CONCRETIONSCONCRETIONS in in the Dakota the Dakota SandstoneSandstoneBy: Melissa BattlerBy: Melissa BattlerB.Sc. Geology, University of WaterlooB.Sc. Geology, University of Waterloo

OutlineOutline What is a Concretion?What is a Concretion? Where to Find MDRS Where to Find MDRS

ConcretionsConcretions When were these When were these

Concretions Discovered?Concretions Discovered? Why are Concretions Why are Concretions

Significant to Mars Analog Significant to Mars Analog Studies?Studies?

Conclusions: How to Conclusions: How to Identify MDRS ConcretionsIdentify MDRS Concretions

AcknowledgementsAcknowledgements

What is a concretion?What is a concretion?Short Answer:Short Answer:

A mass or nodule of mineral matter, usually oval or A mass or nodule of mineral matter, usually oval or nearly spherical in shape, and occurring in sedimentary nearly spherical in shape, and occurring in sedimentary rock. It is formed by the accumulation of mineral matter in rock. It is formed by the accumulation of mineral matter in the pore spaces of the sediment, usually around a fossil or the pore spaces of the sediment, usually around a fossil or fossil fragment acting as a nucleus. Most concretions are fossil fragment acting as a nucleus. Most concretions are very dense and compact, and are usually composed of very dense and compact, and are usually composed of calcite, silica, or iron oxide. The material making up the calcite, silica, or iron oxide. The material making up the concretion is believed to come from the surrounding rock, concretion is believed to come from the surrounding rock, being redeposited around the nucleus. Concretions range in being redeposited around the nucleus. Concretions range in diameter from a fraction of an inch to many feet, although diameter from a fraction of an inch to many feet, although most are but a few inches in diameter. Perhaps the best most are but a few inches in diameter. Perhaps the best known are the flint nodules found in chalk deposits such as known are the flint nodules found in chalk deposits such as those at Dover, England. Concretions having radiating those at Dover, England. Concretions having radiating cracks filled with mineral matter are called turtle stones, or cracks filled with mineral matter are called turtle stones, or septaria. septaria.

Columbia Encyclopedia, Sixth Edition, Copyright (c) 2004: Columbia Encyclopedia, Sixth Edition, Copyright (c) 2004: http://www.encyclopedia.com/html/c1/concreti.asphttp://www.encyclopedia.com/html/c1/concreti.asp

Longer Answer:Longer Answer:

A A concretionconcretion is a solid is a solid mineralmineral inclusion within a inclusion within a rockrock strata that is oval or spherical in strata that is oval or spherical in shape. They form within layers of shape. They form within layers of sedimentarysedimentary strata that have already been deposited. The strata that have already been deposited. The cementation occurs due to processes independent from the primary cementation in which cementation occurs due to processes independent from the primary cementation in which the layers of sedimentary rock were adhesed together. This secondary cementation often the layers of sedimentary rock were adhesed together. This secondary cementation often makes the concretion harder and more resistant to makes the concretion harder and more resistant to weatheringweathering than the host strata. than the host strata.

Though the processes by which concretions form are poorly characterized, it is believed Though the processes by which concretions form are poorly characterized, it is believed they form during the they form during the diagenesisdiagenesis of a deposit, usually shortly after the enclosing sediment of a deposit, usually shortly after the enclosing sediment has been buried. They are believed to occur when a considerable amount of cementing has been buried. They are believed to occur when a considerable amount of cementing material precipitates locally around a nucleus, often organic, such as a leaf, tooth, piece of material precipitates locally around a nucleus, often organic, such as a leaf, tooth, piece of shell or shell or fossilfossil..

Concretions vary in shape, hardness and size, ranging from objects that require a Concretions vary in shape, hardness and size, ranging from objects that require a magnifying lens to be clearly visible to huge bodies three meters in diameter and weighing magnifying lens to be clearly visible to huge bodies three meters in diameter and weighing several hundred pounds. several hundred pounds.

Concretions are usually similar in color to the rock in which they are found. They are Concretions are usually similar in color to the rock in which they are found. They are commonly composed of a commonly composed of a carbonatecarbonate mineral such as mineral such as calcitecalcite; an amorphous or ; an amorphous or microcrystalline form of microcrystalline form of silicasilica such as such as chertchert, , flintflint, or , or jasperjasper; or sometimes an iron oxide or ; or sometimes an iron oxide or hydroxide such as hydroxide such as goethitegoethite. They can also be composed of other sedimentary minerals that . They can also be composed of other sedimentary minerals that include include dolomitedolomite, , ankeriteankerite, , sideritesiderite, , pyritepyrite, , baritebarite and and gypsumgypsum, to name a few., to name a few.

