I found this suspicious structure in fragments of Iron ore (magnetite). Its original structure is difficult to me. The main belt is a metamorphic volcano-sedimentary environment with relative proposed age of Neoproterozoic to lower Paleozoic.
It resembles some volcanic structure, sedimentary structure or even fossil or stromatolite?
Looks like a trace fossil to me. Contact Dan Hembree at Ohio University He should know. Damian Nance.
At first glance I thought it is mullion, but the zoomed pic proves that I was wrong.
From my point of view, it could be tool marks. I never worked with Neoproterozoic rocks, however I've been working in volcanic and volcano-sedimentary rocks of Cretaceous age. I have seen those structures in volcanic turbidites. The image could correspond to a tool mark affected by to sets of fractures.
I would rather agree with Isaac: The thin diagonally running structures look like a network of (tectonic) fractures/fissures. The more broadly undulating relief might represent some sedimentary structures of abiogenic origin, such as flute casts or tool marks.
Looking at the zoomed picture of the structure by Hasan Malistani, I agree with Michel Buchwitz that the structure is tectonic. I believe the structure is similar to the one I saw in the Bima Sandstone based on which published a paper titled Microstructures in the Cretaceous Bima Sandstone.....The structure in question is called deformation band. It has been referred to by other workers as strike-slip faults.
I agree with some of you. I see two different features: a) a network of filled fractures-fissures comprising two sets at an angle close to 30°, b) an undulating surface that reminds me of tool marks at a bed base. Are these metamorphosed sediments of deep marine origin???? To determine the protolith could help to find the right answer.........
Give more details about the continuity of structure, the type of rock and the bed (if it is bedding, in situ) on which one can find theses structures
Also in my opinion, the structures in the picture may be interpreted as flute cast ( or something similar) developed at the bed base. Less clear, it seems to me the presence of structures of tectonic origin. To fix this you should verify if the structures crosscut the layer
Less clear, for more information you need petrographic examination, but in my point view, most possibly seems as tool marks as "like Catenary ripples" which is generate cross-laminae that are curvy but have a unidirectional swoop. They show a pattern similar to what a repeated "W" would look like. Like the sinuous and linguoid ripples, this form of ripple is created by unidirectional flow in lower flow regime " as in Tcde turbidites" with the dip at an angle to the flow as well as downstream. as well as some feature can be seen in zoomed view, like iron nodules. So these two structures can be interpreted as deep sea sedimentation.
"Vertical " and broad structure looks like sedimentary or volcanic ( what rock Is exactly that sample?)
"Oblique" lines ( in two diferent directions ) look like deformation bands (shear, shear tension) or like veinlets cemented with a weatheing-resistant mineral ( again , what is the rock?)
Cheers and best regards
I see gneissic texture in a schistose rock ( alternative bands from mafic and felsic minerals). It is very difficult to gees the structure affected on the rock from this very local field photo. But i gees it may be stretched mineral lineation due to regional metamorphism and tectonics.
if you did a thin section and you find goethite colloform on the surface of the sample, so what you see here on the surface is weathering features such dissolution following two sets of joints. However, you should know if these intersected structures are contiunous inside the sample or not.
To my idea, it is fault surface structure (Slip scratch ) if these is orientation when you touch it with hand.
It is difficult to interpret the structure from this field photo but I guess it is looks like crenulation lineation
I err toward Mohamed's interp. I have seen similar structures produced when a rock breaks parallel to the contact of a crenulated vein. The smaller structures look like a vein network. A cross-section of the sample at a high angle to the lineation would be useful.
Is the rock silicified too? It seem to me that the surface is a product of nicely weathered deformed rock. It seem that there are at least two (probably three) deformational events expressed in the deformational pattern. As the rock seem very finrgrained the structures are not visible elsewhere below the surface, except some filled fractures (e.g. on the left side of your photo I attached, red lines). Together with violet marked veinlets they cut older folds (green lines). Which is the reason for the origin of the folds, should be seen under the microscope. Coluld be also some type of sedimentary structure, as you said that the rock has volcanosedimentary origin.
Considering it is a metamorphic rocks, they should be crenulations.
Hi hasan,
This is a surface of metamorphic cleveage. At least two major compressional events can be seen on the cleveage surface, perpendicular each to other. So, this is purely a metamorphic structure. You can see even the flow of metamorprhic fluids, this is not a sedimentary flute cast behaviour.
To me this structure is very similar to effect of running water on a volcano-sedimentary
rock and oblique line which looks systematic, may develop due to tectonic activity and it seems the area may have been affected by extensional forces in two different direction!
I would throw my hat into the basket with Isaac and Michael. These marks look to me like scour marks and get produced when coarser material gets dragged over muddy substrate. Check it our on the web under sole marks or flute marks and you will find tons of info - maybe you even have a photo from the side where we could see the morphology of these - or break one open and post another image - cheers
This structure could be also a shatter cone? These structures are associated with a meteorite impact. In shatter cones, the fractures (linear features) form a cone, they all converge to a single point. Cheers
The presented photo at this plan did not give the possibility for a simple interpretation. It could be as well as metamorphic as sinsedimentary structure. Supplementary information obtained at section perpendicular to the presented plan even a thin section, will help for the correct interpretation. It will be good to have a more regional view on the same layer.
