Sedimentology - Science topic

Thank you for your suggestion. The radiocarbon dates focus on bulk organic matter, i.e. total organic carbon content( TOC) while the OSL dates focus on the quartz grains for luminescence study. As the area lies on plain land there are no hydrothermal influences

Dear Colleague,

It is very possible to use DDR 3 for manual acquisition of 3D resistivity data but however requires intensive labour, prolonged duration on the field, more financial expenditure as the survey may spill into the following day if not completed.

The smartest way to embark on the acquisition, is by designing a spreadsheet that accepts all field parameters and automatically computes the apparent resistivity for effective monitoring of data trend.

It therefore advisable to input all recordings on a smart phone or tab when using DDR 3 for 3D acquisition.

Regards,

Alaka.

The calculation you are doing is to account for (exclude) the presence of apatite (Ca₅[PO₄]₃(OH, F, Cl), in which (ideally) there are 5 moles of CaO and 1.5 moles of P₂O₅. So, for every mole of P₂O₅ you need to subtract 3.33 (10/3) moles of CaO assuming it is all in apatite, then see how much CaO is left over.

However, depending on the rock type, not all the P₂O₅ (or indeed any of it) needs to be in apatite. For example, in metapelites, it might be in monazite. You should also check that you have converted your bulk compositions to molecular rather than weight percent values. Lastly, all analyses are associated with uncertainties that need to be accounted for.

What negative values are you getting?

Good luck.

You may have a look at the website "Triassic Stratigraphy"

or "The European Keuper: Stratigraphy and Facies"

Best regards

K.-P. Kelber

Hello Muhammad Sarim - the pag file contains the information for the report, for example the layout. There should be a special folder where there files are stored,, similar to the way this is handled in the Zetasizer software.

If this does not help, reach out to the help desk https://www.materials-talks.com/help-for-my-instrument-one-step-away/

Dear Dr. Matysek,

It is always a bit difficult to hand down a remote-controlled expertise.

1. I was first pondering over the so-called keratophyre issue which also forms fine-grained ash tuff ?

It is in my opinion not a normal petrogenic but hydrothermal alteration process which brought about 80 % K feldspar together with calcite

2. is the XX shape in the last SEM image pointing to adularia XX? High K-feldspar contents may occur in the low sulfidation-type alteration (?)

3. I know abnormally high sanidine contents from hotspot volcanism taking place in the Mongolian plateau during the Tertiary and Quaternary. This vast eruptive igneous activity brought about mainly alkaline basanites and olivine basalts. There , sanidine formed instead of leucite. The rocks also are accountable for placers enriched in sanidine, olivine (“peridot”), garnet (enriched in pyrope) and last-but-least sparked the discovery of 50 micro-diamonds. The K2O/Na2O ratio is below 5 and did not qualify the area as highly prospective for diamond-bearing "lamproites". What is yours?

4. A reworking has to be excluded due to the fine grain-size (?). Are there agglomerates or breccias?

These are some thoughts which are still rather un-oriented in one or the other direction.

At the moment I would go along with points 3 and 4.

HGD

The criteria that can be used to distinguish between tsunami deposits and storm deposits includes: the frequency of the deposits, the nature of neighbouring Facies associations and the sedimentary structure associations

The frequency of storm deposits is greater in a sedimentary series than those of tsunamis, to the point that sometimes we can have a succession of several hundred meters consisting almost essentially of storm facies as is the case for the Ordovician series of Morocco

Storm action is recorded from land to distal offshore so storm deposits must be associated with other shallow deposits: foreshore, shoreface, offshore or delta deposits. While tsunami deposits can occur in various environments ranging from the coast to the deep sea.

Storm deposits generally exhibit a wider variety of sedimentary facies than tsunami deposits.

Tsunami deposits may include sedimentary structures that reflect the combination of oscillatory currents and turbulent unidirectional currents. For example tsunami deposits of the Oligo Miocene of the NW Rif (Morocco) include layers of constant thickness displaying hummocky cross-stratification or Micro-hummocky cross stratification and large flute casts and groove casts at their base

Hello,

distinguishing kaolinite and dickite by XRD is not that complicated. It is necessary to prepare the least structured preparation (cuvette filled from above or behind, powdered preparation, preparation mixed with plastic binder etc.) and possibly use the Rietveld method with the insertion of models of both minerals. The positions of relatively weak non-basal lines are decisive.

