#lithification and diagenesis

[earthstory]

Petosky Stone

Michigan's stage stone is a lovely fossil coral dating from the late Devonian to early Carboniferous that was spread around parts of the state much more recently by grinding ice sheets during the recent ice ages, often as eroded rounded pebbles. Hexagonaria percarinata (named for the hexagonal patterns) belongs to an extinct group of corals called rugose that characterise reef building organisms of the Paleozoic. In those days what is now Michigan was the floor of a shallow equatorial sea filled with coral reefs.

In some areas then entire head of fossilised colonies transformed into limestone can be discovered in the Traverse group strata, though most are recovered on the beaches of Lake Michigan, where annual frosts heave and turn stones each winter revealing new specimens. A polish on the lapidary's bench is necessary to reveal the patterns in their full glory. Each hexagon was the home of a polyp that lived within the colony, who then fed via the tentacles that emerged from the central mouth. A small number of specimens have a rosy hue due traces of iron that infiltrated during the process of the reef turning into rock (called lithification or diagenesis).

The common name comes from that of an Ottawa chief called Pet O Saga (meaning rising sun), reputedly half French, who established himself as a fur trader in the last quarter of the 19th century. The stone has been a popular souvenir of the area since the Victorian era.

Loz

Image credit: Cobalt 123

http://www.petoskeyarea.com/petoskey-stone-73/ http://www.michigan.gov/documents/deq/ogs-gimdl-GGPS_263213_7.pdf http://web2.geo.msu.edu/geogmich/petoskystone.html

[juniperpublishersoceanography]

Towards A Better Integration of the Sediment Biogeochemistry in the Modelling of the Coastal Systems- Juniper Publishers

Abstract

Ecological models have been signficantly improved during the last decades, leading to more realistic predictions of coastal water processes under different forcing. Even though benthic sediments play an important role in biogeochemical processes occurring in the water column, in the past, very few modelling studies have taken into account these contributions. Recent efforts are being put into the implementation of coupled models, including the biogeochemistry processes occurring at both the upper benthic layer and the water column. This step is important, as along with the river supply, benthic nutrient regeneration can contribute significantly to the phytoplankton growth and the primary production. During the validation process, due to the important number of parameters involving these models, the application of Sensitivity Analysis for selecting the most important model parameters is highly needed. The importance of these processes and tools in the ecological modelling of coastal systems is discussed in this paper.

Introduction

Very few modelling studies of coastal water systems, namely lagoon and estuarine waters, have been focused on the relationship between the biogeochemical status of the water column and the benthic sediment. In general the last one is considered as a rigid boundary, isolated from the water column and not allowed to exchange matter. Nevertheless, sediments play an important role in the biogeochemical processes occurring in the water column of coastal systems, making up, by far, the most important reservoir of nitrogen [1]. They play a key role with respect to the plankton activity: they act as regenerators of mineral nutrients for the water column, often supplying an important fraction of the nitrogen requirements by phytoplankton. During the transport and deposition, they may undergo many changes resulting from several physical, chemical and biological processes.

Diagenesis is the denomination that characterises any chemical, physical, or biological changes undergone by sediment after their initial deposition and during and after their lithification [2-5]. In general, most of the sediments biogeochemistry processes are restricted to the upper layer of the sediment column, in general, and more specifically the upper decimetres [4]. These processes can be nowadays predicted with the help of improved powerful tools, such as mathematical models, relying on both data and modern computing resources [6,7].

The assessment of the biogeochemical status of the water column, including the interplay of the sediment layer, although scientifically affordable, remains a major issue and a challenge of the modern ecological modelling of coastal water systems. There are no conceptual or technical difficulties in applying empirical parameterizations of sediment biogeochemistry models to large spatial scales, namely coastal systems. However, because these models are typically tuned to match observations at specific sites there is no guarantee they will make good predictors across larger spatial scales. Therefore, major difficulty lies in evaluating fluxes predicted by the models against observations [8-10]. Furthermore, resuspension of sediments are not, in general, taken into account while its inclusion will increase the reliability of the models to represent these environments [11].

Sediment biogeochemistry models are based on a mechanistic understanding of sediment processes, including nonlinear feedback mechanisms and temporal dependencies such as delays or storage of organic matter [9,10,12]. As such they are more flexible and have the potential to correctly predict system responses to changes in eutrophication status or oxygen supply, e.g., the sediment flux model applied to data from a mesocosm eutrophication experiment [8,13]. They are commonly based on mass conservation approaches, expressing balances between vertical transport contributions of selected species and biogeochemical interactions between them. In the case of most estuaries and lagoons, as they tend to be, in general, more nitrogen than phosphorus limited [14] it is very important to quantify the nitrogen cycle in the sediment.

