Wednesday, May 28, 2008

Where on Google Earth #128

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After a long time I managed to get another WoGE correct and can host the 128th edition! I decided to make it a pretty tough one. Scale and North arrow have been removed. In return I will not invoke the Schott Rule. Anyone can reply on the location with a few geological details right away. As always either give the coordinates or an exact geographic location. This location is of importance for the scientific understanding of a certain geological issue. You can read about it in many textbooks.



Good luck!

Tuesday, May 27, 2008

podClast episode 4 on goodSchist

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Those of you who did not notice the latest episode of the podClast, yet, should go and listen to it on Chris Town's goodSchist blog. It's a bit of a different style this time and moderated by Chris and Dave Schumacher who also runs Geology News.

Saturday, May 24, 2008

Weekend Field Foto - a fold with a fault

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I've been so busy with following the Accretionary Wedge carnival, writing my own contribution for it, studying and writing/reading about nonsulfides I totally forgot about posting a weekend field foto! Shame on me! Silver Fox has the habit of posting field fotos of faults from her field work. So today I decided to search for a nice fault and think I may have found a nice one. It is a foto from Brittany, yep, the same field trip I already mentioned so often! In one of those bays you can observe folded layers of sand- and siltstone thrusted (is that the right english word?) onto shales. I'm going to have to consult my notes about the exact location and the exact formation, however, all of these rocks are from the Lower Palaeozoic.



It was a bit tricky deciding from where the fold originally came. We were unable to find useful slickensides and measing the fold with a compass isn't exactly easy either. Would be nice to go back there and have some "fun".

How I understand Nonsulfide Zn-Pb deposits

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Some time ago I wrote about the Special Issue on Nonsulfide Zn-Pb deposits published in the Ore Geology Reviews magazine. I finally got around to spending a bit of time reading those articles and making a few, simplified notes that I would like to share. Why are Nonsulfide deposits so interesting or why is the focus moving back to them after a long period of dis-interested in many parts of the world?
Most commonly nonsulfide deposits host a series of different minerals that all share a common characteristic: They lack sulfur and are usually oxides, hydroxides or carbonates. The benefication process for ores compromised of these minerals is somewhat more complicated than for sulfides, however, with the increase in environmental protection the benefit of sulfur absence in the ores is returning nonsulfides back to the agenda.
Mineralogically the most common minerals are smithonite, hydrozincite, hemimorphite, cerussite, and willemite along with gangue (calcite, gypsum, barite, etc.) and other ore minerals.
The principle idea in the entire Special Issue is that the formation of Nonsulfide Zn-Pb deposits requires the hypogene or supergene weathering of primary sulfide ores by oxidised fluids and subsequent reprecipation of the metals.
It needs a mechanism to allow for weathering and formation of oxidised fluids. Palaeoweathering, carstification and reprecipation in carstic cavities do play an important role in this process. Also these fluids need a pathway in the form of faults, joints, etc.
The influence of meteoric fluids and the penetration downward along faults and carst into the primary sulfides is one central mechanism. In Eastern Belgium the fluids likely were a mix of hydrothermal fluids and meteoric waters. Additionally the presence of willemite in nonsulfide deposits in Eastern Belgium appears to be connected to low salinity and high silica, oxidised fluids. Although the presence of willemite is often associated with high temperature hydrothermal fluids easily above 100°C, in the Belgian deposits their formation must have taken place well below 70°C under arid weathering conditions with a high silica activity or by low temperature hydrothermal fluids.
The emplacement of nonsulfides can be divided into two phases based on examples from Iran: An "oxidation stage" and a following "post-oxidation stage". Low amounts of Fe-minerals in the primary sulfide ore will controll the oxidation process. When oxidised they will lower the pH, carbonate host rocks will neutralise the acids and release CO2 which controls the paragenetic sequence (I don't quite understand how though). Last but not least the presence of oxidising bacteria, that i.e. oxidise pyrit, can increase the oxidation rate of sulfides to more easily facilitate the formation of nonsulfides. Last but not least a buffer is needed for the acid stabilising process and subsequent neutralisation.

The relationship of sulfide and nonsulfide ores in deposits from Belgium. The influence of palaeoweathering on the deposits should be obvious.

To make a quick summary the essentials for the formation of Nonsulfide Zn-Pb deposits are: Palaeoclimate and weathering, host-rock lithologies (to supply a buffer for acid neutralisation), the mineralogy of the primary sulfide ores and ore body geometry/tectonics to develop pathways of fluid migration and reprecipation in carstic cavities or replacement of the primary sulfides.

