Desk-based Assessment & Deposit-centred Approach, worked example: M25 junction 2 improvement Francis Wenban-Smith Heritage in Practice CPD course Birkbeck, University of London 15th September 2017 CAHO-Contracting Palaeolithic pre-construction archaeology Department of Archaeology
Worked example: M25 junction 2 improvement - introduction CAHO- Contracting Real-world example Demonstrate general approaches Wider view - deposits, landscape - Palaeolithic remains - general potential Closer view: Palaeolithic Character Areas - map + attribute table - deposit character - Palaeolithic remains - more-specific potential
Wider view: landscape and geology CAHO- Contracting Wider view: landscape and geology 175 174 173 172 171 170 169 551 552 553 554 555 556 557 558 559 560
Wider view: landscape and geology - keys CAHO- Contracting Wider view: landscape and geology - keys Drift Solid
Wider view: proforma, DBA output 1: - deposits CAHO- Contracting , Drift - Head - Head Gravel - Alluvium - Dartford Silt - Taplow Gravel - Lynch Hill Gravel - Boyn Hill Gravel - Black Park Gravel - undifferentiated terrace gravel - Slopewash [Terrace?] - Overbank flooding, intertidal, marsh - Aeolian/loessic? Alluvial? Slopewash? - Fluvial: high/low energy? Channels? Alluvium? Land- surfaces? - residual surface finds, or from un- mapped Pleistocene deposits [or maybe a mistake in the data] - Gentle burial? Derivation? - More vigorous burial? Derivation? - High integrity, low disturbance - High integrity, low disturbance? - Varied disturbance: probably generally low, occasionally more- disturbed and reworked, and occasionally totally undisturbed - need to consider most-likely deposit type Solid LC - London Clay LMB - Lambeth Group T - Thanet Sand UCk - Upper Chalk
Wider view: Palaeolithic remains - HER, SRPP (map) CAHO- Contracting Wider view: Palaeolithic remains - HER, SRPP (map) 3km radius records of known find- spots: A, E, G HER=SRPP? SRPP a bit awkward Has out-of-date landline & geo- mapping Nonetheless, good source: - prior to 1993 - primary references
Wider view: Palaeolithic remains - HER, SRPP (site information) CAHO- Contracting Wider view: Palaeolithic remains - HER, SRPP (site information)
Wider view: Palaeolithic remains - map sites onto deposits CAHO- Contracting Wider view: Palaeolithic remains - map sites onto deposits 175 Accurate, Estimated General Important 174 173 172 171 170 169 551 552 553 554 555 556 557 558 559 560
Wider view: general potential - collate site info, DBA w-i-p CAHO- Contracting Wider view: general potential - collate site info, DBA w-i-p not a formal “output” my working method, w-i-p add site names add/investigate key primary references relies on accuracy of HER info need to second-guess most-likely geological provenance “Undiff. T” = “Plateau Gravel”
Wider view: general potential CAHO- Contracting Wider view: general potential - collate site info by deposit, consider process/potential DBA - output 2 - Wider view of deposit types and associated Palaeolithic remains application of Deposit- centred Approach problem of “most- likely” vs “maybe” extrapolate info from wider area into site PCAs “Absence of evidence..” from previously- uninvestigated deposits
- site location, topography CAHO- Contracting Narrow view, PCAs: - site location, topography
CAHO- Contracting Narrow view, PCAs: - geo overlay
- geo overlay + PCAs layout CAHO- Contracting Narrow view, PCAs: - geo overlay + PCAs layout
- PCAs information and attribute summary CAHO- Contracting Narrow view, PCAs: - PCAs information and attribute summary various discussion points models of site formation in terraces addressing uncertainty? following known high potential, or investigating whether potential problem of addressing rare but important remains: - the “till” question - the “London” question - general potential