Relationships between geomagnetic field (GF) variations, paleoclimates, and Milankovitch cycles have increasingly attracted the attention of researchers mainly because of the assumption that GF may have acted as a climate forcing, suggesting that GF variations and orbital forcing may be linked in a complex synergistic way, especially, during interglacials and interstadials. We first performed an exhaustive analysis of the relationship between GF, a paleotemperature proxy, astroclimatic parameters, and the summer solstice mean daily insolation at 65 N over the last 500 kyr. We evaluated the relationship between the variables at the orbital scale, using wavelets, cross wavelets, and multiple cross wavelets. Our novel approach to the subject is the use of a new multiple cross wavelet algorithm, which allowed us to simultaneously analyze several data series and determine the relative phases between the signals. We confirm that the eccentricity modulates the GF behavior, and that the precession could have been related to some short-term GF variations. Both orbital parameters seem to be precursors of GF changes. Also, it is especially interesting to investigate the role of the GF reversion events because they could have acted as an indirect climate forcing, and we focused on the relationship among forcings during Marine Isotope Stage (MIS) 5. During this period, two GF reversions (Blake and post-Blake) could have been associated
with relative climate cooling. The consequent lack or weakening of shielding associated with GF events and downward insolation, both influenced by orbital forcing, could finally have promoted a relative global climate cooling during MIS 5.

A paleomagnetic and rock magnetic study was carried out in the Ediacaran Avellaneda (~570 Ma) and Cerro Negro (~555 Ma) Formations belonging to the La Providencia Group, in the upper part of the Neoproterozoic sedimentary cover of the Tandilia region, in the Río de la Plata craton. The Avellaneda Formation was studied at outcrop level and in three drill cores, yielding a mean characteristic remanence direction of Dec: 21.4◦, Inc: 67.1◦, α95: 4.2◦, k: 23.9, N: 51 and a paleomagnetic pole at 1.0◦ S, 313.4◦ E, A95: 5.9◦. The Cerro Negro Formation yielded a mean characteristic direction of Dec: 22.0◦, Inc: 68.5◦, α95: 10.3◦, k: 20.8, N: 11 obtained from a single drill core, from which a paleomagnetic pole at 3.6◦ S, 307.8◦E, A95: 16.6◦ was computed. Rock magnetic data indicates that magnetic remanence is mainly associated with magnetite and hematite. The paleomagnetic information presented here results in a change in the previously accepted Late Ediacaran apparent polar wander path of the Río de la Plata Craton. The newly obtained poles indicate that Río de la Plata Craton experienced a rapid drift from a low latitudes location (ca. 19◦ S) at ca. 600 Ma to moderately higher latitudes (between 50◦ and 42◦S) from around 580 to 550Ma.

The objective of this contribution is to distinguish characteristic wind speed periodicities from a roughly 19 mthick profile of Arturo Dune (Tierra del Fuego, Argentina), which contains eight interbedded paleosoils. The results include different magnetic properties and ratios measured in 29 aeolian sediment samples. These properties are coercive force (HC), saturation magnetization (MS), low-frequency (470 Hz) magnetic susceptibilities (kLF), anhysteretic remanent magnetization (ARM), among others. The statistical analysis of the variations in the magnetic properties of detrital minerals over time could indirectly indicate prevailing periodicities of the wind rate during the studied interval. The power spectral analysis was done using wavelets and multiple cross wavelets. The analysis by wavelets made it possible to distinguish periodicities in the variations of climatic parameters. A main periodicity of 2824 years was obtained in the different wavelet and multiple cross wavelet analyses of the magnetic parameters. By adding the δ18O series from the deep South Atlantic Ocean to the spectral power analysis, a periodicity of around 3000 years was also obtained. These periodicities could be related to a fundamental solar mode, with a periodicity of 2300 years (Hallstattzeit cycle). Still, they are not conclusive as solid empirical evidence to support sun-climate relationships on a series of millennial suborbital time scales.

The upper Palaeozoic basins of central-western Argentina include continuous fossiliferous successions spanning the Carboniferous-Permian interval. The palynostratigraphic biozones comprise Late Mississippian, Pennsylvanian and Cisuralian assemblages. Recently, new palynofloras of the La Veteada Formation were referred to the Lopingian (late Permian). However, they are characterized by spores and tetrads of Lundbladispora spp. and Densoisporites spp., pollen grains of Lunatisporites pellucidus, L. noviaulensis and Protohaploxypinus samoilovichii, and the alga Syndesmorion stellatum, that distinguish the post-Permian recovery floras worldwide. A new uranium-lead chemical abrasion-isotope dilution-thermal ionization mass spectrometry (U-Pb CA-ID-TIMS) age confirms the Olenekian age of this stratigraphic unit and allows the identification of the first Early Triassic palynofloras in this region of western Gondwana. Comparison and correlation with similar assemblages from the southern and northern hemispheres supports the Early Triassic turnover with an increase of lycopsid cavate spores associated with some diagnostic species of taeniate and non-taeniate bisaccate pollen.

