Multi-Scale Magma Flow-Sorting formed from the amalgamation of intruding magma pulses, and precludes dike, sill, or laccolith emplacement models. We conclude that schlieren-bound structures are faithful recorders of the multi-scale, hypersolidus evolution of upper-crustal magma bodies, and represent useful tools for studying plutonic systems.

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Polygonal fault systems (PFSs) are an enigmatic class of small nontectonic extensional faults. PFSs are predominantly hosted in fine-grained sedimentary tiers and are prevalent along many continental margin basins. The genesis of PFSs is widely debated, and little is known about the time frame for polygonal fault growth. We present the first measurements of throw rates for polygonal faults by measuring the vertical offset of seven age-calibrated horizons mapped using three-dimensional seismic reflection data from the Norwegian Sea. Individual polygonal faults exhibit a range of throw rate profiles through time, ranging from near linear to singly or multiply stepped. The stepped profiles have short-term throw rates ranging from 0 to 18 m/m.y. Time-averaged throw rates of 180 polygonal faults over the entire 2.61–0 Ma interval are normally distributed and range between 1.4 and 10.9 m/m.y. We convert our PFS throw rates to displacement rates and compare these to published displacement rates for gravity-driven and tectonic normal faults. We find that the displacement rates of polygonal faults mark the lower limit of a continuous spectrum of extensional fault displacement rates; they are as much as two orders of magnitude slower than those of gravity-driven faults, and as much as three orders of magnitude slower than those of the fastest-growing tectonic faults. We attribute the ultra-slow kinematic behavior to the nontectonic nature of polygonal faults, where throw accumulates primarily through dewatering of the largely fine-grained sediments composing the host layers for the PFSs, and through differential volumetric strain between the fault footwalls and hanging walls.

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The top 250 m of the PFS tier is chronostratigraphically calibrated by eight dated markers from ODP 644 (Fig. DR2). Seven of which were uniquely distinguished and mapable across the study area. Biostratigraphy -Calcareous NannofossilsThe two youngest stratigraphic markers were biostratigraphically dated by calcareous nannofossil assemblages with the first appearance of E. huxleyi marking the onset of biozone NN21 (0.268 Ma at 22 mbsf), and the last appearance of P. lacunose marking the end of biozone NN19 (0.458 Ma at 51 mbsf) (Eldholm et al., 1987;Berggren et al., 1995;Cohen & Gibbard, 2016). The respective dating of the start of NN21 and end of NN19 have been updated since ODP 644 was published, and we use the current biostratigraphic dating framework outlined by the International Commission on Stratigraphy in our analysis (Cohen & Gibbard, 2016). Diatom, silicoflagellate, radiolarian, planktonic and benthic foraminifer assemblages were also examined but did not yield absolute age dates required for our analysis. Similarly, palynological samples yielded paleoenvironmental insight but no direct age-calibration.