Dear Mr. Daoud,

just this type was investigated in the cited paper:

DILL, H.G., BERNER, Z., KAUFHOLD, S., WEBER, B. and METZ, U. (2013) Facies-related baryte mineralization bearing Cu-Zn sulfides in Miocene estuarine deposits of the upper Rhein Graben (Wetterau, Central Germany).- Sedimentary Geology, 296: 55-71.

Abstract: Abstract

Baryte with or without base metal sulfides is quite common in sediments deposited in open marine environments or in continental sedimentary basins. Its precipitation is caused by hydrothermal processes, related to diagenesis, and frequently mediated by biogenic processes. The current study is focused on siliciclastic sandstones of Miocene (Aquitanian) age in an estuarine environment in the Wetterau region of the Rhein Graben, central Germany. In the estuarine environment only the central basin and the landward delta are host to a diagenetic and subsequent hydrothermal mineralization.

Diagenesis took place under near-ambient ( T ≈ 25°C) conditions and resulted in strong pyritization (-0.75 <Eh < +0.25, pH >5) in the central basin. Diagenesis is more landward represented by a pervasive silicification (pH < 12) in deltaic sandstones.

Epigenetic mineralization (100°-130°C) with pyrite in the central basins was succeeded by Cu-Zn-(Sb) minerals (0.75 < Eh < 0 / 5 < pH < 11), silicification and kaolinisation (2< pH < 9.5) and eventually by the formation of gibbsite (3 <pH<8). At the transition from the delta to the estuarine funnel, baryte is of very widespread occurrence. Its variegated texture and crystal morphology allow for a precise determination of the hydraulic system as marine phreatic, freshwater phreatic, and freshwater vadose. The narrow size of the rift graben and its sealing against the open sea fostered concentration of Ba and enhanced the redox processes. Hypogene brines along with Miocene volcanic activity provided the metals, and marine ingressions in this transitional environment supplied the sulfur. Sulfides were concentrated in the finer-grained rocks because of their enrichment in organic material, while sulfates accumulated in the more permeable coarser sandstones.

H.G.D.

Hi Everyone,

Please find our new Geosphere paper on this topic: Precision and accuracy of modal analysis methods for clastic deposits and rocks: A statistical and numerical modeling approach.

This one is now avaliable online.

Best regards,

Benjamin

The paleoenvironment of this deposit should be studied according to the facies associations. But according to you, and as well as the roundness of the grains, it is probably a glaciofluvial deposit.

Dear Mr. Pellegrino,

We have studied sedimentary basins across the world since many years backed by coal petrographic analyses under different wave length.

The publications below are all available on request for download from the RG server:

With kind regards

H.G.Dill

Primarily, it is likely to be an Fe-bearing calcite or Fe-bearing dolomite which under the influence of oxygen has been altered as to the valence state of Fe. Since trivalent Fe cannot be accommodated into the lattice of carbonate minerals it is expelled from the structure and concentrated as a mixture of Fe oxide hydrates which suitably are denominated as "limonite" (rareky pure goethite). You are on the right track with your assumption.

May be it's too late but the answer is you need to create the chart so that one of the axes is of probability scale. You can do it by calculating z-scores for your cumulative distribution function, which is calculated by NORM.S.INV function in Excel. Put z scores on one axis and the random variable (whatever it is) on the other. The random variable's axis should be of logarithmic scale. That's how you obtain a log-probability chart.

In log-probability chart, they say that a straight line is formed if the random variable is log-normally distributed, and the standard deviation is equal to the the ratio of the values of random variables at CDF= 84.1% and 50%.

My question is where 84.1% comes from.

Also, I wrote an Excel VBA routine that uses Gradient algorithm and iteratively finds the mean and the standard deviation of a log-normally distributed sample once the random variable and corresponding cumulative probabilities are given. I need that 84.1% issue to be solved before I conclude my software and publish it.

Any help is appreciated.

Hello Matias

Now I think that I understand what you are trying to do.

I think you can obtain a quasi-steady-state in your sample but you must wait some time to obtain it. As you have an insulator (your box) under the resistor you may have a problem with increasing temperature in that wall of the box and an increase of heat flowing in your sample.

You can obtain the heat lost through the walls of the box measuring temperature differences between inner and outer surfaces of the box P(lost) = (0,04) (T_in - T_out)/ 0,1. You can also have an idea about the heat lost through lateral sides using several termocouples in the upper surface of your sample located from the center to the lateral part of the samle.

