Ivar Midtkandal

Short- and Long-Term Olivine Weathering in Svalbard: Implications for Mars

Liquid water is essential to life as we know it on Earth; therefore, the search for water on Mars is a critical component of the search for life. Olivine, a mineral identified as present on Mars, has been proposed as an indicator of the duration and characteristics of water because it dissolves quickly, particularly under low-pH conditions. The duration of olivine persistence relative to glass under conditions of aqueous alteration reflects the pH and temperature of the reacting fluids. In this paper, we investigate the utility of 3 methodologies to detect silicate weathering in a Mars analog environment (Sverrefjell volcano, Svalbard). CheMin, a miniature X-ray diffraction instrument developed for flight on NASAs upcoming Mars Science Laboratory, was deployed on Svalbard and was successful in detecting olivine and weathering products. The persistence of olivine and glass in Svalbard rocks was also investigated via laboratory observations of weathered hand samples as well as an in situ burial experiment. Observations of hand samples are consistent with the inference that olivine persists longer than glass at near-zero temperatures in the presence of solutions at pH approximately 7-9 on Svalbard, whereas in hydrothermally altered zones, glass has persisted longer than olivine in the presence of fluids at similar pH at approximately 50 degrees C. Analysis of the surfaces of olivine and glass samples, which were buried on Sverrefjell for 1 year and then retrieved, documented only minor incipient weathering, though these results suggest the importance of biological impacts. The 3 types of observations (CheMin, laboratory observations of hand samples, burial experiments) of weathering of olivine and glass at Svalbard show promise for interpretation of weathering on Mars. Furthermore, the weathering relationships observed on Svalbard are consistent with laboratory-measured dissolution rates, which suggests that relative mineral dissolution rates in the laboratory, in concert with field observations, can be used to yield valuable information regarding the pH and temperature of reacting martian fluids.

Re-created Early Oligocene seabed bathymetry and process-based simulations of the Peïra Cava turbidite system

Abstract: Sea-floor bathymetry is one of the principal controls on the routing of turbidity currents and the subsequent distribution of deposited sediments. Re-created sea-floor bathymetry is thus one of the main inputs for process-based numerical simulation of ancient turbidite systems. The sea floor underlying the Early Oligocene deposits of the Peïra Cava basin (Alpine foreland, southern France) has been re-created from an outcrop dataset by subjecting a surface-based 3D model to stepwise backstripping of overburden and removal of the post-depositional structural overprint. The surfaces that make up the 3D model were constructed based on field data including stratigraphic correlations, structural measurements and geological maps. Since deposition the Peïra Cava turbidites have been folded, faulted, tilted, uplifted and partly eroded, all of which was summarized and then accounted for during re-creation of the palaeo-sea floor. Uncertainties associated with the input parameters used for the re-creation include the lithological composition of the overburden and underburden, palaeo-water depth and structural restoration. The impact of these uncertainties was addressed by creating a range of scenarios within viable ranges for each of the separate parameters and then comparing the relief and geometry of re-created surfaces. Two mid-case palaeobathymetric surfaces were selected and used as input for process-based simulation of turbidity currents using commercially available software designed for modelling density flows. The simulation results were compared with the stratigraphic architecture observed at outcrop. The quality of the correlation was used as a test of how well the re-created palaeobathymetry mimics the true ancient sea floor.

Structural Inheritance and Rapid Rift‐Length Establishment in a Multiphase Rift: The East Greenland Rift System and its Caledonian Orogenic Ancestry

We investigate (i) margin-scale structural inheritance in rifts and (ii) the time scales of rift propagation and rift length establishment, using the East Greenland rift system (EGR) as an example. To investigate the controls of the underlying Caledonian structural grain on the development of the EGR, we juxtapose new age constraints on rift faulting with existing geochronological and structural evidence. Results from K-Ar illite fault dating and syn-rift growth strata in hangingwall basins suggest initial faulting in Mississippian times and episodes of fault activity in Middle-Late Pennsylvanian, Middle Permian, and Middle Jurassic to Early Cretaceous times. Several lines of evidence indicate a close relationship between low-angle late-to-post-Caledonian extensional shear zones (CESZs) and younger rift structure: (i) reorientation of rift fault strike to conform with CESZs, (ii) spatial coincidence of rift-scale transfer zones with CESZs, and (iii) close temporal coincidence between the latest activity (late Devonian) on the preexisting network of CESZs and the earliest rift faulting (latest Devonian to earliest Carboniferous). Lateto post-Caledonian extensional detachments therefore likely acted as a template for the establishment of the EGR. We also conclude that the EGR established its near-full length rapidly, i.e., within 4–20% of rift life. The “constant-length model” for normal fault growth may therefore be applicable at rift scale, but tip propagation, relay breaching, and linkage may dominate border fault systems during rapid lengthening.

Grand Challenges (and Great Opportunities) in Sedimentology, Stratigraphy, and Diagenesis Research

NERC Yorkshire Integrated Catchment Solutions Programme [NE/P011160/1]; NERC National Capability project Climate Linked Atlantic Sector Science Programme (CLASS)