Solid earth geophysics - general

Research and education in solid earth geophysics continued in several fields in 2014. In education, a major modification to the curriculum of solid earth geophysics was implemented. From the fall 2014 semester solid earth geophysics is a specialization line common to the Departments of Physics and the Geosciences and Geography (for details see https://wiki.helsinki.fi/display/SEGeophys/Solid+Earth+Geophysics). From now on, the students entering the solid earth studies can have a BSc degree in physics, theoretical physics or geology with appropriate minors in mathematics, physics and geology. Excluding the course introduction to solid earth geophysics, all solid earth education is given at the Master level.


In 2014 four MSc projects and four PhD projects were ongoing in solid earth geophysics (Toni Veikkolainen, Robert Klein, Dharmindar Maharaj, Juha Korhonen, Erkki-Luoma-Aho) . One PhD project (Toni Veikkolainen) was finished in October. At the end of the year there were three post-doc scientists (Tomas Kohout, Johanna Salminen, Toni Veikkolainen)

Campus drill hole project was initiated in co-operation with the Department of Geosciences and Geography. We aim at drilling a 300 – 500 m deep drill hole on the Kumpula campus in 2015 for education and research. Basic measures were taken for project funding and overall project planning.

The solid earth geophysics laboratory continued providing high quality measurement facilities in paleomagnetism and other rock physical properties. The lab was taken care by Tomas Kohout and assisted by Merja Blomberg, Johanna Salminen and Robert Klein.  Several foreign scientists visited the laboratory for measurements.

For the purposes of geothermal research and borehole geophysics the laboratory instrumentation needs additions in the selection of instruments. Instrumentation for thermal conductivity and diffusivity lab measurements was ordered from LGM Lippman GmbH, Germany. The instrument will be received in spring 2015. Borehole geophysical instrumentation for shallow (< 500 m) holes was ordered from Robertson Geologging Inc., UK. It will also be received in 2015.

Honors to Solid Earth Geophysics personnel in 2014

The IAU (International Astronomical  Union) nominated, at the  ACM2014 meeting in Helsinki, June 30-July 4, 2014,  the asteroid 1979A (1969OY, 2001 YS82) as "Pesonen" according to prof. Lauri J. Pesonen  on his activity in studies of supercontinents, terrestrial meteorite impacts and introducing the course "Planetary Geophysics" at the curriculum of the teaching programme at the University of Helsinki.

Prof. Ilmo Kukkonen received the Rossby Prize 2014 of the Geophysical National Committee of the Swedeish Academy of Sciences on Nov 12, 2014. According to the committee, “Ilmo Kukkonen received the prize for significant and border-crossing work on heat flow of the Earth, structure of the earth’s crust and its properties. Kukkonen has successfully integrated different disciplines in his work and through his international engagement been an ambassador of Nordic geophysics.”

PhD Johanna Salminen was awarded the Early Career Scientist award by International Union of Geodesy and Geophysics for year 2015 (http://www.iugg.org/honors/u_awards.php)  .

Geothermal research

Ilmo Kukkonen continued studies of rock thermal properties for purposes of nuclear waste disposal in bedrock. Posiva Oy, Finland, was consulted in several projects concerning the thermal properties of Olkiluoto (disposal site in SW Finland) rocks, in situ measurement of thermal conductivity and paleoclimatic ground surface temperature inversion of deep borehole temperature data. These were carried out in co-operation with the Geological Survey of Finland and University of Dublin.

St1 Deep Heat company, Finland, was consulted in geothermal energy potential for enhanced geothermal systems (EGS) in the conditions in Finland. The company aims at drilling two 5 – 6 km deep holes for feeding district heating power plants with geothermal energy.

in-situ measurement of thermal conductivity in a borehole

 

Figure 3. Principle of in-situ measurement of thermal conductivity in a borehole. Conduction of heat from a heated cylinder in a borehole and results of theoretical results of probe temperatures during a heating-cooling cycle calculated with a 3D model. Instruments based on this principle have been constructed and operated fro Posiva Oy in co-op with the Geological Survey of Finland (from Kukkonen et al., 2014).

PUBLICATIONS


Peer reviewed public research report (published, in print or accepted)

Kukkonen, I., Korpisalo, A., Suppala, I. & Koskinen, T., 2014. In Situ Determination of Thermal Properties of Rocks in Crystalline Rock Drill Holes with TERO56 and TERO76 Devices. Posiva report 2013-06, 56 p.

