Geology Sonnet 6

Nobody studies fucking iodine.

The halogen too rare for us to care,

But iodate to carbonate’s inclined

So we might have a useful proxy there.

This IO₃ requires oxygen,

And thus does not exist in reduced seas.

Its presence in old carbonates means then

Ozone and oxygen were in the breeze.

Archean carbonates do not have I,

But it appears when O first graced the air.

And thus another tool is forged, whereby

Our planet’s past can be unearthed to share.

  This gas we breathe controls the biosphere.

  We’d like to know what made it first appear.

Dalton S. Hardisty, Zunli Lu,Noah J. Planavsky, Andrey Bekker, Pascal Philippot, Xiaoli Zhou and Timothy W.Lyons (2014) An iodine record of Paleoproterozoic surface ocean oxygenation. Geology 42 619-622.

Abstract

Constraining oxygen levels in the early Precambrian surface ocean has been a longstanding goal, but efforts have been challenged by the availability of suitable proxies. Here we present a novel approach, iodine geochemistry, which broadens our perspective by providing constraints on shallow, carbonate-dominated marine settings. Iodate (IO₃^–) persists exclusively in oxic waters and is the sole iodine species incorporated into carbonate minerals, allowing iodine-to-calcium ratios (I/Ca) in shallow carbonates to be used as a paleoredox indicator. Our data from a series of Mesoarchean through Paleoproterozoic carbonates deposited under shallow-marine conditions reveal a progressive surface ocean oxygenation in the early Paleoproterozoic. These data seem to indicate that a largely anoxic surface ocean extended throughout the Archean until the Great Oxidation Event (GOE) at ca. 2.4 Ga, implying that previous inferences of pre-GOE oxygen production may reflect oxygen oases, transient oxidation events, or oxygen levels below those required for IO₃^– accumulation. The data suggest formation and persistence of IO₃^– and, consequently, surface ocean oxygen concentrations of at least 1 μM during the GOE. Following the initial rise of oxygen, carbonate-associated iodine in globally extensive carbonate units deposited during the Lomagundi positive carbon isotope excursion at ca. 2.22–2.1 Ga suggests a widespread aerobic iodine cycle beyond that operating prior to the event, synchronous with high relative rates of organic carbon burial and apparent expansion of oxidative conditions.

Other geosonnets: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63

See the previous posts in this series for background.

Note that I have edited the last line of this sonnet.

Geology Sonnet 5

Australia is a dry and stable land.

No mountain range, no active slipping fault,

And yet this plain had lava seas erupt.

We call them Kalkarindji flood basalt.

It’s hard to know just when these rocks were formed.

The weathering and rock type complicates

Radiometric dates of dykes that swarmed

When seas contained the first protochordates.

For ten long years they searched the outback rocks

For grains unhurt since fossils first were formed.

In hopes the nucleii-related clocks

Survived half billion years, still undeformed.

  510 MA, a date of some distinction.

  Flood basalts can lead to mass extinction.

F. Jourdan, K. Hodges, B. Sell, U. Schaltegger, M.T.D.Wingate, L.Z. Evins, U. Söderlund, P.W. Haines, D. Phillips and T. Blenkinsop. (2014) High-precision dating of the Kalkarindji large igneous province, Australia, and synchrony with the Early–Middle Cambrian (Stage 4–5) extinction. Geology 42 543-546.

Abstract

The voluminous Kalkarindji flood basalts erupted in Australia during the Cambrian and covered >2 × 10⁶ km². New U-Pb and ⁴⁰Ar/³⁹Ar age data from intrusive rocks and lava flows yielded statistically indistinguishable ages at ca. 511 Ma, suggesting a relatively brief emplacement for this province. A zircon age of 510.7 ± 0.6 Ma shows that this province is temporally indistinguishable at the few-hundred-thousand-year level from the Early–Middle Cambrian (Stage 4–5) boundary age of 510 ± 1 Ma, which marks the first severe extinction of the Phanerozoic and an extended marine anoxia period. Sulfur concentration measurements ranging from less than 50 to 1900 μg/g, and fractal analysis of extensive explosive volcanic breccias, suggest that blasts and phreatomagmatic explosions have contributed to injection of large amounts of sulfur into the stratosphere. In addition, magma intrusions in oil, gas, and sulfate deposits may have generated significant emission of CH₄ and SO₂ which, along with volcanic gases, would have combined to cause an oscillation of the climate and led to the Cambrian extinction.