I must admit that I am still having some problems understanding especially the geochemical details. Dispite this I think that the articles are a wonderful contribution especially for people like me who had no prior contact with this kind of deposits. I can only recommend!
References:
A Special Issue devoted to Nonsulfide Zn–Pb Deposits
H.A. Gilg et al. / Ore Geology Reviews 33 (2008) 117–133
J. Reichert, G. Borg / Ore Geology Reviews 33 (2008) 134–151
J. Schneider et al. / Ore Geology Reviews 33 (2008) 152–167
G. Balassone et al. / Ore Geology Reviews 33 (2008) 168–186
V. Coppola et al. / Ore Geology Reviews 33 (2008) 187–210

Wednesday, May 21, 2008

Gastropoda - Heterostropha (Heterobranchia)

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While the May edition of the Accretionary Wedge (see my contribution) is reaching its climax at Julian's Blog I finally reached the last chapter of theory about the Gastropoda. Today I will write an overview of the Heterobranchia (Heterostropha). In these Gastropods the shell is coiled differently in the Proto- and Teleconch sometimes providing for some peculiar shapes. This phenomen is called Heterostrophism. Usually there is a change from sinistral to dextral coiling between the larva and the adult shell. The Protoconch is two-parted. Heterobranchia are known since the Carboniferous and exist even today. All land snails belong into this sub-class.

Allogastropoda

Architectonica
  • feeds on Coelenterata
  • Triassic - today
  • heterostrophic
  • Protoconch overgrown by Teleconch gives "hole-like" appearance
  • soft substrate, sand flats in shallow water
Nerinea
  • large, similiar to Cerithium but weaker sculpturing
  • Jurassic + Cretaceous (today: Pyramidelloidea)
  • extremely high-towering shell
  • characteristic spiral folds on the newel and whorl walls
  • lagoon environment and Rudist reefs
  • Aperture opening constricted
Valvata
  • marine and terrestrial (freshwater)
  • Upper Jurassic - today
  • northern hemisphere
  • Heterostrophism unrecognisable in shell
  • marshes and Ca-rich water
Opistobranchia
  • shell partially or completely reduced
  • certain since Triassic
  • most primitive form: Cephalaspidea
Acteon
  • typical primitive Opistobranch
  • Carboniferous - today
  • Protoconch at 90° angle to Teleconch
  • carnivor
  • sand-dwelling
Pteropods
  • holoplanctonic
  • planctotrophic
  • foot transformed to fins
  • migrating vertically in the water column
  • hunting with slime filaments for microparticles
  • Palaeocene - today
  • two orders Thecosomata (shell, sinistral, Aragonite) and Gymnosomata (no shell, tentacles)
Sacoglossa
  • bivalve shell
  • bivalve shell develops after metamorphism
  • feeds on Hydrozoans
  • cleptoplastic! therefore often green colored
Pulmonata
  • pallial lung
  • many varied forms
  • Carboniferous - today, radiating since Tertiary
  • Stratigraphic relevance: Tertiary
  • climatic indicators for Quarternary
Archaeopulmonata
  • typical for the transition zone of land to ocean
  • Antracopupa found in Carboniferous coal seams
  • Carboniferous - Jurassic: aquatic
Basommatophora
  • mostly freshwater to terrestrial
  • two families have returned back to marine
  • Lower Jurassic - today
Gyraulus
  • planispiral
  • partially decoils depending on water chemistry
  • Protoconch typically striped
  • small
  • holoartic
  • herbivor?
  • freshwater
Lymaea

Planorbis
  • sinistral
  • Tertiary - today
  • freshwater - terrestrial
  • Ca-rich water
  • low energy environment
Stylomatophora
  • terrestrial
  • stalk eyes
  • herbivor
  • cool and moist environment
Helix
  • small to medium sized
  • typical "snail" appearance
  • Cenozoic?
Pupilla
  • very tiny
  • terrestrial
Clausilia
  • terrestrial
  • turreted shell
  • herbivor
  • Upper Cretaceous - today

Monday, May 19, 2008

Accretionary Wedge - Everything is interconnected

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Julian is asking for our most significant geologic event in this month's episode of The Accretionary Wedge carneval. I may be a bit early but inbetween preparing for my snails exam I found some time. So here is my answer!

Frankly, there is no single geologic event that I could definitly point out as being the most significant in my view. Surely, the Chicxulub impact at the end of the Cretaceous is a sensational event, just as much as as the first forms of life finding their way onto land or the Snowball Earth event as a drastic transition point in the history of our homeplanet. Still I am having troubles identifying an event in Earth History that truly catches my amazement.