Sediment Biogeochemistry Models

Paraska et al. [15] and Testa [9] reviewed the most popular sediment biogeochemistry models. Although the notorious advances, they found the need for a more coherent approach concerning both variables and processes, namely: aligning conceptual models of organic matter transformations with measurable parameters; gathering accurate data for model input and validation; coupling sediment models with ecological and spatially-resolved hydrodynamic models; and making the models more accessible for water quality and biogeochemistry modelling studies by developing a consistent notation through community modelling initiatives.

Recent efforts are being devoted to the implementation of a coupled ecological/sediment biogeochemistry model for a study area, the Ria de Aveiro lagoon in Portugal [16]. The eutrofication model is a standard model, representing four functional groups (phytoplankton, zooplankton, benthic vegetation and detritus). It integrates the nutrient cycling in the water column, the organic and the inorganic nutrients, the dissolved oxygen, the benthic vegetation and the primary production. The sediment model is an add-on module to the main model. Figure 1 presents the conceptual diagram of the benthic sediment biogeochemistry model and the N cycle in the sediments.

The processes involving the nitrogen cycle in the sediment of Figure 2 are described in connection with the ecological/ eutrofication model state variables. The sediment biogeochemistry module consists of three state variables, the sediment organic N (SON), the sediment NH4 (SNH) and the sediment NO3 (SN03 ). A sink of nitrogen is as well included in the model, as immobile sediment nitrogen (SNIM). The sedimentation of organic N or the flux of NH4 and NO3 across the sediment surface connects the state variables to the plankton N, the detritus N and the inorganic IN in the water. The SON in the sediment is mineralised producing NH4, which enters the SNH pool. NH4 in the sediment may either be exchanged with IN in the water or nitrified into NO3 in the uppermost layer of the sediment with the help of O2. The NO3 entering the SNO3 pool may either be denitrified or exchanged with inorganic N in the water.

Model Application: Sensitivity Analysis

Global Sensitivity Analysis (GSA) of environmental models is an important tool aimed to characterize the impact on the model output of changes in the model input factors (e.g. parameters, initial states, input data, time/spatial resolution grid etc). For this purpose a widely-used GSA, named RSA method (Regional Sensitivity Analysis) introduced by Young et al. [17] and Spear & Hornberger [18] is being applied to the study area in order to select the most sensitive model parameters. The method uses a Cumulative Distribution Functions (CDFs) for each model parameter, for which the root mean squared error, RMSE, between the simulation and data for each time step along the simulation period, represents the performance metric used to synthetically measure the model accuracy. Another performance metric is the ‘mvd’ index based onthe Kolmogorov-Smirnov statistic, which is sensible to the ‘distance’ between the unconditional and conditional distributions of the performance metric [19-22].

Figures 2-4 present the first stage results of the model application, representing the sensitivity of two state variable, Total Nitrogen, TN and of the phytoplankton biomass, PC, to a wide range of five selected parameters: the diffusion coefficient of the NO3 and NH4 in the sediment (Diff) the rate of NO3 penetration into sediment (N3R), the sediment mineralisation rate (MinR) the light saturation intensity (Sati) and the phytoplankton maximum intracellular concentration (Pnma). Concerning TN the results evidence two main parameters, Dif and N3 R, representing, respectively, the diffusion processes and the penetration into sediment and governing the exchanges between the sediment layer and the water column. On the other hand, it shows less sensitive to MinR, that is, to mineralisation within the sediment column. On the other hand, PC is sensitive to Sati and Pnm, which are associated to the phytoplankton growth [23].

Conclusion

The importance of including sediment biogeochemistry processes in the ecological modelling of coastal systems was demonstrated. These processes are responsible for regenerating nutrient, namely nitrogen, contributing to the phytoplankton growth and the primary production. On the other hand it is possible that global changes in coastal systems may affect the biogeochemistry of the water column and, therefore, of the benthic sediment. Therefore, coupled models for the water column and the benthos will be increasingly important. In order to setup such complex models very robust sensitivity method and tool will be needed.