Concretions are found in a wide variety of rocks, and are particularly common in Concretions are found in a wide variety of rocks, and are particularly common in shalesshales, , siltstonessiltstones, and , and sandstonessandstones. They often outwardly resemble fossils or rocks that look as if . They often outwardly resemble fossils or rocks that look as if they do not belong to the strata in which they were found. Occasionally, concretions contain they do not belong to the strata in which they were found. Occasionally, concretions contain a fossil either as its nucleus or as a component that was incorporated during its growth, but a fossil either as its nucleus or as a component that was incorporated during its growth, but concretions are not fossils themselves. They appear in nodular patches, concentrated along concretions are not fossils themselves. They appear in nodular patches, concentrated along bedding planes, protruding from weathered cliffsides, randomly distributed over mudhills or bedding planes, protruding from weathered cliffsides, randomly distributed over mudhills or perched on soft pedestals.perched on soft pedestals.

Because of the variety of unusual shapes, sizes and compositions, concretions have been Because of the variety of unusual shapes, sizes and compositions, concretions have been variously interpreted to be variously interpreted to be dinosaurdinosaur eggs, animal and plant fossils (called pseudofossils), eggs, animal and plant fossils (called pseudofossils), extra-terrestrial debris or human artifacts. For this reason, fossil collectors commonly break extra-terrestrial debris or human artifacts. For this reason, fossil collectors commonly break open concretions in their search for fossil animal and plant specimens.open concretions in their search for fossil animal and plant specimens.

The word "concretion" is derived from the The word "concretion" is derived from the LatinLatin "con"-- meaning "together" -- and "con"-- meaning "together" -- and "cresco" -- meaning "to grow.""cresco" -- meaning "to grow."

From Wikipedia, the free encyclopedia: http://en.wikipedia.org/wiki/ConcretionFrom Wikipedia, the free encyclopedia: http://en.wikipedia.org/wiki/Concretion

Dakota Sandstone Dakota Sandstone ConcretionsConcretions

Typical, brown, 1cm spherical concretionsTypical, brown, 1cm spherical concretions

Dakota Sandstone Dakota Sandstone ConcretionsConcretions

Typical concretions on ground + brown layers that Typical concretions on ground + brown layers that look like smeared-out concretionslook like smeared-out concretions

Squished clusters of typical Squished clusters of typical concretions + brown layers that look concretions + brown layers that look like smeared-out concretionslike smeared-out concretions

Dakota Dakota Sandstone Sandstone

ConcretionsConcretions

Dakota Sandstone Dakota Sandstone ConcretionsConcretions

Clusters of typical brown, 1cm spherical concretions, Clusters of typical brown, 1cm spherical concretions, plus loose concretions on groundplus loose concretions on ground

ConcretionConcretion

Iron oxy-hydroxide cement

Calcite cement

Sparite and iron-hydroxide cement inside concretion, micrite rims and pore space outside concretion, ppl & cpl

Petrographic Thin Section Photograph of Petrographic Thin Section Photograph of a Typical (calcite cemented) Concretiona Typical (calcite cemented) Concretion

1mm

Micrite

Iron oxy-hydroxide

cement

Calcite cement

Inside Concretion

Outside Concretion

zoning

Petrographic Thin Section Photograph of Petrographic Thin Section Photograph of an Atypical (iron oxide cemented) an Atypical (iron oxide cemented)

ConcretionConcretion

Zoning in a concretion with micrite rims and iron-hydroxide cement

Where to Find ConcretionsWhere to Find Concretions Concretions can be found in the Concretions can be found in the

Cretaceous Cretaceous Dakota Sandstone Dakota Sandstone FormationFormation around MDRS, near around MDRS, near Hanksville, UtahHanksville, Utah– The Dakota Sandstone Formation is The Dakota Sandstone Formation is

locally a 1 to 20m thick unit of locally a 1 to 20m thick unit of yellow and brownish sandstones yellow and brownish sandstones and conglomerates, capping the and conglomerates, capping the shaley, rainbow coloured hills of the shaley, rainbow coloured hills of the Jurassic Morrison FormationJurassic Morrison Formation

– The Dakota Sst can be further The Dakota Sst can be further subdivided into 6 sub-units; subdivided into 6 sub-units; Unit 3Unit 3 contains concretionscontains concretions

There are several known There are several known concretion sites around MDRS, concretion sites around MDRS, however the full extent has not however the full extent has not yet been mappedyet been mapped