The values obtained will depend on the sample you want to study. In principle if you are studying rock sediments you will obtain low thermal conductivity values (compared with common rock values ) but higher values than 0,04 and you will have heat flowing predominantely in the vertical direction.

Try to not use high temperature values in your experiment. Thermocouples are very good to use in this type of experiments because its volume is very small and they have a rapid answer.

As I said in my first message you are using Joule's effect in your experiment and the power dissipated is P= R I² . The value o I depends on the value of R. You must know the ddp (voltage) at the ends of your resistor ((V=RI).

I think I unswer to your questions but if you have some question more you can contact me.

Best regards

Maria Rosa Duque

Hi Zeinab,

SedLog is fine but I'll recommend to use a vector illustration software like Adobe Illustrator or CorelDraw. Making an illustration will always give more opportunities than the parameters defined by a software like SedLog.

Best,

Adrián

Dear Mr. Akhtar,

sequence stratigraphy methods are widely used in correlation and study of facies distribution in hydrocarbon exploration . I recommend startimg with the classical studies of Wilgus et al. 1988, Emery & Myers 1996, Miall 1997, Posamentier & Allen 1999, and Catuneanu 2003.

With kind regards

H.G.Dill

Delft 3D is a good choice

The question whether it is a fluvial-dominated or wave-dominated delta cannot be decided based upon the data available and should be done by investigating the vertical/ lithologs and also in plain view (e.g. "birdfoot delta" = fluvial) .

Often it is not a true end-member type but a mixture of wave- and fluvial-dominated processes. That is why I tried to convince you to look at this transitional landform between land and sea in a 3-D view to get a full-blown and true picture. It is certainly not an easy task.

H.G.Dill

use this paper for more

Significance of saturation index of certain clay minerals in shallow coastal groundwater, in and around Kalpakkam, Tamil Nadu, India

Well, I'd say that, generally, quartzites do not represent unconformities. However, on a global evolutionary scale, it could be that before terrestrial plants evolved, one could imagine land surface as exposed igneous/metamorphic rocks with no vegetation to trap the finer particles on-land. Therefore, much of the surface (at this time) could have been composed of SiO2 aeolian dunes. If this were the case, your argument might hold up for quartzites older than terrestiral plants (700 Ma) and directly overly basement.

Thank you Sergio Rodriguez. The problem at Erlangen University is the language, many courses are in Dutch.

E. Hajikazemi I.S. Al‐Aasm M. Coniglio

Journal of Petroleum Geology, Vol. 35(2), April 2012, pp 187-206

Abstract

Stable‐isotope and trace‐element analyses from five surface and subsurface sections of the mid‐Cretaceous Sarvak Formation in southern and offshore Iran confirm the presence of the regional‐scale Turonian unconformity and of a more local Cenomanian–Turonian unconformity. The geochemical results indicate the presence of previously unrecognized and/or undifferentiated subaerial exposure surfaces. Sarvak Formation carbonates at or near palaeo‐exposure surfaces show varying degrees of diagenetic modification, and more extensive alteration is associated with longer periods of exposure. The subaerial exposure and associated diagenetic processes greatly influenced reservoir quality and amplified karstification and evolution of porosity in the Upper Sarvak Formation.

The palaeo‐exposure surfaces are identified by their negative δ13C values (as low as – 6.4%) and negative δ18O values (as low as –9.4%), together with low Sr concentrations and relatively high 87Sr/86Sr ratios. These geochemical characteristics are interpreted to be the result of the interaction of the Sarvak Formation carbonates with meteoric waters charged with atmospheric CO2. The meteoric waters also caused karstification and soil formation which in some places extends a few metres below the exposure surfaces. Depleted carbon values were not recorded in areas where palaeosols are not well developed or where the uppermost layers of the Sarvak Formation have been removed by erosion.