Deep Fluids

Ilmo Kukkonen, Professor

In co-operation with the Geological Survey of Finland, the residence times of deep saline fluids were investigated in the Outokumpu Deep Drill Hole, eastern Finland. Results indicate residence times of the order of 20 – 50 million years, and considerable stagnancy of deep fluids in the shield conditions. The results are in agreement with previous studies suggesting original recharging of the fluids to the rock from meteoric fluids under much warmer climatic conditions. Also the correlation of groundwater chemistry and microbial life forms in the deep hole fracture systems is in line with the new results.

Outokumpu Deep Drill Hole

Figure 4. In situ noble gas residence times of and salinity along the Outokumpu Deep Drill Hole (from Kietäväinen et al., 2014).

PUBLICATIONS
A Peer reviewed (published, in print or accepted)


Kietäväinen, R. Ahonen, L., Kukkonen, I.T., Niedermann, S., Wiersberg, S., 2014. Noble gas residence times of saline waters within crystalline bedrock, Outokumpu Deep Drill Hole, Finland. Geochimica et Cosmochimica Acta 145 (2014) 159–174. http://dx.doi.org/10.1016/j.gca.2014.09.012

Purkamo, L., Bomberg, M., Nyyssönen, M., Kukkonen, I., Ahonen, L. and Itävaara, M., 2014. Heterotrophic Communities Supplied by Ancient Organic Carbon Predominate in Deep Fennoscandian Bedrock Fluids. Microb. Ecol. DOI 10.1007/s00248-014-0490-6.

Scientific deep drilling


Ilmo Kukkonen continued preparations  of the scientific deep drilling project DAFNE (Drilling Active Faults in Northern Europe). DAFNE aims at drilling 1 – 2.5 km deep holes in the Pärvie postglacial fault in northern Sweden. The project is an ICDP project developed in an international team co-ordinated by Ilmo Kukkonen and participated by Maria Ask (Luleå TU), Björn Lund (Univ. of Uppsala), (Odleiv Olesen, NGU, Trondheim) and Åke Fagereng (Univ. of Cardiff).


Ilmo Kukkonen served as the Finnish member (via Academy of Finland) of the Executive committee of International Scientific Drilling Program (ICDP).


PUBLICATIONS
A Peer reviewed (published, in print or accepted)

Kukkonen, I.T. and Fridleifsson, O., 2014. Heat and mass transfer. In: B. Horsfield (ed.) ICDP's Science Plan for 2015-2019 (in print).

Paleomagnetism


Johanna Salminen, PhD, post-doctoral scientist


Iron-bearing minerals record the direction of Earth’s magnetic field that has reversed at irregular intervals throughout the Earth history. One aim of paleomagnetic study is to establish the original magnetization direction from different kind of rocks and use this for reconstructing the position of continents at the time of magnetization was acquired. During the year 2014 I sampled several Precambrian formations on Finland, Brazil and Namibia to produce high quality paleomagnetic and geochronology data to reconstruct Paleo- to Mesoproterozoic supercontinent Nuna (Columbia) (Figure 3). These reconstructions are crucial in understanding the dynamics of Earth from core trough mantle and crust up to atmosphere.
Columbia

Figure 5. Configuration and paleogeographic position of the continents within supercontinent Nuna at ca.1.59 Ga, when large igneous provinces and extensional basins were extensively developed (Zhang et al., 2012; Salminen et al., 2014). Widespread 1.6–1.2 Ga large igneous events across the supercontinent may signify early extension related to the breakup of Nuna (Zhang et al., 2012).


Since the age and pattern of Earth’s magnetic field reversals is known from the study of sea floor spreading zones and the dating of volcanic rocks paleomagnetic method (magnetostratigraphy) can be used to determine the age of sedimentary rocks and link the important fossil localities to an absolute time scale. During the year 2014 results from Angolan Cretaceous-Paleogene (Figure 4) and from Chinese Miocene units were published. Study of Chinese Miocene units continued at 2014.

Cretaceous-Paleogene

Figure 6. δ13C chemostratgraphy and magnetostratigraphy of Bentiaba section, Angola (Strganac et al., 2014).

