Physical Properties of Deep Drill Cores : Implications for Meteorite Impact Effects and Crustal Structures

Physical properties provide valuable information about the nature and behavior of rocks and minerals. The changes in rock physical properties generate petrophysical contrasts between various lithologies, for example, between shocked and unshocked rocks in meteorite impact structures or between various lithologies in the crust. These contrasts may cause distinct geophysical anomalies, which are often diagnostic to their primary cause (impact, tectonism, etc). This information is vital to understand the fundamental Earth processes, such as impact cratering and associated crustal deformations. However, most of the present day knowledge of changes in rock physical properties is limited due to a lack of petrophysical data of subsurface samples, especially for meteorite impact structures, since they are often buried under post-impact lithologies or eroded. In order to explore the uppermost crust, deep drillings are required. This dissertation is based on the deep drill core data from three impact structures: (i) the Bosumtwi impact structure (diameter 10.5 km, 1.07 Ma age; Ghana), (ii) the Chesapeake Bay impact structure (85 km, 35 Ma; Virginia, U.S.A.), and (iii) the Chicxulub impact structure (180 km, 65 Ma; Mexico). These drill cores have yielded all basic lithologies associated with impact craters such as post-impact lithologies, impact rocks including suevites and breccias, as well as fractured and unfractured target rocks. The fourth study case of this dissertation deals with the data of the Paleoproterozoic Outokumpu area (Finland), as a non-impact crustal case, where a deep drilling through an economically important ophiolite complex was carried out. The focus in all four cases was to combine results of basic petrophysical studies of relevant rocks of these crustal structures in order to identify and characterize various lithologies by their physical properties and, in this way, to provide new input data for geophysical modellings. Furthermore, the rock magnetic and paleomagnetic properties of three impact structures, combined with basic petrophysics, were used to acquire insight into the impact generated changes in rocks and their magnetic minerals, in order to better understand the influence of impact. The obtained petrophysical data outline the various lithologies and divide rocks into four domains. Based on target lithology the physical properties of the unshocked target rocks are controlled by mineral composition or fabric, particularly porosity in sedimentary rocks, while sediments result from diverse sedimentation and diagenesis processes. The impact rocks, such as breccias and suevites, strongly reflect the impact formation mechanism and are distinguishable from the other lithologies by their density, porosity and magnetic properties. The numerous shock features resulting from melting, brecciation and fracturing of the target rocks, can be seen in the changes of physical properties. These features include an increase in porosity and subsequent decrease in density in impact derived units, either an increase or a decrease in magnetic properties (depending on a specific case), as well as large heterogeneity in physical properties. In few cases a slight gradual downward decrease in porosity, as a shock-induced fracturing, was observed. Coupled with rock magnetic studies, the impact generated changes in magnetic fraction the shock-induced magnetic grain size reduction, hydrothermal- or melting-related magnetic mineral alteration, shock demagnetization and shock- or temperature-related remagnetization can be seen. The Outokumpu drill core shows varying velocities throughout the drill core depending on the microcracking and sample conditions. This is similar to observations by Kern et al., (2009), who also reported the velocity dependence on anisotropy. The physical properties are also used to explain the distinct crustal reflectors as observed in seismic reflection studies in the Outokumpu area. According to the seismic velocity data, the interfaces between the diopside-tremolite skarn layer and either serpentinite, mica schist or black schist are causing the strong seismic reflectivities.Kivien ja mineraalien fysikaaliset ominaisuudet tarjoavat arvokasta tietoa maankuoren materiaalien olemuksesta ja niiden ominaisuuksista. Muutokset kivien fysikaalisissa ominaisuuksissa tuottavat petrofysikaalisia kontrasteja eri kivilajien välillä, kuten esimerkiksi impaktikraatterien impaktikivet ja kohdekivet sekä erilaiset vaihtelut maankuoren kivilajeissa. Nämä kontrastit saattavat aiheuttaa geofysikaalia poikkeavuuksia, jotka havaitaan niiden ensisijaisen synnyn perusteella (impakti, tektoniikka, jne). Kivien fysikaalisten ominaisuuksien määrittäminen on tärkeää tutkiessamme Maapallon kehitysprosesseja, kuten meteoriitti-impaktien ja maankuoren deformaation vaikutuksia. Suurin osa tämän päivän tietämyksestä kivien fysikaalisten ominaisuuksien muutoksista ovat kuitenkin rajallisia johtuen vähäisestä pintakivien petrofysikaalisesta aineistosta. Erityisesti meteoriittikraattereiden pintakivien ominaisuudet ovat osittain puutteellisia, sillä kraatterit ovat usein hautautuneet sedimentteihin tai ne ovat kokeneet merkittävää impaktin jälkeistä eroosiota. Syväkairausten avulla voimme kuitenkin tutkia maankuoren ylimpiä kerroksia. Tämä väitöskirja perustuu kolmen impaktirakenteen syväkairausaineistoon: (i) Bosumtwi impaktikraatteri, Ghana, (ii) Chesapeake Bay impaktikraatteri, USA ja (iii) Chicxulub impaktikraatteri, Meksiko. Näissä kairausnäytteissä esiintyvät kaikki impaktirakenteiden tyypilliset litologiat, kuten impaktin jälkeiset litologiat, impaktikivet, sekä murtuneet ja ehjät kohdekivet. Tämän väitöskirjatyön neljäs osa-aihe käsittelee paleoproterotsooista aineistoa Suomesta Outokummun alueelta. Tässä impaktiin liittymättömässä aiheessa on kyse syväkairauksesta taloudellisesti tärkeän ofioliittikompleksin läpi. Kaikkien neljän osa-aiheen painopisteenä oli yhdistää maan kuoren rakenteelle merkityksellisten kivien petrofysikaalisten perustutkimuksien tulokset. Tulosten avulla tunnistettiin ja karakterisoitiin erilaisia litologioita perustuen niiden fysikaalisiin ominaisuuksiin ja näin saatiin uutta tietoa mahdollisiin geofysikaalisiin mallinnuksiin. Lisäksi kolmen impaktirakenteen kivien magneettiset ja paleomagneettiset ominaisuudet yhdistettynä petrofysikaalisiin ominaisuuksiin auttoivat luomaan käsityksen impaktin aiheuttamista muutoksista kivissä ja niiden magneettisissa mineraaleissa sekä impaktin vaikutuksista kallioperään ja kohdekiviin