Other geosonnets: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63

See the previous posts in this series for background.

How many?

"Sand people always ride single file, to hide their numbers."

Geology Sonnet 4

Enough with carbon, climate variation

Let’s look at rocks from a far older time,

Which lacked much copper mineralization,

And when anorthosites were at their prime.

Earth’s middle age- boring for a reason?

Tectonics were remarkably unchanged.

Ice and iron were both out of season.

A billion years of uniform exchange

Of isotopes, strontium, and S

The active margins ringed the continent.

Slow, steady mantle cooling caused the process

Strong lithosphere held melts incipient

  It ended with Rodinia dispersion

  Which led to Earth’s exciting, current version.

Peter A. Cawood, Chris J. Hawkesworth. (2014) Earth’s middle age. Geology 42 503-506.

Abstract

Earth’s middle age, extending from 1.7 to 0.75 Ga, was characterized by environmental, evolutionary, and lithospheric stability that contrasts with the dramatic changes in preceding and succeeding eras. The period is marked by a paucity of preserved passive margins, an absence of a significant Sr anomaly in the paleoseawater record and in the εHf(t) in detrital zircon, a lack of orogenic gold and volcanic-hosted massive sulfide deposits, and an absence of glacial deposits and iron formations. In contrast, anorthosites and kindred bodies are well developed and major pulses of Mo and Cu mineralization, including the world’s largest examples of these deposits, are features of this period. These trends are attributed to a relatively stable continental assemblage that was initiated during assembly of the Nuna supercontinent by ca. 1.7 Ga and continued until breakup of its closely related successor, Rodinia, ca. 0.75 Ga. The overall low abundance of passive margins is consistent with a stable continental configuration, which also provided a framework for environmental and evolutionary stability. A series of convergent margin accretionary orogens developed along the edge of the supercontinent. Abundant anorthosites and related rocks developed inboard of the plate margin. Their temporal distribution appears to link with the secular cooling of the mantle, at which time the overlying continental lithosphere was strong enough to be thickened and to support the emplacement of large plutons into the crust, yet the underlying mantle was still warm enough to result in widespread melting of the lower thickened crust.

See the previous posts in this series for background.

Other geosonnets: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63

Geology Sonnet 3

Science week geology sonnet number three!  See previous posts for background.

A pox on all those proxies non-unique
Which make interpretation hard to do.
Magnesium to calcium we seek
Sea Temp'rature, and not pCO₂.
So lithium, uranium are used
To disambiguate the Mg curve.
O. umbonatus' data's not recused,
Antarctice ice growth isotopes observe.
But whence the melting in the Miocene?
Here isotopes of carbon join our tale,
And sedimentary burndown in marine
Organic carbon makes the icecap fail.
  Antarctic ice was thawed by CO₂
  Let's try repeating this effect anew.

Elaine M. Mawbey and Caroline H. Lear. (2013) Carbon cycle feedbacks during the Oligocene-Miocene transient glaciation. Geology 41. 963-966.