PUBLICATIONS
A Peer reviewed (published, in print or accepted)
A1    Kaakinen, A., Azizb, H.A., Passey, B.H., Zhang, Z., Liu, L., Salminen, J., Krijgsman, W., and Fortelius, M., (accepted). Age and stratigraphic context of Pliopithecus and associated fauna from Miocene sedimentary strata at Damiao, Inner Mongolia, China. Journal of Asian Earth Sciences.

A1    Salminen, J.M., Klein, R., Mertanen, S., Pesonen, L.J., Fröjdö, S., Mänttäri, I., Eklund, O (in press). Palaeomagnetism and U-Pb geochronology of ca. 1570 Ma intrusives from Åland archipelago, SW Finland – implications for Nuna. In Evans, D.D.D. and Li, X (eds.): Supercontinent Cycles Through Earth History. Geological Society of London Special Publications, Special volume.

A1  Evans, D.A.D., Trindade, R.I.F., Catelani, E.L., D'Agrella-Filho, M.S., Heaman, L.M., Oliveira, E.P. Söderlund, U., Ernst, R.E., Smirnov, A.V., and Salminen, J. M, (in press). Return to Rodinia? Moderate to high paleolatitude of the São Francisco/Congo craton at 920 Ma. Geological Society of London Special Publications, Special volume.

A1    Strganac, C., Jacobs, L. J., Polcyn, M.J., Mateus, O., Myers, T.S., Salminen, J., May, S., Ferguson, K.M.,  Araújo, R., Schulp, A.S., Morais, M.L., da Silva Tavares, T., and Olímpio Gonçalves, 2014. Geological Setting and Paleoecology of the Upper Cretaceous Bench 19 Marine Vertebrate Bonebed at Bentiaba, Angola. Netherlands Journal of Geosciences - Geologie en Mijnbouw for the 4th Triennial International Mosasaur Meeting.

A1    Strganac, C.,  Salminen, J.,  Jacobs, L. J., Polcyn, M.J., Ferguson, K.M.,  Mateus, O., Schulp, A.S., Morais, M.L., da Silva Tavares, T., and Olímpio Gonçalves, 2014.  A. Carbon isotope stratigraphy, magnetostratigraphy, and 40Ar/39Ar age of the Cretaceous South Atlantic coast, Namibe Basin, Angola. Journal of African Earth Sciences, 99, 452-462. http://dx.doi.org/10.1016/j.Jafrearsci.2014.03.003.

A4    Salminen, J., Dinis, J., and Mateus, O., 2014. Preliminary magnetostratigraphy for Jurassic/Cretaceous transition in Porto da Calada, Portugal. 1st International Congress on Stratigraphy (STRATI 2013), to be held in Lisbon, 1–7 July 2013, Proceedings of the First International Congress on Stratigraphy, Springer geology, 4 pages

A1     Klein, R., S., Pesonen, L.J., Salminen, J., and Mertanen, 2014. Paleomagnetic study of Mesoproterozoic Satakunta sandstone, Western Finland. Precambrian Research. doi:10.1016/j.precamres.2013.09.003.
 
A1    Salminen, J., Mertanen, S., Evans, D.A.D., and Wang, Z., 2014. Paleomagnetic and geochemical studies of the Mesoproterozoic Satakunta dyke swarms, Finland, with implications for a Northern Europe – North America (NENA) connection within Nuna supercontinent.  Precambrian Research. 244, 170-191. Doi: 10.1016/j.precamres.2013.08.006.

A1    Salminen, J., Halls, H.C., Mertanen, S., Pesonen, L.J., Vuollo, J., and Söderlund, U., 2014. Paleomagnetic and Geochronological Studies on Paleoproterozoic Diabase Dykes of Karelia, East Finland - Key for Testing the Superia Supercraton. Precambrian Research, 22, 87-99. doi: 10.1016/j.precamres.2013.07.011.

 

Conference  publications
B3      Salminen, J., and Mertanen, S., 2014. New paleomagnetic studies on the Mesoproterozoic units in Southern Finland with implications for Nuna supercontinent. 2014 NORDIC SUPERCONTINENT WORKSHOP October 13-19, 2014 Haraldvangen, Norway.