The Jurassic/Cretaceous boundary and high resolution biostratigraphy of the pelagic sequences of the kurovice section (Outer Western Carpathians, the northern Tethyan margin)

Microfacies and high resolution studies at the Kurovice quarry (Czech Republic, Outer Western Carpathians) on calpionellids, calcareous and non-calcareous dinoflagellate cysts, sporomorphs and calcareous nannofossils, aligned with paleomagnetism, allow construction of a detailed stratigraphy and paleoenvironmental interpretation across the Jurassic/Cretaceous (J/K) boundary. The Kurovice section consists of allodapic and micrite limestones and marlstones. Identified standard microfacies types SMF2, SMF3 and SMF4 indicate that sediments were deposited on a deep shelf margin (FZ 3), with a change, later, into distal basin conditions and sediments (FZ 1). The sequence spans a stratigraphic range from the Early Tithonian calcareous dinoflagellate Malmica Zone, nannoplankton zone NJT 15 and magnetozone M21r to the late Early Berriasian calpionellid Elliptica Subzone of the Calpionella Zone, nannoplankton NK-1 Zone and M17r magnetozone. The J/K boundary is marked by a quantitative increase of small forms of Calpionella alpina, the base of the Alpina Subzone (that corresponds to NJT 17b and M19n.2n) and by the rare occurrence of Nannoconus wintereri. Palynomorphs include Early Berriasian terrestrial elements - non-calcareous dinoflagellate cysts Achomosphaera neptunii, Prolixosphaeridium sp. A and Tehatnadinium evittii. The depositional area for Kurovice was situated at the margin of the NW Tethys. The influence of cold waters from northern latitudes and potential upwellings is highlighted by: 1) the high proportion of radiolarians and sponge spicules, 2) rare calpionellids represented mostly by hyaline forms, 3) the absence of microgranular calpionellids - chitinoidellids, 4) the small percentage of the genera Nannoconus, Polycostella and Conusphaera in nannofossil assemblages, as compared to other sites in Tethys, 5) scarce Nannoconus compressus, which has otherwise been mentioned from the Atlantic area.Web of Science70218215

