Abstract

Haughton is a complex meteorite impact structure of Tertiary age on Devon Island in the Canadian Arctic. The 20.5 km diameter site was formed in essentially flat-lying Paleozoic carbonates, roughly 1700 m in thickness, overlying Precambrian gneisses. The structure comprises three concentric rings surrounding a central basin with interior peaks. The outer ring, diameter 20.5 km, is an annulus of peaks separating the Allen Bay dolomites of the regional plateau from the same unit that has been downdropped towards the crater interior along a series of circumferential faults. The middle ring of peaks, diameter 14–15 km, comprises both faulted Allen Bay dolomites and blocks of the underlying Bay Fiord Formation uplifted 250 m. Hills of the inner, elliptical ring, 3.5–5.5 km in diameter, are also formed from Bay Fiord Formation and the underlying Eleanor River Formation brought up 600 m. An interconnected series of normal faults occupies most of the annulus between the inner and outer rings. Within the central basin occur isolated hills of Bay Fiord and Eleanor River material, again raised a minimum of 700 m. Allochthonous impact breccia, containing shocked clasts of all sedimentary units and the Precambrian crystalline rocks, covers most of the central basin and the inner ring, and occurs in patches within the faulted annulus. A circular, −11 mGal (−11 × 10−5 m s−2) residual Bouguer gravity anomaly, diameter 25 km, is concentric with the structure. A more intense central "low" is tentatively correlated with allochthonous breccia up to 200 m in thickness. A 300 nT positive magnetic anomaly is situated at the crater's centre and possibly reflects the near-surface occurrence of crystalline rocks of the uplifted Precambrian basement. Most of the structural and morphological features at Haughton have counterparts in the thoroughly investigated Ries impact structure, Germany, and the allochthonous breccia is considered equivalent to the suevite deposits of the latter site.The transition between various morphologies in the crater populations of the cratered planets is a function of size, rock type, and planetary gravity. Scaling from lunar data indicates that a multi-ring impact basin in sedimentary rocks may form on Earth at a diameter not much larger than that of Haughton. The morphology of Haughton is considered intermediary between peak ring basins and multi-ring basins.

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