B3       Kaakinen, A., Salminen, J., Zhang, Z., 2014. The magnetostratigraphic age of the mammalian fossil-bearing Oligocene sediments at Ulantatal, Inner Mongolia, China. ISC 2014, Geneva, Switzerland 18 – 22 August 2014.

Visits abroad at 2014
April 2014                  Yale University, USA
March 2014                Universidade de São Paulo, Brazil

 

Field work at 2014
Finland, Namibia, China, and Brazil

Scientific awards
Awarded Early Career Scientist award by International Union of Geodesy and Geophysics for year 2015 ( http://www.iugg.org/honors/u_awards.php) . 

Paleomagnetism (cont.)


Toni Veikkolainen, doctoral student Until October, thereafter PhD, post-doc scientist


The geomagnetic and paleomagnetic research at the department involved testing the Geocentric Axial Dipole (GAD) hypothesis in the Precambrian era, and studying the paleosecular variation (PSV) as well as the field reversals and stability of the geodynamo in smaller timescales of the Earth’s far past. For this purpose, the global online database of Proterozoic and Archaean paleomagnetic data (PALEOMAGIA) was extended, and an additional compilation of high-quality data suitable for PSV analysis was made. The results support a predominantly dipolar character of the temporally averaged geomagnetic field prior to 540 million years ago as well as a smaller reversal rate and a higher stability of the geodynamo in the early Precambrian, and accordingly, they also validate the commonly used paleogeographic reconstruction methods typically relying on the GAD assumption.

Geomagnetic inclination

Figure 7. Geomagnetic inclination distribution for high-quality Precambrian igneous and metamorphic rock data and the best-fitting zonal multipole model (quadrupole is 0 % and octupole is 6 % of the strength of the dominant geocentric axial dipole). Both models are apparently close to the model expected from the GAD alone.

geomagnetic poles

Figure 8. Dspersion of virtual geomagnetic poles (S parameter) plotted against the absolute value of paleolatitude (|λ|) from a set of high-quality observations from PALEOMAGIA, along with Precambrian Model G fit and TAFI fit (0-5 Ma) from previous studies. These curves illustrate the paleosecular variation of the field and particularly its smaller rate in the Precambrian.
Publications

Doctoral dissertation

Veikkolainen, T. (2014). Database-wide studies on the validity of the Geocentric Axial Dipole hypothesis in the Precambrian. Unigrafia, Helsinki, 61p. + 5 original publications.

Peer-reviewed contributions

Veikkolainen, T., Pesonen, L.J. (2014). Palaeosecular variation, field reversals and the stability of the geodynamo in the Precambrian. Geophysical Journal International, 199, 1515-1526.

Veikkolainen, T., Pesonen, L.J., Evans, D.A.D. (2014). PALEOMAGIA - a PHP/MYSQL
database of the Precambrian paleomagnetic data. Studia Geophysica et Geodaetica, 58, 425-441.

Veikkolainen, T., Korhonen, K., Pesonen, L.J. (2014). On the spatial averaging of paleomagnetic data. Geophysica, 50, 49-58.

Veikkolainen, T., Pesonen, L.J., Korhonen, K. (2014). An analysis of geomagnetic field reversals supports the validity of the Geocentric Axial Dipole (GAD) hypothesis in the Precambrian. Precambrian Research, 244, 33-41.

Veikkolainen, T., Evans, D.A.D., Korhonen, K., Pesonen, L.J. (2014). On the low-inclination bias of the Precambrian geomagnetic field. Precambrian Research, 244, 23-32.

Other contributions

Veikkolainen, T., Pesonen, L.J. (2014). The 1.1 Ga North American polarity asymmetry problem in the light of new data from Lake Superior and Arizona rocks. In: 2014 Nordic Supercontinent Workshop, edited by M. Domeier, University of Oslo, p. 61-64.

Veikkolainen, T., Pesonen, L.J., Korhonen, K. (2014). Precambrian geomagnetic field – An overview. In: 2014 Nordic Supercontinent Workshop, edited by M. Domeier, University of Oslo, p. 31-35.

Veikkolainen, T., Pesonen, L.J., Evans, D.A.D. (2014). PALEOMAGIA - An online resource of Precambrian paleomagnetic data. In: 2014 Nordic Supercontinent Workshop, edited by M. Domeier, University of Oslo, p. 20-23.