MDRS

HanksvilleK1

K2

J2J1

N 10km

Cre

tac

eo

us

Ju

ras

sic

Mancos ShaleK2

K1

J2

J1

Dakota Sandstone

Morrison Formation

Entrada Sandstone

Geological Map of the Hanksville area, Geological Map of the Hanksville area, showing general extent of the Dakota showing general extent of the Dakota Sandstone FormationSandstone Formation

Stratigraphic cross-section showing position of Dakota relative to Morrison

Dakota Sandstone

Morrison Formation

Oyster Conglomerate &

Sandstone

Burrowed Sandstone

Coal & Shale

Sandstone with Concretions

Intertonguing Conglomerate & Sandstone

15 m

Units of the Dakota Sandstone FormationUnits of the Dakota Sandstone Formation

Basal Green Conglomerate unit not seen here

Composite Cross Composite Cross SectionSection

Unit #6: Oyster Conglomerate and Sandstone

Unit #5: Burrowed Sandstone

Unit #4: Coal and Shale

Unit #3: Sandstone with Concretions

Unit #2: Intertonguing Conglomerate and Sandstone

Unit #1: Green Conglomerate

15m

Morrison Formation below unconformity

Sample Location

Thin Section

Present erosional surface(Mancos Shale lies conformably above; not seen during this study)

Coal

Sandstone

Cross- bedding

Conglomerate

Shale Concretions

Clasts

Burrows

Oyster fossils

LEGEND

When were these concretions When were these concretions discovered?discovered?

Melissa Battler & Rocky Persaud first Melissa Battler & Rocky Persaud first found the MDRS concretions during found the MDRS concretions during Expedition One, in February 2003Expedition One, in February 2003

Concretions have been documented Concretions have been documented in other parts of the Dakota in other parts of the Dakota Sandstone, such as the 1-2m Sandstone, such as the 1-2m concretions found in Kansas over concretions found in Kansas over 100 years ago100 years ago

The Dakota Sandstone is a very widespread unit, covering many parts of central

USA Kansas concretions

Rocky, Melissa & Matt

UTAH

DakotaDakota

SandstoneSandstone

Why are concretions significant Why are concretions significant to Mars analog studies?to Mars analog studies?

Because concretions are Because concretions are often formed biogenically, often formed biogenically, and therefore indirectly and therefore indirectly indicate the past presence indicate the past presence of lifeof life

Concretions require water Concretions require water to form, and therefore to form, and therefore directly imply the past directly imply the past presence of waterpresence of water

Concretions have been Concretions have been discovered on Mars!!!!!discovered on Mars!!!!!

Mars Mars Exploration Exploration Rover DataRover Data

Concretions on Concretions on Mars!Mars! Opportunity found spherules that appear to be Opportunity found spherules that appear to be

concretions at the Meridiani Planum site!concretions at the Meridiani Planum site!– Solid homogeneous spheres with no banding or Solid homogeneous spheres with no banding or

weathering rings weathering rings – Colour difference between concretions and host Colour difference between concretions and host

rockrock– Weather out in spheresWeather out in spheres

Cluster of 3 spheres had to grow radially Cluster of 3 spheres had to grow radially outwards & then join together, to form this outwards & then join together, to form this shape. This gives strong evidence that these shape. This gives strong evidence that these are concretions of sedimentary origin, and are concretions of sedimentary origin, and notnot pizzoliths of volcanic originpizzoliths of volcanic origin

Martian Outcrop where Martian Outcrop where Concretions were DiscoveredConcretions were Discovered

More Pictures More Pictures of Martian of Martian

ConcretionsConcretions

1cm 1cm

A B

Martian vs. Earth ConcretionsMartian vs. Earth Concretions

Mars MDRS

It is clear that the Mars & MDRS Dakota Sandstone concretions It is clear that the Mars & MDRS Dakota Sandstone concretions look strikingly similar. Isotopic data from the MDRS look strikingly similar. Isotopic data from the MDRS concretions suggest that these were formed biogenically… concretions suggest that these were formed biogenically… perhaps the Mars concretions were too…? We need perhaps the Mars concretions were too…? We need significantly more data to answer this question.significantly more data to answer this question.