Hi, Hasan
apologize for the first answer. After seeng the quantity of other explanations I started to zoom the picture, and it seems to be really as a kind of flute cast imprint. There are visible at least 8 prints of flute casts at the beginning of the prints, documenting the flow from down upwards. I don`t know anything on the intensity of metamorphism... let play between sedimentary and metamorphic features.
Agree that they are flutes or longitudinal meandering grooves, on the base of a turbidite bed perhaps. The finer linear features look like later veins (fracture-fills). Check out J.R.L Allen 1984. Sedimentary Structures. Elsevier. This is the bible of sedimentary structures.
It’s a complex structure; probably flute casts related to different phases to turbulence. But I suspect that’s associated with algal mat. We need more sedimentological investigation and a study of rock?...
It is curious -looking at the whole history of this question- how interpretations of a sedimentary origin alternate
between answers with other waves of a predominantly structural view!
However, as previously mentioned, in my opinion sedimentary structures surely affect the sample and some structural accidents complicate the interpretation.
Thanks for all of your very nice comments, I really learned many things from them.
The main belt is a meta-sedimentary/meta-volcanics but the sample found in fragments of iron ore with no clear deformation. Generally believed that the belt is Neoproterozoic in age but there is no radiometric dating or fossil finding. I found Paleozoic fauna in the hangingwall sequence (see other question) but not in the schists and iron ore layers. My first field interpretation was trace fossils of Ediacaran.
This is only one finding in a relatively large sample size in the footwall sequence, i could not transport it and did not sampled for thin section but as evident in the picture, it look like sedimentary structure, like flute cast and tool mark. There is no internal structure visible in the rock sample if any due to strong replacement process.
The belt has a very complex multistage tectonic mainly trusting and deep fracture zone. The belt now located in the high ridge of western Hindukush mountain in over 4000 m elevation.
I can only post some more pics from the field, hope to help your interpretation.
The contact between iron ore beds and schist band. I found the structures near this contact but not in situ.
Dear Hasan, looking at that outcrop photo (contact between schist and iron ore) and again on the photo of this bedding plane (?) I'm not so sure any longer about ruling out a tectonic (instead of sedimentary) origin.
Some test questions: Did you observe a tectonic foliation oblique to the apparent bedding anywhere within the iron-rich unit? Do these structures seen in the first fotograph occur only widely spaced on individual planes or do they continue inside the rock (i.e. from plane to plane); are there sets of parallel planes where similar lineations with similar orientations occur? Is the range of orientation narrow or wide and do you observe one or several preferred orientations?
As suggested by some others multiple deformation may lead to somewhat similarly looking lineations, especially in schists and slates, and I wonder how crenulation structures look like in iron-rich strata (whose rheological properties probably differ from those of usual metasedimentary rocks).
From the outcrop photo it is clear that the iron ores are monolith and practically not deformed from the late deformation that have affected the underlying chlorite schist. In the inner parts of the iron ores you do not have the characteristic undulations from the sample at the first photo. Most probably it is a deformation structure from the contact itself.
I would agree with Haider Al-Ani. To me it also looks like ripple marks. About the fossils I am not very sure, but otherwise it resembles more like ripple marks then any other soft sedimentary structures. Check any book on sedimentary structures for details.
Interpreting structures from a photo is allways difficult and tricky. At first sight and from the first photo I would say that the major undulations are sedimentary structures (either ripples or groove casts) locally cut by a network of veinlets (tectonic). Looking at the second photo it seems that the base of overhanging layers (top center of the photo) show the same type of undulations, in an otherwise massive deposit. So these seem surface structures caused by dragging of objects in the surface of soft sediment and latter molded by deposition of the following layer. No penetrative structures are visible.
At a first appearance this structure seems to me groove marks ("A linear groove, cut in a muddy substrate by the dragging of an object through the sediment by flowing
water." def. from the Dictionary of Earth Sciences, Oxford). I suspect that in turbiditic sequences such structures could be quite frequent. I hope this comment help you.
I think it is metamorphic rock. You tell us the area is affected from several tectonics phases, and this sample located on the hangingwall of thrust fault.
I'm sure that isn't sedimentary structure.
We can see lineations and folitions in the several orientation.
Structure looks like microfolds (small scale folds) resulting from buckle shortening.