Pesonen, L.J., Veikkolainen, T., Evans, D.A.D. (2014). PALEOMAGIA - A Novel MySQL Paleomagnetic Database for the Precambrian Era with Examples. In: 2014 MagIC Science & Database Workshop Volume, edited by N. Jarboe, Scripps Institution of Oceanography, University of California at San Diego, p. 8-11.

Paleomagnetism (cont.)


Robert Klein, doctoral student


During 2014 I finalized and submitted a paper on the paleomagnetism of Hailuoto sedimentary rocks, finalized data analyses for a paper on the paleomagnetism of Keuruu diabase dykes, and together with Johanna Salminen and Satu Mertanen collected and measured samples from the Häme diabase dyke swarm. Furthermore I applied for and was granted funding for 2015 from the Väisälä Foundation to complete my Ph.D.


Summary of the Hailuoto paleomagnetic results


The results from the Hailuoto study was presented at the Finnish National Colloquium of Geosciences, and submitted to Precambrian Research. In the study we isolated a paleomagnetic pole for Hailuoto which adds to the scattered Ediacaran paleomagnetic data of Baltica and indicate large distances between similar aged paleomagnetic poles (Figure 7). We present reconstructions of Baltica and Laurentia between 616 and 550 Ma (Figure 8), which move Baltica from high latitudes (615 Ma) to low latitudes (550 Ma), and Laurentia from low latitudes (615 Ma) to a polar position (570 Ma) and back to an equatorial position (550 Ma). Our results indicate that the Gaskiers glaciation (ca. 580 Ma) did not occur during the time of the deposition of the Hailuoto sediments.

Polar wander

Figure 9: Apparent polar wander path for Baltica between 616 - 475 Ma

Baltica & Laurentia

Figure 10: Reconstruction of Baltica and Laurentia between 615 Ma and 550 Ma.

Publications

Klein, R., Pesonen, L.J., Salminen, J., Mertanen, S. 2014. Paleomagnetism of Mesoproterozoic Satakunta sandstone, Western Finland. Precambrian Research 244, 156-169.
Salminen, J., Klein, R., Mertanen, S., Pesonen, L.J., Fröjdö, S., Mänttäri, I., Eklund, O. Accepted. Palaeomagnetism and U-Pb geochronology of ca. 1570 Ma intrusives from Åland archipelago, SW Finland – implications for Nuna. Geological Society of London Special Publication.
Klein, R., Salminen, J., Mertanen, S. Submitted. Baltica during the Ediacaran and Cambrian. Precambrian Research.
Klein, R., Mertanen, S. 2014. Baltica durint the Neoproterozoic and Cambrian: A paleomagnetic study on Hailuoto sediments. In: Virtasalo, J., Tuusjaarvi, M. (Eds.) Abstract book: 1st Finnish National Colloquium of Geosciences, Espoo, 19-20 March 2014. Geological Survey of Finland, Guide 58, 39-40. (Poster presentation).

Paleomagnetism (cont.)


Lauri J. Pesonen, Professor emeritus


Highlights of activities in 2014


Professor (emeritus) Lauri J. Pesonen gave an invited lecture series of solid earth geophysics at the Manonmanian Sundaranar University, Tirunveli, Tamil Nadu, India, during June 28-July 4, 2014.


Honors


The IAU (International Astronomical  Union) nominated, at the  ACM2014 meeting in Helsinki, June 30-July 4, 2014,  the asteroid 1979A (1969OY, 2001 YS82) as "Pesonen" according to prof. Lauri J. Pesonen  on his activity in studies of supercontinents, terrestrial meteorite impacts and introducing the course "Planetary Geophysics" at the curriculum of the teaching programme at the University of Helsinki.