What catches my amazement are the formations of different kinds of ore deposits, sediment being deposited, lithified, compressed to hard rock and then ripped apart by internal forces, fluids suddenly moving into the rock, dissolving it, alterating it and precipating new, fascinating components, potential valuable minerals, ores that are then eroded and transported by rivers only to be deposited again, perhaps lithified again.

But that is not an event to me. It is a process and a very long one that happened and happens over and over again in many parts of the world. So I think I am more fascinated by processes. However, we are looking for an event that caught my eye. I have one. A very personal one that happened not so long ago. Understanding Geology and processes behind it all. Grasping what it all means and how it all works.

How did I come to understand geology? By all those field trips, reading and - you may not be surprised - through the Geology of Mineral Deposits and their formation. It may seem strange but only when I began to be interested in how and why deposits form here and not there I also began to investigate the secondary conditions of tectonics, magma differentiation, fluid flow, paragenesises, sedimentology, petrology and palaeontology, etc. Within the last two or three semester the puzzle pieces began falling into the right places all by themselfs. Suddenly I would no longer be standing in a quarry but instead I was standing at the edge of a Mesozoic reef or the Palaeozoic outer shelf or maybe just on the shores of the North Sea - a million years ago. A schist would no longer be just a schist but it was begin telling me a story. I realised something very important: Everything is inter-connected! We are living in a huge, beautiful interconnected system. Nothing is truly isolated from the rest of the world.

I think two periods helped me greatly get to where I am today. My field trip to Brittany and my six months in Peru. In Brittany I understood not just the theory (that I could write down in an exam starting in the first semester) but I understood the implications and processes. There I could see the development in a few kilometers of beach from rifting, deep marine, shallow marine, etc. Then in Peru one day I stood on the beach below Larcomar and thought: "Damn! I am standing on a freaking Subduction zone with an Accretionary Wedge out there in the ocean!"



Rocky intertidal zone and cliffs with wonderful layering close to the town of Crozon, Central Brittany.



The view from Larcomar, Lima, onto the Pacific Ocean and the Island of San Lorenzo.

That gave me quite the shivers. But it was cool. Very cool. I am still at awe when standing in a valley and seeing the glaciers that formed it long ago or seeing a gem in a store and knowing that it can only come from a handful of places on the planet.

To conclude my geological event for this Accretionary Wedge: Understanding Geology and realising that everything is interconnected.

UPDATE: MJC and Ole also posted their contributions!

UPDATE 2: Callan, Geology Happens, Silver Fox, Tuff Cookie, Hypo-Theses, Andrew, Kim, Maria and Brian have now joined, too.

Gastropoda - Neomesogastropoda and Neogastropoda

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Here follows the continuation of yesterday's Caenogastropoda. Subject will be the Neomesogastropoda that have a typically large larval shell, characteristic adult shells and a large foot. Ordovician - today. Also I will review the Neogastropoda.

Natica
  • bellied shell
  • holostome Aperture
  • "Propodien"
  • drilling in sediment and sucking out mussels - round holes caused by acid
  • carnivor
  • lower Cretaceous - today
  • shallow to deep sea
Cypraea
  • Kauri-Snail
  • large final whorl
  • convolute growth
  • herbivor grazing
  • marine
  • tropical - subtropical
  • upper Cretaceous - today
Lamellaria
  • mantle over shell
  • acid from mantle
  • secondary mineralisation of shell
Calyptraea
  • suspension feeder
  • hemisessile
  • consecutive Hermaphrodism
  • upper Cretaceous - today
  • parasitic, coprophagous
  • division into Protoconch and Teleconch
Cassis
  • helmet snail
  • feeds on Echinoderms
  • typical Radula for "drilling" holes
Tonna
  • feeds on sea cucumbers
  • short and wide siphonal channel
  • larva has thick, organic shell and is planctic
Cassis and Tonna - thorns = protection against sinking into sediment

