Karlos G.D. Kochhann’s research while affiliated with Universidade do Vale do Rio dos Sinos and other places

The South Atlantic Ocean emerged after South America and Africa separated, creating various sedimentary basins, such as rift and drift types, that document this tectonic event. Among them, the Sergipe-Alagoas basin stands out, where marine organisms from the Tethys Sea diversified and evolved, including microfossils. Microcrinoids are echinoderms of the class Crinoidea, including the entire order Roveacrinida and its families, known for their delicate forms, adapted to marine plankton and lacking anchoring devices. The genus Sergipecrinus, belonging to the family Roveacrinidae, has been described and identified only between the Aptian/Albian boudary in the Riachuelo Formation dated to approximately 115 to 112 million years ago, making it the oldest genus in the family and providing insights into the early evolution of this group. This study, we investigated the mineralogical composition of Sergipecrinus reticulatus, focusing exclusively on the cup, using various instrumental techniques, including Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-ray Diffraction (XRD) and Spectroscopy Raman. The discovery of Sergipecrinus reticulatus occurred in samples from the SER-03 core drilled in the Sergipe-Alagoas Basin. The holotypes and paratypes are deposited in the Museu de História Geológica do Rio Grande do Sul. In this study, 11 cups from samples distributed along the core were analyzed. The objective was to identify the chemical composition at micro and nanoscale, especially regarding its survival during the anoxic event at the Aptian-Albian boundary, recorded in core sample SER-03. The EDS results indicated a predominance of calcium uniformly distributed in the cup, while X-ray diffraction and Raman spectroscopy predominantly characterized the presence of calcite, along with trace elements resulting from weathering, such as muscovite, bytownite, sanidine, celadonite, and quartz. Echinoderms in general, including crinoids, typically have a magnesian calcite composition, and our results revealed only calcite, which is contrary to expectations. This suggests the hypothesis that Sergipecrinus reticulatus, with their planktonic mode of life, used only calcite, in contrast to benthic echinoderms, which incorporate magnesian calcite.

During the Jurassic and Early Cretaceous, Earth's magnetic field experienced a high frequency of polarity reversals. This hyperactivity period is followed by a ∼38 Myr prolonged period of stable normal polarity from the Aptian until the Santonian, known as the Cretaceous Normal Superchron (CNS; chron C34n, from 121.4 to 83.65 Ma). However, the CNS might have been characterized by more variability than previously thought, but the current database is uneven in its spatial and temporal distribution. In this study, we integrate paleomagnetic and biostratigraphic data from the SER-03 sedimentary core, drilled onshore in the Sergipe-Alagoas Basin, NE Brazilian margin, South Atlantic Ocean. The 183-m cored interval spans 5.2 Myr (114.7–109.5 Ma), including the Aptian–Albian transition. It records the evolution from restricted marine settings to the complete opening of the South Atlantic Ocean. Magnetic remanence and rock magnetic parameters, such as magnetic susceptibility, anhysteretic remanent magnetization and isothermal remanent magnetization, were measured. Rock magnetic analyses indicated that primary magnetizations were preserved throughout the interval, with detrital magnetite identified as the primary magnetic carrier, predominantly in the pseudo-single domain and low-coercivity states. Normalizations by χ, ARM15mT and IRM15mT were used to determine relative paleointensity curves and were compared to the curve resulting from the pseudo-Thellier method. The SER-03 relative paleointensity record shows marked changes in both intensity and inclination. Inclination instability results are comparable with those found in volcanic rocks from surrounding the region. The high-resolution SER-03 magnetic record revealed that the field variability was higher than expected during the CNS, but remaining substantially lower than during other periods, such as the late Jurassic. The new SER-03 can serve as a dating and correlation tool for coeval records.

