Among the most significant cartographic documents produced by Italian geology in the final years of the nineteenth century, this Carta Geotectonica della Terra di Bari holds a place of paramount importance: not only for the sophistication of its graphic execution but above all for the extraordinary scientific synthesis it manages to condense in order to describe one of the most complex and fascinating territories on the peninsula.
The map is oriented in the customary manner, with the Adriatic coast running along the top edge and the jagged profile of the Lucanian-Campanian Apennines sloping down into the lower left quadrant, rendered using a gray-scale shading technique of great orographic precision.
The map come from Geomorfogenia della Provincia di Bari, by Francesco Virgilio published in 1900 in Trani by the publisher Valdemaro Vecchi.
The Legend and Meaning of Colors
The representation system adopted by Virgilio follows the great tradition of nineteenth-century geological cartography, dividing the territory into stratigraphic series distinguished by geological era and lithological composition, each assigned a conventional color that can be identified using the “Explanation of Colors and Symbols” located in the upper right corner of the sheet.
The dominant olive green, which covers most of the mapped area, corresponds to the oldest Cretaceous formations: specifically, the limestones and rudist formations, the marls or marly clays of the Turonian-Aptian-Albian (Late and Early Cretaceous), as well as the limestone-dolomite rocks of the Cenomanian-Rudomanian. This is the limestone basement of the Murgia, the vast karst plateau that forms the structural backbone of the entire province and which emerges here in its entirety.
The broad yellow-ochre layer that overlays the green along the slopes and in the foothills indicates the presence of Pliocene formations: the yellow sands and sandy clays of the Sicilian Stage and the marls and marine clays of the Astian and Piacenzian Stages. This band, particularly evident along the coastal margin and on the eastern slopes of the Murgia, bears witness to the advance of the Pliocene sea into a territory that had previously been above water.
The vivid red, concentrated in patches of striking visual impact along the southwestern margin and in the deepest valley gullies, indicates Pleistocene diluvial floods, conglomerates, and crystalline puddingstones (Diluvium). These torrential-alluvial deposits mark the periods of greatest morphological dynamism in the region during the glacial phases of the Quaternary.
The turquoise blue-green, used sparingly but to great effect along the coastal strip, refers to recent Holocene formations: recent alluvial deposits, red soils, and dunes of the present period, along with the San Francesco di Bari carparo tuffs—the characteristic sandy-porous bioclastic limestones that have always been the primary building material for Bari’s historic architecture.
The conventional symbols superimposed on the colors complete the structural picture: antithinal lines (dashed), faults (solid red lines), and stratigraphic sections (arrows indicating the direction of dip) form a tectonic grid that reveals the deep geometry of the territory. The point symbols, on the other hand, indicate the locations of limestone, tuff, and clay quarries—a detail that also gives the map economic and industrial documentary value.
The Terms Geotectonics and Geomorphogenesis
The title of the map, Carta Geotectonica, and that of the work from which it is taken, Geomorfogenia della Provincia di Bari, refer to two concepts that, at the end of the 19th century, were still in the midst of theoretical development.
Geotectonics—or geological tectonics—is the branch of Earth sciences that studies the deformational structures of the lithosphere: folds, faults, thrust faults, and fracture systems that bear witness to the movements of rock masses over geological time. A geotectonic map, therefore, does not merely describe the distribution of surface terrain but seeks to reconstruct the mechanical history of the subsurface, interpreting the current arrangement of strata as the result of compressive, extensional, or shear forces acting at depth. In the case of the Bari region, Virgilio identifies and maps the large anticlinal structures of the Murgia, oriented in the Apennine direction (NW-SE), and the fault systems that influence its drainage and karst morphology.
Geomorphogenesis is an even rarer and more ambitious term: it refers to the study of the origin and evolution of landforms—that is, the process through which the Earth’s surface has taken on its current configurations as a result of the combined effects of tectonics, erosion, karst processes, climatic variations, and sea-level changes. The term is essentially equivalent to what modern dynamic geomorphology would define as the genetic study of the landscape. Virgilio’s use of this neologism reveals a specific scientific background: that of late-19th-century geographical positivism, influenced by the German school of Friedrich Ratzel and David’s theories on cyclic erosion, but filtered through the vibrant southern naturalist tradition.
Francesco Virgilio was a geologist and naturalist active in Puglia between the late 19th century and the early 20th century. His training took place against the backdrop of the revival of the natural sciences in post-unification Italy, when the Royal Geological Office—founded in 1867—was conducting a systematic survey of the peninsula and inspiring a generation of local researchers to supplement national efforts with detailed investigations at the provincial level. Virgilio devoted himself, with methodological rigor, to the study of the geological structure of the province of Bari, addressing not only the stratigraphy of the terrain—from the Cretaceous basement to the Pliocene-Pleistocene overlies—but also the karst morphology of the Murge, the erosional phenomena of the “lame,” and the coastal dynamics of the Apulian Adriatic. His 1900 work *Geomorphogenia* represents the culmination of this effort: a work that synthesizes years of field surveys into a coherent interpretive framework, capable of interpreting the landscape as the result of a long and complex geological history. His name appears consistently in 20th-century Apulian scientific literature, a sign that his contribution was not confined to the time of its publication but became a foundational reference for subsequent generations of regional geologists.