Ficus
  • today: deep sea and shelf
  • relict of the upper Cretaceous
  • vermicular food
  • very long trunk
  • marine
  • subtropical - tropical
  • fossorial for food
Since Turonian/Maastrichian development to Neogastropoda
  • Aperture siphonostome
  • long siphonal channel
  • Ordovician - today
  • carnivor since upper Cretaceous (?)
Buccinum
  • final whorl large and bellied-rounded
  • Aperture wide with short, cut-out siphonal channel
  • carnivor
  • upper Cretaceous - today
  • tastes good with pepper and boiled in sea water
Melongena
  • brackish
  • feeds on mussels
  • good facies indicator
  • Caribbean, Paratethys
  • Radula: 3 teeth per row (evolutionary trend)
Syrinx
  • largest, shell-carrying snail
  • tropical Australia
  • max. 90 cm!
  • carnivor
Nassarius
  • tropical - subtropical
  • Estuary
  • dug in, agile
  • carnivor
  • 1 to 2 cm
  • no larval stage
  • mud flats
Conus
  • highly toxic!
  • carnivor, feeds on fish
  • transformed Radula tooth
  • Palaeocene - today
  • short Columella
  • long and thin Aperture
  • toxogloss
  • marine, tropical
Terebra
  • toxogloss, 2 teeth
  • vermicular food
  • digs into soft sediment
  • may be confused with Cerithium!
Turris
  • newel-like shell
  • toxogloss
  • "anal sinus"
  • Cretaceous - today
  • down to deep sea, Artic, tropical
  • 2. siphonal exit
  • typical Asthetics
Cancellaria
  • parasitic on sharks
  • tropical
  • upper Cretaceous
Mitra
  • thick shell
  • tropical shallow seas
  • might live in sediment
Voluta
  • no planctic Ontogeny
  • giant Protoconch
  • often tabby appearance
Murex
  • shell spheroidal - egg-shaped
  • thorny extensions
  • intertidal - soft sediment
  • carnivor
  • "purple snail"
  • Miocene - today
  • easy to recognise
Corallophila
  • parasitic in Corals
  • sessile
  • etches itself into Corals
  • Indo-Pacific
  • planctotrophic
Next: Heterostropha

Solution of Weekend Fun No. 6

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As Ron, MJC and Silver Fox have guessed correctly the sample from this weekend's weekend fun is largly Sphalerite. Ron restrained himself to naming the Quartz glomerocrysts that can also be found intergrown with milky Quartz and sulfides on the backside of the sample (but very tiny). All the big cubic crystals are tetrahedral (few truely idiomorph) Sphalerite. Considering the dark color these Sphalerites likely have a high iron content. I don't know how high and if it would be enough to consider these Marmatite. On a few spots the Sphalerite is actually almost transparent and has an orange to reddish color. Furthermore we have massive Galenite, Pyrite (but no large crystals Silver Fox) and Chalkopyrite on the outer edges of the sample. The sample is a gift from Peru. I assume it comes from a vein type deposite somewhere in the Andes of Peru or Bolivia.

Sunday, May 18, 2008

Gastropoda - Caenogastropoda

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The Caenogastropoda are one of the most diverse sub-class of Gastropoda and include a wide range of shell shapes, habitats and uses for facies reconstruction. A short description of the most useful orders will be presented.

Architaeniglossa

Viviparus
  • shell shapes gyrocscopic to speroidal
  • worldwide in freshwater
  • Jura - today (species since Carboniferous)
  • drainage lakes, rivers
  • shell primarily organic, mineralisation in the uterus
Ampullaria
  • Apple Snail
  • today: South America, Asia, Africa
  • Cretaceous - today
  • shell sinistral, slightly asymmetric
  • forms clutch
  • subtropical - tropical
  • can withstand droughts
  • terrestrial
Cerithimorpha

Cerithium
  • perhaps oldest Caenogastropoda
  • Aperture not holostome
  • Trias - today
  • warm lakes, also marine
  • photic zone, Mangroves
  • herbivor, detritus
  • soft grounds
  • may cement itself to surface
Melanoides
  • marine - brackish
  • worldwide in tropics
  • Miocene - today
  • Parthenogenesis
  • high resistance
  • rhipidogloss
Melanopsis
  • today: mainly in New Zealand
  • typical for Paratethys
  • eggs in estuary conditions, adults in freshwater
Littorinimorpha

