Tectonics & Sedimentation

Neoproterozoic-Devonian stratigraphic evolution of the eastern Murzuq Basin, Libya: a tale of tilting in the central Sahara

by Daniel Le Heron

Le Heron, D.P., Meinhold, G., Bergig, K. in press. basin Research, doi: 10.1111/j.1365-2117.2012.00555.x

The Murzuq Basin is one of the most petroliferous basins of North Africa. Its remote eastern flank, has been largely... more The Murzuq Basin is one of the most petroliferous basins of North Africa. Its remote eastern flank, has been largely ignored since early reconnaissance work in the 1950s and 1960s. This paper presents new stratigraphic and sedimentological data on the Neoproterozoic through Devonian succession from the Mourizidie and Dor el Gussa regions. The Neoproterozoic to Cambrian Mourizidie and Hasawnah formations in the eastern part of the Mourizidie dip to the east and north-east, resting directly on late Precambrian metasediments and granitoids. These strata record the initial progradation of sand-dominated braidplain systems upon peneplained Precambrian basement. Rhyolite clasts in the Hasawnah Formation may record tectonically driven uplift and unroofing in the southern Tibesti Massif or tectonomagmatic rejuvenation to the south of this massif. In the western part of the Mourizidie region, Late Ordovician through Silurian strata (Mamuniyat and Tanezzuft–Akakus formations) directly overlie late Precambrian metasediments and granitoids, and dip at a low angle toward the west into the Murzuq Basin. Elsewhere at the eastern Murzuq Basin flank, in Dor el Gussa, Late Ordovician glaciogenic sediments rest with angular unconformity upon shallow marine sandstones of Cambrian–Ordovician age. This angular unconformity may also occur in the Mourizidie region and indicates widespread tectonism, either as a result of a Middle–Late Ordovician orogenic event, far-field tectonism related to the opening of the Rheic Ocean along the northern margin of Gondwana, or alternatively crustal depression associated with the growth of Late Ordovician ice sheets. Unconformity development was also probably associated with glacial incision. Following ice sheet retreat, isostatic rebound during deglaciation resulted in uplift of tens to hundreds of metres, locally removing all Cambrian and Ordovician formations. Rising sea levels in the Silurian led to deposition of the Tanezzuft Formation on Precambrian basement in the northwestern Mourizidie region.

Evolving heavy mineral assemblages reveal changing exhumation and trench tectonics in the Mesozoic Chugach accretionary complex, South-Central Alaska

by Peter Clift

Published in Geological Society of America Bulletin 124(5/6), 989–1006, doi: 10.1130/B30594.1.
Full authorship is Clift, P.D., Wares, N.M., Amato, J.M., Pavlis, T.L., Hole, M.J., Worthman, C. and Day, E.

The Gulf of Alaska is one of the largest ac- cretionary complexes on Earth. In this study, we examined the earliest... more The Gulf of Alaska is one of the largest ac- cretionary complexes on Earth. In this study, we examined the earliest phase of accretion in the Mesozoic McHugh Complex and Val- dez Groups, exposed in SE Alaska. The old- est preserved fragment, the Mesomélange assemblage, is Jurassic (ca. 160–140 Ma) and consists of an ~3-km-thick structural package of strongly deformed shaley materi- als with slices of oceanic cherts and basalts. Heavy minerals indicate dominant erosion from a magmatic arc source uplifted after the collision of the Wrangellia and the Tal- keetna oceanic arc. A tectonic erosion event affected the forearc just prior to ca. 120 Ma and was likely caused by seamount collision, ridge subduction, or both. This was followed at 105 Ma by mass wasting of sandstone and conglomerates, preserved as the Graywacke- Conglomerate assemblage (ca. 105–83 Ma). Heavy minerals indicate continued flux from arc sources, but with significant changes suggesting a larger, more diverse catchment area. Erosion of deeper crustal sources pro- vided high-Mg diopside and garnets to the trench. Faster sediment flux was caused by rock uplift triggered by final accretion of the Wrangellia-Peninsula terrane to North America. The start of large-scale accretion in Alaska roughly coincided with the initia- tion of Shimanto Complex accretion in Japan and can be understood as primarily linked to sediment supply driven by plate-margin tec- tonics rather than climatically induced ero- sion onshore.