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[whenjocastasayyesnobodycansayno]

GEO Test

-Earth is 4.56 billion years old, we know bc radioactive decay of certain elements known since 1952 -13.8 billion years old is the universe, more significant -Powers of 10 used to express super small or large numbers (logs) -All parts of Universe are flying away from each other, 15 billion years ago they were all in one place. Then bigbang happened STARS -Use light spectrum to determine what it is, using prism. Dark lines will pop out due to the wavelength of certain gases absorbing the light. Different chemical elements absorb different wavelengths. -Red to purple, fast to slowest. Slower colors refract more. -Radio, radar, infrared, visible, ultraviolet, x-rays, gamma -Electrons get excited and absorbs energy and goes from ground to excited. Amount of energy absorbed can be attributed to an exact element. BIGBANG -Georges Lamaitre was like “cosmic egg that exploded -Edwin Hubble was like “Red Shift”, which was stars further away from us show greatest shift in their absorption lines towards red art in spectrum. -Doppler effect, change in frequency from velocity of object. can be used to calculate retreat velocity. Light is not effected because it moves too fast. However, the change in frequency does not represent the earth and sun moving in different directions but just the relative velocities they have, they’re moving in the same direction, one is just faster. Galaxies that are farther away are moving faster. SYNTHESIS OF ELEMENTS -He H and a bit of Li in the beginning -pther elements came from large stars through nuclear fusion -Use up hydrogen/helium? they explode. become supernova. one supernova per century per galaxy. These keep converting 2% of galaxies H (73%) and He (25%) into heavier elements. -To do this, nuclear fusions occur at 15 million degrees STARS HEATING -It gets bigger and heavier elements burn at the center, creating heavier elements. Needs more heat to do this. NEBULAR HYPOTHESIS -heavier elements hit each other lose kinetic energy and get hot and form a ball -dust particles hit each other and make planets. Planetesimals make terrestial planets, -Mars sized planet hit Earth, a bunch of debris is released. Gravity pulled it back in and it eventually became the Moon. It tilted the Earth too. CHEMISTRY -Planets dominated by Fe. Si, O, Mg -Odd numbered protons of elements are less abundant METEORITES -hits planets and could fall on Earth, like from Mars EARLY EARTH -accretion of meter sized bodies -transfer of kinetic energy to heat -compression (gravitational collapse) -radioactive decay of elements CORE OF EARTH -200-100 million years after accretion, temperatures at depths of 400-800 km below Earth’s surface reach Fe’s melting point -Fe pulled into center’s core, 1/6 of the volume and 1/3 of the mass. Moon doesn’t have much iron. LAYERS OF EARTH -Crust until 40 km -Mantle until 2890km -Liquid iron Outer Core until 5150 -Solid iron inner core until 6370 EARTH -Oxygen 30% -Iron 35% -silicone 15% -Mg 13% -others are calcium aluminum sulfur and nickel -crust has more of everything MINERAL -a homogenous natural solid, with a definite but not fixed chemical composition -formed by inorganic processes usually IONIC BONDING -ions of opposite charges attracted to each other. non-directional bonds (NaCl) -covalent bonding is when electrons are shared between atoms. much stronger and more stable. Directional (CO2 or diamonds) -metallic bonds, moderately strong and non directional (copper) good electric conductor -van der waals, weak, electostatic, nondirectional SIZES -Cations smaller than all anions -Ionic Radius determines what can fit around it, known as co-ordination POLYMORPHS -have same chemical formulas different structures -sheets bonded together with van der waals bonds MINERALS -SOHCNBSPS -oxygen is the most common anion -silicone is the most common cation in the crust -silicates are most common in crust. feldspar most common one -Difference in Electronegativity correlates with ionic bonding in silicates -tetrahedrons make up silicates, Si-O is the strongest bond. Negative triangles bonded thru positively charged ions -Types: isolated (olivine) ,Single chain (pyroxene), double chain (Mica), sheet silicate (Muscovite or Talc), and framework silicate (feldspar or quartz) CARBONATES -absorbs CO2 - second most abundant group in crust -common in limestone -calcite (double refraction occurs), aragonite, dolomite -CO4 impossible bc carbon cation is too small. CO3 forms instead.  