The Jurassic/Cretaceous boundary and high resolution biostratigraphy of the pelagic sequences of the kurovice section (Outer Western Carpathians, the northern Tethyan margin)

Microfacies and high resolution studies at the Kurovice quarry (Czech Republic, Outer Western Carpathians) on calpionellids, calcareous and non-calcareous dinoflagellate cysts, sporomorphs and calcareous nannofossils, aligned with paleomagnetism, allow construction of a detailed stratigraphy and paleoenvironmental interpretation across the Jurassic/Cretaceous (J/K) boundary. The Kurovice section consists of allodapic and micrite limestones and marlstones. Identified standard microfacies types SMF 2, SMF 3 and SMF 4 indicate that sediments were deposited on a deep shelf margin (FZ 3), with a change, later, into distal basin conditions and sediments (FZ 1). The sequence spans a stratigraphic range from the Early Tithonian calcareous dinoflagellate Malmica Zone, nannoplankton zone NJT 15 and magnetozone M 21r to the late Early Berriasian calpionellid Elliptica Subzone of the Calpionella Zone, nannoplankton NK-1 Zone and M 17r magnetozone. The J/K boundary is marked by a quantitative increase of small forms of Calpionella alpina, the base of the Alpina Subzone (that corresponds to NJT 17b and M 19n.2n) and by the rare occurrence of Nannoconus wintereri. Palynomorphs include Early Berriasian terrestrial elements — non-calcareous dinoflagellate cysts Achomosphaera neptunii, Prolixosphaeridium sp. A and Tehamadinium evittii. The depositional area for Kurovice was situated at the margin of the NW Tethys. The influence of cold waters from northern latitudes and potential upwellings is highlighted by: 1) the high proportion of radiolarians and sponge spicules, 2) rare calpionellids represented mostly by hyaline forms, 3) the absence of microgranular calpionellids — chitinoidellids, 4) the small percentage of the genera Nannoconus, Polycostella and Conusphaera in nannofossil assemblages, as compared to other sites in Tethys, 5) scarce Nannoconus compressus, which has otherwise been mentioned from the Atlantic area

Integrated stratigraphy and palaeoenvironment of the Berriasian peri-reefal limestones at Štramberk (Outer Western Carpathians, Czech Republic)

A high-resolution multidisciplinary study of two profiles in the Kotouc Quarry at Stramberk was carried out to define the age and palaeoenvironmental setting of the peri-reefal Stramberk Limestone. Calpionellids of the Alpina and Ferasini subzones of the standard Calpionella Zone confirm an early Berriasian age for both studied sequences. The presence of the calcareous nannofossils Nannoconus kamptneri minor and ?Speetonia colligate supports this stratigraphic interpretation. An ammonite assemblage with Pseudosubplanites grandis was found corresponding to the upper part of the lower Berriasian (Grandis Subzone). Foraminiferan assemblages contain several taxa previously reported from the Valanginian. Magnetostratigraphy verifies that the studied sections span the magnetozones M18r to M18n. Rock magnetic measurements indicate magnetite as the carrier of characteristic remanent magnetization. A palaeolatitude suggested location at 36 degrees N. Microfacies indicate palaeoenvironments of slope (FZ 4), platform margin reefs, sand shoals (FZ 5, FZ 6) and possibly patch-reefs in the inner platform (FZ 7). The presence of calpionellids and the polychaete Terebella lapilloides suggests deposition within the deeper parts of the outer ramp of a platform slope, with redeposited clasts derived from nearby reef slopes and/or talus. This research contributes to the Berriasian Working Group's efforts to define the Tithonian-Berriasian boundary.Web of Science532art. no. UNSP 10925