Abstract:

Ice sheet models suggest that once formed, the large, high-altitude East Antarctic Ice Sheet was relatively self-stabilizing, due to its cold upper surface. The ice sheet hysteresis problem results from an inability to reconcile this expectation with geological evidence for episodes of ice sheet retreat. A classic example of this problem is manifested in benthic foraminiferal oxygen isotope records across the Oligocene-Miocene boundary (ca. 23 Ma), which display a transient ∼1‰ excursion to higher values. The inferred increase and subsequent decrease in ice volume has been linked to advance and retreat of the Antarctic ice sheet across the continental shelf. However, oxygen isotope records alone do not provide unambiguous records of temperature and ice volume, hindering assessment of the driving mechanism for these variations. Here we present new benthic foraminiferal Mg/Ca, Li/Ca, and U/Ca records across the Oligocene-Miocene boundary from Ocean Drilling Program Sites 926 and 929. Our records demonstrate that Atlantic bottom-water temperatures varied cyclically, with the main cooling and warming steps followed by ice growth and decay respectively. We suggest that enhanced organic carbon burial acted as a positive feedback as climate cooled. Several lines of evidence suggest that the deglaciation was associated with an input of carbon to the ocean-atmosphere system, culminating in a previously unidentified seafloor dissolution event. We suggest that one of the initial sources of carbon was organic matter oxidation in ocean sediments. This study demonstrates that carbon cycle feedbacks should be considered when evaluating the stability of ancient ice sheets.

Other geosonnets: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63

Geology Sonnet 2

As mentioned previously, I am writing Geology Sonnets for National Science Week.  These are articles from the high-profile scientific journal Geology, presented in the form of Elizabethan verse. I don’t know how many of these I will get through this week, but here is the second:

The Central Atlantic Magmatic Province

Erupted tholeiitic and potassic.

C O two upset atmospheric balance.

Eco-collapse ended the Triassic.

Green sulfur bacteria’s isotopes

Show photic zone euxinia prevailed.

Stomatal size decreased (show microscopes)

And carbon biomass was soon curtailed.

Compound-specific isotopes will tell

Which phytoplankton thrived in these tough times,

While wax from leaves and calcite from a shell

Record recovery in clastic slimes.

The Triassic ended as it began.

Can those extinctions be surpassed by man?

Caroline M.B. Jaraula, Kliti Grice, Richard J. Twitchett, Michael E. Böttcher, Pierre LeMetayer, Apratim G. Dastidar and L. Felipe Opazo. (2013) Elevated pCO₂ leading to Late Triassic extinction, persistent photic zone euxinia, and rising sea levels. Geology 41 955-958.

Abstract

The Late Triassic mass extinction event is the most severe global warming–related crisis to have affected important extant marine groups such as scleractinian corals, and offers potential insights into climate change scenarios. Here we present evidence from Chlorobi-derived biomarkers of episodic and persistent photic zone euxinia. From biomarkers and stable carbon isotopes, we present evidence of rapid mixing of atmospheric and oceanic carbon reservoirs. Global versus regional trends are resolved in kerogen organic matter type, carbonate δ¹³C, and bulk and pyrite δ³⁴S. This suite of data demonstrates for the first time a comprehensive organic and stable isotope geochemical reconstruction of events leading up to the Late Triassic extinction event and its aftermath. The cascade of events prior to, during, and after the extinction is remarkably similar to those reported for the Late Permian extinction, the largest extinction event of the Phanerozoic. We predict that similar conditions will have occurred during all past episodes of rapid global warming and biotic crisis that are associated with similar rises in pCO₂.

Other geosonnets: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63

Geology Sonnets!

Here in Australia, it is National Science Week, and I have been surprised and delighted at the bizarre and creative ways that many people around Canberra have been celebrating science.  It is inspirational, to the point where I might try to join in.  So in this spirit, I give you Geology Sonnets.  These are articles from the high-profile scientific journal Geology, presented in the form of Elizabethan verse. I don’t know how many of these I will get through this week, but here is the first:

Just Sixty-six million short years ago

(Though Deccan volcanism coincides)

The Yucatan was smote a cosmic blow

And the Gulf shelf collapsed in those fell tides

Late Cretaceous sediments were scoured,

Deposited as “boundary cocktail.”