Dear Prof Qasim Jan, Nusrat K Siddiqui and Munazzam Mehar,

My PhD work related to the spatio-temporal evolution of Kohat Potwar fold-thrust belts of Pakistan, I have collected samples from the entire Salt Range (Khewra, Karoli, Pail, Sakesar, Nammal, Zaluch, and Daud Khail sections) and Kohat. I used Apatite Helium and Fission track dating methods to document cooling ages. Interestingly Precambrian Samples gave similar AFT ages like Permain Samples around between 200-250 Ma. The ages are obviously partially reset but having similar ages was not expected. We conducted extensive thermal modeling of data and every model showed a cooling event in Late Paleozoic. We concluded that the Late Paleozoic rifting event reported In Kashmir, Zanskar and Peshawar effected the Salt Range. In my opinion, the trap is most probably related to Late Paleozoic rifting episode considering similar age magmatism in Kashmir.

I collected a small Khewra trap sample that is still sitting at my desk, It was not tempting to be tried for apatite. If Munazzam is interested i could try to separate zircons that will be no more than 3 days job, I would be free to do in December. The paper is in the final phase of review in Terra Nova, we are expecting a reply this week. If positive I will send you a copy. However, my thesis will be available online soon as I am defending thesis on 20th November.

Please compare the terminology of the terms "sedimentology" and "sedimentary petrology" given by the Glossary of Geology, Second Edition, Robert L. Bates and Julia A. Jackson, Editors (1980), and please decide for yourself what the similarities and differences are:

"sedimentology" (quotation): "The scientific study of sedimentary rocks and of the processes by which they were formed; the description, classification, origin, and interpretation of sediments. Sometimes miscalled 'sedimentation'."

"sedimentary petrology" (quotation): "The study of the composition, characteristics, and origin of sediments and sedimentary rocks. Often miscalled 'sedimentation'."

Best regards,

Guenter Grundmann

Dear Colleagues,

to distinguish the three end-member types of deltas (wave-. fluvial-.tide-dominated) should not be done based upon the description of some textures and structures. The delta front is the subaqueous part of the delta which is mainly built up under the influence of marine high energy processes, such as longhshore drift, wave and tidal actions. There may be discordant beds which have derived from fluvial reworking but they have not been mentioned in your record. You excluded a strong tidal impact which could have been indentified by the overall stacking of bedsets. So I assume you are studying currently a wave-dominated part. My general recommendation is try and investigate the entire delta (I do not know how much of it you have insight into ?) plot it and collect all data. The risk to over-interpret one part while others are ignored is high.

With kind regards

H.G.Dill

I agree with Dr Dill it is mostly Liesegang structures.

We recorded it from Late Jurassic and Cretaceous formations in Kurdistan.

Some of them are very rich with organic matter and others are rich with iron oxide.

- Aeolian silt and sand grains have frosted surfaces due to the the abrasion that they suffered when impacted to each other's.

- Aeolian silt might be better sorted than fluvial silts, while fluvial silts tend to be mixed with fine sand and clays and often have organic matter content.

-In a fluvial system, silts and finer sediments are related to flooding plains, so when the river level grows up and cover the plains around the river, after the energy decreases, the silts, clays and organic matter particles deposit on the flooding plain. Silts also occur in abandoned channels in meandering river systems.

Thank you so much. Will check that.

Dear Mr. Web,

to unequivocally interpret this section as a turbidite it is too small an insight into the entire lithological unit. If it were part of it, it would be the subfacies of a section cutting the BOUMA subsequences B (parallel laminated sandstone representing the upper flow regime) passing into subsection C (ripple-cross laminated sandstone representing the lower-flow regime). The relative amounts of the subsections shown in this outcrop, however, are not very much convincing me to direct my thoughts in this direction. I recommend mapping the area on a smaller scale and on the other hand looking for sole marks, cut-and-fill structures and reaction surfaces. I do not have doubt in the sedimentary stratification but for a precise analysis of the depositional environment and the up and down of the sequence I have not enough evidence.

With kind regards H.G.Dill

Dear Dr. Idries

These fine-grained sandstones show a rock parting on a different scale and intensity which allows the infiltration of (meteoric) fluids to a different extent and leave behind a residue of Fe-oxide hydrates (“limonite”). The latter “mineral” gives rise to the concentric structures resembling the contour lines of topographic map which reflect the different altitudes. It is a near-surface (supergene) process.

With kind regards

H.G.Dill

Your email

Isotropic contraction cracks, in this case most probably dessication cracks.

