Polygonal tepee structures of Arabia

Abstract Tepee structures are upward‐buckling fracture rims that form a reticulated network of polygonal boundaries when viewed from an aerial perspective. These structures are thought to result from crystallisation forces of cement, causing lateral expansion of consolidating sedimentary materials. Tepee structures are indicative of subaerial exposure and can serve as stratigraphic markers in ancient carbonate sequences. While tepee structures are common in ancient carbonate sequences, in modern settings, they have only been described in the Arabian Gulf. The discovery of fields of polygonal structures, on satellite images of the Red Sea Island of Sheybarah, Saudi Arabia, motivated the authors to assess their genesis and distribution in Arabia. The objectives are to describe in detail tepees and their arrangement in polygonal patterns, investigate the timing of their formation and constrain the relative timing of tepee generation. Furthermore, this study investigates, based on a detailed satellite image survey, whether similar polygonal features can be identified around the Arabian Peninsula. The polygonal crusts on Sheybarah Island are found in intertidal to supratidal settings overlying a well‐lithified ravinement surface. They are composed of locally derived poorly sorted sand‐to‐pebble‐sized coral, mollusc and foraminifera debris of predominantly aragonite and high Mg‐calcite mineralogy with minor admixtures of siliciclastics. Based on petrographic analysis, microbial‐induced cement precipitation is the major lithification agent. Lithification occurs in the upper intertidal zone based on the ubiquitous presence of keystone vugs. Radiocarbon ( 14 C) dates reveal elevation‐aligned ages between approximately 1.5 and 3.0 ka BP, allowing the reconstruction of late Holocene minor sea‐level changes aligned with major global climate variations. Hence, polygonal tepee structures may serve as proxies for sea‐level changes. Of 126 occurrences of polygonal fields identified from satellite images, 89 in the Red Sea are probably composed of polygonal reefs. The authors hypothesise that polygonal coral reefs originated on tepee crust.