That structure is looks like thrust tectonic. Age of Neoproterozoic
I found this tool mark picture on the internet, it seems very similar but more recent:
I agree on the photo the features look very much like tool marks with an additional finer network of veins or fractures. However, if this is a slab of metamorphic magnetite a sedimentary structure would not be my first guess. As Ashit mentioned small scale tectonic undulations or buckle folds would make more sense. It really depends on your observations. Tool marks only effect the bedding surface, whereas folding should be pervasive throughout the rock sample and in the outcrop, indeed.
looks like shatter cone structure typically found in meteorite impacted rocks, for confirmation ask the meteorite specialist Andrew Glikson
cheers
Miri < [email protected]>
I doubt if it is a shatter cone but still look at the pictures attached and try to make a 3 D image of the sample of which you have put the picture here. If it is conical and penetrative then you must look for shatter cones in your area.
No, i am not seeing any shatter cone in the samples and there is no evidence of meteorite impact at all!
These look like crenulation lineations to me. Check the other face to see if there is evidence of the crenulation (microfolds) for which these lineations define the plunge, plunge direction.
I suppose that thse structures are sedimentary (ripple marks), superimposed by crenulation cleavage.(left side of the photo).
Seems to be ripple marks, we should know what is exactly the rock supporting it (volcanic or sedimentary ?)
In my oppinion, the picture looks like wrinkle structures related to algal/microbial mats such as those described by Noffke (2006, 2007 or 2009) and Porada and Bouoogri (2007). The structure seems like orientated mats by wind or water flows.
Please have a look at the attached image, (figure 3 in Porada and Bouoogri, 2007). Pay special attention to images A and C.
So, I have a similar thought to H. Halistani's when he said "my first field interpretation was trace fossils of Ediacaran".
Sorry, the picture above don´t seem to load. You can still find it in Porada and Bourougri (2007)
I have seen similar structures in the early Cambrian Puncoviscana Formation (NE Argentina). It looks to me that the conjugate structures predate the more pervasive, straight (up-down-trending) structures. Additionally, I think that the more pervasive structurues are associated with a mechanism of deformation.
This could be the cast of rill structure formed by any river or streams
There is no preserved evidence of fossils and stromatolites. The ridge -like structures could be formed by flow erosion, owing to different cement composition.
I interpret them as texture "signs underwater jets" (see slide)
I agree with the fracture/fissure interpretation: fracture --> erosion --> deposition of secondary cabonates.
If it is in igneous or metamorphic rock it could be lineations of tectonic origin or grooves and ridgesIparallel to shearing displacement. if it is of sedimentary origin it is a sedimentary structure like flute casts or ripple marks.....
It is much better to make element detection. Perhaps, the ridge-like structures get more high iron or silicon than surrounding rock.
Despite lots of ideas presented here I would rather agree with Abdullah Diabat. I saw similar structures in Bafq area Central Iran in metamorphosed-metasomatised sediments.
The Magnetite origin in this area (Jami et al 2007) is more igneous-metasomatic. So I think it is more tectonic related lineations. The other possibility is endulations during methamorphism and/or metasomatism.
This is deffinietly a sedimentary structure. A longitudinal current in origin. Some tectonic deformation cannot be excluded, but not as the main origin of the feature.
Definitely not microbial sedimentary structures (MISS) - they're too large, and don't look right - and there's no evidence to suggest a biological origin (i.e. I don't think they are fossils either). As for tool marks, what's the tool? This is Neoproterozoic, there's no plants and very little in the way of animal life that could create tool marks.
To my opinion it looks like ripple marks if the Iron ore is bedded BMQ/BHQ type. Please look into this possibility also.
What is the nature of the rock: sedimentary or volcanic. If this rock is sedimentary (I do not think) !!.
If this is volcanic rock that would flow as lava (lava strung; = the string structure in the form of strings).
In my opinion, you'd better see other samples and then find the distribution characters of this structure and then you should konw what it is.It's hard to identify the structure only by a picture.
I mostly agree with Michael Buchwitz. These look pretty much like sole marks at the base of turbiditic beds. These are erosive structures formed by eddies at the base of dense, turbulent flows (turbidites) They are usually named as "longitudinal scours" or "ridges and furrows".
It can becrenulation folds or wavy character signs. To tell without the sample difficultly more precisely
Sole marks... from someone who has seen a lot of them :-) But is always dangerous out of context.
Appear flute casts or tool marks. The diagonal lineations must have a structural origin
I'd like to see the cross section but I suggest soft sediment deformation rolls. Sediments can slowly creep and slide downslope as when a sand is deposited on a more hydrous mud on a slope. The downslope asymmetry and sag would make one side of the roll a different angle than the other, unlike tool marks which are symmetric. I do not see many impingement points or deeper impact sites as are typical of tool marks. Soft sediment deformation is a safer call than to label them as turbidity current generated features. there are 3 crossing fracture systems, with the one parallel to the break at the top of the rock being the least well developed. These fracture systems are likely brittle deformation, post lithification.
You could also check the case of having "fold rodding lineation" (crenulation lineation). The specific sample, could easily be a remnant of fold limp, so the parallel structures could be the aformentioned structure.
About the network of fractures I agree with Michael.
Regards
Ioannis Alexandridis
This type of structure normally found in sediments that to a river joining to sea. Due to wave action of sea and flow of water in the river the sediments have deposited the form of oformation type.
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