Dear Mr. Nejad,

your attempt to interpret the carbonate (micro) facies is very ambitious and is in my opinion not the correct way because the term facies is a far-reaching one to discuss the origin of a rock unit, in this case a sedimentary one where all available features of different scales need to be considered. The late Professor Walliser from Göttingen University once showed us a hand specimen and said: “ You should not create a new orogeny using only one hand specimen”. With kind regards H.G.Dill

Hi Jorge

I agree it's certainly possible. However, since XRF only detects the Fe content not the O content, the meaured Fe content will not change as a result of its oxidation state: this was the point I was aiming to make.

Kindest Regards

Paul.

No oolite at all, but calcispheres (= calciodinoflagellate cysts) -@ Som Nath Kundal -

Dear Rajamanickam,

Perhaps you can use trace element discriminant diagrams given by Pearce et al 1984 if you have analyzed those trace elements. You can try to discriminate between granitic sources of quartz in your quartzite, being aware that quartz from all sources are now mixed together. In case, if the source area of quartz was dominant in one of those granite types, you may end up in a good conclusion.

Best Wishes!

LRK

Dear Mr. Shan,

with some caveats, your spectra point to gypsum/anhydrite and kaolinite-group minerals, both of which herald a secondary acidic environment and oxidizing conditions. It is a local alteration spot. There a relics of mica and feldspar still present

Kind regards

H.G.Dill

Dr Jérôme Juilleret additions to the photo nicely highlight the depositional and post-depositional events of this sequence. Although the oxidation can be caused by several processes, in profiles such as this, it has been my experience in the western U.S., southern Italy, Jordan and Iran, that they occur under conditions of fluctuating water table, and their location in a profile is often linked to zones of lateral movement of ground water across a sedimentary profile due to the presence of zones of increased grain size. These more permeable units allow more rapid movement ground water. When these units occur at the top of the ground water table, oxidation also commonly occurs. The variable occurrence of these units in your profile more than likely record different levels of your water table

Dear Sir

I think the links below will benefit you in your search

Best Regards

Dear Damien,

One of the reasons could be the sistematic difference of oxidation potential between the REE, which leads to different grades of adsorption of these elements into iron oxyhydroxides, organic matter and phopsphates particles present on the sea water. For more details you can check the work of Sholkovitz et al. (1994) - Ocean particle chemistry: the fractionation of rare earth elements between suspended particles and seawater. Geochimica et Cosmochimica Acta.

Other reasons could be related to post reworking processes, such as taphonomic process: Auer et al. (2017) - The impact of transport processes on rare earth element patterns in marine authigenic and biogenic phosphates. Geochimica et Cosmochimica Acta.

Best regards,

Emilio

For an overview of various methods, see:

February 9th, 2012 Size and shape characterization in soils and sediments

https://www.brainshark.com/malvern/vu?pi=241199769&text=M021507&r3f1=

I still think improved version of Markov Chain I.e. partial independence or quasi independence method are very useful in analysing cyclicity in the sequence.The only thing that matters was the collection of data and I personally used these methods in the borehole data given by the agencies working on the coal reserves. It is very good and one can get result within no time.If it is correlated with Harper's binomial method than nothing beats it's usefulness.I do not think it is outdated.For your information there is another method which correlate the borehole sequence in space is cross association method.One can look my paper with Prof Tewari appeared in Jour.Asian Geology in 2009.

No such empirical formula exits to obtain Clay % from Fine content (silt+clay). The A-line in the plasticity chart enables you to see if the majority of (silt+clay) fraction is clay if it plots above the A-line and silt if it plots below the A-line. However, it could be organic soils as well!

Gentlemen - I believe you will find this document of great interest:

sajad

grain size , arrangement and cementation and matrix, diagnises , fossils.

heavy and clay minerals are good indicators...

For example

Chemical analysis of sediment and ratios like Ca/Fe, Sr values, K/Al will give provinances

Please have a look at enclosed PDF..

Dear Massimo, thank you very much.

Regards

Alessandro

Yes, exactly, the exact definitions are still not available and the terms are used in slightly different meaning, depending on the author. I find the classification of Moncrieff (1989) the best so far and it is commonly used in glacial geology, which is my playground. Hope, this was helpful.

Christopher:

There is no straightforward answer to your question as the subject needs to be explained in detail. However, this link would provide you with basic and useful insights:

Best

Syed

Jamal:

Have a look at this link for essential insights:

Best

Syed

Dear colleague:

There is a wide range of marks and traces in the field of inorganic and organic sedimentology which have some implications on the paleobathymetry of sedimentary strata. The same holds true for the floral and faunal remains in paleontology. There are much more publications, items and species of assistance to address this issue than room available in this Q&A process on Researchgate.

