!
Looking on Google Earth at Kilbourne Hole and nearby Hunt Hole, you see one peculiar thing – there is a prominent ridge on the eastern side of the crater, but not the western side. This is thought to be due to westerly winds (i.e., winds out of the west blowing eastward) during the eruption that pushed most of the ash to the east. The wind in west Texas and southeastern New Mexico usually blows out of the west, and since this eruption only occurred ~25,000 years ago, I think that explanation makes good sense.
In the above photo, you can see the ridges on the eastern side of the crater, and I made a simple cross section showing the formation of the ridges and dunes from the explosion. Type in these coordinates in Google Earth to get you there – take a look at it yourself! 31°58’19.35″N, 106°57’45.23″W.
Looking north, you can see the right hand side (eastern) ridge is much higher than the western ridge. This is due to the wind blowing the exploded ash and bombs eastward. The crater is large – 2 x 3 km and 12 m deep – looks impressive from the ground:
One of the biggest attractions at Kilbourne Hole are the xenoliths full of beautiful green olivine – Callan has some nice photos here. However, we came to look at the base surge deposits on the rim of the crater, which formed when ash was falling after the explosion and piling up into big dunes and ridges on the eastern side of the crater. They are impressive, and quite thick:
In the above photo you can see many dune forms, which are all made of accretionary lapilli, which are basically sand-size ash clumps. If you want to learn more about these kinds of deposits, take a look at this thesis. A detailed photo of the lapilli is below.
Note that these deposits are normally graded (biggest grains on the bottom), as is common in many places where sediment gravity flows deposit sediment. Almost all turbidites are normally graded – see here and here for more info. And if you ever drive through the area, do yourself a favor and take a trip out to Kilbourne Hole (only takes 1 hour from downtown El Paso) – you’ll be glad you did.
Geologists are always taking multi-picture panoramas of outcrops and other geologically interesting phenomena, but then have to go back to the office and use photoediting software to stitch them together into a seamless image. The problem lies that the stitching is often imperfect due to photo overlap and the resultant images are hard to view on the computer because they are so large.
Gigapan (http://gigapan.com/) found a way to make this process better – you stick your camera into a small tripod mounted robot and tell it to take a large panorama (aka a gigapan), and then use Gigapan software to stitch it together and upload it onto the internet. The online viewer is pretty slick, and as you zoom in the resolution improves. In short, it is definitely the way to view large photographs interactively. You can even tag parts of a photo with a description of what is there.
Zoltan over at Hindered Settling introduced me to this whole Gigapan process (check out his Gigapan page too) , and we have taken many gigapans together. However, I wanted to try it on my own, so I took the robot out to the Guadalupe Mountains to test it out. My camera skills arent spectacular, so my first gigapan has a few vignetting issues, but it is still really cool. Since I was using a telephoto lens, this image is made up of 351 photos, resulting in almost a 3 gigapixel image!
This subject of the photo is a place called Slaughter Canyon, a prograding and aggrading Permian carbonate shelf margin. You can clearly see the progressively younger reef fronts moving from lower left to upper right. You can also see the very steep forereef slopes exposed just to the right of the cliffy, massive reef fronts – the one at far right is the best and longest slope, and gives an indication of the relief on this margin ( about 300 m). Here is a diagram showing the general morphology of that carbonate reef – if you could have walked around here in the Permian, this area may have looked somewhat similar to the modern coast near Oman, with dry desert on land and a carbonate reef in the shallow ocean.
The image below should link to the actual gigapan, but here is a link too. Be sure to push the full screen button and scroll around to see the full resolution. Enjoy!