Littorina
  • marine
  • tidal zone and rocky shores
  • herbivor
  • since Triassic/Palaeocene?
  • vivipar
  • thick shell, gyroscopic shape
  • Apex blunt
  • Aperture askew
  • important for Holocene Baltic Sea stratigraphy
Hydrobia
  • small, long-cone-shaped
  • mainly freshwater but also marine-brackish
  • gigantism
  • Jurassic - today
  • decoiled forms
  • herbivor
  • wide suture
Strombimorpha
  • low to high-trochispiral shell
  • Aperture with channe or newel
  • Ordovician??? Triassic - today
Strombus
  • Bahamas
  • Jurassic - today
  • giant forms
  • epibenthic
  • shelf, sublittoral to littoral and soft substrates
  • subtropic - tropical
  • "fighting conch"
Tibia
  • deep sea
  • soft substrates, cannot move in sediment
  • long siphonal tube
  • carnivor?
Heteropoda
  • shell mainly reduced
  • foot changed to fins
  • carnivor
  • trunk-like head
  • lower Jurassic - today
  • endoplanctonic
  • facies independent
Atlanta
  • planispiral and keel
  • Jurassic/Palaeocene??? - today
  • mm - cm size
  • Protoconch always varied
  • Teleconch planispiral
  • in all oceans
Ptenoglossa
  • named after ptenogloss Radula
Janthina
  • purple - blueish color
  • Cenozoic
  • foam raft
  • carnivor (jellyfish)
Epitonium
  • tropics
  • benthic
  • carnivor
  • Triassic - today
  • cone-shaped, coiled
  • near-by algae or sea anemones
To be continued...

Friday, May 16, 2008

Weekend Fun No. 6

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Another edition of weekend fun and mineral guessing! This one is a rather large example. Ball-pen included for scale. The background is the kitchen table, it's plastic. Don't be distracted! The rust-colored spots are much too rust-like, however, it is the best foto I could take. There are several minerals to be identified. How many can you find and what are they?



Have fun!

Thursday, May 15, 2008

My First Geology Tool

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Dave from Geology News posted about his first ever field trip way back in 2001. That's the same year I began studying at university. However, I had enrolled in Geotechnical and Mining Engineering that year only to drop out of that and switch to geology three semesters later. Sadly I do not have any fotos of my first field trips. So I decided to make a short foto session with my first ever geology tools instead. Gladly I kept all of them (except the tiny acid bottle that fell apart).

So what was my first geo-tool? Of course it was my hammer!



But was it really my very first? Not quite. Remember I started out with Geotechnical and Mining Engineering! In my first year I already worked for two months in a large open pit lignite mine west of Cologne. So the first tool I ever had is my helmet:



I am very glad I have it. It saved my head more than once. Actually I had two helmets, however, the one I used in the Berchtesgaden Salt Mine had to be replaced after only 3 days because the ceiling above us decided to drop a few kilogramms of rock onto our raft during maintenance work. Poor helmet had a dent and hole in it the size of a grapefruit. Yep,it was a raft on a lake inside a mine. Long story.

What are your first geology tools?

Wednesday, May 14, 2008

Gastropoda - Neritimorpha

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I am sure a few of you can no longer stand seeing or reading about snails but there will be more today. Don't dispear! Today's contribution will be rather short.

Neritimorpha

The Neritimorpha include the Neritoidea, Neritopsoidea, Platyceratoidea and Hydrocenoidea. Common characteristics are good preservation of highly variable color paterns, a protoconch consisting of aragonite and a teleconch consisting of calcite. In many species the larva is marine but the adults live in freshwater. Few species are completely adapted to living in freshwater conditions.

Neritopsoidea

Theodoxus
  • representative of the Paratethys
  • habitat: rivers, brackish water
  • salinity: 2 - 15 ‰ but lives mainly in freshwater
  • no larval stadium because they would be swept away by currents in rivers
  • no connection to the ocean necessary
  • protoconch spheroidal
Nerita
  • marine
  • whorls partially dissolved thus no columella visible
  • few terrestrial species

Tuesday, May 13, 2008

Gastropoda - Archaeogastropoda

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Today I will try to give a brief overview of the most important members of the Archaeogastropoda. I will discuss shortly the three most important super-orders with examples of important orders or families.

The Archaeogastropoda are likely the oldest Gastropods dating back to the Ordovician, perhaps Cambrian. They still exist today as a sub-class. The protoconch is one-piece with only one whorl. Often the inner layer of the shell is composed of nacre. The aperture is holostome. Most species are herbivor and develop lecitotrophic larva. They are all endogastritic. Radula most commonly rhipidogloss or docogloss.

Unless otherwise noted all examples are of marine origin.