Fault array evolution in extensional basins: insights from statistical analysis of gravel deposits in the Cecina River (Tuscany, Italy)

by Andrea Ciampalini

A. CIAMPALINI, I. CONSOLONI, G. SARTI, Sedimentology 58, Issue 7, pages 1895–1913, 2011

Two statistical analyses of gravel clasts from the Lower Pleistocene deposits in the Lower Cecina Valley (Tuscany,... more Two statistical analyses of gravel clasts from the Lower Pleistocene deposits in the Lower Cecina Valley (Tuscany, Italy) have been combined to unravel changes in the palaeo-drainage system. Data from 16 outcrops were collected and 6400 clasts described. Facies analysis, micro-palaeontology and macro-palaeontology and petrographic characteristics of the gravel deposits have highlighted the presence of three allostratigraphic units. Clast lithology is the main discriminator among these units. Cluster and principal component analyses of the 6400 clasts have improved understanding of the stratigraphy of the Lower Pleistocene deposits and constrain the re-routing of the lower palaeo-Cecina River from a supposedly south-east to north-west direction to the present east to west direction. Short rivers feeding small fan deltas represented by the oldest allostratigraphic units were abandoned in the Lower Pleistocene, when the re-routing of the Cecina River caused the capture of these streams. This evolution suggests a change in the tectonic regime of the area. The fan deltas developed on the hanging wall of normal faults sub-parallel to the coast; a change to a transtensile tectonic regime caused the deviation of the main river channel toward the present coast and the formation of a pull-apart basin, which is now exploited by the Cecina River. This study illustrates the value of lithological analyses of gravel deposits for understanding the tectonic evolution of an area.

Thermochronology of mineral grains in the Song Hong and Mekong Rivers, Vietnam

by Peter Clift

Sedimentologic evolution of a submarine canyon in a forearc basin, Late Cretaceous Rosario Formation, San Carlos, Mexico

by Cathy Busby

Morris, W. R., and Busby-Spera, C. J., 1988, Sedimentologic evolution of a submarine canyon in a forearc basin, Late Cretaceous Rosario Formation, San Carlos, Mexico:  Am. Assoc. Petroleum Geologists, v. 72/6, p. 717-737.

Evolution of a Middle Jurassic back-arc basin, Cedros Island, Baja California: Evidence from a marine volcaniclastic apron

by Cathy Busby

Busby-Spera, C. J., 1988b, Evolution of a Middle Jurassic back-arc basin, Cedros Island, Baja California:  Evidence from a marine volcaniclastic apron:  Geol. Soc. America Bull., v. 100, p. 218-233.

Speculative tectonic model for the Early Mesozoic arc of the southwest Cordilleran United States

by Cathy Busby

Busby-Spera, C. J., 1988a, Speculative tectonic model for the Early Mesozoic arc of the southwest Cordilleran United States:  Geology, v. 16, p. 1121-1125.

Evolution of a multi-vent volcanic complex within a subsiding arc graben depression

by Cathy Busby

Riggs, N. R., and Busby-Spera, C. J., 1990, Evolution of a multi-vent volcanic complex within a subsiding arc graben depression: Mount Wrightson Formation, southern Arizona.  Geol. Soc. America Bull., v. 102, no. 8, p. 1114-1135.

Early Mesozoic evolution of the western U.S. Cordillera

by Cathy Busby

Saleeby, J. B., and Busby-Spera, C. J., 1992, Early Mesozoic evolution of the western U.S. Cordillera, In B. C. Burchfiel, P. W. Lipman and M. L. Zoback (eds.) The Cordilleran Orogen:  Conterminus United States:  Decade of North American Geology, Geological Society of America, v. G-3, p. 107-168.

Mid-Cretaceous crustal extension recorded in deep-marine half-graben fill, Cedros Island

by Cathy Busby

Smith, D. P., and Busby, C. J., 1993a, Mid-Cretaceous crustal extension recorded in deep-marine half-graben fill, Cedros Island, Mexico.  Geol. Soc. America Bull., v. 105, p. 547-562.

Jurassic magmatism in the central Mojave Desert: implications for arc paleogeography and preservation of continental volcanic sequences

by Cathy Busby

Schermer, E. R. and Busby, C. J., 1994, Jurassic magmatism in the central Mojave Desert: implications for arc paleogeography and preservation of continental volcanic sequences:  Geol. Soc. America Bull., v. 106, p. 767-790.

Jurassic magmatism and sedimentation in the Palen Mountains, southeastern California

by Cathy Busby

Adams, B.N., Busby, C.J. and Mattinson, J.M., 1997, Jurassic magmatism and sedimentation in the Palen Mountains, southeastern California:  Implications for regional tectonic controls on the Mesozoic magmatic arc:  Geol. Soc. America Bull., v. 109, p. 1464-1484.