I wish you much success

H.G.Dill

AAS cannot be used for measuring 210Pb! It can be measured by 3 methods. 1) Alpha Spectroscopy ; 2) Gamma spectrometry (as mentioned by Arribere) and 3) MC-ICP-MS. By Alpha Spectroscopy, 210Pb activities of sediments can be analyzed indirectly by measuring the activity of its granddaughter 210Po (half life=138.4 d) which is in radioactive equilibrium with 210Pb (half life=22.3 yr). A polonium tracer and chemistry is involved. You may read references. There is some good literature describing the method (e.g., Koide, M., Soutar, A., Goldberg, E.D., 1972. Marine sedimentology with

210Pb. Earth and Planetary Science Letters 14, 442–446. The experts believe that the sensitivity of this method is better than Gamma spectroscopy. But in Gamma, the advantage is the non-destructive technique and does not involve chemistry. You may read an attached paper where this technique is used. In any case, some of the experts suggest that 210Pb cannot be used as a single dating tool and should be used in combination with other methods (say 137Cs...).

Please check out this article:

About mottled texture, can you post a couple of detailed representative photos?

It is clear that a job of cleaning and using the 3D scanning technique would help a lot. However, looking briefly and apparently the first plates appear to be benthic foraminifera of the genus Textularia; The third plate reminds me of benthic foraminifera of the genus Ammonia and the last plate really needs to be more worked on in the cleaning and for me they are difficult to be identified.

Are you referring to northern border of the Indian plate, or the present day political border of India? The latter is not easy to answer very simply. As you know, India is a large country and its geology shows considerable change from Assam to Kashmir. There are juxtaposed fold-thrust belts, suture zones, HP-UHP rocks, island arcs, Asiatic (formerly Gondwanic) blocks and of course the Siwaliks. 

You might like to contact Wadia Institute of Himalayan Gelogy, Dehradun, India, and Dept of Earth Sciences, Indian Institute of Technology, Roorkee, India. Their e-mails should e available on the internet.

Best, Qasim

Dear Rzgar,

Your answer far from the Pascal's question. He is talking about cap carbonate after glaciation age, while you are talking about sealing cap carbonate in reservoir. Pascal, you can read some papers about dolomite cap carbonate in Scotland, Death Valley, Namibia. Here are some references:

Anderson, Ross P., et al. "Microstructures in metasedimentary rocks from the Neoproterozoic Bonahaven Formation, Scotland: Microconcretions, impact spherules, or microfossils?." Precambrian Research 233 (2013): 59-72.

Brasier, M. D., and G. Shields. "Neoproterozoic chemostratigraphy and correlation of the Port Askaig glaciation, Dalradian Supergroup of Scotland." Journal of the Geological Society 157.5 (2000): 909-914.

Shields, Graham A., et al. "Barite-bearing cap dolostones of the Taoudéni Basin, northwest Africa: sedimentary and isotopic evidence for methane seepage after a Neoproterozoic glaciation." Precambrian Research 153.3 (2007): 209-235.

Prave, A. R. "Two diamictites, two cap carbonates, two δ13C excursions, two rifts: the Neoproterozoic Kingston Peak Formation, Death Valley, California." Geology 27.4 (1999): 339-342.

Corsetti, Frank A., and John P. Grotzinger. "Origin and significance of tube structures in Neoproterozoic post-glacial cap carbonates: example from Noonday Dolomite, Death Valley, United States." Palaios 20.4 (2005): 348-362.

Bosak, T., et al. "Agglutinated tests in post-Sturtian cap carbonates of Namibia and Mongolia." Earth and Planetary Science Letters 308.1 (2011): 29-40.

Hoffmann, K-H., et al. "U-Pb zircon date from the Neoproterozoic Ghaub Formation, Namibia: constraints on Marinoan glaciation." Geology 32.9 (2004): 817-820.

Best regards,

Iris:

You may like to have a look at this link:

Best

Syed

oh Dr. your perfect hunting Great Extinction of end Jurassic ....in Pic . show small &young ammonite in highly biodiversity in global death .....

suture line is Nautoloid clearly .

and this fossils in hard ground because global climate change causses from catastrophic (Activity of volcanic )

congratulation 

inter my account ..the same paper from south iraq