Patellogastropoda
  • cup-like shell
  • apex points backward
  • shell mostly calcitic
  • embryonic shell planispiral and sinistral
Patella
  • main genus
  • shell with radial ribs
  • suction foot
  • U-shaped muscular impression
  • no nacre
  • habitat/life: sublittoral, grazing, hard substrates, not tropical
  • Trias - today
Vetigastropoda

Pleurotomaria
  • "slit-band" - and partially open incission into the shell (does anyone know what is the proper english language word for this?)
  • nacre
  • today: abyssal
  • mesozoic: shelf
Haliotis
  • ear-like shell
  • nacre
  • thick muscular impression
  • cup-shape secundary, teleconch coiled
  • "slit-holes" - holes instead of a "slit-band"
  • lower tidal zone, grazing, herbivor
  • cooler water
  • Cretaceous - today
Trochus
  • grazers, herbivor
  • edges
  • flat basis
  • operculum
Calliostoma
  • Cretaceous - today
  • eats Hydrozoans
Turbo
  • grows concentrically
  • calcitic???
Fissurella
  • cup-like shell
  • no nacre
  • porcellane-like shell
  • "breathing hole" on top
  • tropics
  • Trias - today
  • beware of confusion with Patella!
Scissurella
  • derived from Fissurella?
  • appearance similiar to Pleurotomaria
  • "slit-band"
Bellerophontida
  • planispiral coiling
  • "slit-band"
  • thick shell
  • no nacre
  • Cambrian - Trias
  • exogastritic!
  • questionable classification! Maybe it's a Monoplacophora?

Monday, May 12, 2008

Gastropod shell, body and radula

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Today a brief overview of the most important Gastropod terms and vocabulary will be given together with short explainations. We will start with the shell of the Gastropod which is the most commonly preserved fossil remain of a Gastropod (Snails).

The shell is usually composed of the mineral Aragonite. The shell walls can be simplified into three layers called, from outside to inside: Periostracum, Ostracum and Hypostracum.
  • Periostracum: a thin organic layer which forms the outside of the Gastropod shell and protects it from dissolution
  • Ostracum: layer of calcium carbonate prisms orientated vertically to the surface held together by a proteine. It forms inbetween the fresh Periostracum and the mantle.
  • Hypostracum: thin, inner-most layer of horizontal calcium carbonate platelets covered by Nacre on the most inner layer.
Shell shapes can be generalised into three different types, excluding those Gastropods that have lost their shell. These are cup- or cone-shaped like in Patella, planispiral like in Planorbis or trochispiral like in Turbo. Due to their asymmetric nature these shells posess a chirality. Meaning they can be either left-handed (sinistral) or right-handed (dextral). Most species are dextral, few sinistral, some may have individuals of either.



The common features of a shell are:
  • Apex, the tip of the shell.
  • Columella, a spiralised cone in the centre.
  • Aperture, the only opening of the shell which may have different shapes.
  • Siphonal channel, an extension of the Aperture
  • Suture, the junction of whorls
Other important terms:
  • Protoconch: the larval shell
  • Teleconch: the adult shell
  • endogastritic: the spiral points away from the head
  • exogastritic: the spiral points towards the head
  • Torsion: rotation of the visceral mass, mantle and shell by 180° with respect to the head that brings the anus and mantle cavitiy above the head. Detorsion in some Gastropod species towards the side or complete detorsion.
  • Spirality: spiralling of the upper part of the visceral mass usually to the right
The Gastropod body is divided into four parts: head, foot, mantle (pallium) and visceral mass. With the exception of the Pulmonata (who have a pallial lung) all Gastropods have a pair of gills that can be reduced to one gill in more developed species.

An important feature in the classification of recent Gastropods is the Radula. There are several types of Radulas. It exists a trend in the development of the Radula to reduce the number of teeth. Few teeth can be an indication of a carnivor way of life. The most extreme case maybe being Conus (Danger: highly toxic!) with only a single tooth that is used to poison the prey. There are central teeth (Rhachis-tooth), teeth on the sides (Admedian-teeth) and marginal teeth.
  • rhipidogloss: most primitive type with most teeth
  • docogloss: fewer teeth, no marginal teeth
  • taeniogloss: few teeth per row
  • ptenogloss: numerous identical teeth
  • rhachigloss: mostly only central teeth and seldom marginal tooth
  • toxogloss: one tooth in the centre with hooks. Toxic!

Sunday, May 11, 2008

Gastropod Systematics

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Currently I am preparing for my last ordinary class "exam". Actually it is my 2nd try. I passed the parts about amphineura and conchifera, well, with the exception of the gastropoda. I think that is because my professor here is a real gastropod expert and a huge fan of these slimy beasts. I figured I make a virtue out of my little problem and start a small series about gastropoda. It will largely be based on my class notes and scripts. Basicly I am trying to make me learn it by turning studying into blog posts. I was never a great fan of fossils thus I hope to turn studying these beasts into fun somehow. I will start with something simple that does not involve much background knowledge. These post will mostly deal with gastropods from the fossil record. Please take note that there are different systematics. I will use the one we learn at university. I take no guarantee for completeness or correctness of my contributions here.