HARDNESS diamond > corundum > topaz > quartz > feldspar > apatite > fluorite > calcite > gypsum > talc CLEAVAGE -mineral breaks into specific planes and places. into a specific orientation -fracture, the way a mineral breaks in the absence of cleavage (conchoidal, fibrous, and irregular)  -idiochromatic is when color is always the same, allochromatic is when trace elements can be seen, opaque just reflect light off their surface -Earth is cooling down by radiation conduction and convection of heat -We know this bc meteorites and seismic waves. Earthquakes happen when bodies of rock move past each other. A fault is a locus of earthquake movement. Normal Faults, Thrust faults (cause tsunamis). Long term predictions are imprecise and short term ones are precise but hard.  SEISMIC WAVES -waves that begin in the initial compression or tension of the rock -measured with seismographs -p-waves (compressional) 6-8 km per second. parallel to direction of movement. Similar to sound waves. -s-waves (shear) 4-5 km per second. Perpendicular to direction of movement. Do not pass through liquids. Similar to ocean waves.  -Surface waves, slowest but most damaging -Velocity depends on the type of material and pressure -when waves move from one type of material to another, they change speed and direction. -In light (refraction), velocity decreases as density increases bc denser things have more chemical bonds which slow the light down. -Seismic velocities, upward curves in p and s waves in mantle show that it’s increasing downwards. Refraction occurs in outer core bc liquid for p-waves.  DENSITY OF EARTH -continental crush 2.8 g/cm3 -oceanic crust 3.2  -asthenosphere 3.3 -in seismic topography, hotter regions are less dense  ISOSTASY -Buoyancy of low-density rock masses that are “floating on” higher density rocks. this explains roots of mountain belts - continents are like icebergs. what’s above the surface is balanced by material below surfaces. Higher ones must be thicker. GLACIAL REBOUND -glacier forms and thickens. crust bends downwards to support. warming happens, ice melts. ground rebounds. EARTH’S INTERNAL HEAT -original heat -conduction -convection -radioactive decay -temperature increases with depth, the geotherm curve MAGNETIC FIELD -declination is the horizontal angle between the magnetic north and true north -inclination is an angle made with horizontal. -Magnetic reversals exist, a change in polarity. Abrupt, takes only 1000 years.  -Magnetic Epoch is a period of time when magnetism is dominantly one polarity -north oriented polarity is called normal, south oriented polarity is called reverse -geomagnetic time-scale helps us track reversals ROCKS -Igneous, melting of rocks in hot deep crust and upper mantle, formed by crystallization. -genetic classification, intrusive means they were crystallized from slowly cooling magma intruded from the crust. extrusive means they were crystallized from rapidly cooling magma extruded on the surface of the earth as lava or pyroclastic material.  -others include felsic, intermediate, mafic, ultramafic.  -sedimentary, weathering and erosion of rocks exposed at surface, formed by deposition, burial, and lithification -resulted from consolidation of previously existing rock and accumulated in layers. classified based on size of particles.  -ice is a transport medium. sediments using this are called tillite.  -metamorphic, rocks under high temperatures in deep crust and upper mantle, formed by recrystallization with new minerals.  ROCK CYCLES Metamorphic + Migmitization and Melting = Igneous  + Weathering, Erosion, Deposition, and transportation= sedimentary + Burial, Heat, Pressure= Metamorphic PLATE TECTONICS -Outer portion of Earth has 20 plates that move relative to each other. This causes mountain ranges. Can help predict locations of earthquakes and volcanoes -Lithosphere- outer rigid shell of earth. Where plates are -asthenosphere- mantle beneath lithosphere, acts as its conveyor belt -transform fault boundary, slide horizontally by each other, divergent boundaries, plates move apart and create new lithosphere, convergent boundaries, plates collide and one is pulled into the mantle and recycled.  -three types of convergent boundaries, ocean-ocean (linear belts of high seismic activity, high heat flow arc of volcanoes, bordered by submarine trenches)  , ocean-continent (active volcano, compression of upper crust), continent-continent (subduction or deformation of crust) CONTINENTAL DRIFT - The concept that large-scale horizontal movements of outer portions of the earth are what’s responsible for major topographical features such as mountains or ocean basins.  -Geographic fit of all the continents is used as evidence. Pangea -Evidence from sea floor included the age of the ocean’s crust, bathymetry, magnetic data. Sea floor had significant variance in magnetic field. These changes reflected Earth’s changes in the magnetic field. None of the rocks were older than 100-200 Ma, while on continents they could be up to 4000 Ma ROCKS ACHIEVING MAGNETISM -Magnetic objects align with Earths magnetic field once they cool below 580 celsius or Curie’s Temperature -Anomaly, change in intensity of magnetic field at some point.  