Peer refereed articles: Category A1


1. Pisarevsky, S. A., Elming, S-A., Pesonen, L. J. & Li, Z-X., 2014. Mesoproterozoic paleogeography: Supercontinent and beyond.  Precambrian Research, 244, 207-225.
2. Veikkolainen, T., Evans, D. A. D., Korhonen, K. & Pesonen, L. J. 2014. On the low-inclination bias of the Precambrian geomagnetic field. Precambrian Research, 244, 23-32.
3. Veikkolainen, T., Pesonen, L.& Korhonen, K., 2014. An analysis of geomagnetic field reversals supports the validity of the Geocentric Axial Dipole (GAD) hypothesis in the Precambrian. Precambrian Research, 244, 33-41.
4. Salminen, J., Halls, H. C., Mertanen, S., Pesonen, L. J., Vuollo, J. & Söderlund, U., 2014. Paleomagnetic and geochronological studies on Paleoproterozoic diabase dykes of Karelia, East Finland - Key for testing the Superia supercraton. Precambrian Research, 244, 87-99.
5. Klein, R., Pesonen, L. J., Salminen, J. & Mertanen, S. 05.2014 Paleomagnetism of Mesoproterozoic Satakunta sandstone, Western Finland. Precambrian Research, 244,156-169.
 6. Belica, M. E., Piispa, E. J., Meert, J. G., Pesonen, L. J., Plado, J., Pandit, M. K., Kamenov, G. D. & Celestino, M., 2014. Proterozoic mafic dyke swarms from the Dharwar craton: paleomagnetic poles for India from 2.37 to 1.88 Ga and rethinking the Columbia supercontinent. Precambrian Research, 244, 100-122.
7. Pesonen, L. J., Halls, H. C. & Mertanen, S., 2014. Precambrian supercontinents.  Precambrian Research, 244, 1-4.
8. Veikkolainen, T. H. K., Korhonen, K. & Pesonen, L. 2014. On the spatial averaging of paleomagnetic data. Geophysica, 50, No.1, 49-58.
9. Veikkolainen, T, Pesonen, L.J., 2014. Palaeosecular variation, field reversals and the stability of the geodynamo in the Precambrian. Geophysical Journal International, 199, No.3, 1515-1526.
10. Veikkolainen, T. H. K., Pesonen, L. & Evans, D. A. D., 2014. PALEOMAGIA - A PHP/MYSQL database of Precambrian paleomagnetic data. Studia Geophysica et Geodaetica, 58, No. 3, p. 425-441.

Conference Proceedings...Category B3


11. Pesonen, L.J., Veikkolainen, T., Evans, D.A.D., 2014. PALEOMAGIA - A Novel MySQL Paleomagnetic Database for the Precambrian Era with Examples. In: Workshop Volume, 2014 MagIC Science & Database Workshop, Scripps Institution of Oceanography, University of California, San Diego, Ca, USA, 8-11.
12. Veikkolainen, T. H. K. & Pesonen, L. 2014. PALEOMAGIA - An online resource of Precambrian paleomagnetic data. In: 2014 Nordic Supercontinent Workshop, October 13-19, 2014, Haraldvangen, Norway. Centre for Earth Evolution and Dynamics, University of Oslo, p. 20-23.
13. Veikkolainen, T. H. K., Pesonen, L. & Korhonen, K. 2014. Precambrian geomagnetic field - An overview. In: 2014 Nordic Supercontinent Workshop, October 13-19, 2014, Haraldvangen, Norway. Centre for Earth Evolution and  Dynamics, University of Oslo, p. 31-35.
14. Veikkolainen, T. H. K. & Pesonen, L.,  2014. The 1.1 Ga North American polarity asymmetry problem in the light of new data from Lake Superior and Arizona rocks. In: 2014 Nordic Supercontinent Workshop, October 13-19, 2014, Haraldvangen, Norway. Centre for Earth Evolution and Dynamics, University of Oslo, p.  61-64.
15. Pesonen, L.J., 2014. Nordic paleomagnetic workshops - a historical view. In: 2014 Nordic Supercontinent Workshop, October 13-19, 2014, Haraldvangen, Norway. Centre for Earth Evolution and Dynamics, University of Oslo, p. 10-16.
16. Maharaj, D. & Pesonen, L.J. 2014. Creating a Precambrian kimberlite paleomagnetic database for the Rodinia and Columbia supercontinents. In: 2014 Nordic Supercontinent Workshop, October 13-19, 2014, Haraldvangen, Norway. Centre for Earth Evolution and Dynamics, University of Oslo, p. 47-50.
17 Piispa, E.J., Smirnov, A., Pesonen, Lauri.J., and Mitchell, R., 2014. Paleomagnetism of the ~ 1144 Ma lamprophyre dykes in the eastern Lake Superior region, Ontario, Canada - Evidence of early Midcontinent Rift volcanism. In: 2014 Nordic Supercontinent Workshop, October 13-19, 2014, Haraldvangen, Norway. Centre for Earth Evolution and Dynamics, University of Oslo, p. 55-56.