Gastropod Systematics

There are four sub-classes of gastropods relevant to this discussion. These are the Archaeogastropoda, Neritimorpha, Caenogastropoda and Heterostropha (also named Heterobranchia). The main sub-classes are again sub-divided into super-orders.

Archaeogastropoda
  • Patellogastropoda
  • Bellerophontida
  • Vetigastropoda
Neritimorpha
  • Neritoidea
  • Neritopsoidea
  • Platyceratoidea
  • Hydrocenoidea
Caenogastropoda
  • Architaenioglossa
  • Ceritimorpha
  • Littorinimorpha
  • Strombimorpha
  • Heteropoda
  • Ptenoglossa
  • Latrogastropoda with Neomesogastropoda and Neogastropoda
Heterostropha
  • Allogastropoda
  • Ophistobranchia
  • Pulmonata
This for the start. More tomorrow or later. If you are familiar with gastropod systematics you might notice differences with the ones you know. It is giving me quite a fight really comparing the difference kinds of classification and learning the one my professor prefers. Again, these are the ones taught in class and the classes, orders, families and so on that I need to know in the exam.

podClast 3 on goodSchist

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podClast 3 has gone on air today at goodSchist! The 3rd implementation of the geoblogospheric podcast sees Ron, Chris, Brian and Ralph discuss recent activities on Chaiten volcanoe and Gigapan projects. Like always it is worth to listen in!

Enjoy!

Friday, May 9, 2008

Weekend Field Foto - drilling in the mountains

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Today you can see another shot from my time in Peru. On this foto you can see the installation of a drill ready for action. The location is about 2 hours by car from the Mina Arcata at an altitude of around 5.000 m asl. A pretty exhausting altitude. If you compare this foto with previous contributions you may recognise the veins and dikes in the background. The crew here is exploring for low/high sulphidation epithermal Au-Ag veins in the volcanics of Central/Southern Peru. I really should be reading up more on the local geology of the place. Unfortunately I only spent 8 days at this location. Due to severe form of altitude sickness I had to return to Lima and never got the chance to really know the geology. The local geologist mailed me this foto after my departure.



Perhaps I get the chance to see more of the local geology of the high Andes at the XIV Congreso Peruano de Geologia even if my current interest is more focused on other kinds of deposits.

Wednesday, May 7, 2008

XIV Congreso Peruano de Geologia

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GeoCosas already reported about it a while back. After my thesis plans have all been sunk by now due to financing issues and new opportunities are only available starting november the XIV Congreso Peruano de Geologia and XIII Congreso Latinoamericanode Geologia seems like the perfect choice to bring that extra time to some good use. I was long planing to visit friends in Lima, Peru, whom I haven't seen in more than 3 years. This sounds like a really good reason to go!

Largely a congress aimed at resource geologists this seems like paradise to go and see. They have juicy courses that I can hardly sit still when reading about like:

“Unconventional Zinc Deposits – Lessons to Learn from Supergene Metallogenesis” with G. Borg

“SEG Workshop Lead-Zinc deposits” with Richard Tosdale, David Leach, Lluís Fontboté y Larry Meinert

OK, these are just two of the courses that get me all excited about but there are plenty more of high interest! Of course there symposias and special lectures on Amazonian Geology or Earthquakes and Seismicity in South America, as well!

Also there will be a lot of field trips to some famous mines within Peru and South America.

I better begin saving up some money to afford the flight and fees! I wonder if anyone else from the Geoblogosphere will be attending it.

I've been tagged: Six Word Meme

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Silver Fox from Looking for Detachment tagged me for the Six Word Meme. Frankly, I am very puzzled what to say. So let's first review the rules:

1. Write your own six word memoir.
Okay. Six words only. That's a tough one.

2. Post it on your blog and include a visual illustration if you’d like.
Done. Visuals? Nope.

3. Link to the person that tagged you in your post and to this original post if possible so we can track it as it travels across the blogosphere.
Silver Fox. Don't know the starting point.


4. Tag five more blogs with links.
I tag Antimonite, EffJot, GeoCosas, Limonit Blog and SlingShot Thought.


5. And don’t forget to leave a comment on the tagged blogs with an invitation to play.
Will do.

And my six word memoir is: Never give up! Never stop fighting!

Perhaps that is hard to understand for you without knowing my background. Thanks to a lot of people that is gladly far behind me.