The PANG 0003 well records a siliciclastic sedimentary succession corresponding to the Tunas Formation (Permian) in the Claromecó Basin area (Buenos Aires province, Argentina). The aim of this paper is to establish a relationship between fracture frequency in the PANG 0003 exploration well and AMS parameters, as it is a novel research topic that would contribute to the knowledge of the Claromecó basin. Opening-mode I and mode II/III fractures were found in 729 m of unoriented core between 901 m and 170 m recovered. Fracture attributes: inclination, aperture, height, and cement presence are represented by four fracture sets according to the inclination angle; representative kinematic aperture data range from 0 to 5 mm and height constrain by core dimensions. Cement presence is represented by quartz, calcite, and minor pyrite. Fracture description were distributed in lower, middle and upper section of the well according to their fracture frequency (number of fractures per meter). Lower section is represented by a high fracture frequency (13 fractures/meter), which notably diminishes to the middle and upper section of the well (3 fractures/meter). The results indicate that the fracture frequency increases in depth and has a direct relationship with AMS parameters, such as degree of anisotropy (Pj) and magnetic foliation (F). According to previous studies in Sierras Australes outcrops and subsurface for Tunas Formation, tectonic imprint decreases its expression from base to top of the unit and has a positive correlation with fractures studies on cores. This relationship could be used as an alternative methodology to distinguish intervals of high number of fractures in subsurface, in this particular case, for the Claromecó Basin.

We present 3D thermal and rheological models of a key intra-plate locality of South America: the southernmost limit of the Río de la Plata Craton area (which encompasses the Claromecó Basin, the Sierras Australes, and the Colorado Basin). Both models were calculated on the basis of a previously published 3D lithospheric scale density model, after the population of the different units with thermal and rheological properties. Firstly, the steady-state conductive thermal field was modelled using different thermal properties in accordance with the assumed lithological composition of the units. Moving forward, the strength distribution was calculated considering the resulting thermal field and published rheological properties for common rock types as input for the different layers that compose the 3D density configuration of the area. Our main results suggest that the thickness and composition of the crust exert a first-order control on the present-day thermal field of the area and, subsequently, on the lithospheric strength. Particularly, we identified a rheologically weak lithospheric zone that coincides with previously proposed inherited Paleozoic structures of Gondwana. This inherited lithospheric fabric could have controlled the opening of the Colorado Rift Basin during the early Late Jurassic. In that sense, the present day high strength of the Rio Negro and Colorado transfer zones associated with the mafic infill of Colorado rifting in the Mesozoic suggests that the weak zones should have necessarily been developed during (at least) Paleozoic to early Mesozoic times.
This supports the hypothesis that the reactivation and interaction of the latter with the Gondwanic weak lithospheric zone could have deformed and uplifted the Sierras Australes during the Gondwanides Orogeny.

We present new chronological data for the southernmost sector of the Eastern Sierras Pampeanas system of central Argentina. Recent excavations at the Cueva Los Bancos site in Sierra del Morro hill provided a date of ca. 9400 calendar years ago. This is the earliest absolute chronology of this sector, considered an ecotone between mountains and plains. Data provided will allow us to include this site in the discussion of the initial peopling of the region.

To understand the subsurface stratigraphy and structure of the Laguna Merín Basin (LMB), data from 42 magnetotelluric stations were interpreted by performing 1-D and 2-D inversions along three profiles perpendicular to the main basin borders. The Aiguá-India Muerta-Chuy Lineament (AICL) constitutes the southern boundary of the LMB and is characterised by a subvertical sinistral transtensional fault with a general orientation of N85°E. The basin's northern boundary, represented by the Cebollatí-Merín Lineament (CML), is characterised by a set of echelon dextral transpressional faults with a general orientation of N50°. Both faulting sets are associated with maximal horizontal stress oriented NE-SW. The infill of the LMB comprises thick Jurassic-Cretaceous igneous rocks (average of ~1500 m) overlying a crystalline Precambrian basement and overlain by ≤500 m-thick Cretaceous-Cenozoic sedimentary sequences. Likewise, a very deep (> 3500 m) conductive body was identified in the basement between the CML and AICL, coincident with the highest values of gravimetric Bouguer anomalies recorded in Uruguay. Shallow Cretaceous-Cenozoic sedimentary sequences show resistivities between 1 and 25 Ω.m, an average thickness of 250 m, and a maximum thickness of 500 m. The deeper Jurassic/Cretaceous igneous rocks show average resistivities between 40 and 252 Ω.m, and a maximum thickness of nearly 2000 m with intercalations of conductive layers (< 25 Ω.m) of unknown nature in the lower half of the basin infill. A tentative 3-D model is proposed to represent the early stage of magmatic emplacement during the opening of the South Atlantic Ocean.