STRUCTURE AND TECTONICS ACROSS THREE TECTONIC CYCLES. BEARINGS ON PREHISTORIC QUARRY ARCHITECTURE, EXTRACTION TECHNOLOGIES, AND RESULTING CHAIN DU OPERATOIRE

In eastern North America, chert occurs in three distinct tectonic provinces. Each province records the lithostratigraphic response to regional tectonic processes. Tectonic cycle 1 contains Cambrian-Ordovician chert bearing carbonates that initially are fairly uniform and grade up section into more varied lithologies. Tectonic processes complexly folded and faulted the terrain and elevated temperature/pressure conditions to upper greenschist facies. Prehistoric quarries tend to occur in parallel linear belts; however, the quarries are small. The petrofabric complexity of the chert dictates that quarries require an elaborate extraction technology for successful mining. Mining tool kits need to be petrologically diverse and heavily curated. The chain of operation is elongate and extensive (up to 48 steps).

Second tectonic cycle rocks are Lower Silurian to Lower Devonian facies that exhibit greater variability than the older carbonates. Middle Devonian lithologies are more uniform and occur as shallow subtidal facies. These rocks contain broad, plunging to doubly plunging, folds that formed under lower greenschist facies. Moderate numbers of intermediate size quarries occur in arcuate/hook shaped patterns. Less deformed raw materials require less elaborate quarry extraction technologies. Intermediate levels of curation of petrologically similar quarry tool kits suffice for quarry extraction. The less deformed nature of the raw material results in an intermediate chain du opertoire (24 to 36 steps).

In tectonic cycle 3, lithostratigraphically uniform chert facies occur within the intermediate to deeper subtidal facies of Mississippian age and along shallow subtidal and near shoreline environments of the Pennsylvanian. Gently warped strata, extensive fault-bounded stratigraphic sequences, and low pressure/temperature conditions allow for smaller numbers of extremely large quarry landscapes. Quarries occur within intra-formational circular patterns and require the simplest quarry extraction technology, resulting in a very short chain du operatoire (12-18 steps). These quarries require the lowest levels of curation of petrologically monotonous quarry tool kits.