The proposal of a GSSP for the Berriasian Stage (Cretaceous System): Part 2

In part 1 of this work we discussed the possibilities for the selection of a GSSP for the Berriasian Stage of the Cretaceous System, based on prevailing practical methods for correlation in that J/K interval, traditional usage and the consensus over the best boundary markers that had developed in the last forty years. This consensus has developed further, based on the results of multidisciplinary studies on numerous sites over the last decade. Here in Part 2 we give an account of the application of those results by the Berriasian Working Group (ISCS), and present the stratigraphic evidence that justifies the selection of the locality of Tré Maroua (Hautes-Alpes, SE France) as the proposed GSSP. We describe a 45 m-thick section in the Calcaires Blancs vocontiens – that part of the formation covering the calpionellid Chitinoidella, Remanei. Intermedia, Colomi, Alpina, Ferasini, Elliptica and Simplex biozones. The stratigraphic data collected here has been compiled as part of a wider comparative study of complementary Vocontian Basin sites (with localities at Charens, St Bertrand, Belvedere and Le Chouet). Evidence from Tré Maroua thus sits in this substantial regional biostratigraphic and magnetostratigraphic context. For the purposes of the GSSP definition, here we particularly concentrate on the unbroken sequence and biotic markers in the interval immediately below the boundary, the Colomi Subzone (covering circa 675,000 years), and immediately above, the Alpina Subzone (covering circa 725,000 years). Particularly significant fossil datums identified in the Tré Maroua profile are the primary basal Berriasian marker, the base of the Alpina Subzone (a widespread event marked by dominance of small Calpionella alpina, with rare Crassicollaria parvula and Tintinopsella carpathica): the base of the Berriasian Stage is placed at the base of bed 14, which coincides with the base of the Alpina Subzone. Secondary markers bracketing the base of the Calpionella Zone are the FOs of the calcareous nannofossil species Nannoconus wintereri, close below the boundary, and the FO of Nannoconus steinmannii minor, close above. The Tithonian/Berriasian boundary level occurs within M19n.2n, in common with many documented sites, and is just below the distinctive reversed magnetic subzone M19n.1r (the so-called Brodno reversal). We present data which is congruent with magnetostratigraphic and biostratigraphic data from other key localities in France and in wider regions (Le Chouet, Saint Bertrand, Puerto Escaño, Rio Argos, Bosso, Brodno, Kurovice, Theodosia…), and thus the characteristics and datums identified at Tré Maroua are key for correlation and, in general, they typify the J/K boundary interval in Tethys and connected sea

