GEOMAGNETIC NETWORK ANALYSIS: A HIGH RESOLUTION PALEOMAGNETIC BASED CHRONOSTRATIGRAPHIC APPROACH PARTICULARLY WELL-SUITED FOR THE NORTHEAST PACIFIC-WESTERN NORTH AMERICAN REGION

Chronology is a fundamental challenge that confronts our understanding of global systems. Radiocarbon is a remarkable tool for meeting this challenge in diverse environments that are less than around 50,000 years old. However, beyond this time interval dating becomes substantially more difficult. Centennial to millennial variations in direction and intensity of the geomagnetic field, known as paleomagnetic secular variation (PSV), offer an environmentally independent signal that can be used for detailed stratigraphic alignment; however, the difficulty is the lack of common templates for comparison. To get around that, we outline an approach we call geomagnetic network analysis (GNA), where correlations are based on the reasonable assumption that sediments within a limited geographic region have experienced a common geomagnetic history. This assumption means that prior knowledge of the record, although helpful, is not required. As a result, GNA allows regional organization of chronological constraints (dates, tephra, tuning approaches, etc.) from multiple sequences to be combined into a single age-depth profile. The caveats for GNA are: 1) that the region must be small enough that the records under consideration were influenced by a common geomagnetic field, and 2) that the field was faithfully recorded in an archive at or near the time of deposition and preserved in a generally unaltered state at each site (essentially the same as for any paleo-geomagnetic record). In our initial assessment, we find that inclination is regionally coherence in the Northeast Pacific-Western North American region, implying that: 1) these variations are due to large scale geomagnetic dynamics (which we will discuss), and 2) because inclination is often the easiest paleomagnetic parameter to recover, that GNA is particularly well suited for stratigraphic correlation in this region (we will provide examples), both within the radiocarbon era and likely beyond.