Stratigraphy

Stratigraphy is the study of layers. In archaeology it is the method of excavating and recording a site as a sequence of superimposed deposits, so that the order in which those deposits formed can be read directly from the ground. Each layer, or stratum, represents a phase of building, occupation, destruction or abandonment, and the objects sealed within it, above all pottery, date that phase relative to the ones above and below it.

The governing principle is straightforward: undisturbed deposits accumulate from the bottom up, so a layer is later than everything beneath it and earlier than everything above. What makes the method so productive in the Ancient Near East is the tell, an artificial mound built up over centuries as mudbrick settlements collapsed and were rebuilt on their own rubble. A tell is a stratigraphic sequence in physical form, and excavated carefully it yields an ordered history of the site.

Stratigraphy on its own establishes relative order rather than calendar dates. Absolute dates enter the sequence when a layer produces something independently datable: an imported vessel of known type, an inscription naming a ruler, a datable scarab, or organic material suitable for radiocarbon analysis. Pottery chronology is the bridge between the two. Because ceramic forms, wares and decoration changed steadily and regionally, a corpus of pottery anchored at a few points to fixed dates can then date every layer in which those forms appear.

---

Etymology and Biblical Usage

The term combines the Latin "stratum," meaning a layer or covering, with the Greek "-graphia," meaning writing or description. It entered English through geology in the 19th century, where the ordering of rock strata was worked out first, and passed from geology into archaeology.

Stratigraphy has no biblical usage. It is a modern technical term for a modern technical procedure, and neither the word nor the practice appears in the Old Testament or in any ancient Near Eastern source. Its bearing on Scripture is entirely indirect: it is one of the tools by which the material setting of the biblical world is recovered, ordered and dated.

Historical Context

The method's founding application in the region came in 1890, when Flinders Petrie spent six weeks excavating Tell el-Hesi for the Palestine Exploration Fund. Erosion had cut away one flank of the mound, exposing its layers in section, and Petrie recorded the pottery from each layer separately rather than treating the mound as a single deposit. He found that every layer carried its own distinctive wares and that those wares changed in a consistent order from bottom to top. Assigning approximate dates to the main types, he produced the first ceramic sequence for the Levant and showed that a tell could be dated by its pottery layer by layer. Petrie identified the site as biblical Lachish, an identification later abandoned, but the method outlived the misidentification and is what the 1890 season is remembered for.

Frederick Jones Bliss continued the work at Tell el-Hesi in 1891 and 1892, cutting down through the mound level by level and distinguishing eleven occupational levels that he grouped into eight superimposed "cities." Between them, Petrie's ceramic sequence and Bliss's stratified city sequence supplied the chronological framework that Levantine archaeology has worked from ever since.

Comparable work was under way elsewhere. At Troy, Wilhelm Dörpfeld's seasons of 1893 and 1894 resolved the mound at Hisarlik into nine successive settlements, correcting the confusion left by Heinrich Schliemann's earlier trenching. At Jericho, Kathleen Kenyon's excavations of 1952 to 1958 applied the Wheeler-Kenyon box-grid technique, in which balks of unexcavated earth are left standing between adjacent squares so that the exposed section faces can be drawn and the layers followed as the dig proceeds. Refined from Mortimer Wheeler's earlier work at Verulamium, the technique became standard practice across the region.

Archaeological Evidence

Stratified tells across Mesopotamia, Egypt and the Levant supply the raw material for the method. Megiddo is among the most thoroughly worked examples: the University of Chicago expedition of 1925 to 1939 distinguished twenty major occupation levels, numbered from Stratum I at the surface down to Stratum XX at virgin soil, recording successive fortifications, gates, temples and destruction horizons. The pottery recovered from each stratum supplies the chronological markers that hold the sequence together.

Stratigraphic control also governs how every other class of find is read. An inscription, a seal or a scarab carries dating weight only when its find-spot within the sequence is secure. An object recovered from a disturbed context, or bought from a dealer with no recorded provenance, has lost the information that would have placed it in time. Careful recording of the layer is therefore as much a part of the evidence as the object taken from it.

Distinctions & Relationships

Stratigraphy is not the same as typology, though the two are used together. Typology classifies objects by form, ware and decoration and arranges those classes into a developmental series. Stratigraphy tests that series against the ground, since a typological sequence is only as sound as the layered deposits that confirm its order. Petrie's achievement at Tell el-Hesi was to lock the two together.

Nor is stratigraphy confined to pottery. Walls, floors, foundation trenches, pits, fills, ash horizons and collapsed mudbrick are all stratigraphic units, and the relationships between them, which one cuts another and which one seals another, are what the excavator records. Radiocarbon dating, dendrochronology and archaeomagnetic analysis supply independent dates, but they date samples; it is the stratigraphic record that establishes what those samples belong to.