The proposal of a GSSP for the Berriasian Stage (Cretaceous System): Part 2

International audienceIn part 1 of this work we discussed the possibilities for the selection of a GSSP for the Berriasian Stage of the Cretaceous System, based on prevailing practical methods for correlation in that J/K interval, traditional usage and the consensus over the best boundary markers that had developed in the last forty years. This consensus has developed further, based on the results of multidisciplinary studies on numerous sites over the last decade. Here in Part 2 we give an account of the application of those results by the Berriasian Working Group (ISCS), and present the stratigraphic evidence that justifies the selection of the locality of Tré Maroua (Hautes-Alpes, SE France) as the proposed GSSP. We describe a 45 m-thick section in the Calcaires Blancs vocontiens – that part of the formation covering the calpio­nellid Chitinoidella, Remanei. Intermedia, Colomi, Alpina, Ferasini, Elliptica and Simplex biozones. The stratigraphic data collected here has been compiled as part of a wider comparative study of complementary Vocontian Basin sites (with localities at Charens, St Bertrand, Belvedere and Le Chouet). Evidence from Tré Maroua thus sits in this substantial regional biostratigraphic and magnetostratigraphic context. For the purposes of the GSSP definition, here we particularly concentrate on the unbroken sequence and biotic markers in the interval immediately below the boundary, the Colomi Subzone (covering circa 675,000 years), and immediately above, the Alpina Subzone (covering circa 725,000 years). Particularly significant fossil datums identified in the Tré Maroua profile are the primary basal Berriasian marker, the base of the Alpina Subzone (a widespread event marked by dominance of small Calpionella alpina, with rare Crassicollaria parvula and Tintinopsella carpathica): the base of the Berriasian Stage is placed at the base of bed 14, which coincides with the base of the Alpina Subzone. Secondary markers bracketing the base of the Calpionella Zone are the FOs of the calcareous nannofossil species Nannoconus wintereri, close below the boundary, and the FO of Nannoconus steinmannii minor, close above. The Tithonian/Berriasian boundary level occurs within M19n.2n, in common with many documented sites, and is just below the distinctive reversed magnetic subzone M19n.1r (the so-called Brodno reversal). We present data which is congruent with magnetostratigraphic and biostratigraphic data from other key localities in France and in wider regions (Le Chouet, Saint Bertrand, Puerto Escaño, Rio Argos, Bosso, Brodno, Kurovice, Theodosia…), and thus the characteristics and datums identified at Tré Maroua are key for correlation and, in general, they typify the J/K boundary interval in Tethys and connected seas

The proposal of a GSSP for the Berriasian Stage (Cretaceous System): Part 2

International audienceIn part 1 of this work we discussed the possibilities for the selection of a GSSP for the Berriasian Stage of the Cretaceous System, based on prevailing practical methods for correlation in that J/K interval, traditional usage and the consensus over the best boundary markers that had developed in the last forty years. This consensus has developed further, based on the results of multidisciplinary studies on numerous sites over the last decade. Here in Part 2 we give an account of the application of those results by the Berriasian Working Group (ISCS), and present the stratigraphic evidence that justifies the selection of the locality of Tré Maroua (Hautes-Alpes, SE France) as the proposed GSSP. We describe a 45 m-thick section in the Calcaires Blancs vocontiens – that part of the formation covering the calpio­nellid Chitinoidella, Remanei. Intermedia, Colomi, Alpina, Ferasini, Elliptica and Simplex biozones. The stratigraphic data collected here has been compiled as part of a wider comparative study of complementary Vocontian Basin sites (with localities at Charens, St Bertrand, Belvedere and Le Chouet). Evidence from Tré Maroua thus sits in this substantial regional biostratigraphic and magnetostratigraphic context. For the purposes of the GSSP definition, here we particularly concentrate on the unbroken sequence and biotic markers in the interval immediately below the boundary, the Colomi Subzone (covering circa 675,000 years), and immediately above, the Alpina Subzone (covering circa 725,000 years). Particularly significant fossil datums identified in the Tré Maroua profile are the primary basal Berriasian marker, the base of the Alpina Subzone (a widespread event marked by dominance of small Calpionella alpina, with rare Crassicollaria parvula and Tintinopsella carpathica): the base of the Berriasian Stage is placed at the base of bed 14, which coincides with the base of the Alpina Subzone. Secondary markers bracketing the base of the Calpionella Zone are the FOs of the calcareous nannofossil species Nannoconus wintereri, close below the boundary, and the FO of Nannoconus steinmannii minor, close above. The Tithonian/Berriasian boundary level occurs within M19n.2n, in common with many documented sites, and is just below the distinctive reversed magnetic subzone M19n.1r (the so-called Brodno reversal). We present data which is congruent with magnetostratigraphic and biostratigraphic data from other key localities in France and in wider regions (Le Chouet, Saint Bertrand, Puerto Escaño, Rio Argos, Bosso, Brodno, Kurovice, Theodosia…), and thus the characteristics and datums identified at Tré Maroua are key for correlation and, in general, they typify the J/K boundary interval in Tethys and connected seas