The bforams@mikrotax database focuses on deep-sea foraminifera from the Cretaceous through Cenozoic, providing a comprehensive, universally accessible taxonomic resource. Based on nannotax and pforams@mikrotax, this database provides an easy-to-use website for experts, researchers, and early career scientists, promoting stability in identifications and nomenclature. By providing detailed descriptions, images, citations, and expert opinions, bforams@mikrotax is becoming a crucial tool for paleoenvironmental, paleoceanographic, paleoclimatic, biostratigraphic, paleobiological studies, and foraminiferal geochemical analyses. The “Main Catalog” provides monographic coverage of 1,600 key taxa, including lists of junior synonyms, updated primary and secondary type images, morphological descriptions, paleobathymetry, and graphical stratigraphic range bars. The “Original Description Catalog” includes information from the original species designations, type specimen repository and locality information, and images of the primary type specimens. The bforams@mikrotax database will provide an invaluable research, reference, and teaching tool for students and researchers across all levels of expertise.

O fim do Cretáceo é marcado por grande perda da diversidade nos ambientes marinhos no qual os organismos planctônicos foram severamente afetados. Estes episódios coincidem com o impacto do bólido extraterrestre e os impulsos vulcânicos do Deccan. Durante estes períodos de estresse ambiental, as calcisferas (dinocistos calcários) proliferaram mesmo na ausência de outros competidores. Partindo do pressuposto que fatores como a diagênese podem afetar as estruturas carbonáticas durante o processo de biomineralização, o presente trabalho tem por objetivo avaliar quimicamente as estruturas de calcisferas depositadas no início do Daniano em diferentes localizações: (i) ODP Site 1262, Walvis Ridge, Oceano Atlântico Sul; (ii) Seção Cerro Azul, Bacia de Neuquén, Argentina e (iii) ODP Site 738, Kerguelen Plateau, Oceano Indico. Para fins comparativos, análises de FRX (n=68) foram realizadas nos sedimentos, visando comparar as intensidades dos mesmos elementos avaliados nas estruturas dos dinocistos. Devido ao pequeno tamanho dos espécimens (~5μm), as intensidades das concentrações de elementos como Ca, Fe, Mn, Cr, Ni e Zn foram medidas por microfluorescência de raios x (μXRF- síncrotron), línha de luz CARNAÚBA localizada no Sírius-UNICAMP. Os resultados ilustram que os níveis de elementos siderófilos analisados em sedimentos, apresentaram altas intensidades no limite Cretáceo-Paleógeno (Seção Cerro Azul) e nos primeiros momentos do Daniano (ODP sites 1262 e 738). Em relação a abundância das Cervisiella nos diferentes locais avaliados, percebe-se que a maior abundância está relacionada ao Oceano Atlântico Sul: Site 1262 (acme ~80%) e Seção Cerro Azul (acme ~67%). Já nas amostras do Oceano Indico foi identificado um aumento significativo na ocorrência dos espécimens, porém, o acme não ultrapassa a ~35%. Os resultados de μXRF sugerem maior concentração de cálcio (originalmente preservada), nos indivíduos oriundos do Oceano Indico. Enquanto para o Oceano Atlântico Sul, os espécimens parecem ter sido substituídos por outros elementos como: predominantemente níquel na Seção Cerro Azul e predominantemente zinco em indivíduos durante o evento Dan-C2 no Walvis Ridge. Nos demais espécimes ao longo do perfil avaliado, puderam ser mensuradas as razões isotópicas de δ13C/12C e δ18O/16O. Os dados isotópicos medidos nas calcisferas possuem um padrão semelhante ao observado na análise dos sedimentos (bulk). Os resultados preliminares em nanoescala sugerem a importância de estudos microestruturais para avaliar a efetividade da incorporação de elementos químicos no processo de biomineralização de produtores primários.