OCEAN? -Ocean crust being constantly formed, crystallized from magma and into basalt -Earth maintains a constant diameter, so despite the new growth, old crust is being destroyed in trenches and sent back to the mantle DEFROMATION -happens alongside metamorphism -different fabrics form different grade  - Diagenesis, Low Grade, Intermediate Grade, High Grade TRANSPORT IN SEDIMENTARY ROCKS -affects roundness and sphericity and sorting  -sorting is the measure of variation in the range of grain sizes of a rock or sediment. If they’re well-sorted, they’ve been acted on by water or wind. Poorly sorted sediment hasn’t left it’s original place or was deposited by a glacier.  PROPORTIONS OF SEDIMENTARY ROCK -Siltstone and Mudstone and Shale is 75% -carbonate rocks are 14% -sandstone conglomerate are 11% -calcium carbonate is less soluble in warm water WEATHERING TERMS -bedrock is unaltered rock -broken pieces of rock above the bedrock is the regolith -mineral and organic material is called soil MECHANICAL WEATHERING -Frost is when water expands by 9% upon freezing  -Thermal Expansion is when different thermal expansion of minerals causes stress in rocks -Organic Activity could be from tree roots to microorganisms -Mechanical Abrasion is when things go bump CHEMICAL WEATHERING -Principal agent is water -minerals need this bc when they’re formed deep inside Earth they can’t be stable on conditions on the surface of Earth -bicarbonate ions hasten weathering CARBON CYCLE -Low temperatures and decreases in CO2 reduce weathering leading to an increase in CO2, leads to warming which leads to more weathering which reduces CO2 which leads to cooling.  WIND -rate of sand transport moves exponentially with wind speed.  -Deflation is when strong winds gradually lower the elevation of the ground by removing sand particles.  -Desert Pavement is a surface of gravel too big for wind to transport, a deflation lag. Concentrated by selective removal of finer-grained sediment. -Loess is wind blown dust WATER -Only 4.04% of Earth’s water is freshwater.  POROSITY -Percent void space in a rock or sediment.  -amount of water that could be potentially stored in rock -Varies with sorting, amount of cement, fracturing  PERMEABILITY -ability of a material to transfer a fluid -aquifer is a geological unit capable of storing water in sufficient quantities to supply wells -Types of Aquifer’s include: Unconfined (the permeable layer extends to surface), confined (p. layer is overlain and underlain by less p. layer) WATER TABLE -top of saturated zone in groundwater -level that water will rise in a hole -level to which water will rise in an unconfined aquifer HYDROTHERMAL SYSTEMS -Hot springs, which form when heated groundwater reaches the surface -Geysers form when a complicated plumbing system allows steam pressure to be built up, causing intermittent eruptions. RHYTHM OF ICE AGES -Eccentricity of Earth’s orbit around the sun (100k years) -Tilt of Earth’s rotation axis (41k) -Precession (rotational wobble, 19k-21k years) -Earth went from greenhouse to icehouse SNOWBALL EARTH HYPOTHESIS -some say all of Earth was covered in glacial ice and only melted when volcanoes erupted, raising CO2 content, facilitating global warming -Earth seems to do this in cycles. Ice builds up due to runaway albedo effect, with white ice reflecting radiation back into space. Then without weathering due to the ice, CO2 couldn’t be taken up by it. Buildup of CO2 causes warming again. RELATIVE DATING -How old a rock is compared to surrounding rocks -Younger ones on the top -principle of superposition is when the oldest rocks are on the bottom -Principle of Original Horizontality is when layered strata are deposited in horizontal or nearly horizontal or nearly parallel to the Earth’s surface ABSOLUTE DATING -actual number of years since rock was formed PALEONTOLOGY -study of life in past based on the fossil of plants and animals -used to help determine r. age and envionment of deposition -unconformity is a buried surface of erosion -disconformity is a break in deposition. no erosion -If there is deformation, angular unconformity is produced Carbon has a half life of 5730 years

AGES -Universe is about 15Ga Solar system is 4.6 Ga Oldest rock is 4000 Ma ZIRCON DATING used to help determine age. Uranium can substitute in small quantities.  -its dense and easy to separate. Each Zircon makes it possible to obtain two ages and see if they agree.  OLDEST PARTS OF CONTINENTS -shields or cratons  -central, older portions of continents -lower elevation and relatively flat -basement complex of metamorphic and igneous rocks

[decepticonfetti]

Terminology to take note of, in no particular order :

- lithification

- diagenesis

- metasomatism

- foliation

- slatey cleavage

- subduction

- connate fluids

These are your geology notes. Study good, test next friday.