Conference contributions, Abstracts


18. Piispa, E.,  Smirnov, A.  and  Pesonen, L., 2014.  Mesoproterozoic Midcontinent Rift intrusives in Thunder Bay area, Ontario, Canada: a paleomagnetic review. In: Miller, J. (Ed.), 60th Annual Meeting of the Institute of Lake Superior Geology, May 14-17, 2014, Hibbing, Minnesota, USA. Programme and Abstracts, p. 99-100.
19. Foucher, M., Renee, R., Piispa, E.,  Smirnov, A. and and Pesonen, L. 2014. Evolution of the Midcontinent Rift system: Paleomagnetic, rock magnetic and anisotropy of magnetic susceptibility study of the Mesoproterozoic Baraga - Marquette dike swarm, MI, USA. In: Miller, J. (Ed.), 60th Annual Meeting of the Institute of Lake Superior Geology, May 14-17, 2014, Hibbing, Minnesota, USA. Programme and Abstracts, p. 49.
20. Jacobson, D.,  Piispa, E.,  Smirnov, A. and  Pesonen, L., 2014.  Silica Remobilization in the Biwabik Iron Formation, Minnesota, USA. In: Miller, J. (Ed.), 60th Annual Meeting of the Institute of Lake Superior Geology, May 14-17, 2014, Hibbing, Minnesota, USA. Programme and Abstracts, p. 61.
21. Piispa, E., Foucher, M., Chmielewski, J., Smirnov, A. and Pesonen, L.J., 2014. Paleomagnetism of the ~ 1.1 Ga Baraga-Marquette (BM) dykes (Michigan, USA). In: Abstracts of the AGU Fall Meeting, San Fransisco, 15-19 December, 2014 (paper GP43A-3638).


Edited volumes


22. Pesonen, L.J., Halls, H.C., Mertanen, S. and Cawood, P. (Guest Editors), 2014. Precambrian Supercontinents. Special issue, Precambrian Research, v. 244, May 2014, 316 pp.

Permafrost studies


Tomas Kohout, Phd, post-doctoral scientist


Geophysics field research focused on non-invasive prospection of palsas (sporadic permafrost features) in Peerajärvi area, Lapland. Using ground penetrating radar (GPR) it was possible to determine dimensions of palsas permanently frozen ice core.

Relevant publication list can be found here:
https://tuhat.halvi.helsinki.fi/portal/en/persons/tomas-kohout%285906f4a3-3bbf-4da7-bd35-1fc6df66b097%29/publications.html

Peerajärvi palsa

Figure 11. Ground penetrating radar (GPR) section of the Peerajärvi palsa.

 

Planetary geophysics


Tomas Kohout, PhD, post-doctoral scientist

Planetary geophysics research focused on laboratory simulations of space weathering and its effects in reflected light spectrum, physical properties of meteorites and internal structure of cosmic dust particles.
As a result of space weathering simulations it was found that space weathering progress logarithmically with time. This explains observed rapid onset of space weathering on fresh planetary surfaces, while old mature planetary surfaces are saturated and do not show substantial spectral changes.
Meteorite physical properties investigations focused on Chelyabinsk and Košice meteorite falls. While Košice meteorites are homogeneous, Chelyabinsk meteorites shows variations in their shock level. While light-colored meteorites are of low shock level, dark-colored meteorites are heavily shocked with signs of partial or complete melting. Such shock is caused by ancient space collision of Chelyabinsk parent body with another asteroid.
Investigations of cosmic dust using X-ray microtomography revealed changes in its internal structure during high velocity atmospheric entry. At low entry velocities no changes are observed. At high entry velocities partial melting of the dust particles occurs during deceleration associated with temporary increase in porosity followed by subsequent complete melting and porosity reduction.

Relevant publication list can be found here:
https://tuhat.halvi.helsinki.fi/portal/en/persons/tomas-kohout%285906f4a3-3bbf-4da7-bd35-1fc6df66b097%29/publications.html

 

 

cosmicdustparticle

Figure 12. Micrometeorite. Tomography section of partially molten porous cosmic dust particle (approximately 170 micrometers in size).