Archaeological Stratigraphy & Luminescence Metrics: Dating Frameworks Of The Southwest

1. Chronostratigraphic Frameworks and Quaternary Depositional Contexts

The archaeological chronology of the Bibbullmun Sovereign Nation is anchored in rigorous chronostratigraphic sequences spanning subterranean karstic deposits, aeolian coastal dunes, and inland fluvial terraces.¹ Establishing chronological frameworks across Southwest Australia requires deciphering complex Quaternary sedimentary processes shaped by alternating glacial and interglacial cycles.² Sedimentary matrices in key archaeological sites—such as Devil's Lair, Upper Swan, and Tunnel Cave—feature deep, undisturbed stratification where cultural debris, combustion features, and lithic debitage are encapsulated within chronologically secure sediment horizons.³ These stratigraphies provide an unbroken empirical record of continuous human occupation extending from early Marine Isotope Stage 3 through the terminal Pleistocene and into the Late Holocene.⁴

2. Radiocarbon Calibration and High-Precision AMS Methodologies

Radiocarbon dating (14C) remains a primary chronometric pillar in Southwest geoarchaeology, though early conventional dates often yielded apparent underestimates due to post-depositional humic acid contamination and calibration limits.⁵ The application of ultrafiltration and acid-base-wet oxidation with stepped combustion (ABOx-SC) paired with Accelerator Mass Spectrometry (AMS) has fundamentally revolutionized chronology.⁶ At Devil's Lair, ABOx-SC AMS dating of macroscopic charcoal from in situ hearth features extended the reliable radiocarbon frontier beyond 45,000 cal BP, demonstrating human presence in the Southwest well prior to the Last Glacial Maximum.⁷ Calibration using the IntCal20 and SHCal20 southern hemisphere curves has resolved historical anomalies, ensuring chronological precision for cultural transitions.⁸

3. Optically Stimulated Luminescence (OSL) and Thermoluminescence Metrics

To overcome the 50,000-year ceiling of radiocarbon dating and directly date sedimentary deposition, Optically Stimulated Luminescence (OSL) and Thermoluminescence (TL) methodologies have been widely implemented.⁹ Single-aliquot regenerative-dose (SAR) protocols applied to sand-sized quartz grains measure the time elapsed since sediment was last exposed to daylight.¹⁰ In the fluvial terraces of the Upper Swan site, OSL dating corroborated early radiocarbon determinations of 38,000 BP, confirming that human stone-knappers discarded quartz flakes upon alluvial levee banks during Marine Isotope Stage 3.¹¹ Luminescence metrics also verify the rapid aeolian stabilization of Tamala Limestone dunes along the coastline, defining the exact temporal windows during which ancestral Bibbullmun populations utilised coastal rock shelters.¹²

4. Taphonomic Integrity, Pedogenesis, and Stratigraphic Inviolability

Rigorous geomorphic validation requires assessing post-depositional bioturbation, floralturbation, and sediment mixing to prove stratigraphic inviolability.¹³ Detailed soil micromorphology, granulometric analysis, and magnetic susceptibility profiling across Southwest archaeological sites confirm that cultural layers represent intact, unmixed occupational floors rather than reworked assemblages.¹⁴ The congruence of independent radiometric and luminescence chronologies establishes an empirical foundation verifying that the Bibbullmun Sovereign Nation possesses unbroken, scientifically auditable custodianship extending across 50,000 years of Southwest environmental history.¹⁵