Evolutionary model for convergent margins facing large ocean basins: Mesozoic Baja California (Mexico)

by Cathy Busby

Busby, C.J., Smith, D.P., Morris, W.R. and Adams, B., 1998, Evolutionary model for convergent margins facing large ocean basins:  Mesozoic Baja California (Mexico):  Geology, v. 26, no. 3, p. 227-230.

Tectonic and sedimentary controls on the composition of backarc volcaniclastic rocks

by Cathy Busby

Critelli, S., Marsaglia, K., and Busby, C., 2002, Tectonic and sedimentary controls on the composition of backarc volcaniclastic rocks; Geological Society of America Bulletin, v. 114, no. 5, p. 515 – 527

Continental growth at convergent margins facing large ocean basins: a case study from Mesozoic Baja California, Mexico

by Cathy Busby

Busby, C.J., 2004, Continental growth at convergent margins facing large ocean basins: a case study from Mesozoic Baja California, Mexico: Tectonophysics, v. 392, p. 241-277.

Volcanic facies architecture of an intra-arc strike-slip basin, Santa Rita Mountains, Arizona

by Cathy Busby

Busby, C.J. and Bassett, K., 2007, Volcanic facies architecture of an intra-arc strike-slip basin, Santa Rita Mountains, Arizona: Bulletin of Volcanology, v. 70, no. 1, p. 85

Volcaniclastic sedimentation and volcanism during the rifting of Western Pacific backarc basins

by Peter Clift

Slow rates of subduction erosion estimated from subsidence and tilting of the Tonga forearc

by Peter Clift

Tectonics of the Baikal rift deduced from volcanism and sedimentation: a review oriented to the Baikal and Hovsgol Lake systems

by Alexei Ivanov

Landscape development within a young collision zone: implications for post-Tethyan evolution of the Upper Tigris River system in southeastern Turkey

by Kathleen Nicoll

--> Citation: Nicoll, K. 2010. 'Landscape development within a young collision zone: implications for post- Tethyan evolution of the Upper Tigris River system in southeastern Turkey', International Geology Review, 52: 4, 404 -422. doi 10.1080/00206810902951072. http://dx.doi.org/10.1080/00206810902951072
For reprints, please contact me via email: kathleen.nicoll@gmail.com

ABSTRACT The geomorphic evolution of the upper basin of the Tigris (Dicle) River in southeastern Turkey reflects the... more ABSTRACT The geomorphic evolution of the upper basin of the Tigris (Dicle) River in southeastern Turkey reflects the interplay of surface processes and the development of topographic relief and lithospheric deformation since the closing of the Southern Neo-Tethyan (formerly Bitlis) Ocean. The study of the Tigris system is a proxy for understanding the deep crustal processes associated with the active Alpine – Himalayan mountain belt. The drainage morphology is linked to the uplift of the eastern Taurus Mountains and deformation of the Arabian foreland system following continent – continent collision. Initial review of landscape features at aerial and field scales confirms that the evolution of the Tigris has been complex, and that valley morphology varies by reach. Within the headwater reach, the Tigris is a transverse river system that flows across metamorphic rocks of the Bitlis – Zagros Suture Zone. Ongoing deformation in the Lake Hazar region bounded by the East Anatolian Fault Zone controls the topographic divide between the watershed draining north to the Euphrates and south to the Tigris. At the junction of the Arabian Plate, the river may be viewed as an antecedent stream system that developed since the Miocene. In the reach near Diyarbakir, valley development (and possibly incision) has been influenced by recent effusive volcanism. East of Diyarbakir, evaporitic karst processes are currently causing sapping, piping, and subsurface collapse as well as valley widening, which is concentrated in folds paralleling the suture zone and orogen to the north. The evolution of the Upper Tigris over the past 13 Myr can be reconstructed as a function of vertical movement (e.g. base-level changes, tectonic uplift, doming, downwarp, and sagging), horizontal deformation (e.g. folding, faulting, compression, and extension), volcanism, weathering, and erosion (e.g. dissolution processes, karstic erosion, and sapping). It is important to assess the first-order tectonic controls on the evolving fluvial systematics of the Tigris so that its sedimentary and geomorphic records can be used to reconstruct hydroclimatic changes affecting this part of the Near East during antiquity.