Unsorted forams, lime mudstone, powered

By Chicxulub-induced collapse of shale

The wildcatters call the seismic line

“Middle Cretaceous Unconformity”

Not middle, end; deluvian, malign,

Complete destructive uniformity

The Mesozoic ended with this splat

So Gerta Keller, please hang up your hat

Richard A. Denne, Erik D. Scott, David P. Eickhoff, James S.Kaiser, Ronald J. Hill, and Joan M. Spaw (2013) Massive Cretaceous-Paleogene boundary deposit, deep-water Gulf of Mexico: New evidence for widespread Chicxulub-induced slope failure.

Geology 41, 983-986

Abstract

The single largest-known mass wasting deposit has been identified at the Cretaceous-Paleogene (K-Pg) boundary in the deep-water Gulf of Mexico, in 31 industry-drilled wells and on seismic data, corresponding to the “MCU” (middle Cretaceous unconformity) horizon. The deposit has an average thickness of 10–20 m on the upper slope and 90–200 m on the lower slope and basin floor, and is on an unconformity that represents 9 m.y. to 85 m.y. The deposit contains the distinctive association of lithic fragments, impact-derived material, and reworked microfossils (i.e., the Cretaceous-Tertiary boundary “cocktail”) associated with the Chicxulub impact, and is predominantly composed of graded pelagic carbonates. These new findings substantiate widespread slope failure induced by the Chicxulub impact and provide further evidence of a single impact coincident with the K-Pg mass extinction.
Other geosonnets: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63

Indian e-commerce

On my recent trip to India, one of the big stories in the newspaper was the rise of consumer good e-commerce.  Flipkart, an Indian company founded by the ex-Amazon Bansal brothers, recently announce that it had raised over one billion dollars of funding for expansion projects.  A day later, Amazon announced that it would be investing two billion dollars in its Indian subsidiaries.  Of course, this is unsurprising.  India is modernizing quickly, and IT is one of the lead drivers of economic growth.  I was in Palo Alto, the northern end of Silicon Valley, a few years back, and waiting for my flight in the Kolkata domestic terminal a few weeks ago, I was struck by the number of IT nerd look-alikes sporting the flat combed hair, short-sleeve shirt, pants and laptop look. I was in stark contrast to the traditional party clothes of Eid, which was two days before.  So the rush into this business is no great surprise.  But what worries me is how the social consequences of this particular business expansion might be.

In Australia, e-commerce has finally cut into traditional retail no a broad scale, with retail growth flat, and employment and tax revenue falling.  This has contributed to social dissatisfaction and hand wringing, but even with the recent cuts to Australia’s economic safety net, the effect on the overall way of lie has been modest. This is because Australia is a wealth y country, and has a relatively intact safety net.  So even with these employment disruptions, everyone has food to eat, safe drinking water, health cover, etc.

However, this is not the case in India, where native startup Flipkart and internet giant Amazon have recently announced more than 3 billion dollars of investment, with the intent of growing their sales by billions of dollars per year.  India has a lot of retailers; with an estimated 40 million of them, they outnumber Australia’s entire population by almost a factor of two.  And unlike the corporate-dominated retail scene in Australia, 95% of the Indian retail sector is owner-operator family style shops.  In general, these are businesses with limited training and financial means.  There isn’t much of a social safety net, as a number of these folks are barely getting enough to eat as is. 

So what will happen when Indian internet shopping comes of age, and customers no longer have to brave the dangerous dirty, difficult streets of their megapolii to buy consumer goods?  In rich countries, people displaced by technological change have retrained using the educational system, fallen back on the social safety net, or managed to simply get by with less.  But never has such a vulnerable segment of the population been targeted by such an efficient set of competitors.

I hope development allows India to grow its way out of this potential pitfall.  But I am not optimistic.  The same paper announcing the new Amazon investment also reported that Indian Overseas Bank was suffering from an unexpected loss in microcredit loan repayments. It would be unfortunate if the geeky rivalry between Bezos and the Bansal brothers resulted in the first iFamine.