1cm 1cm

A B

Mars MDRS

Conclusions: How to Find Conclusions: How to Find Concretions around MDRSConcretions around MDRS

Look in yellow, fine-grained sandstone unit of the Look in yellow, fine-grained sandstone unit of the Dakota Sandstone Formation (Unit 3)Dakota Sandstone Formation (Unit 3)– For a more complete description of Unit 3, refer to For a more complete description of Unit 3, refer to

http://chapters.marssociety.org/canada/expedition-http://chapters.marssociety.org/canada/expedition-mars.org/ExpeditionAlpha/crew/Proposal.MelissaBattler.pdfmars.org/ExpeditionAlpha/crew/Proposal.MelissaBattler.pdf

Look for weathering-resistant spherical balls of Look for weathering-resistant spherical balls of sandstone, roughly 1cm in diametersandstone, roughly 1cm in diameter– I.e. harder than the surrounding host-rockI.e. harder than the surrounding host-rock

Might be oval-shaped, or appear to be smeared into Might be oval-shaped, or appear to be smeared into layerslayers

Can be brown, black, white, or orangeCan be brown, black, white, or orange Note:Note: these are just guidelines. It is possible that these are just guidelines. It is possible that

atypical concretions exist within the Dakota atypical concretions exist within the Dakota Sandstone, and it is also possible that concretions Sandstone, and it is also possible that concretions may exist within other geological units around may exist within other geological units around MDRSMDRS

ResourcesResources Paleoenvironmental Interpretation of the Dakota Sandstone as a Mars Analog, Paleoenvironmental Interpretation of the Dakota Sandstone as a Mars Analog,

focusing on Concretionsfocusing on Concretions http://chapters.marssociety.org/canada/expedition-http://chapters.marssociety.org/canada/expedition-mars.org/ExpeditionAlpha/crew/Proposal.MelissaBattler.pdf mars.org/ExpeditionAlpha/crew/Proposal.MelissaBattler.pdf

Columbia Encyclopedia, Sixth Edition, Copyright (c) 2004:Columbia Encyclopedia, Sixth Edition, Copyright (c) 2004: http://www.encyclopedia.com/html/c1/concreti.asphttp://www.encyclopedia.com/html/c1/concreti.asp

From Wikipedia, the free encyclopedia:From Wikipedia, the free encyclopedia: http://en.wikipedia.org/wiki/Concretion http://en.wikipedia.org/wiki/Concretion Hintze, L.F. 1988. Geologic History of Utah: A Field Guide to Utah’s Rocks. Hintze, L.F. 1988. Geologic History of Utah: A Field Guide to Utah’s Rocks.

Edited by Edited by B.J.Kowallis. Brigham Young University Geology Studies, Special B.J.Kowallis. Brigham Young University Geology Studies, Special Publication 7, 202pp.Publication 7, 202pp.

Lawyer, G.F. 1972. Sedimentary Features and Paleoenvironment of the Dakota Lawyer, G.F. 1972. Sedimentary Features and Paleoenvironment of the Dakota Sandstone (Early Upper Cretaceous) Near Hanksville, Utah. Brigham Young Sandstone (Early Upper Cretaceous) Near Hanksville, Utah. Brigham Young University Research Studies, Geology Series, 19: 89-120. University Research Studies, Geology Series, 19: 89-120.

Mozley, P.S. 1996. The Internal Structure of Carbonate Concretions in Mozley, P.S. 1996. The Internal Structure of Carbonate Concretions in Mudrocks: a Critical Evaluation of the Conventional Concentric Model of Mudrocks: a Critical Evaluation of the Conventional Concentric Model of Concretion Growth. Sedimentary Geology, 103: 85-91.Concretion Growth. Sedimentary Geology, 103: 85-91.

Shaffer, H.L. 1937. Concretions in the Dakota Sandstone. The Compass of Shaffer, H.L. 1937. Concretions in the Dakota Sandstone. The Compass of Sigma Gamma Epsilon, 17: 87-90. Sigma Gamma Epsilon, 17: 87-90.

Stamm, N. 2002. USGS National Geologic Map Database - Geologic Unit Name: Stamm, N. 2002. USGS National Geologic Map Database - Geologic Unit Name: Dakota. http://ngmsvr.wr.usgs.gov/lex-bin/make_unit.pl?1082756974&7833&0.Dakota. http://ngmsvr.wr.usgs.gov/lex-bin/make_unit.pl?1082756974&7833&0.

Webster, G. and Brown, D. 2004. Mineral in Mars 'Berries' Adds to Water Story. Webster, G. and Brown, D. 2004. Mineral in Mars 'Berries' Adds to Water Story. NASA News Release: 2004-088, March 18, 2004. NASA News Release: 2004-088, March 18, 2004. http://marsrovers.jpl.nasa.gov/home/index.htmlhttp://marsrovers.jpl.nasa.gov/home/index.html