Seymour Island, located in the northeastern part of the Antarctic Peninsula, is famous for the widespread occurrence of fossils dating from the Late Cretaceous to the late Eocene. The PALEOCLIMA Project, carried out scientific expeditions in 2019–20 and 2022–23 with the aim of collecting rocks and fossils seeking information about climate changes over the last 66 million years. During these collections, four important deposits of echinoderm fossils were described, in the López de Bertodano (Maastrichtian-Paleocene), Sobral (Paleocene) and La Meseta (Eocene) formations. This study presents preliminary data on the taxonomic classication of echinoderms collected during eldworks. In the López Bertodano formation, dozens of sea urchin spines were collected. Some of them belong to, them are the species Cyathocidaris nordenskjoldi Neraudeau, Crame & Kooser, 2000, C. patera Neraudeau, Crame & Kooser, 2000, and others are new species, at least three families not yet mentioned in this formation (in prep.). In the Sobral Formation, in a stratigraphic section of approximately 15 meters, two intervals were described with the accumulation of columnals of crinoids of the genus Metacrinus Carpenter, 1884. In the La Meseta Formation, towards to base of the section, a single specimen of Stigmatopygus andersoni Lambert, 1910, was found, an echinoderm from the Echinoidea class with excellent preservation that inhabited shallow waters. In the middle part of the stratigraphic section, a level rich in specimens of Zoroaster marambioensis Palópolo, Brezina, Casadio, Gri n & Santillana, 2021, an echinoderm from the class Asteroidea that inhabited shallow waters, was described. In the next activities of this study, analyses using X-ray diffraction, Scanning Electron Microscopy and X-ray microtomography are planned to understand how and under what conditions the preservation of these fossils occurred, and refine the taxonomy of some specimens. [PROANTAR PALEOCLIMA: 442676/2018-2; FLORANTAR: 442765/2018-5]

The Cerro Azul Section provides a continuous record of the Cretaceous-Paleogene (K-Pg) transition in a shallow marine context of the South Atlantic Ocean in the Neuquén Basin. Ostracod assemblages were severely affected by environmental changes across the event. Excellent ostracod preservation at the Cerro Azul Section allows to infer paleoecological preferences of four Danian species based on carbon and oxygen stable isotopes. The studied species were Paracypris bertelsae Ceolin and Whatley, 2015, Cytherella spp., Togoina argentinensis and Henryhowella (Wichmannella) meridionalis (Bertels, 1974). To assess the reliability of ostracod δ13C and δ18O values as paleoenvironmental proxies, we pre-characterized valves with micro x-ray microdiffraction (μXRD) and microRaman (μRaman spectroscopy). Togoina argentinensis and Henryhowella (Wichmannella) meridionalis present in their major calcitic compositions, with small differences of crystallinity within intervals of environmental stress, but no authigenic phases formed during diagenesis. δ13C and δ18O values depict clear interspecific differences between smooth specimens and ornamented specimens. These differences in stable isotope values were likely controlled by microhabitat preferences, which would be comparable with patterns described for benthic foraminifera as well as paleonutrients variations, suing Ba/Ti and P/Ti ratios.

A Ilha Seymour, localizada a nordeste da Península Antártica, é famosa pela ampla ocorrência de fósseis que datam do final do Cretáceo até o final do Eoceno. O Projeto PALEOCLIMA, coordenado por pesquisadores da UNISINOS, realizou em 2019-20 e 2022-23 expedições científicas com o objetivo de coletar rochas e fósseis buscando informações sobre as mudanças climáticas dos últimos 66 Ma. Durante estas coletas, foram descritas dois importantes depósitos de fósseis de equinodermos, nas formações Sobral (Paleoceno) e La Meseta (Eoceno). Este estudo apresenta dados preliminares sobre a classificação taxonômica dos equinodermos coletados durante as atividades de campo. No afloramento da Formação Sobral, em uma seção estratigráfica de aproximadamente 15 metros, foram descritos dois intervalos com acumulação de pedúnculos de crinóides do gênero Metacrinus. Na Formação La Meseta, na porção basal da seção, foi encontrado um único exemplar de Stigmatopygus andersoni, equinodermo da classe Echinoidea com excelente preservação que habitava águas rasas. Já na porção média da seção estratigráfica, foi descrito um nível rico em exemplares de Zoroaster marambioensis, equinodermo da classe Asteroidea que habitava águas rasas. Os exemplares de Z. marambioensis foram encontrados articulados no campo, mas durante a coleta se fragmentaram em várias partes. Nas próximas atividades deste estudo, planeja-se análises em Difração de Raios-X e Microscópio Eletrônico de Varredura para entender como e em que condições ocorreu a preservação destes fósseis. [PROANTAR: 442676/2018-2]