Tuesday, May 6, 2008

Tag clouds band waggon

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Everyone is doing the tag cloud thing and using it to visualise their papers, blogs and other kinds of publications. Brian started it and now Chuck, Rebecca, Maria, Kim, Chris, Silver Fox, Julian, Tuff Cookie, Callan and Dave followed up. After teaching the TagCrowd to ignore all the common and tiny German words I managed to use this funny tool on my seminar paper I also wrote about in my blog. Somehow the German special letters of ä, ö, ü, ß and others give it problems but the playing around removed most senseless words. So here it is!



created at TagCrowd.com


Another round of Blogs

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Unfortunately I do not speak any Italian because I recently discovered Geologia online, a blog on geology on Italian with very interesting contributions as far as my laughable Spanish, Latin and Romanian help me to understand. Also I came across the Ramblings of a Geologist by Katherine Allen. Then I found Cryology and Co. focusing entirely on Glaciers and phenomena of cold climatic conditions. Last but not least the Stratamodel Blog. I don't want to promote the company behind it - I don't know it at all, however, the blog about their fieldwork in Niger is fantastic!

Monday, May 5, 2008

Zinnwaldite - Weekend fun solution

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The solution to the last implementation of my ongoing series called weekend fun is Zinnwaldite. Zinnwaldite is a rare member of the mica group containing lithium and iron. Nowadays used for the description of the series siderophyllite-polylithionite. It's occurence is limited to special granites, pegmatites and greisens. The paragenesis usually includes quartz, fluorite, feldspars, apatite and tin-minerals. The example shown is from the German side of the German-Czech border close to Sadisdorf or Altenberg (I didn't keep notes on private trips unfortunately). The type locality is a few km south in the Czech Republic and called Zinnwald/Cinovec in the Ore Mountains of Eastern Germany. To see some more and good fotos of Zinnwaldite go check out the Mineralienatlas.

Sunday, May 4, 2008

Rock Videos

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Oh my god! You have to see these ancient videos on sedimentary rocks! If you are too bored to leave the room for your class, here is the alternative! The music is kind of prehistoric though. I can literally see the drummer sitting in the cave.



There is an entire series like these about sedimentary rocks featuring at least 6 episodes. Those videos must be from the 70ties or 80ties I assume. Lovely...

Don't miss out on the series on metamorphic rocks! It is just as wonderfull!



Check out the other videos, too!

P.S. Be a bit careful on some of the other videos. Some don't seem 100% up-to-date anymore.

Friday, May 2, 2008

Weekend Fun - guessing the mineral

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My bookshelf collapsed yesterday morning. In the debris I found these nice minerals that I collected a few years ago very close to the actual type-locality for this mineral. There were nice vein-like bodies of this mineral also accompanied by a number of other minerals. It was a bit of a risk collecting next to a big collaps funnel of old mine workings. So a piece of advise for all your mineral collecting fans - be careful, never collect alone, always have your cellphones with you!



Anyways. What do you see on the above image? Pencil for scale...

Weekend Field Foto - Hoatzins in primeval jungle

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Like in previous episodes of my weekend field fotos I will use more than one foto. To be frank this was not directly a geology related field trip but a private tour in my time in Peru to the Peruvian Amazonas close-by to the city of Iquitos. We stayed in a lodge around 140km upstream from Iquitos in the middle of the jungle. So why do I post these fotos? It is because the jungle foto is so much like I personally image the jungles and swamps of the Dinosaurs to have looked like. Strange, unpenetrable and with weird animals.



Those trees, I don't have a clue how they are called, really gave me the shivers once I first saw them. They remind me a lot of color illustrations of the jungles and swamps of the Dinosaurs and are so much as I imagine them to be like. To make this impression even better we had the rare chance to encounter one of the most enigmatic birds that exist. Living Hoatzins!



It is a rare bird specialised on eating gras, leafs and green fruits. Unlike any other bird it has a weird disgestive system with fermentation much like modern cattle have it. The young birds even have claws on their wings to help climbing in the trees though they recede in adults. No other modern relatives exist and based on DNA analysis it has been placed in its own order Opisthocomiformes. It was quite a battle to keep the balance standing upright on the dugout canoe and I was extremely glad to have bought a digital camera with a BIG zoom. Those birds are very shy and flee at even the slightest disturbance. We had to keep a significant distance to not disturb them breeding. Although not on the list of threatened species they are hard to find. Their prehistoric appearance reminds of Archaeopteryx but there is no connection as far as I know, claws on their wings are likely a modern adaptation. You can see one Hoatzin bird on the lower foto right in the centre. One of the best fotos I managed to take.